/*
*******************************************************************************
*   Copyright (C) 1996-2006, International Business Machines
*   Corporation and others.  All Rights Reserved.
*******************************************************************************
*   file name:  ucol_res.cpp
*   encoding:   US-ASCII
*   tab size:   8 (not used)
*   indentation:4
*
* Description:
* This file contains dependencies that the collation run-time doesn't normally
* need. This mainly contains resource bundle usage and collation meta information
*
* Modification history
* Date        Name      Comments
* 1996-1999   various members of ICU team maintained C API for collation framework
* 02/16/2001  synwee    Added internal method getPrevSpecialCE
* 03/01/2001  synwee    Added maxexpansion functionality.
* 03/16/2001  weiv      Collation framework is rewritten in C and made UCA compliant
* 12/08/2004  grhoten   Split part of ucol.cpp into ucol_res.cpp
*/

#include "unicode/utypes.h"

#if !UCONFIG_NO_COLLATION
#include "unicode/uloc.h"
#include "unicode/coll.h"
#include "unicode/tblcoll.h"
#include "unicode/caniter.h"
#include "unicode/ustring.h"

#include "ucol_bld.h"
#include "ucol_imp.h"
#include "ucol_tok.h"
#include "ucol_elm.h"
#include "uresimp.h"
#include "ustr_imp.h"
#include "cstring.h"
#include "umutex.h"
#include "ustrenum.h"
#include "putilimp.h"
#include "utracimp.h"
#include "cmemory.h"

U_CDECL_BEGIN
static void U_CALLCONV
ucol_prv_closeResources(UCollator *coll) {
  if(coll->rb != NULL) { /* pointing to read-only memory */
      ures_close(coll->rb);
  }
  if(coll->elements != NULL) {
      ures_close(coll->elements);
  }
}
U_CDECL_END

/****************************************************************************/
/* Following are the open/close functions                                   */
/*                                                                          */
/****************************************************************************/
static UCollator*
tryOpeningFromRules(UResourceBundle *collElem, UErrorCode *status) {
  int32_t rulesLen = 0;
  const UChar *rules = ures_getStringByKey(collElem, "Sequence", &rulesLen, status);
  return ucol_openRules(rules, rulesLen, UCOL_DEFAULT, UCOL_DEFAULT, NULL, status);

}


// API in ucol_imp.h

U_CFUNC UCollator*
ucol_open_internal(const char *loc,
                   UErrorCode *status)
{
    const UCollator* UCA = ucol_initUCA(status);

    /* New version */
    if(U_FAILURE(*status)) return 0;


    UCollator *result = NULL;
    UResourceBundle *b = ures_open(U_ICUDATA_COLL, loc, status);

    /* we try to find stuff from keyword */
    UResourceBundle *collations = ures_getByKey(b, "collations", NULL, status);
    UResourceBundle *collElem = NULL;
    char keyBuffer[256];
    // if there is a keyword, we pick it up and try to get elements
    if(!uloc_getKeywordValue(loc, "collation", keyBuffer, 256, status)) {
        // no keyword. we try to find the default setting, which will give us the keyword value
        UErrorCode intStatus = U_ZERO_ERROR;
        // finding default value does not affect collation fallback status
        UResourceBundle *defaultColl = ures_getByKeyWithFallback(collations, "default", NULL, &intStatus);
        if(U_SUCCESS(intStatus)) {
            int32_t defaultKeyLen = 0;
            const UChar *defaultKey = ures_getString(defaultColl, &defaultKeyLen, &intStatus);
            u_UCharsToChars(defaultKey, keyBuffer, defaultKeyLen);
            keyBuffer[defaultKeyLen] = 0;
        } else {
            *status = U_INTERNAL_PROGRAM_ERROR;
            return NULL;
        }
        ures_close(defaultColl);
    }
    collElem = ures_getByKeyWithFallback(collations, keyBuffer, collElem, status);

