/*
**********************************************************************
*   Copyright (C) 2001 IBM and others. All rights reserved.
**********************************************************************
*   Date        Name        Description
*  07/02/2001   synwee      Creation.
**********************************************************************
*/

#include "unicode/usearch.h"
#include "unicode/ustring.h"
#include "unicode/uchar.h"
#include "unormimp.h"
#include "ucol_imp.h"
#include "usrchimp.h"
#include "cmemory.h"

// internal definition ---------------------------------------------------

#define LAST_BYTE_MASK_          0xFF
#define SECOND_LAST_BYTE_SHIFT_  8
#define SUPPLEMENTARY_MIN_VALUE_ 0x10000

static const uint16_t *FCD_ = NULL;

// internal methods -------------------------------------------------

/**
* Getting the mask for collation strength
* @param strength collation strength
* @return collation element mask
*/
static
inline uint32_t getMask(UCollationStrength strength) 
{
    switch (strength) 
    {
    case UCOL_PRIMARY:
        return UCOL_PRIMARYORDERMASK;
    case UCOL_SECONDARY:
        return UCOL_SECONDARYORDERMASK | UCOL_PRIMARYORDERMASK;
    default:
        return UCOL_TERTIARYORDERMASK | UCOL_SECONDARYORDERMASK | 
               UCOL_PRIMARYORDERMASK;
    }
}

/**
* This is to squeeze the 21bit ces into a 256 table
* @param ce collation element
* @return collapsed version of the collation element
*/
static
inline int hash(uint32_t ce) 
{
    // the old value UCOL_PRIMARYORDER(ce) % MAX_TABLE_SIZE_ does not work
    // well with the new collation where most of the latin 1 characters
    // are of the value xx000xxx. their hashes will most of the time be 0
    // to be discussed on the hash algo.
    return UCOL_PRIMARYORDER(ce) % MAX_TABLE_SIZE_;
}

/**
* Initializing the fcd tables.
* Internal method, status assumed to be a success.
* @param status output error if any, caller to check status before calling 
*               method, status assumed to be success when passed in.
*/
static
inline void initializeFCD(UErrorCode *status) 
{
    if (FCD_ == NULL) {
        FCD_ = unorm_getFCDTrie(status);
    }
}

/**
* Gets the fcd value for a character at the argument index.
* This method takes into accounts of the supplementary characters.
* @param str UTF16 string where character for fcd retrieval resides
* @param offset position of the character whose fcd is to be retrieved, to be 
*               overwritten with the next character position, taking 
*               surrogate characters into consideration.
* @param strlength length of the argument string
* @return fcd value
*/
static
inline uint16_t getFCD(const UChar   *str, int32_t *offset, 
                             int32_t  strlength)
{
    int32_t temp = *offset;
    uint16_t    result;
    UChar       ch   = str[temp];
    result = unorm_getFCD16(FCD_, ch);
    temp ++;
    
    if (result && temp != strlength && UTF_IS_FIRST_SURROGATE(ch)) {
        ch = str[temp];
        if (UTF_IS_SECOND_SURROGATE(ch)) {
            result = unorm_getFCD16FromSurrogatePair(FCD_, result, ch);
            temp ++;
        } else {
            result = 0;
        }
    }
    *offset = temp;
    return result;
}

/**
* Getting the modified collation elements taking into account the collation 
* attributes
* @param strsrch string search data
* @param sourcece 
* @return the modified collation element
*/
static
inline uint32_t getCE(const UStringSearch *strsrch, uint32_t sourcece)
{
    // note for tertiary we can't use the collator->tertiaryMask, that
    // is a preprocessed mask that takes into account case options. since
    // we are only concerned with exact matches, we don't need that.
    sourcece &= strsrch->ceMask;
    
    if (strsrch->toShift) {
        // alternate handling here, since only the 16 most significant digits
        // is only used, we can safely do a compare without masking
        // if the ce is a variable, we mask and get only the primary values
        // no shifting to quartenary is required since all primary values
        // less than variabletop will need to be masked off anyway.
        if (strsrch->variableTop > sourcece) {
            if (strsrch->strength == UCOL_QUATERNARY) {
                sourcece &= UCOL_PRIMARYORDERMASK;
            }
            else { 
                sourcece = UCOL_IGNORABLE;
            }
        }
    }

    return sourcece;
}

/** 
* Allocate a memory and returns NULL if it failed.
* Internal method, status assumed to be a success.
* @param size to allocate
* @param status output error if any, caller to check status before calling 
*               method, status assumed to be success when passed in.
* @return newly allocated array, NULL otherwise
*/
static
inline void * allocateMemory(uint32_t size, UErrorCode *status) 
{
    uint32_t *result = (uint32_t *)uprv_malloc(size);
    if (result == NULL) {
        *status = U_MEMORY_ALLOCATION_ERROR;
    }
    return result;
}

/**
* Adds a uint32_t value to a destination array.
* Creates a new array if we run out of space. The caller will have to 
* manually deallocate the newly allocated array.
* Internal method, status assumed to be success, caller has to check status 
* before calling this method. destination not to be NULL and has at least 
* size destinationlength.
* @param destination target array
* @param offset destination offset to add value
* @param destinationlength target array size, return value for the new size
* @param value to be added
* @param increments incremental size expected
* @param status output error if any, caller to check status before calling 
*               method, status assumed to be success when passed in.
* @return new destination array, destination if there was no new allocation
*/
static
inline uint32_t * addTouint32_tArray(uint32_t   *destination,       
                                     uint32_t    offset, 
                                     uint32_t   *destinationlength, 
                                     uint32_t    value,
                                     uint32_t    increments, 
                                     UErrorCode *status) 
{
    uint32_t newlength = *destinationlength;
    if (offset + 1 == newlength) {
        newlength += increments;
        uint32_t *temp = (uint32_t *)allocateMemory(
                                         sizeof(uint32_t) * newlength, status);
        if (U_FAILURE(*status)) {
            return NULL;
        }
        uprv_memcpy(temp, destination, sizeof(uint32_t) * offset);
        *destinationlength = newlength;
        destination        = temp;
    }
    destination[offset] = value;
    return destination;
}

/**
* Initializing the ce table for a pattern.
* Stores non-ignorable collation keys.
* Table size will be estimated by the size of the pattern text. Table 
* expansion will be perform as we go along. Adding 1 to ensure that the table 
* size definitely increases.
* Internal method, status assumed to be a success.
* @param strsrch string search data
* @param status output error if any, caller to check status before calling 
*               method, status assumed to be success when passed in.
* @return total number of expansions 
*/
static
inline uint16_t initializePatternCETable(UStringSearch *strsrch, 
                                         UErrorCode    *status)
{
    UPattern *pattern            = &(strsrch->pattern);
    uint32_t  cetablesize        = INITIAL_ARRAY_SIZE_;
    uint32_t *cetable            = pattern->CEBuffer;
    uint32_t  patternlength      = pattern->textLength;
    UCollationElements *coleiter = strsrch->utilIter;
            
    if (coleiter == NULL) {
        coleiter = ucol_openElements(strsrch->collator, pattern->text, 
                                     patternlength, status);
        // status will be checked in ucol_next(..) later and if it is an 
        // error UCOL_NULLORDER the result of ucol_next(..) and 0 will be 
        // returned.
        strsrch->utilIter = coleiter;
    }
    else {
        uprv_init_collIterate(strsrch->collator, pattern->text,
                         pattern->textLength,
                         &coleiter->iteratordata_);
    }
        
    if (pattern->CE != cetable && pattern->CE) {
        uprv_free(pattern->CE);
    }
        
    uint16_t  offset      = 0;
    uint16_t  result      = 0;
    uint32_t  ce;

    while ((ce = ucol_next(coleiter, status)) != UCOL_NULLORDER &&
           U_SUCCESS(*status)) {
        uint32_t newce = getCE(strsrch, ce);
        if (newce) {
            uint32_t *temp = addTouint32_tArray(cetable, offset, &cetablesize, 
                                  newce,
                                  patternlength - ucol_getOffset(coleiter) + 1, 
                                  status);
            if (U_FAILURE(*status)) {
                return 0;
            }
            offset ++;
            if (cetable != temp && cetable != pattern->CEBuffer) {
                uprv_free(cetable);
            }
            cetable = temp;
        }
        result += ucol_getMaxExpansion(coleiter, ce) - 1;
    }

    cetable[offset]   = 0;
    pattern->CE       = cetable;
    pattern->CELength = offset;

    return result;
}

/**
* Initializes the pattern struct.
* Internal method, status assumed to be success.
* @param strsrch UStringSearch data storage
* @param status output error if any, caller to check status before calling 
*               method, status assumed to be success when passed in.
* @return expansionsize the total expansion size of the pattern
*/ 
static
inline int16_t initializePattern(UStringSearch *strsrch, UErrorCode *status) 
{
          UPattern   *pattern     = &(strsrch->pattern);
    const UChar      *patterntext = pattern->text;
          int32_t     length      = pattern->textLength;
          int32_t index       = 0;

    pattern->hasPrefixAccents = getFCD(patterntext, &index, length) >> 
                                                     SECOND_LAST_BYTE_SHIFT_;
    index = length;
    UTF_BACK_1(patterntext, 0, index);
    pattern->hasSuffixAccents = getFCD(patterntext, &index, length) & 
                                                             LAST_BYTE_MASK_;
    // since intializePattern is an internal method status is a success.
    return initializePatternCETable(strsrch, status);   
}

/**
* Initializing shift tables, with the default values.
* If a corresponding default value is 0, the shift table is not set.
* @param shift table for forwards shift 
* @param backshift table for backwards shift
* @param cetable table containing pattern ce
* @param cesize size of the pattern ces
* @param expansionsize total size of the expansions
* @param defaultforward the default forward value
* @param defaultbackward the default backward value
*/
static
inline void setShiftTable(int16_t   shift[], int16_t backshift[], 
                          uint32_t *cetable, int32_t cesize, 
                          int16_t   expansionsize,
                          int16_t   defaultforward,
                          int16_t   defaultbackward)
{
    // estimate the value to shift. to do that we estimate the smallest 
    // number of characters to give the relevant ces, ie approximately
    // the number of ces minus their expansion, since expansions can come 
    // from a character.
    int32_t count;
    for (count = 0; count < MAX_TABLE_SIZE_; count ++) {
        shift[count] = defaultforward;
    }
    cesize --; // down to the last index
    for (count = 0; count < cesize; count ++) {
        // number of ces from right of array to the count
        int temp = defaultforward - count - 1;
        shift[hash(cetable[count])] = temp > 1 ? temp : 1;
    }
    shift[hash(cetable[cesize])] = 1;
    // for ignorables we just shift by one. see test examples.
    shift[hash(0)] = 1;
    
    for (count = 0; count < MAX_TABLE_SIZE_; count ++) {
        backshift[count] = defaultbackward;
    }
    for (count = cesize; count > 0; count --) {
        // the original value count does not seem to work
        backshift[hash(cetable[count])] = count > expansionsize ? 
                                          count - expansionsize : 1;
    }
    backshift[hash(cetable[0])] = 1;
    backshift[hash(0)] = 1;
}

/**
* Building of the pattern collation element list and the boyer moore strsrch
* table.
* The canonical match will only be performed after the default match fails.
* For both cases we need to remember the size of the composed and decomposed
* versions of the string. Since the Boyer-Moore shift calculations shifts by
* a number of characters in the text and tries to match the pattern from that 
* offset, the shift value can not be too large in case we miss some 
* characters. To choose a right shift size, we estimate the NFC form of the 
* and use its size as a shift guide. The NFC form should be the small 
* possible representation of the pattern. Anyways, we'll err on the smaller
* shift size. Hence the calculation for minlength.
* Canonical match will be performed slightly differently. We'll split the 
* pattern into 3 parts, the prefix accents (PA), the middle string bounded by 
* the first and last base character (MS), the ending accents (EA). Matches 
* will be done on MS first, and only when we match MS then some processing
* will be required for the prefix and end accents in order to determine if
* they match PA and EA. Hence the default shift values 
* for the canonical match will take the size of either end's accent into 
* consideration. Forwards search will take the end accents into consideration
* for the default shift values and the backwards search will take the prefix
* accents into consideration.
* If pattern has no non-ignorable ce, we return a illegal argument error.
* Internal method, status assumed to be success.
* @param strsrch UStringSearch data storage
* @param status  for output errors if it occurs, status is assumed to be a
*                success when it is passed in.
*/ 
static
inline void initialize(UStringSearch *strsrch, UErrorCode *status) 
{
    int16_t expandlength  = initializePattern(strsrch, status);   
    if (U_SUCCESS(*status) && strsrch->pattern.CELength > 0) {
        UPattern *pattern = &strsrch->pattern;
        int32_t   cesize  = pattern->CELength;

        int16_t minlength = cesize > expandlength ? cesize - expandlength : 1;
        pattern->defaultShiftSize    = minlength;
        setShiftTable(pattern->shift, pattern->backShift, pattern->CE,
                      cesize, expandlength, minlength, minlength);
        return;
    }
    strsrch->pattern.defaultShiftSize = 0;
}

/**
* Determine whether the target text in UStringSearch bounded by the offset 
* start and end is one or more whole units of text as 
* determined by the breakiterator in UStringSearch.
* @param strsrch string search data 
* @param start target text start offset
* @param end target text end offset
*/
static
inline UBool isBreakUnit(const UStringSearch *strsrch, int32_t start, 
                               int32_t    end)
{
    UBreakIterator *breakiterator = strsrch->search->breakIter;
    if (breakiterator) {
        int32_t startindex = ubrk_first(breakiterator);
        int32_t endindex   = ubrk_last(breakiterator);
        
        // out-of-range indexes are never boundary positions
        if (start < startindex || start > endindex ||
            end < startindex || end > endindex) {
            return FALSE;
        }
        // otherwise, we can use following() on the position before the 
        // specified one and return true of the position we get back is the 
        // one the user specified
        UBool result = (start == startindex || 
                ubrk_following(breakiterator, start - 1) == start) && 
               (end == endindex || 
                ubrk_following(breakiterator, end - 1) == end);
        if (result) {
            // iterates the individual ces
                  UCollationElements *coleiter  = strsrch->utilIter;
            const UChar              *text      = strsrch->search->text + 
                                                                      start;
                  UErrorCode          status    = U_ZERO_ERROR;
            ucol_setText(coleiter, text, end - start, &status);
            for (int32_t count = 0; count < strsrch->pattern.CELength;
                 count ++) {
                uint32_t ce = getCE(strsrch, ucol_next(coleiter, &status));
                if (ce == UCOL_IGNORABLE) {
                    count --;
                    continue;
                }
                if (U_FAILURE(status) || ce != strsrch->pattern.CE[count]) {
                    return FALSE;
                }
            }
            uint32_t nextce = ucol_next(coleiter, &status);
            while (ucol_getOffset(coleiter) == (end - start)
                   && getCE(strsrch, nextce) == UCOL_IGNORABLE) {
                nextce = ucol_next(coleiter, &status);
            }
            if (ucol_getOffset(coleiter) == (end - start)
                && nextce != UCOL_NULLORDER) {
                // extra collation elements at the end of the match
                return FALSE;
            }
        }
        return result;
    }
    return TRUE;
}

