/*
******************************************************************************
*
*   Copyright (C) 1999-2001, International Business Machines
*   Corporation and others.  All Rights Reserved.
*
******************************************************************************
*   file name:  udata.c
*   encoding:   US-ASCII
*   tab size:   8 (not used)
*   indentation:4
*
*   created on: 1999oct25
*   created by: Markus W. Scherer
*/

#include "unicode/utypes.h"
#include "unicode/putil.h"
#include "umutex.h"
#include "cmemory.h"
#include "cstring.h"
#include "unicode/udata.h"
#include "unicode/uversion.h"
#include "uhash.h"
#include "ucln_cmn.h"

#include "udatamem.h"
#include "umapfile.h"
#include "ucmndata.h"

/***********************************************************************
*
*   Notes on the organization of the ICU data implementation
*
*      All of the public API is defined in udata.h
*
*      The implementation is split into several files...
*
*         - udata.c  (this file) contains higher level code that knows about
*                     the search paths for locating data, caching opened data, etc.
*
*         - umapfile.c  contains the low level platform-specific code for actually loading
*                     (memory mapping, file reading, whatever) data into memory.
*
*         - ucmndata.c  deals with the tables of contents of ICU data items within
*                     an ICU common format data file.  The implementation includes
*                     an abstract interface and support for multiple TOC formats.
*                     All knowledge of any specific TOC format is encapsulated here.
*
*         - udatamem.c has code for managing UDataMemory structs.  These are little
*                     descriptor objects for blocks of memory holding ICU data of
*                     various types.
*/

/* configuration ---------------------------------------------------------- */

/* If you are excruciatingly bored turn this on .. */
/* #define UDATA_DEBUG 1 */


#if defined(UDATA_DEBUG)
#   include <stdio.h>
#endif


/***********************************************************************
*
*    static (Global) data
*
************************************************************************/
static UDataMemory *gCommonICUData = NULL;    /* Pointer to the common ICU data.           */
                                              /*   May be updated once, if we started with */
                                              /*   a stub or subset library.               */

static UDataMemory *gStubICUData   = NULL;    /* If gCommonICUData does get updated, remember */
                                              /*   the original one so that it can be cleaned */
                                              /*   up when ICU is shut down.                  */

static UHashtable  *gCommonDataCache = NULL;  /* Global hash table of opened ICU data files.  */


UBool
udata_cleanup()
{
    if (gCommonDataCache) {             /* Delete the cache of user data mappings.  */
        uhash_close(gCommonDataCache);  /*   Table owns the contents, and will delete them. */
        gCommonDataCache = NULL;        /*   Cleanup is not thread safe.                */
    }

    if (gCommonICUData != NULL) {
        udata_close(gCommonICUData);    /* Clean up common ICU Data             */
        gCommonICUData = NULL;
    }

    if (gStubICUData != NULL) {
        udata_close(gStubICUData);      /* Clean up the stub ICU Data             */
        gStubICUData = NULL;
    }


    return TRUE;                   /* Everything was cleaned up */
}


/*
 * setCommonICUData.   Set a UDataMemory to be the global ICU Data
 */
static void
setCommonICUData(UDataMemory *pData,     /*  The new common data.  Belongs to caller, we copy it. */
                 UDataMemory *oldData,   /*  Old ICUData ptr.  Overwrite of this value is ok,     */
                                         /*     of any others is not.                             */
                 UBool       warn,       /*  If true, set USING_DEFAULT warning if ICUData was    */
                                         /*    changed by another thread before we got to it.     */
                 UErrorCode *pErr)
{
    UDataMemory  *newCommonData = UDataMemory_createNewInstance(pErr);
    if (U_FAILURE(*pErr)) {
        return;
    }