    UResourceBundle *binary = NULL;

    if(*status == U_MISSING_RESOURCE_ERROR) { /* We didn't find the tailoring data, we fallback to the UCA */
        *status = U_USING_DEFAULT_WARNING;
        result = ucol_initCollator(UCA->image, result, UCA, status);
        // if we use UCA, real locale is root
        result->rb = ures_open(U_ICUDATA_COLL, "", status);
        result->elements = ures_open(U_ICUDATA_COLL, "", status);
        if(U_FAILURE(*status)) {
            goto clean;
        }
        ures_close(b);
        result->hasRealData = FALSE;
    } else if(U_SUCCESS(*status)) {
        int32_t len = 0;
        UErrorCode binaryStatus = U_ZERO_ERROR;

        binary = ures_getByKey(collElem, "%%CollationBin", NULL, &binaryStatus);

        if(binaryStatus == U_MISSING_RESOURCE_ERROR) { /* we didn't find the binary image, we should use the rules */
            binary = NULL;
            result = tryOpeningFromRules(collElem, status);
            if(U_FAILURE(*status)) {
                goto clean;
            }
        } else if(U_SUCCESS(*status)) { /* otherwise, we'll pick a collation data that exists */
            const uint8_t *inData = ures_getBinary(binary, &len, status);
            UCATableHeader *colData = (UCATableHeader *)inData;
            if(uprv_memcmp(colData->UCAVersion, UCA->image->UCAVersion, sizeof(UVersionInfo)) != 0 ||
                uprv_memcmp(colData->UCDVersion, UCA->image->UCDVersion, sizeof(UVersionInfo)) != 0 ||
                colData->version[0] != UCOL_BUILDER_VERSION)
            {
                *status = U_DIFFERENT_UCA_VERSION;
                result = tryOpeningFromRules(collElem, status);
            } else {
                if(U_FAILURE(*status)){
                    goto clean;
                }
                if((uint32_t)len > (paddedsize(sizeof(UCATableHeader)) + paddedsize(sizeof(UColOptionSet)))) {
                    result = ucol_initCollator((const UCATableHeader *)inData, result, UCA, status);
                    if(U_FAILURE(*status)){
                        goto clean;
                    }
                    result->hasRealData = TRUE;
                } else {
                    result = ucol_initCollator(UCA->image, result, UCA, status);
                    ucol_setOptionsFromHeader(result, (UColOptionSet *)(inData+((const UCATableHeader *)inData)->options), status);
                    if(U_FAILURE(*status)){
                        goto clean;
                    }
                    result->hasRealData = FALSE;
                }
                result->freeImageOnClose = FALSE;
            }
        }
        result->rb = b;
        result->elements = collElem;
        len = 0;
        binaryStatus = U_ZERO_ERROR;
        result->rules = ures_getStringByKey(result->elements, "Sequence", &len, &binaryStatus);
        result->rulesLength = len;
        result->freeRulesOnClose = FALSE;
    } else { /* There is another error, and we're just gonna clean up */
        goto clean;
    }

    result->validLocale = NULL; // default is to use rb info

    if(loc == NULL) {
        loc = ures_getLocale(result->rb, status);
    }
    result->requestedLocale = (char *)uprv_malloc((uprv_strlen(loc)+1)*sizeof(char));
    /* test for NULL */
    if (result->requestedLocale == NULL) {
        *status = U_MEMORY_ALLOCATION_ERROR;
        goto clean;
    }
    uprv_strcpy(result->requestedLocale, loc);

    ures_close(binary);
    ures_close(collations); //??? we have to decide on that. Probably affects something :)
    result->resCleaner = ucol_prv_closeResources;
    return result;

clean:
    ures_close(b);
    ures_close(collElem);
    ures_close(collations);
    ures_close(binary);
    return NULL;
}

U_CAPI UCollator*
ucol_open(const char *loc,
          UErrorCode *status)
{
  UTRACE_ENTRY_OC(UTRACE_UCOL_OPEN);
  UTRACE_DATA1(UTRACE_INFO, "locale = \"%s\"", loc);
  UCollator *result = NULL;

  u_init(status);
#if !UCONFIG_NO_SERVICE
  result = Collator::createUCollator(loc, status);
  if (result == NULL)
#endif
  {
    result = ucol_open_internal(loc, status);
  }
  UTRACE_EXIT_PTR_STATUS(result, *status);
  return result;
}

U_CAPI UCollator* U_EXPORT2
ucol_openRules( const UChar        *rules,
                int32_t            rulesLength,
                UColAttributeValue normalizationMode,
                UCollationStrength strength,
                UParseError        *parseError,
                UErrorCode         *status)
{
  uint32_t listLen = 0;
  UColTokenParser src;
  UColAttributeValue norm;
  UParseError tErr;

  if(status == NULL || U_FAILURE(*status)){
    return 0;
  }

  u_init(status);
  if (U_FAILURE(*status)) {
      return NULL;
  }

  if(rules == NULL || rulesLength < -1) {
    *status = U_ILLEGAL_ARGUMENT_ERROR;
    return 0;
  }

  if(rulesLength == -1) {
    rulesLength = u_strlen(rules);
  }

  if(parseError == NULL){
    parseError = &tErr;
  }

  switch(normalizationMode) {
  case UCOL_OFF:
  case UCOL_ON:
  case UCOL_DEFAULT:
    norm = normalizationMode;
    break;
  default:
    *status = U_ILLEGAL_ARGUMENT_ERROR;
    return 0;
  }