/**
* Getting the next base character offset if current offset is an accent, 
* or the current offset if the current character contains a base character. 
* accents the following base character will be returned
* @param text string
* @param textoffset current offset
* @param textlength length of text string
* @return the next base character or the current offset
*         if the current character is contains a base character.
*/
static
inline int32_t getNextBaseOffset(const UChar       *text, 
                                           int32_t  textoffset,
                                           int32_t      textlength)
{
    if (textoffset < textlength) {
        int32_t temp = textoffset;
        if (getFCD(text, &temp, textlength) >> SECOND_LAST_BYTE_SHIFT_) {
            while (temp < textlength) { 
                int32_t result = temp;
                if ((getFCD(text, &temp, textlength) >> 
                     SECOND_LAST_BYTE_SHIFT_) == 0) {
                    return result;
                }
            }
            return textlength;
        }
    }
    return textoffset;
}

/**
* Gets the next base character offset depending on the string search pattern
* data
* @param strsrch string search data
* @param textoffset current offset, one offset away from the last character
*                   to search for.
* @return start index of the next base character or the current offset
*         if the current character is contains a base character.
*/
static
inline int32_t getNextUStringSearchBaseOffset(UStringSearch *strsrch, 
                                                  int32_t    textoffset)
{
    if (strsrch->pattern.hasSuffixAccents && 
        textoffset < strsrch->search->textLength) {
              int32_t      textlength = strsrch->search->textLength;
              int32_t  temp       = textoffset;
        const UChar       *text       = strsrch->search->text;
        UTF_BACK_1(text, 0, temp);
        if (getFCD(text, &temp, textlength) & LAST_BYTE_MASK_) {
            return getNextBaseOffset(text, textoffset, textlength);
        }
    }
    return textoffset;
}

/**
* Shifting the collation element iterator position forward to prepare for
* a following match. If the last character is a unsafe character, we'll only
* shift by 1 to capture contractions, normalization etc.
* Internal method, status assumed to be success.
* @param text strsrch string search data
* @param textoffset start text position to do search
* @param ce the text ce which failed the match.
* @param patternceindex index of the ce within the pattern ce buffer which
*        failed the match
* @param status output error if any, caller to check status before calling 
*               method, status assumed to be success when passed in.
* @return final offset
*/
static
inline int32_t shiftForward(UStringSearch *strsrch,
                                int32_t    textoffset,
                                uint32_t       ce,
                                int32_t        patternceindex,
                                UErrorCode    *status)
{
    if (strsrch->search->isOverlap) {
        if (textoffset > 0) {
            textoffset ++;
        }
        else {
            textoffset = strsrch->pattern.defaultShiftSize;
        }
    }
    else {
        if (ce != UCOL_NULLORDER) {
            int32_t shift = strsrch->pattern.shift[hash(ce)];
            // this is to adjust for characters in the middle of the 
            // substring for matching that failed.
            int32_t adjust = strsrch->pattern.CELength - patternceindex;
            if (adjust > 1 && shift >= adjust) {
                shift -= adjust - 1;
            }
            textoffset += shift;
        }
        else {
            textoffset += strsrch->pattern.defaultShiftSize;
        }
    }
        
    textoffset = getNextUStringSearchBaseOffset(strsrch, textoffset);
    // check for unsafe characters
    // * if it is the start or middle of a contraction: to be done after 
    //   a initial match is found
    // * thai or lao base consonant character: similar to contraction
    // * high surrogate character: similar to contraction
    // * next character is a accent: shift to the next base character
    if (textoffset <= strsrch->search->textLength) {
        ucol_setOffset(strsrch->textIter, textoffset, status);
    }
    return textoffset;
}

/**
* sets match not found 
* @param strsrch string search data
* @param status output error status if any
*/
static
inline void setMatchNotFound(UStringSearch *strsrch, UErrorCode *status) 
{
    // this method resets the match result regardless of the error status.
    strsrch->search->matchedIndex = USEARCH_DONE;
    strsrch->search->matchedLength = 0;
    if (strsrch->search->isForwardSearching) {
        ucol_setOffset(strsrch->textIter, strsrch->search->textLength, 
                       status);
    }
    else {
        ucol_setOffset(strsrch->textIter, 0, status);
    }
}

/**
* Gets the offset to the next safe point in text.
* ie. not the middle of a contraction, swappable characters or supplementary
* characters.
* @param collator collation sata
* @param text string to work with
* @param textoffset offset in string
* @param textlength length of text string
* @return offset to the next safe character
*/
static
inline int32_t getNextSafeOffset(const UCollator   *collator, 
                                     const UChar       *text,
                                           int32_t  textoffset,
                                           int32_t      textlength)
{
    int32_t result = textoffset; // first contraction character
    while (result != textlength && ucol_unsafeCP(text[result], collator)) {
        result ++;
    }
    return result; 
}

/** 
* This checks for accents in the potential match started with a .
* composite character.
* This is really painful... we have to check that composite character do not 
* have any extra accents. We have to normalize the potential match and find 
* the immediate decomposed character before the match.
* The first composite character would have been taken care of by the fcd 
* checks in checkForwardExactMatch.
* This is the slow path after the fcd of the first character and 
* the last character has been checked by checkForwardExactMatch and we 
* determine that the potential match has extra non-ignorable preceding
* ces.
* E.g. looking for \u0301 acute in \u01FA A ring above and acute, 
* checkExtraMatchAccent should fail since there is a middle ring in \u01FA
* Note here that accents checking are slow and cautioned in the API docs.
* Internal method, status assumed to be a success, caller should check status
* before calling this method
* @param strsrch string search data
* @param start index of the potential unfriendly composite character
* @param end index of the potential unfriendly composite character
* @param status output error status if any.
* @return TRUE if there is non-ignorable accents before at the beginning
*              of the match, FALSE otherwise.
*/

static
UBool checkExtraMatchAccents(const UStringSearch *strsrch, int32_t start,
                                   int32_t    end,     
                                   UErrorCode    *status)
{
    UBool result = FALSE;
    if (strsrch->pattern.hasPrefixAccents) {
              int32_t  length = end - start;
              int32_t  offset = 0;
        const UChar       *text   = strsrch->search->text + start;
        
        UTF_FWD_1(text, offset, length);
        // we are only concerned with the first composite character
        if (unorm_quickCheck(text, offset, UNORM_NFD, status) == UNORM_NO) {
            int32_t safeoffset = getNextSafeOffset(strsrch->collator, 
                                                       text, 0, length);
            if (safeoffset != length) {
                safeoffset ++;
            }
            UChar   *norm = NULL;
            UChar    buffer[INITIAL_ARRAY_SIZE_];
            int32_t  size = unorm_normalize(text, safeoffset, UNORM_NFD, 0, 
                                            buffer, INITIAL_ARRAY_SIZE_, 
                                            status);    
            if (U_FAILURE(*status)) {
                return FALSE;
            }
            if (size >= INITIAL_ARRAY_SIZE_) {
                norm = (UChar *)allocateMemory((size + 1) * sizeof(UChar),
                                               status);
                // if allocation failed, status will be set to 
                // U_MEMORY_ALLOCATION_ERROR and unorm_normalize internally
                // checks for it.
                size = unorm_normalize(text, safeoffset, UNORM_NFD, 0, norm, 
                                       size, status);
                if (U_FAILURE(*status) && norm != NULL) {
                    uprv_free(norm);
                    return FALSE;
                }
            }
            else {
                norm = buffer;
            }

            UCollationElements *coleiter  = strsrch->utilIter;
            ucol_setText(coleiter, norm, size, status);
            uint32_t            firstce   = strsrch->pattern.CE[0];
            UBool               ignorable = TRUE;
            uint32_t            ce        = UCOL_IGNORABLE;
            while (U_SUCCESS(*status) && ce != firstce) {
                offset = ucol_getOffset(coleiter);
                if (ce != firstce && ce != UCOL_IGNORABLE) {
                    ignorable = FALSE;
                }
                ce = ucol_next(coleiter, status);
            }
            UChar32 codepoint;
            UTF_PREV_CHAR(norm, 0, offset, codepoint);
            result = !ignorable && (u_getCombiningClass(codepoint) != 0);

            if (norm != buffer) {
                uprv_free(norm);
            }
        }
    }

    return result;
}

/**
* Used by exact matches, checks if there are accents before the match. 
* This is really painful... we have to check that composite characters at
* the start of the matches have to not have any extra accents. 
* We check the FCD of the character first, if it starts with an accent and 
* the first pattern ce does not match the first ce of the character, we bail.
* Otherwise we try normalizing the first composite 
* character and find the immediate decomposed character before the match to 
* see if it is an non-ignorable accent.
* Now normalizing the first composite character is enough because we ensure 
* that when the match is passed in here with extra beginning ces, the 
* first or last ce that match has to occur within the first character.
* E.g. looking for \u0301 acute in \u01FA A ring above and acute, 
* checkExtraMatchAccent should fail since there is a middle ring in \u01FA
* Note here that accents checking are slow and cautioned in the API docs.
* @param strsrch string search data
* @param start offset 
* @param end offset
* @return TRUE if there are accents on either side of the match, 
*         FALSE otherwise
*/
static
UBool hasAccentsBeforeMatch(const UStringSearch *strsrch, int32_t start,
                                  int32_t    end) 
{
    if (strsrch->pattern.hasPrefixAccents) {
        UCollationElements *coleiter  = strsrch->textIter;
        UErrorCode          status    = U_ZERO_ERROR;
        // we have been iterating forwards previously
        uint32_t            ignorable = TRUE;
        uint32_t            firstce   = strsrch->pattern.CE[0];

        ucol_setOffset(coleiter, start, &status);
        uint32_t ce  = getCE(strsrch, ucol_next(coleiter, &status));
        if (U_FAILURE(status)) {
            return TRUE;
        }
        while (ce != firstce) {
            if (ce != UCOL_IGNORABLE) {
                ignorable = FALSE;
            }
            ce = getCE(strsrch, ucol_next(coleiter, &status));
            if (U_FAILURE(status)) {
                return TRUE;
            }
        }
        if (!ignorable && inNormBuf(coleiter)) {
            // within normalization buffer, discontiguous handled here
            return TRUE;
        }

        // within text
        int32_t temp = start;
        UBool accent = (getFCD(strsrch->search->text, &temp, 
                               strsrch->search->textLength) >> 
                                                    SECOND_LAST_BYTE_SHIFT_); 
        if (!accent) {
            return checkExtraMatchAccents(strsrch, start, end, &status);
        }
        if (!ignorable) {
            return TRUE;
        }
        if (start > 0) {
            temp = start;
            UTF_BACK_1(strsrch->search->text, 0, temp);
            if (getFCD(strsrch->search->text, &temp, 
                       strsrch->search->textLength) & LAST_BYTE_MASK_) {
                ucol_setOffset(coleiter, start, &status);
                ce = ucol_previous(coleiter, &status);
                if (U_FAILURE(status) || 
                    (ce != UCOL_NULLORDER && ce != UCOL_IGNORABLE)) {
                    return TRUE;
                }
            }
        }
    }
  
    return FALSE;
}

/**
* Used by exact matches, checks if there are accents bounding the match.
* Note this is the initial boundary check. If the potential match
* starts or ends with composite characters, the accents in those
* characters will be determined later.
* Not doing backwards iteration here, since discontiguos contraction for 
* backwards collation element iterator, use up too many characters.
* E.g. looking for \u030A ring in \u01FA A ring above and acute, 
* should fail since there is a acute at the end of \u01FA
* Note here that accents checking are slow and cautioned in the API docs.
* @param strsrch string search data
* @param start offset of match
* @param end end offset of the match
* @return TRUE if there are accents on either side of the match, 
*         FALSE otherwise
*/
static
UBool hasAccentsAfterMatch(const UStringSearch *strsrch, int32_t start,               
                                 int32_t    end) 
{
    if (strsrch->pattern.hasSuffixAccents) {
        const UChar       *text       = strsrch->search->text;
              int32_t  temp       = end;
              int32_t      textlength = strsrch->search->textLength;
        UTF_BACK_1(text, 0, temp);
        if (getFCD(text, &temp, textlength) & LAST_BYTE_MASK_) {
            uint32_t            firstce  = strsrch->pattern.CE[0];
            UCollationElements *coleiter = strsrch->textIter;
            UErrorCode          status   = U_ZERO_ERROR;
            ucol_setOffset(coleiter, start, &status);
            while (getCE(strsrch, ucol_next(coleiter, &status)) != firstce) {
                if (U_FAILURE(status)) {
                    return TRUE;
                }
            }
            int32_t count = 1;
            while (count < strsrch->pattern.CELength) {
                if (getCE(strsrch, ucol_next(coleiter, &status)) 
                    == UCOL_IGNORABLE) {
                    // Thai can give an ignorable here.
                    count --;
                }
                if (U_FAILURE(status)) {
                    return TRUE;
                }
                count ++;
            }
            uint32_t ce = getCE(strsrch, ucol_next(coleiter, &status));
            if (U_FAILURE(status)) {
                return TRUE;
            }
            if (ce != UCOL_NULLORDER && ce != UCOL_IGNORABLE) {
                if (ucol_getOffset(coleiter) <= end) {
                    return TRUE;
                }
                if (getFCD(text, &end, textlength) >> SECOND_LAST_BYTE_SHIFT_) {
                    return TRUE;
                }
            }
        }
    }
    return FALSE;
}

/**
* Checks if the offset runs out of the text string
* @param offset 
* @param textlength of the text string
* @return TRUE if offset is out of bounds, FALSE otherwise
*/
static
inline UBool isOutOfBounds(int32_t textlength, int32_t offset)
{
    return offset < 0 || offset > textlength;
}

/**
* Checks for identical match
* @param strsrch string search data
* @param start offset of possible match
* @param end offset of possible match
* @return TRUE if identical match is found
*/
static
inline UBool checkIdentical(const UStringSearch *strsrch, int32_t start, 
                                  int32_t    end) 
{
    int32_t length = end - start;
    if (strsrch->strength != UCOL_IDENTICAL) {
        return TRUE;
    }

    UErrorCode status = U_ZERO_ERROR;
    int decomplength = unorm_decompose(NULL, -1, 
                                       strsrch->search->text + start, length, 
                                       FALSE, FALSE, &status);
    if (decomplength != unorm_decompose(NULL, -1, strsrch->pattern.text, 
                                        strsrch->pattern.textLength, FALSE, 
                                        FALSE, &status)) {
        return FALSE;
    }
    decomplength ++;
    UChar *text    = (UChar *)uprv_malloc(decomplength * sizeof(UChar));
    UChar *pattern = (UChar *)uprv_malloc(decomplength * sizeof(UChar));
    unorm_decompose(text, decomplength, strsrch->search->text + start, 
                    length, FALSE, FALSE, &status);
    unorm_decompose(pattern, decomplength, strsrch->pattern.text, 
                    strsrch->pattern.textLength, FALSE, FALSE, &status);
    UBool result = (uprv_memcmp(pattern, text, decomplength * sizeof(UChar)) 
                    == 0);
    uprv_free(text);
    uprv_free(pattern);
    return result;
}