    /*  For the assignment, other threads must cleanly see either the old            */
    /*    or the new, not some partially initialized new.  The old can not be        */
    /*    deleted - someone may still have a pointer to it lying around in           */
    /*    their locals.                                                              */
    UDatamemory_assign(newCommonData, pData);
    umtx_lock(NULL);
    if (gCommonICUData==oldData) {
        gStubICUData   = gCommonICUData;   /* remember the old Common Data, so it can be cleaned up. */
        gCommonICUData = newCommonData;
    }
    else {
        if  (warn==TRUE) {
            *pErr = U_USING_DEFAULT_WARNING;
        }
        uprv_free(newCommonData);
    }
    umtx_unlock(NULL);
    return;
}


static char *
strcpy_returnEnd(char *dest, const char *src) {
    while((*dest=*src)!=0) {
        ++dest;
        ++src;
    }
    return dest;
}

/*------------------------------------------------------------------------------
 *                                                                              
 *  computeDirPath   given a user-supplied path of an item to be opened,             
 *                         compute and return 
 *                            - the full directory path to be used 
 *                              when opening the file.
 *                            - Pointer to null at end of above returned path    
 *
 *                       Parameters:
 *                          path:        input path.  Buffer is not altered.
 *                          pathBuffer:  Output buffer.  Any contents are overwritten.
 *
 *                       Returns:
 *                          Pointer to null termination in returned pathBuffer.
 *
 *                    TODO:  This works the way ICU historically has, but the
 *                           whole data fallback search path is so complicated that
 *                           proabably almost no one will ever really understand it,
 *                           the potential for confusion is large.  (It's not just 
 *                           this one function, but the whole scheme.)
 *                            
 *------------------------------------------------------------------------------*/
char *
uprv_computeDirPath(const char *path, char *pathBuffer) {
    char   *finalSlash;       /* Ptr to last dir separator in input path, or null if none. */
    int32_t pathLen;          /* Length of the returned directory path                     */
    
    finalSlash = 0;
    if (path != 0) {
        finalSlash = uprv_strrchr(path, U_FILE_SEP_CHAR);
    }
    
    *pathBuffer = 0;
    if (finalSlash == 0) {
        /* No user-supplied path.  
         * Copy the ICU_DATA path to the path buffer and return that*/
        const char *icuDataDir;
        icuDataDir=u_getDataDirectory();
        if(icuDataDir!=NULL && *icuDataDir!=0) {
            return strcpy_returnEnd(pathBuffer, icuDataDir);
        } else {
            /* there is no icuDataDir either.  Just return the empty pathBuffer. */
            return pathBuffer;
        }
    } 
    
    /* User supplied path did contain a directory portion.
     * Copy it to the output path buffer */
    pathLen = (int32_t)(finalSlash - path + 1);
    uprv_memcpy(pathBuffer, path, pathLen);
    *(pathBuffer+pathLen) = 0;
    return pathBuffer+pathLen;
}


static const char *
findBasename(const char *path) {
    const char *basename=uprv_strrchr(path, U_FILE_SEP_CHAR);
    if(basename==NULL) {
        return path;
    } else {
        return basename+1;
    }
}

static const char *
packageNameFromPath(const char *path)
{
    if((path == NULL) || (*path == 0)) {
        return U_ICUDATA_NAME;
    }

    path = findBasename(path);

    if((path == NULL) || (*path == 0)) {
        return U_ICUDATA_NAME;
    }

    return path;
}


/*----------------------------------------------------------------------*
 *                                                                      *
 *   Cache for common data                                              *
 *      Functions for looking up or adding entries to a cache of        *
 *      data that has been previously opened.  Avoids a potentially     *
 *      expensive operation of re-opening the data for subsequent       *
 *      uses.                                                           *
 *                                                                      *
 *      Data remains cached for the duration of the process.            *
 *                                                                      *
 *----------------------------------------------------------------------*/

typedef struct DataCacheElement {
    char          *name;
    UDataMemory   *item;
} DataCacheElement;