  UCollator *UCA = ucol_initUCA(status);

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

  ucol_tok_initTokenList(&src, rules, rulesLength, UCA, status);
  listLen = ucol_tok_assembleTokenList(&src,parseError, status);

  if(U_FAILURE(*status)) {
    /* if status is U_ILLEGAL_ARGUMENT_ERROR, src->current points at the offending option */
    /* if status is U_INVALID_FORMAT_ERROR, src->current points after the problematic part of the rules */
    /* so something might be done here... or on lower level */
#ifdef UCOL_DEBUG
    if(*status == U_ILLEGAL_ARGUMENT_ERROR) {
      fprintf(stderr, "bad option starting at offset %i\n", src.current-src.source);
    } else {
      fprintf(stderr, "invalid rule just before offset %i\n", src.current-src.source);
    }
#endif
    ucol_tok_closeTokenList(&src);
    return NULL;
  }
  UCollator *result = NULL;
  UCATableHeader *table = NULL;

  if(src.resultLen > 0 || src.removeSet != NULL) { /* we have a set of rules, let's make something of it */
    /* also, if we wanted to remove some contractions, we should make a tailoring */
    table = ucol_assembleTailoringTable(&src, status);
    if(U_SUCCESS(*status)) {
      // builder version
      table->version[0] = UCOL_BUILDER_VERSION;
      // no tailoring information on this level
      table->version[1] = table->version[2] = table->version[3] = 0;
      // set UCD version
      u_getUnicodeVersion(table->UCDVersion);
      // set UCA version
      uprv_memcpy(table->UCAVersion, UCA->image->UCAVersion, sizeof(UVersionInfo));
      result = ucol_initCollator(table, 0, UCA, status);
      result->hasRealData = TRUE;
      result->freeImageOnClose = TRUE;
    }
  } else { /* no rules, but no error either */
    // must be only options
    // We will init the collator from UCA
    result = ucol_initCollator(UCA->image, 0, UCA, status);
    // And set only the options
    UColOptionSet *opts = (UColOptionSet *)uprv_malloc(sizeof(UColOptionSet));
    /* test for NULL */
    if (opts == NULL) {
        *status = U_MEMORY_ALLOCATION_ERROR;
        goto cleanup;
    }
    uprv_memcpy(opts, src.opts, sizeof(UColOptionSet));
    ucol_setOptionsFromHeader(result, opts, status);
    result->freeOptionsOnClose = TRUE;
    result->hasRealData = FALSE;
    result->freeImageOnClose = FALSE;
  }

  if(U_SUCCESS(*status)) {
    UChar *newRules;
    result->dataVersion[0] = UCOL_BUILDER_VERSION;
    if(rulesLength > 0) {
      newRules = (UChar *)uprv_malloc((rulesLength+1)*U_SIZEOF_UCHAR);
      /* test for NULL */
      if (newRules == NULL) {
          *status = U_MEMORY_ALLOCATION_ERROR;
          goto cleanup;
      }
      uprv_memcpy(newRules, rules, rulesLength*U_SIZEOF_UCHAR);
      newRules[rulesLength]=0;
      result->rules = newRules;
      result->rulesLength = rulesLength;
      result->freeRulesOnClose = TRUE;
    }
    result->rb = NULL;
    result->elements = NULL;
    result->validLocale = NULL;
    result->requestedLocale = NULL;
    ucol_setAttribute(result, UCOL_STRENGTH, strength, status);
    ucol_setAttribute(result, UCOL_NORMALIZATION_MODE, norm, status);
  } else {
cleanup:
    if(result != NULL) {
      ucol_close(result);
    } else {
      if(table != NULL) {
        uprv_free(table);
      }
    }
    result = NULL;
  }

  ucol_tok_closeTokenList(&src);