/**
* Checks to see if the match is repeated
* @param strsrch string search data
* @param start new match start index
* @param end new match end index
* @return TRUE if the the match is repeated, FALSE otherwise
*/
static
inline UBool checkRepeatedMatch(UStringSearch *strsrch,
                                int32_t    start,
                                int32_t    end)
{
    int32_t lastmatchindex = strsrch->search->matchedIndex;
    UBool       result;
    if (lastmatchindex == USEARCH_DONE) {
        return FALSE;
    }
    if (strsrch->search->isForwardSearching) {
        result = start <= lastmatchindex;
    }
    else {
        result = start >= lastmatchindex;
    }
    if (!strsrch->search->isOverlap) {
        if (strsrch->search->isForwardSearching) {
            result = start < lastmatchindex + strsrch->search->matchedLength;
        }
        else {
            result = end > lastmatchindex;
        }
    }
    return result;
}

/**
* Gets the collation element iterator's current offset.
* @param coleiter collation element iterator
* @param forwards flag TRUE if we are moving in th forwards direction
* @return current offset 
*/
static
inline int32_t getColElemIterOffset(const UCollationElements *coleiter,
                                              UBool               forwards)
{
    int32_t result = ucol_getOffset(coleiter);
    // intricacies of the the backwards collation element iterator
    if (!forwards && inNormBuf(coleiter) && !isFCDPointerNull(coleiter)) {
        result ++;
    }
    return result;
}

/**
* Checks match for contraction. 
* If the match ends with a partial contraction we fail.
* If the match starts too far off (because of backwards iteration) we try to
* chip off the extra characters depending on whether a breakiterator has
* been used.
* Internal method, error assumed to be success, caller has to check status 
* before calling this method.
* @param strsrch string search data
* @param start offset of potential match, to be modified if necessary
* @param end offset of potential match, to be modified if necessary
* @param status output error status if any
* @return TRUE if match passes the contraction test, FALSE otherwise
*/

static
UBool checkNextExactContractionMatch(UStringSearch *strsrch, 
                                     int32_t   *start, 
                                     int32_t   *end, UErrorCode  *status) 
{
          UCollationElements *coleiter   = strsrch->textIter;
          int32_t             textlength = strsrch->search->textLength;
          int32_t         temp       = *start;
    const UCollator          *collator   = strsrch->collator;
    const UChar              *text       = strsrch->search->text;
    // This part checks if either ends of the match contains potential 
    // contraction. If so we'll have to iterate through them
    if ((*end < textlength && ucol_unsafeCP(text[*end], collator)) || 
        (*start + 1 < textlength 
         && ucol_unsafeCP(text[*start + 1], collator))) {
        int32_t expansion  = getExpansionPrefix(coleiter);
        UBool   expandflag = expansion > 0;
        ucol_setOffset(coleiter, *start, status);
        while (U_SUCCESS(*status) && expansion > 0) {
            // getting rid of the redundant ce, caused by setOffset.
            // since backward contraction/expansion may have extra ces if we 
            // are in the normalization buffer, hasAccentsBeforeMatch would 
            // have taken care of it.
            // E.g. the character \u01FA will have an expansion of 3, but if
            // we are only looking for acute and ring \u030A and \u0301, we'll
            // have to skip the first ce in the expansion buffer.
            ucol_next(coleiter, status);
            if (ucol_getOffset(coleiter) != temp) {
                *start = temp;
                temp  = ucol_getOffset(coleiter);
            }
            expansion --;
        }

        if (U_FAILURE(*status)) {
            return FALSE;
        }

        uint32_t *patternce       = strsrch->pattern.CE;
        int32_t   patterncelength = strsrch->pattern.CELength;
        int32_t   count           = 0;
        while (count < patterncelength) {
            uint32_t ce = getCE(strsrch, ucol_next(coleiter, status));
            if (ce == UCOL_IGNORABLE) {
                continue;
            }
            if (expandflag && count == 0 && ucol_getOffset(coleiter) != temp) {
                *start = temp;
                temp   = ucol_getOffset(coleiter);
            }
            if (U_FAILURE(*status) || ce != patternce[count]) {
                (*end) ++;
                *end = getNextUStringSearchBaseOffset(strsrch, *end);  
                return FALSE;
            }
            count ++;
        }
    } 
    return TRUE;
}

/**
* Checks and sets the match information if found.
* Checks 
* <ul>
* <li> the potential match does not repeat the previous match
* <li> boundaries are correct
* <li> exact matches has no extra accents
* <li> identical matchesb
* <li> potential match does not end in the middle of a contraction
* <\ul>
* Otherwise the offset will be shifted to the next character.
* Internal method, status assumed to be success, caller has to check status 
* before calling this method.
* @param strsrch string search data
* @param textoffset offset in the collation element text. the returned value
*        will be the truncated end offset of the match or the new start 
*        search offset.
* @param status output error status if any
* @return TRUE if the match is valid, FALSE otherwise
*/
static
inline UBool checkNextExactMatch(UStringSearch *strsrch, 
                                 int32_t   *textoffset, UErrorCode *status)
{
    UCollationElements *coleiter = strsrch->textIter;
    int32_t         start    = getColElemIterOffset(coleiter, FALSE);        
        
    if (!checkNextExactContractionMatch(strsrch, &start, textoffset, status)) {
        return FALSE;
    }

    // this totally matches, however we need to check if it is repeating
    if (!isBreakUnit(strsrch, start, *textoffset) ||
        checkRepeatedMatch(strsrch, start, *textoffset) || 
        hasAccentsBeforeMatch(strsrch, start, *textoffset) || 
        !checkIdentical(strsrch, start, *textoffset) ||
        hasAccentsAfterMatch(strsrch, start, *textoffset)) {
        (*textoffset) ++;
        *textoffset = getNextUStringSearchBaseOffset(strsrch, *textoffset);  
        return FALSE;
    }
        
    // totally match, we will get rid of the ending ignorables.
    strsrch->search->matchedIndex  = start;
    strsrch->search->matchedLength = *textoffset - start;
    return TRUE;
}

/**
* Getting the previous base character offset, or the current offset if the 
* current character is a base character
* @param text string
* @param textoffset one offset after the current character
* @return the offset of the next character after the base character or the first 
*         composed character with accents
*/
static
inline int32_t getPreviousBaseOffset(const UChar       *text, 
                                               int32_t  textoffset)
{
    if (textoffset > 0) {
        while (TRUE) {
            int32_t result = textoffset;
            UTF_BACK_1(text, 0, textoffset);
            int32_t temp = textoffset;
            uint16_t fcd = getFCD(text, &temp, result);
            if ((fcd >> SECOND_LAST_BYTE_SHIFT_) == 0) {
                if (fcd & LAST_BYTE_MASK_) {
                    return textoffset;
                }
                return result;
            }
            if (textoffset == 0) {
                return 0;
            }
        }
    }
    return textoffset;
}

/**
* Getting the indexes of the accents that are not blocked in the argument
* accent array
* @param accents array of accents in nfd terminated by a 0.
* @param accentsindex array of indexes of the accents that are not blocked
*/
static
inline int getUnblockedAccentIndex(UChar *accents, int32_t *accentsindex)
{
    int32_t index     = 0;
    int32_t     length    = u_strlen(accents);
    UChar32     codepoint = 0;
    int         cclass    = 0;
    int         result    = 0;
    int32_t temp;
    while (index < length) {
        temp = index;
        UTF_NEXT_CHAR(accents, index, length, codepoint);
        if (u_getCombiningClass(codepoint) != cclass) {
            cclass        = u_getCombiningClass(codepoint);
            accentsindex[result] = temp;
            result ++;
        }
    }
    accentsindex[result] = length;
    return result;
}

/**
* Appends 3 UChar arrays to a destination array.
* Creates a new array if we run out of space. The caller will have to 
* manually deallocate the newly allocated array.
* Internal method, status assumed to be success, caller has to check status 
* before calling this method. destination not to be NULL and has at least 
* size destinationlength.
* @param destination target array
* @param destinationlength target array size, returning the appended length
* @param source1 null-terminated first array
* @param source2 second array
* @param source2length length of seond array
* @param source3 null-terminated third array
* @param status error status if any
* @return new destination array, destination if there was no new allocation
*/
static
inline UChar * addToUCharArray(      UChar      *destination,  
                                     int32_t    *destinationlength, 
                               const UChar      *source1, 
                               const UChar      *source2,
                                     int32_t     source2length, 
                               const UChar      *source3, 
                                     UErrorCode *status) 
{
    int32_t source1length = source1 ? u_strlen(source1) : 0;
    int32_t source3length = source3 ? u_strlen(source3) : 0;            
    if (*destinationlength < source1length + source2length + source3length + 
                                                                           1) 
    {
        destination = (UChar *)allocateMemory(
          (source1length + source2length + source3length + 1) * sizeof(UChar),
          status);
        // if error allocating memory, status will be 
        // U_MEMORY_ALLOCATION_ERROR
        if (U_FAILURE(*status)) {
            *destinationlength = 0;
            return NULL;
        }
    }
    if (source1length != 0) {
        uprv_memcpy(destination, source1, sizeof(UChar) * source1length);
    }
    if (source2length != 0) {
        uprv_memcpy(destination + source1length, source2, 
                    sizeof(UChar) * source2length);
    }
    if (source3length != 0) {
        uprv_memcpy(destination + source1length + source2length, source3, 
                    sizeof(UChar) * source3length);
    }
    *destinationlength = source1length + source2length + source3length;
    return destination;
}

/**
* Running through a collation element iterator to see if the contents matches
* pattern in string search data
* @param strsrch string search data
* @param coleiter collation element iterator
* @return TRUE if a match if found, FALSE otherwise
*/
static
inline UBool checkCollationMatch(const UStringSearch      *strsrch, 
                                       UCollationElements *coleiter)
{
    int         patternceindex = strsrch->pattern.CELength;
    uint32_t   *patternce      = strsrch->pattern.CE;
    UErrorCode  status = U_ZERO_ERROR;
    while (patternceindex > 0) {
        uint32_t ce = getCE(strsrch, ucol_next(coleiter, &status));
        if (ce == UCOL_IGNORABLE) {
            continue;
        }
        if (U_FAILURE(status) || ce != *patternce) {
            return FALSE;
        }
        patternce ++;
        patternceindex --;
    }
    return TRUE;
}

/**
* Rearranges the front accents to try matching.
* Prefix accents in the text will be grouped according to their combining 
* class and the groups will be mixed and matched to try find the perfect 
* match with the pattern.
* So for instance looking for "\u0301" in "\u030A\u0301\u0325"
* step 1: split "\u030A\u0301" into 6 other type of potential accent substrings
*         "\u030A", "\u0301", "\u0325", "\u030A\u0301", "\u030A\u0325", 
*         "\u0301\u0325".
* step 2: check if any of the generated substrings matches the pattern.
* Internal method, status is assumed to be success, caller has to check status
* before calling this method.
* @param strsrch string search match
* @param start first offset of the accents to start searching
* @param end start of the last accent set
* @param status output error status if any
* @return USEARCH_DONE if a match is not found, otherwise return the starting
*         offset of the match. Note this start includes all preceding accents.
*/
static
int32_t doNextCanonicalPrefixMatch(UStringSearch *strsrch, 
                                       int32_t    start,
                                       int32_t    end,     
                                       UErrorCode    *status)
{
    const UChar       *text       = strsrch->search->text;
          int32_t      textlength = strsrch->search->textLength;
          int32_t  tempstart  = start;

    if ((getFCD(text, &tempstart, textlength) & LAST_BYTE_MASK_) == 0) {
        // die... failed at a base character
        return USEARCH_DONE;
    }

    int32_t offset = getNextBaseOffset(text, tempstart, textlength);
    start = getPreviousBaseOffset(text, tempstart);

    UChar       accents[INITIAL_ARRAY_SIZE_];
    // normalizing the offensive string
    unorm_normalize(text + start, offset - start, UNORM_NFD, 0, accents, 
                    INITIAL_ARRAY_SIZE_, status);    
    if (U_FAILURE(*status)) {
        return USEARCH_DONE;
    }
        
    int32_t         accentsindex[INITIAL_ARRAY_SIZE_];      
    int32_t         accentsize = getUnblockedAccentIndex(accents, 
                                                                 accentsindex);
    int32_t         count      = (2 << (accentsize - 1)) - 2;  
    UChar               buffer[INITIAL_ARRAY_SIZE_];
    UCollationElements *coleiter   = strsrch->utilIter;
    while (U_SUCCESS(*status) && count > 0) {
        UChar *rearrange = strsrch->canonicalPrefixAccents;
        // copy the base characters
        for (int k = 0; k < accentsindex[0]; k ++) {
            *rearrange ++ = accents[k];
        }
        // forming all possible canonical rearrangement by dropping
        // sets of accents
        for (int i = 0; i <= accentsize - 1; i ++) {
            int32_t mask = 1 << (accentsize - i - 1);
            if (count & mask) {
                for (int j = accentsindex[i]; j < accentsindex[i + 1]; j ++) {
                    *rearrange ++ = accents[j];
                }
            }
        }
        *rearrange = 0;
        int32_t  matchsize = INITIAL_ARRAY_SIZE_;
        UChar   *match     = addToUCharArray(buffer, &matchsize,
                                           strsrch->canonicalPrefixAccents,
                                           strsrch->search->text + offset,
                                           end - offset,
                                           strsrch->canonicalSuffixAccents,
                                           status);
            
        // if status is a failure, ucol_setText does nothing.
        // run the collator iterator through this match
        ucol_setText(coleiter, match, matchsize, status);
        if (U_SUCCESS(*status)) {
            if (checkCollationMatch(strsrch, coleiter)) {
                if (match != buffer) {
                    uprv_free(match);
                }
                return start;
            }
        }
        count --;
    }
    return USEARCH_DONE;
}

/**
* Gets the offset to the safe point in text before textoffset.
* ie. not the middle of a contraction, swappable characters or supplementary
* characters.
* @param collator collation sata
* @param text string to work with
* @param textoffset offset in string
* @param textlength length of text string
* @return offset to the previous safe character
*/
static
inline uint32_t getPreviousSafeOffset(const UCollator   *collator, 
                                      const UChar       *text,
                                            int32_t  textoffset)
{
    int32_t result = textoffset; // first contraction character
    while (result != 0 && ucol_unsafeCP(text[result - 1], collator)) {
        result --;
    }
    if (result != 0) {
        // the first contraction character is consider unsafe here
        result --;
    }
    return result; 
}