/*
 * Deleter function for DataCacheElements.
 *         udata cleanup function closes the hash table; hash table in turn calls back to
 *         here for each entry.
 */
static void  U_EXPORT2 U_CALLCONV DataCacheElement_deleter(void *pDCEl) {
    DataCacheElement *p = (DataCacheElement *)pDCEl;
    udata_close(p->item);              /* unmaps storage */
    uprv_free(p->name);                /* delete the hash key string. */
    uprv_free(pDCEl);                  /* delete 'this'          */
}

 /*   udata_getCacheHashTable()
 *     Get the hash table used to store the data cache entries.
 *     Lazy create it if it doesn't yet exist.
 */
static UHashtable *udata_getHashTable() {
    UErrorCode err = U_ZERO_ERROR;

    if (gCommonDataCache != NULL) {
        return gCommonDataCache;
    }
    umtx_lock(NULL);
    if (gCommonDataCache == NULL) {
        gCommonDataCache = uhash_open(uhash_hashChars, uhash_compareChars, &err);
        uhash_setValueDeleter(gCommonDataCache, DataCacheElement_deleter);
    }
    umtx_unlock(NULL);

    if (U_FAILURE(err)) {
        return NULL;      /* TODO:  handle this error better.  */
    }
    return gCommonDataCache;
}


static UDataMemory *udata_findCachedData(const char *path)
{
    UHashtable        *htable;
    UDataMemory       *retVal = NULL;
    DataCacheElement  *el;
    const char        *baseName;

    baseName = findBasename(path);   /* Cache remembers only the base name, not the full path. */
    htable = udata_getHashTable();
    umtx_lock(NULL);
    el = (DataCacheElement *)uhash_get(htable, baseName);
    umtx_unlock(NULL);
    if (el != NULL) {
        retVal = el->item;
    }
#ifdef UDATA_DEBUG
    fprintf(stderr, "Cache: [%s] -> %p\n", baseName, retVal);
#endif
    return retVal;
}


static UDataMemory *udata_cacheDataItem(const char *path, UDataMemory *item, UErrorCode *pErr) {
    DataCacheElement *newElement;
    const char       *baseName;
    int32_t           nameLen;
    UHashtable       *htable;
    UDataMemory      *oldValue = NULL;

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

    /* Create a new DataCacheElement - the thingy we store in the hash table -
     * and copy the supplied path and UDataMemoryItems into it.
     */
    newElement = uprv_malloc(sizeof(DataCacheElement));
    if (newElement == NULL) {
        *pErr = U_MEMORY_ALLOCATION_ERROR;
        return NULL;
    }
    newElement->item = UDataMemory_createNewInstance(pErr);
    if (U_FAILURE(*pErr)) {
        return NULL;
    }
    UDatamemory_assign(newElement->item, item);

    baseName = findBasename(path);
    nameLen = (int32_t)uprv_strlen(baseName);
    newElement->name = uprv_malloc(nameLen+1);
    if (newElement->name == NULL) {
        *pErr = U_MEMORY_ALLOCATION_ERROR;
        return NULL;
    }
    uprv_strcpy(newElement->name, baseName);

    /* Stick the new DataCacheElement into the hash table.
    */
    htable = udata_getHashTable();
    umtx_lock(NULL);
    oldValue = uhash_get(htable, path);
    if (oldValue != NULL) {
        *pErr = U_USING_DEFAULT_WARNING; }
    else {
        uhash_put(
            htable,
            newElement->name,               /* Key   */
            newElement,                     /* Value */
            pErr);
    }
    umtx_unlock(NULL);

#ifdef UDATA_DEBUG
    fprintf(stderr, "Cache: [%s] <<< %p : %s\n", newElement->name, 
            newElement->item, u_errorName(*pErr));
#endif

    if (*pErr == U_USING_DEFAULT_WARNING || U_FAILURE(*pErr)) {
        uprv_free(newElement->name);
        uprv_free(newElement->item);
        uprv_free(newElement);
        return oldValue;
    }

    return newElement->item;
}


/*----------------------------------------------------------------------*==============
 *                                                                      *
 *  Path management.  Could be shared with other tools/etc if need be   *
 * later on.                                                            *
 *                                                                      *
 *----------------------------------------------------------------------*/