  return result;
}

U_CAPI int32_t U_EXPORT2
ucol_getRulesEx(const UCollator *coll, UColRuleOption delta, UChar *buffer, int32_t bufferLen) {
  UErrorCode status = U_ZERO_ERROR;
  int32_t len = 0;
  int32_t UCAlen = 0;
  const UChar* ucaRules = 0;
  const UChar *rules = ucol_getRules(coll, &len);
  if(delta == UCOL_FULL_RULES) {
    /* take the UCA rules and append real rules at the end */
    /* UCA rules will be probably coming from the root RB */
    ucaRules = ures_getStringByKey(coll->rb,"UCARules",&UCAlen,&status);
    /*
    UResourceBundle* cresb = ures_getByKeyWithFallback(coll->rb, "collations", NULL, &status);
    UResourceBundle*  uca = ures_getByKeyWithFallback(cresb, "UCA", NULL, &status);
    ucaRules = ures_getStringByKey(uca,"Sequence",&UCAlen,&status);
    ures_close(uca);
    ures_close(cresb);
    */
  }
  if(U_FAILURE(status)) {
    return 0;
  }
  if(buffer!=0 && bufferLen>0){
      *buffer=0;
      if(UCAlen > 0) {
        u_memcpy(buffer, ucaRules, uprv_min(UCAlen, bufferLen));
      }
      if(len > 0 && bufferLen > UCAlen) {
        u_memcpy(buffer+UCAlen, rules, uprv_min(len, bufferLen-UCAlen));
      }
  }
  return u_terminateUChars(buffer, bufferLen, len+UCAlen, &status);
}

static const UChar _NUL = 0;

U_CAPI const UChar* U_EXPORT2
ucol_getRules(    const    UCollator       *coll,
        int32_t            *length)
{
    if(coll->rules != NULL) {
        *length = coll->rulesLength;
        return coll->rules;
    }
    else {
        *length = 0;
        return &_NUL;
    }
}

U_CAPI UBool U_EXPORT2
ucol_equals(const UCollator *source, const UCollator *target) {
  UErrorCode status = U_ZERO_ERROR;
  // if pointers are equal, collators are equal
  if(source == target) {
    return TRUE;
  }
  int32_t i = 0, j = 0;
  // if any of attributes are different, collators are not equal
  for(i = 0; i < UCOL_ATTRIBUTE_COUNT; i++) {
    if(ucol_getAttribute(source, (UColAttribute)i, &status) != ucol_getAttribute(target, (UColAttribute)i, &status) || U_FAILURE(status)) {
      return FALSE;
    }
  }

  int32_t sourceRulesLen = 0, targetRulesLen = 0;
  const UChar *sourceRules = ucol_getRules(source, &sourceRulesLen);
  const UChar *targetRules = ucol_getRules(target, &targetRulesLen);

  if(sourceRulesLen == targetRulesLen && u_strncmp(sourceRules, targetRules, sourceRulesLen) == 0) {
    // all the attributes are equal and the rules are equal - collators are equal
    return(TRUE);
  }
  // hard part, need to construct tree from rules and see if they yield the same tailoring
  UBool result = TRUE;
  UParseError parseError;
  UColTokenParser sourceParser, targetParser;
  int32_t sourceListLen = 0, targetListLen = 0;
  ucol_tok_initTokenList(&sourceParser, sourceRules, sourceRulesLen, source->UCA, &status);
  ucol_tok_initTokenList(&targetParser, targetRules, targetRulesLen, target->UCA, &status);
  sourceListLen = ucol_tok_assembleTokenList(&sourceParser, &parseError, &status);
  targetListLen = ucol_tok_assembleTokenList(&targetParser, &parseError, &status);