/**
* Cleaning up after we passed the safe zone
* @param strsrch string search data
* @param safetext safe text array
* @param safebuffer safe text buffer
* @param coleiter collation element iterator for safe text
*/
static
inline void cleanUpSafeText(const UStringSearch *strsrch, UChar *safetext,
                                  UChar         *safebuffer)
{
    if (safetext != safebuffer && safetext != strsrch->canonicalSuffixAccents) 
    {
       uprv_free(safetext);
    }
}

/**
* Take the rearranged end accents and tries matching. If match failed at
* a seperate preceding set of accents (seperated from the rearranged on by
* at least a base character) then we rearrange the preceding accents and 
* tries matching again.
* We allow skipping of the ends of the accent set if the ces do not match. 
* However if the failure is found before the accent set, it fails.
* Internal method, status assumed to be success, caller has to check status
* before calling this method.
* @param strsrch string search data
* @param textoffset of the start of the rearranged accent
* @param status output error status if any
* @return USEARCH_DONE if a match is not found, otherwise return the starting
*         offset of the match. Note this start includes all preceding accents.
*/
static
int32_t doNextCanonicalSuffixMatch(UStringSearch *strsrch, 
                                       int32_t    textoffset,
                                       UErrorCode    *status)
{
    const UChar              *text           = strsrch->search->text;
    const UCollator          *collator       = strsrch->collator;
          int32_t             safelength     = 0;
          UChar              *safetext;
          int32_t             safetextlength;
          UChar               safebuffer[INITIAL_ARRAY_SIZE_];
          UCollationElements *coleiter       = strsrch->utilIter;
          int32_t         safeoffset     = textoffset;

    if (textoffset != 0 && ucol_unsafeCP(strsrch->canonicalSuffixAccents[0], 
                                         collator)) {
        safeoffset     = getPreviousSafeOffset(collator, text, textoffset);
        safelength     = textoffset - safeoffset;
        safetextlength = INITIAL_ARRAY_SIZE_;
        safetext       = addToUCharArray(safebuffer, &safetextlength, NULL, 
                                         text + safeoffset, safelength, 
                                         strsrch->canonicalSuffixAccents, 
                                         status);
    }
    else {
        safetextlength = u_strlen(strsrch->canonicalSuffixAccents);
        safetext       = strsrch->canonicalSuffixAccents;
    }

    // if status is a failure, ucol_setText does nothing
    ucol_setText(coleiter, safetext, safetextlength, status);
    // status checked in loop below

    uint32_t *ce        = strsrch->pattern.CE;
    uint32_t  celength  = strsrch->pattern.CELength;
    int       ceindex   = celength - 1;
    UBool     isSafe    = TRUE; // indication flag for position in safe zone
    
    while (ceindex >= 0) {
        uint32_t textce = ucol_previous(coleiter, status);
        if (U_FAILURE(*status)) {
            if (isSafe) {
                cleanUpSafeText(strsrch, safetext, safebuffer);
            }
            return USEARCH_DONE;
        }
        if (textce == UCOL_NULLORDER) {
            // check if we have passed the safe buffer
            if (coleiter == strsrch->textIter) {
                cleanUpSafeText(strsrch, safetext, safebuffer);
                return USEARCH_DONE;
            }
            cleanUpSafeText(strsrch, safetext, safebuffer);
            safetext = safebuffer;
            coleiter = strsrch->textIter;
            ucol_setOffset(coleiter, safeoffset, status);
            // status checked at the start of the loop
            isSafe = FALSE;
            continue;
        }
        textce = getCE(strsrch, textce);
        if (textce != UCOL_IGNORABLE && textce != ce[ceindex]) {
            // do the beginning stuff
            int32_t failedoffset = getColElemIterOffset(coleiter, FALSE);
            if (isSafe && failedoffset >= safelength) {
                // alas... no hope. failed at rearranged accent set
                cleanUpSafeText(strsrch, safetext, safebuffer);
                return USEARCH_DONE;
            }
            else {
                if (isSafe) {
                    failedoffset += safeoffset;
                    cleanUpSafeText(strsrch, safetext, safebuffer);
                }
                
                // try rearranging the front accents
                int32_t result = doNextCanonicalPrefixMatch(strsrch, 
                                        failedoffset, textoffset, status);
                if (result != USEARCH_DONE) {
                    // if status is a failure, ucol_setOffset does nothing
                    ucol_setOffset(strsrch->textIter, result, status);
                }
                if (U_FAILURE(*status)) {
                    return USEARCH_DONE;
                }
                return result;
            }
        }
        if (textce == ce[ceindex]) {
            ceindex --;
        }
    }
    // set offset here
    if (isSafe) {
        int32_t result     = getColElemIterOffset(coleiter, FALSE);
        // sets the text iterator here with the correct expansion and offset
        int32_t    leftoverces = getExpansionPrefix(coleiter);
        cleanUpSafeText(strsrch, safetext, safebuffer);
        if (result >= safelength) { 
            result = textoffset;
        }
        else {
            result += safeoffset;
        }
        ucol_setOffset(strsrch->textIter, result, status);
        if (U_FAILURE(*status)) {
            return USEARCH_DONE;
        }
        strsrch->textIter->iteratordata_.toReturn = 
                       setExpansionPrefix(strsrch->textIter, leftoverces);
        return result;
    }
    
    return ucol_getOffset(coleiter);              
}

/**
* Trying out the substring and sees if it can be a canonical match.
* This will try normalizing the end accents and arranging them into canonical
* equivalents and check their corresponding ces with the pattern ce.
* Suffix accents in the text will be grouped according to their combining 
* class and the groups will be mixed and matched to try find the perfect 
* match with the pattern.
* So for instance looking for "\u0301" in "\u030A\u0301\u0325"
* step 1: split "\u030A\u0301" into 6 other type of potential accent substrings
*         "\u030A", "\u0301", "\u0325", "\u030A\u0301", "\u030A\u0325", 
*         "\u0301\u0325".
* step 2: check if any of the generated substrings matches the pattern.
* Internal method, status assumed to be success, caller has to check status 
* before calling this method.
* @param strsrch string search data
* @param textoffset end offset in the collation element text that ends with 
*                   the accents to be rearranged
* @param status error status if any
* @return TRUE if the match is valid, FALSE otherwise
*/
static
UBool doNextCanonicalMatch(UStringSearch *strsrch, 
                           int32_t    textoffset, 
                           UErrorCode    *status)
{
    const UChar       *text = strsrch->search->text;
          int32_t  temp = textoffset;
    UTF_BACK_1(text, 0, temp);
    if ((getFCD(text, &temp, textoffset) & LAST_BYTE_MASK_) == 0) {
        UCollationElements *coleiter = strsrch->textIter;
        int32_t         offset   = getColElemIterOffset(coleiter, FALSE);
        if (strsrch->pattern.hasPrefixAccents) {
            offset = doNextCanonicalPrefixMatch(strsrch, offset, textoffset, 
                                                status);
            if (U_SUCCESS(*status) && offset != USEARCH_DONE) {
                ucol_setOffset(coleiter, offset, status);
                return TRUE;
            }
        }
        return FALSE;
    }

    if (!strsrch->pattern.hasSuffixAccents) {
        return FALSE;
    }

    UChar       accents[INITIAL_ARRAY_SIZE_];
    // offset to the last base character in substring to search
    int32_t baseoffset = getPreviousBaseOffset(text, textoffset);
    // normalizing the offensive string
    unorm_normalize(text + baseoffset, textoffset - baseoffset, UNORM_NFD, 
                               0, accents, INITIAL_ARRAY_SIZE_, status);    
    // status checked in loop below
        
    int32_t accentsindex[INITIAL_ARRAY_SIZE_];
    int32_t size = getUnblockedAccentIndex(accents, accentsindex);

    // 2 power n - 1 minus the full set of accents
    int32_t  count = (2 << (size - 1)) - 2;  
    while (U_SUCCESS(*status) && count > 0) {
        UChar *rearrange = strsrch->canonicalSuffixAccents;
        // copy the base characters
        for (int k = 0; k < accentsindex[0]; k ++) {
            *rearrange ++ = accents[k];
        }
        // forming all possible canonical rearrangement by dropping
        // sets of accents
        for (int i = 0; i <= size - 1; i ++) {
            int32_t mask = 1 << (size - i - 1);
            if (count & mask) {
                for (int j = accentsindex[i]; j < accentsindex[i + 1]; j ++) {
                    *rearrange ++ = accents[j];
                }
            }
        }
        *rearrange = 0;
        int32_t offset = doNextCanonicalSuffixMatch(strsrch, baseoffset, 
                                                        status);
        if (offset != USEARCH_DONE) {
            return TRUE; // match found
        }
        count --;
    }
    return FALSE;
}

/**
* Gets the previous base character offset depending on the string search 
* pattern data
* @param strsrch string search data
* @param textoffset current offset, current character
* @return the offset of the next character after this base character or itself
*         if it is a composed character with accents
*/
static
inline int32_t getPreviousUStringSearchBaseOffset(UStringSearch *strsrch, 
                                                      int32_t textoffset)
{
    if (strsrch->pattern.hasPrefixAccents && textoffset > 0) {
        const UChar       *text = strsrch->search->text;
              int32_t  offset = textoffset;
        if (getFCD(text, &offset, strsrch->search->textLength) >> 
                                                   SECOND_LAST_BYTE_SHIFT_) {
            return getPreviousBaseOffset(text, textoffset);
        }
    }
    return textoffset;
}

/**
* Checks match for contraction. 
* If the match ends with a partial contraction we fail.
* If the match starts too far off (because of backwards iteration) we try to
* chip off the extra characters
* Internal method, status assumed to be success, caller has to check status 
* before calling this method.
* @param strsrch string search data
* @param start offset of potential match, to be modified if necessary
* @param end offset of potential match, to be modified if necessary
* @param status output error status if any
* @return TRUE if match passes the contraction test, FALSE otherwise
*/
static
UBool checkNextCanonicalContractionMatch(UStringSearch *strsrch, 
                                         int32_t   *start, 
                                         int32_t   *end, 
                                         UErrorCode    *status) 
{
          UCollationElements *coleiter   = strsrch->textIter;
          int32_t             textlength = strsrch->search->textLength;
          int32_t         temp       = *start;
    const UCollator          *collator   = strsrch->collator;
    const UChar              *text       = strsrch->search->text;
    // This part checks if either ends of the match contains potential 
    // contraction. If so we'll have to iterate through them
    if ((*end < textlength && ucol_unsafeCP(text[*end], collator)) || 
        (*start < textlength && ucol_unsafeCP(text[*start + 1], collator))) {
        int32_t expansion  = getExpansionPrefix(coleiter);
        UBool   expandflag = expansion > 0;
        ucol_setOffset(coleiter, *start, status);
        while (U_SUCCESS(*status) && expansion > 0) {
            // getting rid of the redundant ce, caused by setOffset.
            // since backward contraction/expansion may have extra ces if we 
            // are in the normalization buffer, hasAccentsBeforeMatch would 
            // have taken care of it.
            // E.g. the character \u01FA will have an expansion of 3, but if
            // we are only looking for acute and ring \u030A and \u0301, we'll
            // have to skip the first ce in the expansion buffer.
            ucol_next(coleiter, status);
            if (ucol_getOffset(coleiter) != temp) {
                *start = temp;
                temp  = ucol_getOffset(coleiter);
            }
            expansion --;
        }

        if (U_FAILURE(*status)) {
            return FALSE;
        }

        uint32_t *patternce       = strsrch->pattern.CE;
        int32_t   patterncelength = strsrch->pattern.CELength;
        int32_t   count           = 0;
        int32_t   textlength      = strsrch->search->textLength;
        while (count < patterncelength) {
            uint32_t ce = getCE(strsrch, ucol_next(coleiter, status));
            // status checked below, note that if status is a failure
            // ucol_next returns UCOL_NULLORDER
            if (ce == UCOL_IGNORABLE) {
                continue;
            }
            if (expandflag && count == 0 && ucol_getOffset(coleiter) != temp) {
                *start = temp;
                temp   = ucol_getOffset(coleiter);
            }

            if (count == 0 && ce != patternce[0]) {
                // accents may have extra starting ces, this occurs when a 
                // pure accent pattern is matched without rearrangement
                // text \u0325\u0300 and looking for \u0300
                uint32_t expected = patternce[0]; 
                if (getFCD(text, start, textlength) & LAST_BYTE_MASK_) {
                    ce = getCE(strsrch, ucol_next(coleiter, status));
                    while (U_SUCCESS(*status) && ce != expected && 
                           ce != UCOL_NULLORDER &&
                           ucol_getOffset(coleiter) <= *end) {
                        ce = getCE(strsrch, ucol_next(coleiter, status));
                    }
                }
            }
            if (U_FAILURE(*status) || ce != patternce[count]) {
                (*end) ++;
                *end = getNextUStringSearchBaseOffset(strsrch, *end);  
                return FALSE;
            }
            count ++;
        }
    } 
    return TRUE;
}

/**
* Checks and sets the match information if found.
* Checks 
* <ul>
* <li> the potential match does not repeat the previous match
* <li> boundaries are correct
* <li> potential match does not end in the middle of a contraction
* <li> identical matches
* <\ul>
* Otherwise the offset will be shifted to the next character.
* Internal method, status assumed to be success, caller has to check the 
* status before calling this method.
* @param strsrch string search data
* @param textoffset offset in the collation element text. the returned value
*        will be the truncated end offset of the match or the new start 
*        search offset.
* @param status output error status if any
* @return TRUE if the match is valid, FALSE otherwise
*/
static
inline UBool checkNextCanonicalMatch(UStringSearch *strsrch, 
                                     int32_t   *textoffset, 
                                     UErrorCode    *status)
{
    // to ensure that the start and ends are not composite characters
    UCollationElements *coleiter = strsrch->textIter;
    // if we have a canonical accent match
    if ((strsrch->pattern.hasSuffixAccents && 
        strsrch->canonicalSuffixAccents[0]) || 
        (strsrch->pattern.hasPrefixAccents && 
        strsrch->canonicalPrefixAccents[0])) {
        strsrch->search->matchedIndex  = getPreviousUStringSearchBaseOffset(
                                                    strsrch,
                                                    ucol_getOffset(coleiter));
        strsrch->search->matchedLength = *textoffset - 
                                                strsrch->search->matchedIndex;
        return TRUE;
    }

    int32_t start = getColElemIterOffset(coleiter, FALSE);
    if (!checkNextCanonicalContractionMatch(strsrch, &start, textoffset, 
                                            status) || U_FAILURE(*status)) {
        return FALSE;
    }
    
    start = getPreviousUStringSearchBaseOffset(strsrch, start);
    // this totally matches, however we need to check if it is repeating
    if (checkRepeatedMatch(strsrch, start, *textoffset) || 
        !isBreakUnit(strsrch, start, *textoffset) || 
        !checkIdentical(strsrch, start, *textoffset)) {
        (*textoffset) ++;
        *textoffset = getNextBaseOffset(strsrch->search->text, *textoffset, 
                                        strsrch->search->textLength);
        return FALSE;
    }
    
    strsrch->search->matchedIndex  = start;
    strsrch->search->matchedLength = *textoffset - start;
    return TRUE;
}