#define U_DATA_PATHITER_BUFSIZ  1024   /* paths can't be longer than this */

typedef struct 
{
    const char *path;                              /* working path (u_icudata_Dir) */
    const char *nextPath;                          /* path following this one */
    const char *basename;                          /* item's basename (icudt22e_mt.res)*/
    const char *suffix;                            /* item suffix (can be null) */

    uint32_t     basenameLen;                      /* length of basename */
    char        itemPath[U_DATA_PATHITER_BUFSIZ];  /* path passed in with item name */

    char        pathBuffer[U_DATA_PATHITER_BUFSIZ];  /* output path for this it'ion */

    UBool       checkLastFour;                       /* if TRUE then allow paths such as '/foo/myapp.dat'  to match, checks last 4 chars of suffix with last 4 of path, then previous chars. */
    
}  UDataPathIterator;

/** 
 * Initialize (or re-initialize) a user-supplied UDataPathIterator
 * Note: UDataPathIterator does not allocate storage, so it doesn't need to be closed.
 * 
 * @param iter  The iterator to be initialized. Its current state does not matter. 
 * @param path  The full pathname to be iterated over.  If NULL, defaults to U_ICUDATA_NAME 
 * @param item  Item to be searched for.  Can include full path, such as /a/b/foo.dat 
 * @param suffix  Optional item suffix, if not-null (ex. ".dat") then 'path' can contain 'item' explicitly. Ex:   'stuff.dat' would be found in '/a/foo:/tmp/stuff.dat:/bar/baz' as item #2.   '/blarg/stuff.dat' would also be found.
 */
static void udata_pathiter_init(UDataPathIterator *iter, const char *path, const char *item, const char *suffix, UBool doCheckLastFour)
{
#ifdef UDATA_DEBUG
        fprintf(stderr, "SUFFIX1=%s [%p]\n", suffix, suffix);
#endif
    /** Path **/
    if(path == NULL) {
        iter->path = u_getDataDirectory();
    } else {
        iter->path = path;
    }

    /** Item **/
    iter->basename = findBasename(item);
    iter->basenameLen = uprv_strlen(iter->basename);

    if(iter->basename == NULL) {
        iter->nextPath = NULL;
        return;
    }

    /** Item path **/
    if(iter->basename == item) {
        iter->itemPath[0] = 0;
        iter->nextPath = iter->path;
    } else { 
        uprv_strncpy(iter->itemPath, item, iter->basename - item);
        iter->itemPath[iter->basename-item]=0;
        iter->nextPath = iter->itemPath;
    }
#ifdef UDATA_DEBUG
        fprintf(stderr, "SUFFIX=%s [%p]\n", suffix, suffix);
#endif
    
    if(suffix != NULL) {
        iter->suffix = suffix;
    } else {
        iter->suffix = "";
    }

    iter->checkLastFour = doCheckLastFour;
    
#ifdef UDATA_DEBUG
    fprintf(stderr, "%p: init %s -> [path=%s], [base=%s], [suff=%s], [itempath=%s], [nextpath=%s], [checklast4=%s]\n",
            iter,
            item,
            iter->path,
            iter->basename,
            iter->suffix,
            iter->itemPath,
            iter->nextPath,
            iter->checkLastFour?"TRUE":"false");
#endif

}

/**
 * Get the next path on the list.
 *
 * @param iter The Iter to be used 
 * @param len  If set, pointer to the length of the returned path, for convenience. 
 * @return Pointer to the next path segment, or NULL if there are no more.
 */
static const char *udata_pathiter_next(UDataPathIterator *iter, int32_t *outPathLen)
{
    const char *path = NULL;
    int32_t     pathLen = 0;
    const char *pathBasename;

    if(outPathLen != NULL) {
        *outPathLen = 0;
    }

    do
    {
        if( iter->nextPath == NULL ) {
            return NULL;
        }
        
        path = iter->nextPath;
        