  if(sourceListLen != targetListLen) {
    // different number of resets
    result = FALSE;
  } else {
    UColToken *sourceReset = NULL, *targetReset = NULL;
    UChar *sourceResetString = NULL, *targetResetString = NULL;
    int32_t sourceStringLen = 0, targetStringLen = 0;
    for(i = 0; i < sourceListLen; i++) {
      sourceReset = sourceParser.lh[i].reset;
      sourceResetString = sourceParser.source+(sourceReset->source & 0xFFFFFF);
      sourceStringLen = sourceReset->source >> 24;
      for(j = 0; j < sourceListLen; j++) {
        targetReset = targetParser.lh[j].reset;
        targetResetString = targetParser.source+(targetReset->source & 0xFFFFFF);
        targetStringLen = targetReset->source >> 24;
        if(sourceStringLen == targetStringLen && (u_strncmp(sourceResetString, targetResetString, sourceStringLen) == 0)) {
          sourceReset = sourceParser.lh[i].first;
          targetReset = targetParser.lh[j].first;
          while(sourceReset != NULL && targetReset != NULL) {
            sourceResetString = sourceParser.source+(sourceReset->source & 0xFFFFFF);
            sourceStringLen = sourceReset->source >> 24;
            targetResetString = targetParser.source+(targetReset->source & 0xFFFFFF);
            targetStringLen = targetReset->source >> 24;
            if(sourceStringLen != targetStringLen || (u_strncmp(sourceResetString, targetResetString, sourceStringLen) != 0)) {
              result = FALSE;
              goto returnResult;
            }
            // probably also need to check the expansions
            if(sourceReset->expansion) {
              if(!targetReset->expansion) {
                result = FALSE;
                goto returnResult;
              } else {
                // compare expansions
                sourceResetString = sourceParser.source+(sourceReset->expansion& 0xFFFFFF);
                sourceStringLen = sourceReset->expansion >> 24;
                targetResetString = targetParser.source+(targetReset->expansion & 0xFFFFFF);
                targetStringLen = targetReset->expansion >> 24;
                if(sourceStringLen != targetStringLen || (u_strncmp(sourceResetString, targetResetString, sourceStringLen) != 0)) {
                  result = FALSE;
                  goto returnResult;
                }
              }
            } else {
              if(targetReset->expansion) {
                result = FALSE;
                goto returnResult;
              }
            }
            sourceReset = sourceReset->next;
            targetReset = targetReset->next;
          }
          if(sourceReset != targetReset) { // at least one is not NULL
            // there are more tailored elements in one list
            result = FALSE;
            goto returnResult;
          }


          break;
        }
      }
      // couldn't find the reset anchor, so the collators are not equal
      if(j == sourceListLen) {
        result = FALSE;
        goto returnResult;
      }
    }
  }

returnResult:
  ucol_tok_closeTokenList(&sourceParser);
  ucol_tok_closeTokenList(&targetParser);
  return result;

}

U_CAPI int32_t U_EXPORT2
ucol_getDisplayName(    const    char        *objLoc,
            const    char        *dispLoc,
            UChar             *result,
            int32_t         resultLength,
            UErrorCode        *status)
{

  if(U_FAILURE(*status)) return -1;
  UnicodeString dst;
  if(!(result==NULL && resultLength==0)) {
    // NULL destination for pure preflighting: empty dummy string
    // otherwise, alias the destination buffer
    dst.setTo(result, 0, resultLength);
  }
  Collator::getDisplayName(Locale(objLoc), Locale(dispLoc), dst);
  return dst.extract(result, resultLength, *status);
}

U_CAPI const char* U_EXPORT2
ucol_getAvailable(int32_t index)
{
  return uloc_getAvailable(index);
}

U_CAPI int32_t U_EXPORT2
ucol_countAvailable()
{
  return uloc_countAvailable();
}

#if !UCONFIG_NO_SERVICE
U_CAPI UEnumeration* U_EXPORT2
ucol_openAvailableLocales(UErrorCode *status) {
    // This is a wrapper over Collator::getAvailableLocales()
    if (U_FAILURE(*status)) {
        return NULL;
    }
    StringEnumeration *s = Collator::getAvailableLocales();
    if (s == NULL) {
        *status = U_MEMORY_ALLOCATION_ERROR;
        return NULL;
    }
    return uenum_openStringEnumeration(s, status);
}
#endif

// Note: KEYWORDS[0] != RESOURCE_NAME - alan

static const char* RESOURCE_NAME = "collations";

static const char* KEYWORDS[] = { "collation" };

#define KEYWORD_COUNT (sizeof(KEYWORDS)/sizeof(KEYWORDS[0]))

U_CAPI UEnumeration* U_EXPORT2
ucol_getKeywords(UErrorCode *status) {
    UEnumeration *result = NULL;
    if (U_SUCCESS(*status)) {
        return uenum_openCharStringsEnumeration(KEYWORDS, KEYWORD_COUNT, status);
    }
    return result;
}

U_CAPI UEnumeration* U_EXPORT2
ucol_getKeywordValues(const char *keyword, UErrorCode *status) {
    // hard-coded to accept exactly one collation keyword
    // modify if additional collation keyword is added later
    if (U_SUCCESS(*status) &&
        keyword==NULL || uprv_strcmp(keyword, KEYWORDS[0])!=0) {
        *status = U_ILLEGAL_ARGUMENT_ERROR;
        return NULL;
    }
    return ures_getKeywordValues(U_ICUDATA_COLL, RESOURCE_NAME, status);
}