/**
* Shifting the collation element iterator position forward to prepare for
* a preceding match. If the first character is a unsafe character, we'll only
* shift by 1 to capture contractions, normalization etc.
* Internal method, status assumed to be success, caller has to check status 
* before calling this method.
* @param text strsrch string search data
* @param textoffset start text position to do search
* @param ce the text ce which failed the match.
* @param patternceindex index of the ce within the pattern ce buffer which
*        failed the match
* @param status output error if any
* @return final offset
*/
static
inline int32_t reverseShift(UStringSearch *strsrch,
                                int32_t    textoffset,
                                uint32_t       ce,
                                int32_t        patternceindex,
                                UErrorCode    *status)
{         
    if (strsrch->search->isOverlap) {
        if (textoffset != strsrch->search->textLength) {
            textoffset --;
        }
        else {
            textoffset -= strsrch->pattern.defaultShiftSize;
        }
    }
    else {
        if (ce != UCOL_NULLORDER) {
            int32_t shift = strsrch->pattern.backShift[hash(ce)];
            
            // this is to adjust for characters in the middle of the substring 
            // for matching that failed.
            int32_t adjust = patternceindex;
            if (adjust > 1 && shift > adjust) {
                shift -= adjust - 1;
            }
            textoffset -= shift;
        }
        else {
            textoffset -= strsrch->pattern.defaultShiftSize;
        }
    }        
    textoffset = getPreviousUStringSearchBaseOffset(strsrch, textoffset);
    if (textoffset >= 0) {
        ucol_setOffset(strsrch->textIter, textoffset, status);
    }
    return textoffset;
}

/**
* Checks match for contraction. 
* If the match starts with a partial contraction we fail.
* Internal method, status assumed to be success, caller has to check status 
* before calling this method.
* @param strsrch string search data
* @param start offset of potential match, to be modified if necessary
* @param end offset of potential match, to be modified if necessary
* @param status output error status if any
* @return TRUE if match passes the contraction test, FALSE otherwise
*/
static
UBool checkPreviousExactContractionMatch(UStringSearch *strsrch, 
                                     int32_t   *start, 
                                     int32_t   *end, UErrorCode  *status) 
{
          UCollationElements *coleiter   = strsrch->textIter;
          int32_t             textlength = strsrch->search->textLength;
          int32_t         temp       = *end;
    const UCollator          *collator   = strsrch->collator;
    const UChar              *text       = strsrch->search->text;
    // This part checks if either ends of the match contains potential 
    // contraction. If so we'll have to iterate through them
    if ((*end < textlength && ucol_unsafeCP(text[*end], collator)) || 
        (*start < textlength && ucol_unsafeCP(text[*start + 1], collator))) {
        int32_t expansion  = getExpansionSuffix(coleiter);
        UBool   expandflag = expansion > 0;
        ucol_setOffset(coleiter, *end, status);
        while (U_SUCCESS(*status) && expansion > 0) {
            // getting rid of the redundant ce
            // since forward contraction/expansion may have extra ces
            // if we are in the normalization buffer, hasAccentsBeforeMatch
            // would have taken care of it.
            // E.g. the character \u01FA will have an expansion of 3, but if
            // we are only looking for A ring A\u030A, we'll have to skip the 
            // last ce in the expansion buffer
            ucol_previous(coleiter, status);
            if (ucol_getOffset(coleiter) != temp) {
                *end = temp;
                temp  = ucol_getOffset(coleiter);
            }
            expansion --;
        }

        if (U_FAILURE(*status)) {
            return FALSE;
        }

        uint32_t *patternce       = strsrch->pattern.CE;
        int32_t   patterncelength = strsrch->pattern.CELength;
        int32_t   count           = patterncelength;
        while (count > 0) {
            uint32_t ce = getCE(strsrch, ucol_previous(coleiter, status));
            // status checked below, note that if status is a failure
            // ucol_previous returns UCOL_NULLORDER
            if (ce == UCOL_IGNORABLE) {
                continue;
            }
            if (expandflag && count == 0 && 
                getColElemIterOffset(coleiter, FALSE) != temp) {
                *end = temp;
                temp  = ucol_getOffset(coleiter);
            }
            if (U_FAILURE(*status) || ce != patternce[count - 1]) {
                (*start) --;
                *start = getPreviousBaseOffset(text, *start);
                return FALSE;
            }
            count --;
        }
    } 
    return TRUE;
}

/**
* Checks and sets the match information if found.
* Checks 
* <ul>
* <li> the current match does not repeat the last match
* <li> boundaries are correct
* <li> exact matches has no extra accents
* <li> identical matches
* <\ul>
* Otherwise the offset will be shifted to the preceding character.
* Internal method, status assumed to be success, caller has to check status
* before calling this method.
* @param strsrch string search data
* @param collator 
* @param coleiter collation element iterator
* @param text string
* @param textoffset offset in the collation element text. the returned value
*        will be the truncated start offset of the match or the new start 
*        search offset.
* @param status output error status if any
* @return TRUE if the match is valid, FALSE otherwise
*/
static
inline UBool checkPreviousExactMatch(UStringSearch *strsrch, 
                                     int32_t   *textoffset, 
                                     UErrorCode    *status)
{
    // to ensure that the start and ends are not composite characters
    int32_t end = ucol_getOffset(strsrch->textIter);        
    if (!checkPreviousExactContractionMatch(strsrch, textoffset, &end, status)
        || U_FAILURE(*status)) {
            return FALSE;
    }
        
    // this totally matches, however we need to check if it is repeating
    // the old match
    if (checkRepeatedMatch(strsrch, *textoffset, end) || 
        !isBreakUnit(strsrch, *textoffset, end) ||
        hasAccentsBeforeMatch(strsrch, *textoffset, end) ||
        !checkIdentical(strsrch, *textoffset, end) || 
        hasAccentsAfterMatch(strsrch, *textoffset, end)) {
        (*textoffset) --;
        *textoffset = getPreviousBaseOffset(strsrch->search->text, 
                                            *textoffset);
        return FALSE;
    }
    strsrch->search->matchedIndex = *textoffset;
    strsrch->search->matchedLength = end - *textoffset;
    return TRUE;
}

/**
* Rearranges the end accents to try matching.
* Suffix accents in the text will be grouped according to their combining 
* class and the groups will be mixed and matched to try find the perfect 
* match with the pattern.
* So for instance looking for "\u0301" in "\u030A\u0301\u0325"
* step 1: split "\u030A\u0301" into 6 other type of potential accent substrings
*         "\u030A", "\u0301", "\u0325", "\u030A\u0301", "\u030A\u0325", 
*         "\u0301\u0325".
* step 2: check if any of the generated substrings matches the pattern.
* Internal method, status assumed to be success, user has to check status 
* before calling this method.
* @param strsrch string search match
* @param start offset of the first base character
* @param end start of the last accent set
* @param status only error status if any
* @return USEARCH_DONE if a match is not found, otherwise return the ending
*         offset of the match. Note this start includes all following accents.
*/
static
int32_t doPreviousCanonicalSuffixMatch(UStringSearch *strsrch, 
                                           int32_t    start,
                                           int32_t    end,     
                                           UErrorCode    *status)
{
    const UChar       *text       = strsrch->search->text;
          int32_t  tempend    = end;

    UTF_BACK_1(text, 0, tempend);
    if (!(getFCD(text, &tempend, strsrch->search->textLength) & 
                                                           LAST_BYTE_MASK_)) {
        // die... failed at a base character
        return USEARCH_DONE;
    }
    end = getNextBaseOffset(text, end, strsrch->search->textLength);

    if (U_SUCCESS(*status)) {
        UChar       accents[INITIAL_ARRAY_SIZE_];
        int32_t offset = getPreviousBaseOffset(text, end);
        // normalizing the offensive string
        unorm_normalize(text + offset, end - offset, UNORM_NFD, 0, accents, 
                        INITIAL_ARRAY_SIZE_, status);    
        
        int32_t         accentsindex[INITIAL_ARRAY_SIZE_];      
        int32_t         accentsize = getUnblockedAccentIndex(accents, 
                                                         accentsindex);
        int32_t         count      = (2 << (accentsize - 1)) - 2;  
        UChar               buffer[INITIAL_ARRAY_SIZE_];
        UCollationElements *coleiter = strsrch->utilIter;
        while (U_SUCCESS(*status) && count > 0) {
            UChar *rearrange = strsrch->canonicalSuffixAccents;
            // copy the base characters
            for (int k = 0; k < accentsindex[0]; k ++) {
                *rearrange ++ = accents[k];
            }
            // forming all possible canonical rearrangement by dropping
            // sets of accents
            for (int i = 0; i <= accentsize - 1; i ++) {
                int32_t mask = 1 << (accentsize - i - 1);
                if (count & mask) {
                    for (int j = accentsindex[i]; j < accentsindex[i + 1]; j ++) {
                        *rearrange ++ = accents[j];
                    }
                }
            }
            *rearrange = 0;
            int32_t  matchsize = INITIAL_ARRAY_SIZE_;
            UChar   *match     = addToUCharArray(buffer, &matchsize,
                                           strsrch->canonicalPrefixAccents,
                                           strsrch->search->text + start,
                                           offset - start,
                                           strsrch->canonicalSuffixAccents,
                                           status);
            
            // run the collator iterator through this match
            // if status is a failure ucol_setText does nothing
            ucol_setText(coleiter, match, matchsize, status);
            if (U_SUCCESS(*status)) {
                if (checkCollationMatch(strsrch, coleiter)) {
                    if (match != buffer) {
                        uprv_free(match);
                    }
                    return end;
                }
            }
            count --;
        }
    }
    return USEARCH_DONE;
}

/**
* Take the rearranged start accents and tries matching. If match failed at
* a seperate following set of accents (seperated from the rearranged on by
* at least a base character) then we rearrange the preceding accents and 
* tries matching again.
* We allow skipping of the ends of the accent set if the ces do not match. 
* However if the failure is found before the accent set, it fails.
* Internal method, status assumed to be success, caller has to check status 
* before calling this method.
* @param strsrch string search data
* @param textoffset of the ends of the rearranged accent
* @param status output error status if any
* @return USEARCH_DONE if a match is not found, otherwise return the ending
*         offset of the match. Note this start includes all following accents.
*/
static
int32_t doPreviousCanonicalPrefixMatch(UStringSearch *strsrch, 
                                           int32_t    textoffset,
                                           UErrorCode    *status)
{
    const UChar       *text       = strsrch->search->text;
    const UCollator   *collator   = strsrch->collator;
          int32_t      safelength = 0;
          UChar       *safetext;
          int32_t      safetextlength;
          UChar        safebuffer[INITIAL_ARRAY_SIZE_];
          int32_t  safeoffset = textoffset;

    if (textoffset && 
        ucol_unsafeCP(strsrch->canonicalPrefixAccents[
                                 u_strlen(strsrch->canonicalPrefixAccents) - 1
                                         ], collator)) {
        safeoffset     = getNextSafeOffset(collator, text, textoffset, 
                                           strsrch->search->textLength);
        safelength     = safeoffset - textoffset;
        safetextlength = INITIAL_ARRAY_SIZE_;
        safetext       = addToUCharArray(safebuffer, &safetextlength, 
                                         strsrch->canonicalPrefixAccents, 
                                         text + textoffset, safelength, 
                                         NULL, status);
    }
    else {
        safetextlength = u_strlen(strsrch->canonicalPrefixAccents);
        safetext       = strsrch->canonicalPrefixAccents;
    }

    UCollationElements *coleiter = strsrch->utilIter;
     // if status is a failure, ucol_setText does nothing
    ucol_setText(coleiter, safetext, safetextlength, status);
    // status checked in loop below
    
    uint32_t *ce           = strsrch->pattern.CE;
    int32_t   celength     = strsrch->pattern.CELength;
    int       ceindex      = 0;
    UBool     isSafe       = TRUE; // safe zone indication flag for position
    int32_t   prefixlength = u_strlen(strsrch->canonicalPrefixAccents);
    
    while (ceindex < celength) {
        uint32_t textce = ucol_next(coleiter, status);
        if (U_FAILURE(*status)) {
            if (isSafe) {
                cleanUpSafeText(strsrch, safetext, safebuffer);
            }
            return USEARCH_DONE;
        }
        if (textce == UCOL_NULLORDER) {
            // check if we have passed the safe buffer
            if (coleiter == strsrch->textIter) {
                cleanUpSafeText(strsrch, safetext, safebuffer);
                return USEARCH_DONE;
            }
            cleanUpSafeText(strsrch, safetext, safebuffer);
            safetext = safebuffer;
            coleiter = strsrch->textIter;
            ucol_setOffset(coleiter, safeoffset, status);
            // status checked at the start of the loop
            isSafe = FALSE;
            continue;
        }
        textce = getCE(strsrch, textce);
        if (textce != UCOL_IGNORABLE && textce != ce[ceindex]) {
            // do the beginning stuff
            int32_t failedoffset = ucol_getOffset(coleiter);
            if (isSafe && failedoffset <= prefixlength) {
                // alas... no hope. failed at rearranged accent set
                cleanUpSafeText(strsrch, safetext, safebuffer);
                return USEARCH_DONE;
            }
            else {
                if (isSafe) {
                    failedoffset = safeoffset - failedoffset;
                    cleanUpSafeText(strsrch, safetext, safebuffer);
                }
                