        if(iter->nextPath == iter->itemPath) { /* we were processing item's path. */
            iter->nextPath = iter->path; /* start with regular path next tm. */
            pathLen = uprv_strlen(path);
        } else {
            /* fix up next for next time */
            iter->nextPath = uprv_strchr(path, U_PATH_SEP_CHAR);
            if(iter->nextPath == NULL) {
                /* segment: entire path */
                pathLen = uprv_strlen(path); 
            } else {
                /* segment: until next segment */
                pathLen = iter->nextPath - path;
                if(*iter->nextPath) { /* skip divider */
                    iter->nextPath ++;
                }
            }
        }

        if(pathLen == 0) {
            continue;
        }

#ifdef UDATA_DEBUG
        fprintf(stderr, "rest of path (IDD) = %s\n", path);
        fprintf(stderr, "                     ");
        { 
            int qqq;
            for(qqq=0;qqq<pathLen;qqq++)
            {
                fprintf(stderr, " ");
            }

            fprintf(stderr, "^\n");
        }
#endif

        uprv_strncpy(iter->pathBuffer, path, pathLen);
        iter->pathBuffer[pathLen] = 0;

        /* check for .dat files */
        pathBasename = findBasename(iter->pathBuffer);

        if(iter->checkLastFour == TRUE &&
           uprv_strncmp(iter->pathBuffer +(pathLen-4),iter->suffix,4)==0 && /* suffix matches */
           uprv_strncmp(findBasename(iter->pathBuffer),iter->basename,iter->basenameLen)==0  && /* base matches */
           uprv_strlen(pathBasename)==(iter->basenameLen+4)) { /* base+suffix = full len */
            
#ifdef UDATA_DEBUG
            fprintf(stderr, "Have %s file on the path: %s\n", iter->suffix, iter->pathBuffer);
#endif
            /* do nothing */
        }
        else 
        {       /* regular dir path */
            if(iter->pathBuffer[pathLen-1] != U_FILE_SEP_CHAR)  /* trailing sep */
            {
                iter->pathBuffer[pathLen++] = U_FILE_SEP_CHAR;
            }
            
            uprv_strncpy(iter->pathBuffer + pathLen,  /* + basename */
                         iter->basename,
                         iter->basenameLen);

            pathLen += iter->basenameLen;

            if(*iter->suffix)  /* tack on suffix */
            {
                uprv_strcpy(iter->pathBuffer + pathLen,
                            iter->suffix);
                pathLen += uprv_strlen(iter->suffix);
            }
            
        }

        /* return value of path size */
        if( outPathLen ) {
            *outPathLen = pathLen; 
        }

#ifdef UDATA_DEBUG
        fprintf(stderr, " -->  %s\n", iter->pathBuffer);
#endif

        return iter->pathBuffer;

    } while(iter->path);

    /* fell way off the end */
    return NULL;
}


/* ==================================================================================*/


/*----------------------------------------------------------------------*
 *                                                                      *
 *  Add a static reference to the common data  library                  *
 *   Unless overridden by an explicit u_setCommonData, this will be     *
 *      our common data.                                                *
 *                                                                      *
 *----------------------------------------------------------------------*/
extern  const DataHeader U_IMPORT U_ICUDATA_ENTRY_POINT;


/*----------------------------------------------------------------------*
 *                                                                      *
 *   openCommonData   Attempt to open a common format (.dat) file       *
 *                    Map it into memory (if it's not there already)    *
 *                    and return a UDataMemory object for it.           *
 *                                                                      *
 *                    If the requested data is already open and cached  *
 *                       just return the cached UDataMem object.        *
 *                                                                      *
 *----------------------------------------------------------------------*/
static UDataMemory *
openCommonData(const char *path,          /*  Path from OpenCHoice?          */
               UBool isICUData,           /*  ICU Data true if path == NULL  */
               UErrorCode *pErrorCode)
{
    UDataMemory tData;
    UDataPathIterator iter;
    const char *pathBuffer;
    int32_t pathLen;
    const char *inBasename;