U_CAPI int32_t U_EXPORT2
ucol_getFunctionalEquivalent(char* result, int32_t resultCapacity,
                             const char* keyword, const char* locale,
                             UBool* isAvailable, UErrorCode* status) {
    // N.B.: Resource name is "collations" but keyword is "collation"
    return ures_getFunctionalEquivalent(result, resultCapacity, U_ICUDATA_COLL,
                                        "collations", keyword, locale,
                                        isAvailable, TRUE, status);
}

/* returns the locale name the collation data comes from */
U_CAPI const char * U_EXPORT2
ucol_getLocale(const UCollator *coll, ULocDataLocaleType type, UErrorCode *status) {
  return ucol_getLocaleByType(coll, type, status);
}

U_CAPI const char * U_EXPORT2
ucol_getLocaleByType(const UCollator *coll, ULocDataLocaleType type, UErrorCode *status) {
  const char *result = NULL;
  if(status == NULL || U_FAILURE(*status)) {
    return NULL;
  }
  UTRACE_ENTRY(UTRACE_UCOL_GETLOCALE);
  UTRACE_DATA1(UTRACE_INFO, "coll=%p", coll);

  switch(type) {
  case ULOC_ACTUAL_LOCALE:
    // validLocale is set only if service registration has explicitly set the
    // requested and valid locales.  if this is the case, the actual locale
    // is considered to be the valid locale.
    if (coll->validLocale != NULL) {
      result = coll->validLocale;
    } else if(coll->elements != NULL) {
      result = ures_getLocale(coll->elements, status);
    }
    break;
  case ULOC_VALID_LOCALE:
    if (coll->validLocale != NULL) {
      result = coll->validLocale;
    } else if(coll->rb != NULL) {
      result = ures_getLocale(coll->rb, status);
    }
    break;
  case ULOC_REQUESTED_LOCALE:
    result = coll->requestedLocale;
    break;
  default:
    *status = U_ILLEGAL_ARGUMENT_ERROR;
  }
  UTRACE_DATA1(UTRACE_INFO, "result = %s", result);
  UTRACE_EXIT_STATUS(*status);
  return result;
}

U_CAPI void U_EXPORT2
ucol_setReqValidLocales(UCollator *coll, char *requestedLocaleToAdopt, char *validLocaleToAdopt)
{
  if (coll) {
    if (coll->validLocale) {
      uprv_free(coll->validLocale);
    }
    coll->validLocale = validLocaleToAdopt;
    if (coll->requestedLocale) { // should always have
      uprv_free(coll->requestedLocale);
    }
    coll->requestedLocale = requestedLocaleToAdopt;
  }
}

U_CAPI USet * U_EXPORT2
ucol_getTailoredSet(const UCollator *coll, UErrorCode *status)
{
  if(status == NULL || U_FAILURE(*status)) {
    return NULL;
  }
  if(coll == NULL || coll->UCA == NULL) {
    *status = U_ILLEGAL_ARGUMENT_ERROR;
    return NULL;
  }
  UParseError parseError;
  UColTokenParser src;
  int32_t rulesLen = 0;
  const UChar *rules = ucol_getRules(coll, &rulesLen);
  const UChar *current = NULL;
  UBool startOfRules = TRUE;
  // we internally use the C++ class, for the following reasons:
  // 1. we need to utilize canonical iterator, which is a C++ only class
  // 2. canonical iterator returns UnicodeStrings - USet cannot take them
  // 3. USet is internally really UnicodeSet, C is just a wrapper
  UnicodeSet *tailored = new UnicodeSet();
  UnicodeString pattern;
  UnicodeString empty;
  CanonicalIterator it(empty, *status);


  // The idea is to tokenize the rule set. For each non-reset token,
  // we add all the canonicaly equivalent FCD sequences
  ucol_tok_initTokenList(&src, rules, rulesLen, coll->UCA, status);
  while ((current = ucol_tok_parseNextToken(&src, startOfRules, &parseError, status)) != NULL) {
    startOfRules = FALSE;
    if(src.parsedToken.strength != UCOL_TOK_RESET) {
      const UChar *stuff = src.source+(src.parsedToken.charsOffset);
      it.setSource(UnicodeString(stuff, src.parsedToken.charsLen), *status);
      pattern = it.next();
      while(!pattern.isBogus()) {
        if(Normalizer::quickCheck(pattern, UNORM_FCD, *status) != UNORM_NO) {
          tailored->add(pattern);
        }
        pattern = it.next();
      }
    }
  }
  ucol_tok_closeTokenList(&src);
  return (USet *)tailored;
}

#endif /* #if !UCONFIG_NO_COLLATION */