                // try rearranging the end accents
                int32_t result = doPreviousCanonicalSuffixMatch(strsrch, 
                                        textoffset, failedoffset, status);
                if (result != USEARCH_DONE) {
                    // if status is a failure, ucol_setOffset does nothing
                    ucol_setOffset(strsrch->textIter, result, status);
                }
                if (U_FAILURE(*status)) {
                    return USEARCH_DONE;
                }
                return result;
            }
        }
        if (textce == ce[ceindex]) {
            ceindex ++;
        }
    }
    // set offset here
    if (isSafe) {
        int32_t result      = ucol_getOffset(coleiter);
        // sets the text iterator here with the correct expansion and offset
        int32_t     leftoverces = getExpansionSuffix(coleiter);
        cleanUpSafeText(strsrch, safetext, safebuffer);
        if (result <= prefixlength) { 
            result = textoffset;
        }
        else {
            result = textoffset + (safeoffset - result);
        }
        ucol_setOffset(strsrch->textIter, result, status);
        if (U_FAILURE(*status)) {
            return USEARCH_DONE;
        }
        setExpansionSuffix(strsrch->textIter, leftoverces);
        return result;
    }
    
    return ucol_getOffset(coleiter);              
}

/**
* Trying out the substring and sees if it can be a canonical match.
* This will try normalizing the starting accents and arranging them into 
* canonical equivalents and check their corresponding ces with the pattern ce.
* Prefix accents in the text will be grouped according to their combining 
* class and the groups will be mixed and matched to try find the perfect 
* match with the pattern.
* So for instance looking for "\u0301" in "\u030A\u0301\u0325"
* step 1: split "\u030A\u0301" into 6 other type of potential accent substrings
*         "\u030A", "\u0301", "\u0325", "\u030A\u0301", "\u030A\u0325", 
*         "\u0301\u0325".
* step 2: check if any of the generated substrings matches the pattern.
* Internal method, status assumed to be success, caller has to check status
* before calling this method.
* @param strsrch string search data
* @param textoffset start offset in the collation element text that starts 
*                   with the accents to be rearranged
* @param status output error status if any
* @return TRUE if the match is valid, FALSE otherwise
*/
static
UBool doPreviousCanonicalMatch(UStringSearch *strsrch, 
                               int32_t    textoffset, 
                               UErrorCode    *status)
{
    const UChar       *text       = strsrch->search->text;
          int32_t  temp       = textoffset;
          int32_t      textlength = strsrch->search->textLength;
    if ((getFCD(text, &temp, textlength) >> SECOND_LAST_BYTE_SHIFT_) == 0) {
        UCollationElements *coleiter = strsrch->textIter;
        int32_t         offset   = ucol_getOffset(coleiter);
        if (strsrch->pattern.hasSuffixAccents) {
            offset = doPreviousCanonicalSuffixMatch(strsrch, textoffset, 
                                                    offset, status);
            if (U_SUCCESS(*status) && offset != USEARCH_DONE) {
                ucol_setOffset(coleiter, offset, status);
                return TRUE;
            }
        }
        return FALSE;
    }

    if (!strsrch->pattern.hasPrefixAccents) {
        return FALSE;
    }

    UChar       accents[INITIAL_ARRAY_SIZE_];
    // offset to the last base character in substring to search
    int32_t baseoffset = getNextBaseOffset(text, textoffset, textlength);
    // normalizing the offensive string
    unorm_normalize(text + textoffset, baseoffset - textoffset, UNORM_NFD, 
                               0, accents, INITIAL_ARRAY_SIZE_, status);    
    // status checked in loop
        
    int32_t accentsindex[INITIAL_ARRAY_SIZE_];
    int32_t size = getUnblockedAccentIndex(accents, accentsindex);

    // 2 power n - 1 minus the full set of accents
    int32_t  count = (2 << (size - 1)) - 2;  
    while (U_SUCCESS(*status) && count > 0) {
        UChar *rearrange = strsrch->canonicalPrefixAccents;
        // copy the base characters
        for (int k = 0; k < accentsindex[0]; k ++) {
            *rearrange ++ = accents[k];
        }
        // forming all possible canonical rearrangement by dropping
        // sets of accents
        for (int i = 0; i <= size - 1; i ++) {
            int32_t mask = 1 << (size - i - 1);
            if (count & mask) {
                for (int j = accentsindex[i]; j < accentsindex[i + 1]; j ++) {
                    *rearrange ++ = accents[j];
                }
            }
        }
        *rearrange = 0;
        int32_t offset = doPreviousCanonicalPrefixMatch(strsrch, 
                                                          baseoffset, status);
        if (offset != USEARCH_DONE) {
            return TRUE; // match found
        }
        count --;
    }
    return FALSE;
}

/**
* Checks match for contraction. 
* If the match starts with a partial contraction we fail.
* Internal method, status assumed to be success, caller has to check status
* before calling this method.
* @param strsrch string search data
* @param start offset of potential match, to be modified if necessary
* @param end offset of potential match, to be modified if necessary
* @param status only error status if any
* @return TRUE if match passes the contraction test, FALSE otherwise
*/
static
UBool checkPreviousCanonicalContractionMatch(UStringSearch *strsrch, 
                                     int32_t   *start, 
                                     int32_t   *end, UErrorCode  *status) 
{
          UCollationElements *coleiter   = strsrch->textIter;
          int32_t             textlength = strsrch->search->textLength;
          int32_t         temp       = *end;
    const UCollator          *collator   = strsrch->collator;
    const UChar              *text       = strsrch->search->text;
    // This part checks if either ends of the match contains potential 
    // contraction. If so we'll have to iterate through them
    if ((*end < textlength && ucol_unsafeCP(text[*end], collator)) || 
        (*start < textlength && ucol_unsafeCP(text[*start + 1], collator))) {
        int32_t expansion  = getExpansionSuffix(coleiter);
        UBool   expandflag = expansion > 0;
        ucol_setOffset(coleiter, *end, status);
        while (U_SUCCESS(*status) && expansion > 0) {
            // getting rid of the redundant ce
            // since forward contraction/expansion may have extra ces
            // if we are in the normalization buffer, hasAccentsBeforeMatch
            // would have taken care of it.
            // E.g. the character \u01FA will have an expansion of 3, but if
            // we are only looking for A ring A\u030A, we'll have to skip the 
            // last ce in the expansion buffer
            ucol_previous(coleiter, status);
            if (ucol_getOffset(coleiter) != temp) {
                *end = temp;
                temp  = ucol_getOffset(coleiter);
            }
            expansion --;
        }

        if (U_FAILURE(*status)) {
            return FALSE;
        }

        uint32_t *patternce       = strsrch->pattern.CE;
        int32_t   patterncelength = strsrch->pattern.CELength;
        int32_t   count           = patterncelength;
        while (count > 0) {
            uint32_t ce = getCE(strsrch, ucol_previous(coleiter, status));
            // status checked below, note that if status is a failure
            // ucol_previous returns UCOL_NULLORDER
            if (ce == UCOL_IGNORABLE) {
                continue;
            }
            if (expandflag && count == 0 && 
                getColElemIterOffset(coleiter, FALSE) != temp) {
                *end = temp;
                temp  = ucol_getOffset(coleiter);
            }
            if (count == patterncelength && 
                ce != patternce[patterncelength - 1]) {
                // accents may have extra starting ces, this occurs when a 
                // pure accent pattern is matched without rearrangement
                uint32_t    expected = patternce[patterncelength - 1];
                UTF_BACK_1(text, 0, *end);
                if (getFCD(text, end, textlength) & LAST_BYTE_MASK_) {
                    ce = getCE(strsrch, ucol_previous(coleiter, status));
                    while (U_SUCCESS(*status) && ce != expected && 
                           ce != UCOL_NULLORDER &&
                           ucol_getOffset(coleiter) <= *start) {
                        ce = getCE(strsrch, ucol_previous(coleiter, status));
                    }
                }
            }
            if (U_FAILURE(*status) || ce != patternce[count - 1]) {
                (*start) --;
                *start = getPreviousBaseOffset(text, *start);
                return FALSE;
            }
            count --;
        }
    } 
    return TRUE;
}

/**
* Checks and sets the match information if found.
* Checks 
* <ul>
* <li> the potential match does not repeat the previous match
* <li> boundaries are correct
* <li> potential match does not end in the middle of a contraction
* <li> identical matches
* <\ul>
* Otherwise the offset will be shifted to the next character.
* Internal method, status assumed to be success, caller has to check status
* before calling this method.
* @param strsrch string search data
* @param textoffset offset in the collation element text. the returned value
*        will be the truncated start offset of the match or the new start 
*        search offset.
* @param status only error status if any
* @return TRUE if the match is valid, FALSE otherwise
*/
static
inline UBool checkPreviousCanonicalMatch(UStringSearch *strsrch, 
                                         int32_t   *textoffset, 
                                         UErrorCode    *status)
{
    // to ensure that the start and ends are not composite characters
    UCollationElements *coleiter = strsrch->textIter;
    // if we have a canonical accent match
    if ((strsrch->pattern.hasSuffixAccents && 
        strsrch->canonicalSuffixAccents[0]) || 
        (strsrch->pattern.hasPrefixAccents && 
        strsrch->canonicalPrefixAccents[0])) {
        strsrch->search->matchedIndex  = *textoffset;
        strsrch->search->matchedLength = 
            getNextUStringSearchBaseOffset(strsrch, 
                                      getColElemIterOffset(coleiter, FALSE))
            - *textoffset;
        return TRUE;
    }

    int32_t end = ucol_getOffset(coleiter);
    if (!checkPreviousCanonicalContractionMatch(strsrch, textoffset, &end,
                                                status) || 
         U_FAILURE(*status)) {
        return FALSE;
    }

    end = getNextUStringSearchBaseOffset(strsrch, end);
    // this totally matches, however we need to check if it is repeating
    if (checkRepeatedMatch(strsrch, *textoffset, end) || 
        !isBreakUnit(strsrch, *textoffset, end) || 
        !checkIdentical(strsrch, *textoffset, end)) {
        (*textoffset) --;
        *textoffset = getPreviousBaseOffset(strsrch->search->text, 
                                            *textoffset);
        return FALSE;
    }
    
    strsrch->search->matchedIndex  = *textoffset;
    strsrch->search->matchedLength = end - *textoffset;
    return TRUE;
}

// constructors and destructor -------------------------------------------

U_CAPI UStringSearch * U_EXPORT2 usearch_open(const UChar *pattern, 
                                          int32_t         patternlength, 
                                    const UChar          *text, 
                                          int32_t         textlength,
                                    const char           *locale,
                                          UBreakIterator *breakiter,
                                          UErrorCode     *status) 
{
    if (U_FAILURE(*status)) {
        return NULL;
    }
    if (locale) {
        // ucol_open internally checks for status
        UCollator     *collator = ucol_open(locale, status);
        // pattern, text checks are done in usearch_openFromCollator
        UStringSearch *result   = usearch_openFromCollator(pattern, 
                                              patternlength, text, textlength, 
                                              collator, breakiter, status);

        if (result == NULL || U_FAILURE(*status)) {
            if (collator) {
                ucol_close(collator);
            }
            return NULL;
        }
        else {
            result->ownCollator = TRUE;
        }
        return result;
    }
    *status = U_ILLEGAL_ARGUMENT_ERROR;
    return NULL;
}

U_CAPI UStringSearch * U_EXPORT2 usearch_openFromCollator(
                                  const UChar          *pattern, 
                                        int32_t         patternlength,
                                  const UChar          *text, 
                                        int32_t         textlength,
                                  const UCollator      *collator,
                                        UBreakIterator *breakiter,
                                        UErrorCode     *status) 
{
    if (U_FAILURE(*status)) {
        return NULL;
    }
    if (pattern == NULL || text == NULL || collator == NULL) {
        *status = U_ILLEGAL_ARGUMENT_ERROR;
    }

    if (U_SUCCESS(*status)) {
        initializeFCD(status);
        if (U_FAILURE(*status)) {
            return NULL;
        }

        UStringSearch *result;
        if (textlength == -1) {
            textlength = u_strlen(text);
        }
        if (patternlength == -1) {
            patternlength = u_strlen(pattern);
        }
        if (textlength <= 0 || patternlength <= 0) {
            *status = U_ILLEGAL_ARGUMENT_ERROR;
            return NULL;
        }
        
        result = (UStringSearch *)uprv_malloc(sizeof(UStringSearch));
        if (result == NULL) {
            *status = U_MEMORY_ALLOCATION_ERROR;
            return NULL;
        }

        result->collator    = collator;
        result->strength    = ucol_getStrength(collator);
        result->ceMask      = getMask(result->strength);
        result->toShift     =  
             ucol_getAttribute(collator, UCOL_ALTERNATE_HANDLING, status) == 
                                                            UCOL_SHIFTED;
        result->variableTop = ucol_getVariableTop(collator, status);

        if (U_FAILURE(*status)) {
            uprv_free(result);
            return NULL;
        }

        result->search             = (USearch *)uprv_malloc(sizeof(USearch));
        if (result->search == NULL) {
            *status = U_MEMORY_ALLOCATION_ERROR;
            uprv_free(result);
            return NULL;
        }

        result->search->text       = text;
        result->search->textLength = textlength;

        result->pattern.text       = pattern;
        result->pattern.textLength = patternlength;
        result->pattern.CE         = NULL;
        
        result->search->breakIter  = breakiter;
        if (breakiter) {
            ubrk_setText(breakiter, text, textlength, status);
        }

        result->ownCollator           = FALSE;
        result->search->matchedLength = 0;
        result->search->matchedIndex  = USEARCH_DONE;
        result->textIter              = ucol_openElements(collator, text, 
                                                          textlength, status);
        if (U_FAILURE(*status)) {
            usearch_close(result);
            return NULL;
        }

        result->utilIter              = NULL;

        result->search->isOverlap          = FALSE;
        result->search->isCanonicalMatch   = FALSE;
        result->search->isForwardSearching = TRUE;
        result->search->reset              = TRUE;
        
        initialize(result, status);

        if (U_FAILURE(*status)) {
            usearch_close(result);
            return NULL;
        }

        return result;
    }
    return NULL;
}

U_CAPI void U_EXPORT2 usearch_close(UStringSearch *strsrch)
{
    if (strsrch) {
        if (strsrch->pattern.CE != strsrch->pattern.CEBuffer &&
            strsrch->pattern.CE) {
            uprv_free(strsrch->pattern.CE);
        }
        ucol_closeElements(strsrch->textIter);
        ucol_closeElements(strsrch->utilIter);
        if (strsrch->ownCollator && strsrch->collator) {
            ucol_close((UCollator *)strsrch->collator);
        }
        uprv_free(strsrch->search);
        uprv_free(strsrch);
    }
}

// set and get methods --------------------------------------------------

U_CAPI void U_EXPORT2 usearch_setOffset(UStringSearch *strsrch, 
                                        int32_t    position,
                                        UErrorCode    *status)
{
    if (U_SUCCESS(*status) && strsrch) {
        if (isOutOfBounds(strsrch->search->textLength, position)) {
            *status = U_INDEX_OUTOFBOUNDS_ERROR;
        }
        else {
            ucol_setOffset(strsrch->textIter, position, status);
        }
        strsrch->search->matchedIndex  = USEARCH_DONE;
        strsrch->search->matchedLength = 0;
        strsrch->search->reset         = FALSE; 
    }
}

U_CAPI int32_t U_EXPORT2 usearch_getOffset(const UStringSearch *strsrch)
{
    if (strsrch) {
        int32_t result = ucol_getOffset(strsrch->textIter);
        if (isOutOfBounds(strsrch->search->textLength, result)) {
            return USEARCH_DONE;
        }
        return result;
    }
    return USEARCH_DONE;
}
    
U_CAPI void U_EXPORT2 usearch_setAttribute(UStringSearch *strsrch, 
                                 USearchAttribute attribute,
                                 USearchAttributeValue value,
                                 UErrorCode *status)
{
    if (U_SUCCESS(*status) && strsrch) {
        switch (attribute)
        {
        case USEARCH_OVERLAP :
            strsrch->search->isOverlap = (value == USEARCH_ON ? TRUE : FALSE);
            break;
        case USEARCH_CANONICAL_MATCH :
            strsrch->search->isCanonicalMatch = (value == USEARCH_ON ? TRUE : 
                                                                      FALSE);
            break;
        case USEARCH_ATTRIBUTE_COUNT :
        default:
            *status = U_ILLEGAL_ARGUMENT_ERROR;
        }
    }
    if (value == USEARCH_ATTRIBUTE_VALUE_COUNT) {
        *status = U_ILLEGAL_ARGUMENT_ERROR;
    }
}
    