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

    UDataMemory_init(&tData);

    /* ??????? TODO revisit this */ 
    if (isICUData) {
        /* "mini-cache" for common ICU data */
        if(gCommonICUData != NULL) {
            return gCommonICUData;
        }

        tData.pHeader = &U_ICUDATA_ENTRY_POINT;
        udata_checkCommonData(&tData, pErrorCode);
        setCommonICUData(&tData, NULL, FALSE, pErrorCode);
        return gCommonICUData;
    }


    /* request is NOT for ICU Data.  */

    /* Find the base name portion of the supplied path.   */
    /*   inBasename will be left pointing somewhere within the original path string.      */
    inBasename = findBasename(path);
#ifdef UDATA_DEBUG
    fprintf(stderr, "inBasename = %s\n", inBasename);
#endif

    if(*inBasename==0) {
        /* no basename.     This will happen if the original path was a directory name,   */
        /*    like  "a/b/c/".   (Fallback to separate files will still work.)             */
#ifdef UDATA_DEBUG
        fprintf(stderr, "ocd: no basename in %s, bailing.\n", path);
#endif
        *pErrorCode=U_FILE_ACCESS_ERROR;
        return NULL;
    }

   /* Is the requested common data file already open and cached?                     */
   /*   Note that the cache is keyed by the base name only.  The rest of the path,   */
   /*     if any, is not considered.                                                 */
   {
        UDataMemory  *dataToReturn = udata_findCachedData(inBasename);
        if (dataToReturn != NULL) {
            return dataToReturn;
        }
    }

    /* Requested item is not in the cache.
     * Hunt it down, trying all the path locations
     */

    udata_pathiter_init(&iter, u_getDataDirectory(), path, ".dat", TRUE);

    while((UDataMemory_isLoaded(&tData)==FALSE) && 
          (pathBuffer = udata_pathiter_next(&iter, &pathLen)) != NULL)
    {
#ifdef UDATA_DEBUG
        fprintf(stderr, "ocd: trying path %s - ", pathBuffer);
#endif
        uprv_mapFile(&tData, pathBuffer);
#ifdef UDATA_DEBUG
        fprintf(stderr, "%s\n", UDataMemory_isLoaded(&tData)?"LOADED":"not loaded");
#endif
    }

    if (!UDataMemory_isLoaded(&tData)) {
        /* no common data */
        *pErrorCode=U_FILE_ACCESS_ERROR;
        return NULL;
    }

    /* we have mapped a file, check its header */
    udata_checkCommonData(&tData, pErrorCode);


    /* Cache the UDataMemory struct for this .dat file,
     *   so we won't need to hunt it down and map it again next time
     *   something is needed from it.                */
    return udata_cacheDataItem(inBasename, &tData, pErrorCode);
}


#ifdef OS390
#   define MAX_STUB_ENTRIES 7
#else
#   define MAX_STUB_ENTRIES 0
#endif


/*----------------------------------------------------------------------*
 *                                                                      *
 *   extendICUData   If the full set of ICU data was not loaded at      *
 *                   program startup, load it now.  This function will  *
 *                   be called when the lookup of an ICU data item in   *
 *                   the common ICU data fails.                         *
 *                                                                      *
 *                   The parameter is the UDataMemory in which the      *
 *                   search for a requested item failed.                *
 *                                                                      *
 *                   return true if new data is loaded, false otherwise.*
 *                                                                      *
 *----------------------------------------------------------------------*/
static UBool extendICUData(UDataMemory *failedData, UErrorCode *pErr)
{
    /*  If the data library that we are running with turns out to be the
     *   stub library (or, on the 390, the subset library), we will try to
     *   load a .dat file instead.  The stub library has no entries in its
     *   TOC, which is how we identify it here.
     */
    UDataMemory   *pData;
    UDataMemory   copyPData;

    if (failedData->vFuncs->NumEntries(failedData) > MAX_STUB_ENTRIES) {
        /*  Not the stub.  We can't extend.  */
        return FALSE;
    }