U_CAPI USearchAttributeValue U_EXPORT2 usearch_getAttribute(
                                                const UStringSearch *strsrch,
                                                USearchAttribute attribute)
{
    if (strsrch) {
        switch (attribute) {
        case USEARCH_OVERLAP :
            return (strsrch->search->isOverlap == TRUE ? USEARCH_ON : 
                                                        USEARCH_OFF);
        case USEARCH_CANONICAL_MATCH :
            return (strsrch->search->isCanonicalMatch == TRUE ? USEARCH_ON : 
                                                               USEARCH_OFF);
        case USEARCH_ATTRIBUTE_COUNT :
            return USEARCH_DEFAULT;
        }
    }
    return USEARCH_DEFAULT;
}

U_CAPI int32_t U_EXPORT2 usearch_getMatchedStart(
                                                const UStringSearch *strsrch)
{
    if (strsrch == NULL) {
        return USEARCH_DONE;
    }
    return strsrch->search->matchedIndex;
}


U_CAPI int32_t U_EXPORT2 usearch_getMatchedText(const UStringSearch *strsrch, 
                                            UChar         *result, 
                                            int32_t        resultCapacity, 
                                            UErrorCode    *status)
{
    if (U_FAILURE(*status)) {
        return USEARCH_DONE;
    }
    if (strsrch == NULL || resultCapacity < 0 || (resultCapacity > 0 && 
        result == NULL)) {
        *status = U_ILLEGAL_ARGUMENT_ERROR;
        return USEARCH_DONE;
    }

    int32_t     copylength = strsrch->search->matchedLength;
    int32_t copyindex  = strsrch->search->matchedIndex;
    if (copyindex == USEARCH_DONE) {
        u_terminateUChars(result, resultCapacity, 0, status);
        return USEARCH_DONE;
    }

    if (resultCapacity < copylength) {
        copylength = resultCapacity;
    }
    if (copylength > 0) {
        uprv_memcpy(result, strsrch->search->text + copyindex, 
                    copylength * sizeof(UChar));
    }
    return u_terminateUChars(result, resultCapacity, 
                             strsrch->search->matchedLength, status);
}
    
U_CAPI int32_t U_EXPORT2 usearch_getMatchedLength(
                                              const UStringSearch *strsrch)
{
    if (strsrch) {
        return strsrch->search->matchedLength;
    }
    return USEARCH_DONE;
}

U_CAPI void U_EXPORT2 usearch_setBreakIterator(UStringSearch  *strsrch, 
                                               UBreakIterator *breakiter,
                                               UErrorCode     *status)
{
    if (U_SUCCESS(*status) && strsrch) {
        strsrch->search->breakIter = breakiter;
        if (breakiter) {
            ubrk_setText(breakiter, strsrch->search->text, 
                         strsrch->search->textLength, status);
        }
    }
}
    
U_CAPI const UBreakIterator* U_EXPORT2 
usearch_getBreakIterator(const UStringSearch *strsrch)
{
    if (strsrch) {
        return strsrch->search->breakIter;
    }
    return NULL;
}
    
U_CAPI void U_EXPORT2 usearch_setText(      UStringSearch *strsrch, 
                                      const UChar         *text,
                                            int32_t        textlength,
                                            UErrorCode    *status)
{
    if (U_SUCCESS(*status)) {
        if (strsrch == NULL || text == NULL || textlength < -1 || 
            textlength == 0) {
            *status = U_ILLEGAL_ARGUMENT_ERROR;
        }
        else {
            if (textlength == -1) {
                textlength = u_strlen(text);
            }
            strsrch->search->text       = text;
            strsrch->search->textLength = textlength;
            ucol_setText(strsrch->textIter, text, textlength, status);
            strsrch->search->matchedIndex  = USEARCH_DONE;
            strsrch->search->matchedLength = 0;
            strsrch->search->reset         = TRUE;
			if (strsrch->search->breakIter != NULL) {
				ubrk_setText(strsrch->search->breakIter, text, 
							 textlength, status);
			}
        }
    }
}

U_CAPI const UChar * U_EXPORT2 usearch_getText(const UStringSearch *strsrch, 
                                                     int32_t       *length)
{
    if (strsrch) {
        *length = strsrch->search->textLength;
        return strsrch->search->text;
    }
    return NULL;
}

U_CAPI void U_EXPORT2 usearch_setCollator(      UStringSearch *strsrch, 
                                          const UCollator     *collator,
                                                UErrorCode    *status)
{
    if (U_SUCCESS(*status)) {
        if (collator == NULL) {
            *status = U_ILLEGAL_ARGUMENT_ERROR;
            return;
        }
        if (strsrch) {
            if (strsrch->ownCollator && (strsrch->collator != collator)) {
                ucol_close((UCollator *)strsrch->collator);
                strsrch->ownCollator = FALSE;
            }
            strsrch->collator    = collator;
            strsrch->strength    = ucol_getStrength(collator);
            strsrch->ceMask      = getMask(strsrch->strength);
            // if status is a failure, ucol_getAttribute returns UCOL_DEFAULT
            strsrch->toShift     =  
               ucol_getAttribute(collator, UCOL_ALTERNATE_HANDLING, status) == 
                                                                UCOL_SHIFTED;
            // if status is a failure, ucol_getVariableTop returns 0
            strsrch->variableTop = ucol_getVariableTop(collator, status);
            if (U_SUCCESS(*status)) {
                initialize(strsrch, status);
                if (U_SUCCESS(*status)) {
                    uprv_init_collIterate(collator, strsrch->search->text, 
                                          strsrch->search->textLength, 
                                          &(strsrch->textIter->iteratordata_));
					strsrch->utilIter->iteratordata_.coll = collator;
                }
            }
        }
    }
}

U_CAPI UCollator * U_EXPORT2 usearch_getCollator(const UStringSearch *strsrch)
{
    if (strsrch) {
        return (UCollator *)strsrch->collator;
    }
    return NULL;
}

U_CAPI void U_EXPORT2 usearch_setPattern(      UStringSearch *strsrch, 
                                         const UChar         *pattern,
                                               int32_t        patternlength,
                                               UErrorCode    *status)
{
    if (U_SUCCESS(*status)) {
        if (strsrch == NULL || pattern == NULL) {
            *status = U_ILLEGAL_ARGUMENT_ERROR;
        }
        else {
            if (patternlength == -1) {
                patternlength = u_strlen(pattern);
            }
            if (patternlength == 0) {
                *status = U_ILLEGAL_ARGUMENT_ERROR;
                return;
            }
            strsrch->pattern.text       = pattern;
            strsrch->pattern.textLength = patternlength;
            initialize(strsrch, status);
        }
    }
}

U_CAPI const UChar* U_EXPORT2 
usearch_getPattern(const UStringSearch *strsrch, 
                   int32_t       *length)
{
    if (strsrch) {
        *length = strsrch->pattern.textLength;
        return strsrch->pattern.text;
    }
    return NULL;
}

// miscellanous methods --------------------------------------------------

U_CAPI int32_t U_EXPORT2 usearch_first(UStringSearch *strsrch, 
                                           UErrorCode    *status) 
{
    if (strsrch && U_SUCCESS(*status)) {
        strsrch->search->isForwardSearching = TRUE;
        usearch_setOffset(strsrch, 0, status);
        if (U_SUCCESS(*status)) {
            return usearch_next(strsrch, status);
        }
    }
    return USEARCH_DONE;
}

U_CAPI int32_t U_EXPORT2 usearch_following(UStringSearch *strsrch, 
                                               int32_t    position,
                                               UErrorCode    *status)
{
    if (strsrch && U_SUCCESS(*status)) {
        strsrch->search->isForwardSearching = TRUE;
        // position checked in usearch_setOffset
        usearch_setOffset(strsrch, position, status);
        if (U_SUCCESS(*status)) {
            return usearch_next(strsrch, status);   
        }
    }
    return USEARCH_DONE;
}
    
U_CAPI int32_t U_EXPORT2 usearch_last(UStringSearch *strsrch, 
                                          UErrorCode    *status)
{
    if (strsrch && U_SUCCESS(*status)) {
        strsrch->search->isForwardSearching = FALSE;
        usearch_setOffset(strsrch, strsrch->search->textLength, status);
        if (U_SUCCESS(*status)) {
            return usearch_previous(strsrch, status);
        }
    }
    return USEARCH_DONE;
}

U_CAPI int32_t U_EXPORT2 usearch_preceding(UStringSearch *strsrch, 
                                               int32_t    position,
                                               UErrorCode    *status)
{
    if (strsrch && U_SUCCESS(*status)) {
        strsrch->search->isForwardSearching = FALSE;
        // position checked in usearch_setOffset
        usearch_setOffset(strsrch, position, status);
        if (U_SUCCESS(*status)) {
            return usearch_previous(strsrch, status);   
        }
    }
    return USEARCH_DONE;
}
    
/**
* If a direction switch is required, we'll count the number of ces till the 
* beginning of the collation element iterator and iterate forwards that 
* number of times. This is so that we get to the correct point within the 
* string to continue the search in. Imagine when we are in the middle of the
* normalization buffer when the change in direction is request. arrrgghh....
* After searching the offset within the collation element iterator will be
* shifted to the start of the match. If a match is not found, the offset would
* have been set to the end of the text string in the collation element 
* iterator.
* Okay, here's my take on normalization buffer. The only time when there can
* be 2 matches within the same normalization is when the pattern is consists
* of all accents. But since the offset returned is from the text string, we
* should not confuse the caller by returning the second match within the 
* same normalization buffer. If we do, the 2 results will have the same match
* offsets, and that'll be confusing. I'll return the next match that doesn't
* fall within the same normalization buffer. Note this does not affect the 
* results of matches spanning the text and the normalization buffer.
* The position to start searching is taken from the collation element
* iterator. Callers of this API would have to set the offset in the collation
* element iterator before using this method.
*/
U_CAPI int32_t U_EXPORT2 usearch_next(UStringSearch *strsrch,
                                          UErrorCode    *status)
{ 
    if (U_SUCCESS(*status) && strsrch) {
        int32_t  offset     = usearch_getOffset(strsrch);
        USearch     *search     = strsrch->search;
        search->reset           = FALSE;
        int32_t      textlength = search->textLength;
        int32_t  matchedindex = search->matchedIndex;
        if (search->isForwardSearching) {
            if (offset == textlength || matchedindex == textlength || 
                (!search->isOverlap && 
                    (offset + strsrch->pattern.defaultShiftSize > textlength ||
                    (matchedindex != USEARCH_DONE && 
                    matchedindex + search->matchedLength >= textlength)))) {
                // not enough characters to match
                setMatchNotFound(strsrch, status);
                return USEARCH_DONE; 
            }
        }
        else {
            // switching direction. 
            // if matchedIndex == USEARCH_DONE, it means that either a 
            // setOffset has been called or that previous ran off the text
            // string. the iterator would have been set to offset 0 if a 
            // match is not found.
            search->isForwardSearching = TRUE;
            if (matchedindex != USEARCH_DONE) {
                // there's no need to set the collation element iterator
                // the next call to next will set the offset.
                return matchedindex;
            }
        }

        if (U_SUCCESS(*status)) {
            if (strsrch->pattern.CELength == 0) {
                if (matchedindex == USEARCH_DONE) {
                    search->matchedIndex = offset;
                }
                else { // moves by codepoints
                    UTF_FWD_1(search->text, search->matchedIndex, textlength);
                }
                                             
                search->matchedLength = 0;
                ucol_setOffset(strsrch->textIter, search->matchedIndex, 
                               status);
                // status checked below
                if (search->matchedIndex == textlength) {
                    search->matchedIndex = USEARCH_DONE;
                }
            }
            else if (search->isCanonicalMatch) {
                // can't use exact here since extra accents are allowed.
                usearch_handleNextCanonical(strsrch, status);
            }
            else {
                usearch_handleNextExact(strsrch, status);
            }
            
            if (U_FAILURE(*status)) {
                return USEARCH_DONE;
            }
            
            return search->matchedIndex;
        }
    }
    return USEARCH_DONE;
}

U_CAPI int32_t U_EXPORT2 usearch_previous(UStringSearch *strsrch,
                                              UErrorCode *status)
{
    if (U_SUCCESS(*status) && strsrch) {
        int32_t offset;
        USearch *search = strsrch->search;
        if (search->reset) {
            offset                     = search->textLength;
            search->isForwardSearching = FALSE;
            search->reset              = FALSE;
            ucol_setOffset(strsrch->textIter, offset, status);
            if (U_FAILURE(*status)) {
                return USEARCH_DONE;
            }
        }
        else {
            offset = usearch_getOffset(strsrch);
        }
        
        int32_t matchedindex = search->matchedIndex;
        if (search->isForwardSearching == TRUE) {
            // switching direction. 
            // if matchedIndex == USEARCH_DONE, it means that either a 
            // setOffset has been called or that next ran off the text
            // string. the iterator would have been set to offset textLength if 
            // a match is not found.
            search->isForwardSearching = FALSE;
            if (matchedindex != USEARCH_DONE) {
                return matchedindex;
            }
        }
        else {
            if (offset == 0 || matchedindex == 0 ||
                (!search->isOverlap && 
                    (offset < strsrch->pattern.defaultShiftSize ||
                    (matchedindex != USEARCH_DONE && 
                    matchedindex < strsrch->pattern.defaultShiftSize)))) {
                // not enough characters to match
                setMatchNotFound(strsrch, status);
                return USEARCH_DONE; 
            }
        }

        if (U_SUCCESS(*status)) {
            if (strsrch->pattern.CELength == 0) {
                search->matchedIndex = 
                      (matchedindex == USEARCH_DONE ? offset : matchedindex);
                if (search->matchedIndex == 0) {
                    setMatchNotFound(strsrch, status);
                    // status checked below
                }
                else { // move by codepoints
                    UTF_BACK_1(search->text, 0, search->matchedIndex);
                    ucol_setOffset(strsrch->textIter, search->matchedIndex, 
                                   status);
                    // status checked below
                    search->matchedLength = 0;
                }
            }
            else {
                if (strsrch->search->isCanonicalMatch) {
                    // can't use exact here since extra accents are allowed.
                    usearch_handlePreviousCanonical(strsrch, status);
                    // status checked below
                }
                else {
                    usearch_handlePreviousExact(strsrch, status);
                    // status checked below
                }
            }

            if (U_FAILURE(*status)) {
                return USEARCH_DONE;
            }
            
            return search->matchedIndex;
        }
    }
    return USEARCH_DONE;
}


U_CAPI void U_EXPORT2 usearch_reset(UStringSearch *strsrch)
{
    /* 
    reset is setting the attributes that are already in 
    string search, hence all attributes in the collator should
    be retrieved without any problems
    */
    if (strsrch) {
        UErrorCode status            = U_ZERO_ERROR;
        UBool      sameCollAttribute = TRUE;
        uint32_t   ceMask;
        UBool      shift;
        uint32_t   varTop;

        strsrch->strength    = ucol_getStrength(strsrch->collator);
        ceMask = getMask(strsrch->strength);
        if (strsrch->ceMask != ceMask) {
            strsrch->ceMask = ceMask;
            sameCollAttribute = FALSE;
        }
        // if status is a failure, ucol_getAttribute returns UCOL_DEFAULT
        shift = ucol_getAttribute(strsrch->collator, UCOL_ALTERNATE_HANDLING, 
                                  &status) == UCOL_SHIFTED;
        if (strsrch->toShift != shift) {
            strsrch->toShift  = shift;
            sameCollAttribute = FALSE;
        }

        // if status is a failure, ucol_getVariableTop returns 0
        varTop = ucol_getVariableTop(strsrch->collator, &status);
        if (strsrch->variableTop != varTop) {
            strsrch->variableTop = varTop;
            sameCollAttribute    = FALSE;
        }
        if (!sameCollAttribute) {
            initialize(strsrch, &status);
        }
        uprv_init_collIterate(strsrch->collator, strsrch->search->text, 
                              strsrch->search->textLength, 
                              &(strsrch->textIter->iteratordata_));
        strsrch->search->matchedLength      = 0;
        strsrch->search->matchedIndex       = USEARCH_DONE;
        strsrch->search->isOverlap          = FALSE;
        strsrch->search->isCanonicalMatch   = FALSE;
        strsrch->search->isForwardSearching = TRUE;
        strsrch->search->reset              = TRUE;
    }
}

// internal use methods declared in usrchimp.h -----------------------------

UBool usearch_handleNextExact(UStringSearch *strsrch, UErrorCode *status)
{
    if (U_FAILURE(*status)) {
        setMatchNotFound(strsrch, status);
        return FALSE;
    }

    UCollationElements *coleiter        = strsrch->textIter;
    int32_t             textlength      = strsrch->search->textLength;
    uint32_t           *patternce       = strsrch->pattern.CE;
    int32_t             patterncelength = strsrch->pattern.CELength;
    int32_t         textoffset      = ucol_getOffset(coleiter);

    // shifting it check for setting offset
    // if setOffset is called previously or there was no previous match, we
    // leave the offset as it is.
    if (strsrch->search->matchedIndex != USEARCH_DONE) {
        textoffset = strsrch->search->matchedIndex + 
                     strsrch->search->matchedLength;
    }
    
    textoffset = shiftForward(strsrch, textoffset, UCOL_NULLORDER, 
                              patterncelength, status);
    while (U_SUCCESS(*status) && textoffset <= textlength)
    {
        uint32_t    patternceindex = patterncelength - 1;
        uint32_t    targetce;
        UBool       found          = FALSE;
        uint32_t    lastce         = UCOL_NULLORDER;
        
        while (U_SUCCESS(*status)) {
            // finding the last pattern ce match, imagine composite characters
            // for example: search for pattern A in text \u00C0
            // we'll have to skip \u0300 the grave first before we get to A
            targetce = ucol_previous(coleiter, status);
            if (targetce == UCOL_NULLORDER) {
                found = FALSE;
                break;
            }
            targetce = getCE(strsrch, targetce);
            if (targetce == UCOL_IGNORABLE && inNormBuf(coleiter)) { 
                // this is for the text \u0315\u0300 that requires 
                // normalization and pattern \u0300, where \u0315 is ignorable
                continue;
            }
            if (lastce == UCOL_NULLORDER || lastce == UCOL_IGNORABLE) {
                lastce = targetce;
            }
            if (targetce == patternce[patternceindex]) {
                // the first ce can be a contraction
                found = TRUE;
                break;
            }
            if (!hasExpansion(coleiter)) {
                found = FALSE;
                break;
            }
        }

        targetce = lastce;
        
        while (found && patternceindex > 0 && U_SUCCESS(*status)) {
            targetce    = ucol_previous(coleiter, status);
            if (targetce == UCOL_NULLORDER) {
                found = FALSE;
                break;
            }
            targetce    = getCE(strsrch, targetce);
            if (targetce == UCOL_IGNORABLE) {
                continue;
            }

            patternceindex --;
            found = found && targetce == patternce[patternceindex]; 
        }

        if (U_FAILURE(*status)) {
            break;
        }

        if (!found) {
            textoffset = shiftForward(strsrch, textoffset, targetce, 
                                      patternceindex, status);
            // status checked at loop.
            patternceindex = patterncelength;
            continue;
        }
        
        if (checkNextExactMatch(strsrch, &textoffset, status)) {
            // status checked in ucol_setOffset
            ucol_setOffset(coleiter, textoffset, status);
            return TRUE;
        }
        if (textoffset <= textlength) {
            ucol_setOffset(coleiter, textoffset, status);
        }
    }
    setMatchNotFound(strsrch, status);
    return FALSE;
}

UBool usearch_handleNextCanonical(UStringSearch *strsrch, UErrorCode *status)
{
    if (U_FAILURE(*status)) {
        setMatchNotFound(strsrch, status);
        return FALSE;
    }

    UCollationElements *coleiter        = strsrch->textIter;
    int32_t             textlength      = strsrch->search->textLength;
    uint32_t           *patternce       = strsrch->pattern.CE;
    int32_t             patterncelength = strsrch->pattern.CELength;
    int32_t         textoffset      = ucol_getOffset(coleiter);
    UBool               hasPatternAccents = 
       strsrch->pattern.hasSuffixAccents || strsrch->pattern.hasPrefixAccents;
          
    // shifting it check for setting offset
    // if setOffset is called previously or there was no previous match, we
    // leave the offset as it is.
    if (strsrch->search->matchedIndex != USEARCH_DONE) {
        textoffset = strsrch->search->matchedIndex + 
                     strsrch->search->matchedLength;
    }
    
    textoffset = shiftForward(strsrch, textoffset, UCOL_NULLORDER, 
                              patterncelength, status);
    strsrch->canonicalPrefixAccents[0] = 0;
    strsrch->canonicalSuffixAccents[0] = 0;
    
    while (U_SUCCESS(*status) && textoffset <= textlength)
    {
        int32_t     patternceindex = patterncelength - 1;
        uint32_t    targetce;
        UBool       found          = FALSE;
        uint32_t    lastce         = UCOL_NULLORDER;
        
        while (U_SUCCESS(*status)) {
            // finding the last pattern ce match, imagine composite characters
            // for example: search for pattern A in text \u00C0
            // we'll have to skip \u0300 the grave first before we get to A
            targetce = ucol_previous(coleiter, status);
            if (targetce == UCOL_NULLORDER) {
                found = FALSE;
                break;
            }
            targetce = getCE(strsrch, targetce);
            if (lastce == UCOL_NULLORDER || lastce == UCOL_IGNORABLE) {
                lastce = targetce;
            }
            if (targetce == patternce[patternceindex]) {
                // the first ce can be a contraction
                found = TRUE;
                break;
            }
            if (!hasExpansion(coleiter)) {
                found = FALSE;
                break;
            }
        }
        targetce = lastce;
        
        while (found && patternceindex > 0 && U_SUCCESS(*status)) {
            targetce    = ucol_previous(coleiter, status);
            if (targetce == UCOL_NULLORDER) {
                found = FALSE;
                break;
            }
            targetce    = getCE(strsrch, targetce);
            if (targetce == UCOL_IGNORABLE) {
                continue;
            }

            patternceindex --;
            found = found && targetce == patternce[patternceindex]; 
        }

        if (U_FAILURE(*status)) {
            break;
        }

        // initializing the rearranged accent array
        if (hasPatternAccents && !found) {
            strsrch->canonicalPrefixAccents[0] = 0;
            strsrch->canonicalSuffixAccents[0] = 0;
            found = doNextCanonicalMatch(strsrch, textoffset, status);
            if (U_FAILURE(*status)) {
                break;
            }
        }

        if (!found) {
            textoffset = shiftForward(strsrch, textoffset, targetce, 
                                      patternceindex, status);
            // status checked at loop
            patternceindex = patterncelength;
            continue;
        }
        
        if (checkNextCanonicalMatch(strsrch, &textoffset, status)) {
            ucol_setOffset(coleiter, textoffset, status);
            return TRUE;
        }
        if (textoffset <= textlength) {
            // if status is a failure, ucol_setOffset does nothing
            ucol_setOffset(coleiter, textoffset, status);
            // status checked at loop
        }
    }
    setMatchNotFound(strsrch, status);
    return FALSE;
}

UBool usearch_handlePreviousExact(UStringSearch *strsrch, UErrorCode *status)
{
    if (U_FAILURE(*status)) {
        setMatchNotFound(strsrch, status);
        return FALSE;
    }

    UCollationElements *coleiter        = strsrch->textIter;
    uint32_t           *patternce       = strsrch->pattern.CE;
    int32_t             patterncelength = strsrch->pattern.CELength;
    int32_t         textoffset      = ucol_getOffset(coleiter);

    // shifting it check for setting offset
    // if setOffset is called previously or there was no previous match, we
    // leave the offset as it is.
    if (strsrch->search->matchedIndex != USEARCH_DONE) {
        textoffset = strsrch->search->matchedIndex;
    }
    
    textoffset = reverseShift(strsrch, textoffset, UCOL_NULLORDER, 
                              patterncelength, status);
    
    while (U_SUCCESS(*status) && textoffset >= 0)
    {
        int32_t     patternceindex = 1;
        uint32_t    targetce;
        UBool       found          = FALSE;
        uint32_t    firstce        = UCOL_NULLORDER;
        
        while (U_SUCCESS(*status)) {
            // finding the first pattern ce match, imagine composite 
            // characters. for example: search for pattern \u0300 in text 
            // \u00C0, we'll have to skip A first before we get to 
            // \u0300 the grave accent
            targetce = ucol_next(coleiter, status);
            if (targetce == UCOL_NULLORDER) {
                found = FALSE;
                break;
            }
            targetce = getCE(strsrch, targetce);
            if (firstce == UCOL_NULLORDER || firstce == UCOL_IGNORABLE) {
                firstce = targetce;
            }
            if (targetce == UCOL_IGNORABLE) {
                continue;
            }         
            if (targetce == patternce[0]) {
                found = TRUE;
                break;
            }
            if (!hasExpansion(coleiter)) {
                // checking for accents in composite character
                found = FALSE;
                break;
            }
        }

        targetce = firstce;
        
        while (found && (patternceindex < patterncelength) && 
               U_SUCCESS(*status)) {
            targetce    = ucol_next(coleiter, status);
            if (targetce == UCOL_NULLORDER) {
                found = FALSE;
                break;
            }
            targetce    = getCE(strsrch, targetce);
            if (targetce == UCOL_IGNORABLE) {
                continue;
            }

            found = found && targetce == patternce[patternceindex]; 
            patternceindex ++;
        }

        if (U_FAILURE(*status)) {
            break;
        }

        if (!found) {
            textoffset = reverseShift(strsrch, textoffset, targetce, 
                                      patternceindex, status);
            patternceindex = 0;
            continue;
        }
        
        if (checkPreviousExactMatch(strsrch, &textoffset, status)) {
            ucol_setOffset(coleiter, textoffset, status);
            return TRUE;
        }
        if (textoffset >= 0) {
            // if status is a failure, ucol_setOffset does nothing
            ucol_setOffset(coleiter, textoffset, status);
        }
    }
    setMatchNotFound(strsrch, status);
    return FALSE;
}

UBool usearch_handlePreviousCanonical(UStringSearch *strsrch, 
                                      UErrorCode    *status)
{
    if (U_FAILURE(*status)) {
        setMatchNotFound(strsrch, status);
        return FALSE;
    }

    UCollationElements *coleiter        = strsrch->textIter;
    uint32_t           *patternce       = strsrch->pattern.CE;
    int32_t             patterncelength = strsrch->pattern.CELength;
    int32_t         textoffset      = ucol_getOffset(coleiter);
    UBool               hasPatternAccents = 
       strsrch->pattern.hasSuffixAccents || strsrch->pattern.hasPrefixAccents;
          
    // shifting it check for setting offset
    // if setOffset is called previously or there was no previous match, we
    // leave the offset as it is.
    if (strsrch->search->matchedIndex != USEARCH_DONE) {
        textoffset = strsrch->search->matchedIndex;
    }
    
    textoffset = reverseShift(strsrch, textoffset, UCOL_NULLORDER, 
                              patterncelength, status);
    strsrch->canonicalPrefixAccents[0] = 0;
    strsrch->canonicalSuffixAccents[0] = 0;
    
    while (U_SUCCESS(*status) && textoffset >= 0)
    {
        int32_t     patternceindex = 1;
        uint32_t    targetce;
        UBool       found          = FALSE;
        uint32_t    firstce        = UCOL_NULLORDER;
        
        while (U_SUCCESS(*status)) {
            // finding the first pattern ce match, imagine composite 
            // characters. for example: search for pattern \u0300 in text 
            // \u00C0, we'll have to skip A first before we get to 
            // \u0300 the grave accent
            targetce = ucol_next(coleiter, status);
            if (targetce == UCOL_NULLORDER) {
                found = FALSE;
                break;
            }
            targetce = getCE(strsrch, targetce);
            if (firstce == UCOL_NULLORDER || firstce == UCOL_IGNORABLE) {
                firstce = targetce;
            }
            
            if (targetce == patternce[0]) {
                // the first ce can be a contraction
                found = TRUE;
                break;
            }
            if (!hasExpansion(coleiter)) {
                // checking for accents in composite character
                found = FALSE;
                break;
            }
        }

        targetce = firstce;
        
        while (found && patternceindex < patterncelength && 
               U_SUCCESS(*status)) {
            targetce    = ucol_next(coleiter, status);
            if (targetce == UCOL_NULLORDER) {
                found = FALSE;
                break;
            }
            targetce = getCE(strsrch, targetce);
            if (targetce == UCOL_IGNORABLE) {
                continue;
            }

            found = found && targetce == patternce[patternceindex]; 
            patternceindex ++;
        }

        if (U_FAILURE(*status)) {
            break;
        }

        // initializing the rearranged accent array
        if (hasPatternAccents && !found) {
            strsrch->canonicalPrefixAccents[0] = 0;
            strsrch->canonicalSuffixAccents[0] = 0;
            found = doPreviousCanonicalMatch(strsrch, textoffset, status);
            if (U_FAILURE(*status)) {
                break;
            }
        }

        if (!found) {
            textoffset = reverseShift(strsrch, textoffset, targetce, 
                                      patternceindex, status);
            patternceindex = 0;
            continue;
        }

        if (checkPreviousCanonicalMatch(strsrch, &textoffset, status)) {
            ucol_setOffset(coleiter, textoffset, status);
            return TRUE;
        }

        if (textoffset >= 0) {
            ucol_setOffset(coleiter, textoffset, status);
        }
    }
    setMatchNotFound(strsrch, status);
    return FALSE;
}