    /* See if we can explicitly open a .dat file for the ICUData. */
    pData = openCommonData(
               U_ICUDATA_NAME,            /*  "icudt20l" , for example.          */
               FALSE,                     /*  Pretend we're not opening ICUData  */
               pErr);

    /* How about if there is no pData, eh... */

   UDataMemory_init(&copyPData);
   if(pData != NULL) {
      UDatamemory_assign(&copyPData, pData);
      copyPData.map = 0;              /* The mapping for this data is owned by the hash table */
      copyPData.mapAddr = 0;          /*   which will unmap it when ICU is shut down.         */
                                      /* CommonICUData is also unmapped when ICU is shut down.*/
                                      /* To avoid unmapping the data twice, zero out the map  */
                                      /*   fields in the UDataMemory that we're assigning     */
                                      /*   to CommonICUData.                                  */

      setCommonICUData(&copyPData,    /*  The new common data.                                */
                   failedData,        /*  Old ICUData ptr.  Overwrite of this value is ok,    */
                   FALSE,             /*  No warnings if write didn't happen                  */
                   pErr);             /*  setCommonICUData honors errors; NOP if error set    */
    }
    

    return gCommonICUData != failedData;   /* Return true if ICUData pointer was updated.   */
                                    /*   (Could potentialy have been done by another thread racing */
                                    /*   us through here, but that's fine, we still return true    */
                                    /*   so that current thread will also examine extended data.   */
}


/*----------------------------------------------------------------------*
 *                                                                      *
 *   udata_setCommonData                                                *
 *                                                                      *
 *----------------------------------------------------------------------*/
U_CAPI void U_EXPORT2
udata_setCommonData(const void *data, UErrorCode *pErrorCode) {
    UDataMemory dataMemory;

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

    if(data==NULL) {
        *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
        return;
    }

    /* do we already have common ICU data set? */
    if(gCommonICUData != NULL) {
        *pErrorCode=U_USING_DEFAULT_ERROR;
        return;
    }

    /* set the data pointer and test for validity */
    UDataMemory_init(&dataMemory);
    UDataMemory_setData(&dataMemory, data);
    udata_checkCommonData(&dataMemory, pErrorCode);
    if (U_FAILURE(*pErrorCode)) {return;}

    /* we have good data */
    /* Set it up as the ICU Common Data.  */
    setCommonICUData(&dataMemory, NULL, TRUE, pErrorCode);
}


/*---------------------------------------------------------------------------
 *
 *  udata_setAppData
 *
 *---------------------------------------------------------------------------- */
U_CAPI void U_EXPORT2
udata_setAppData(const char *path, const void *data, UErrorCode *err)
{
    UDataMemory     udm;

    if(err==NULL || U_FAILURE(*err)) {
        return;
    }
    if(data==NULL) {
        *err=U_ILLEGAL_ARGUMENT_ERROR;
        return;
    }

    UDataMemory_init(&udm);
    udm.pHeader = data;
    udata_checkCommonData(&udm, err);
    udata_cacheDataItem(path, &udm, err);
}

/*----------------------------------------------------------------------------*
 *                                                                            *
 *  checkDataItem     Given a freshly located/loaded data item, either        *
 *                    an entry in a common file or a separately loaded file,  *
 *                    sanity check its header, and see if the data is         *
 *                    acceptable to the app.                                  *
 *                    If the data is good, create and return a UDataMemory    *
 *                    object that can be returned to the application.         *
 *                    Return NULL on any sort of failure.                     *
 *                                                                            *
 *----------------------------------------------------------------------------*/
static UDataMemory *
checkDataItem
(
 const DataHeader         *pHeader,         /* The data item to be checked.                */
 UDataMemoryIsAcceptable  *isAcceptable,    /* App's call-back function                    */
 void                     *context,         /*   pass-thru param for above.                */
 const char               *type,            /*   pass-thru param for above.                */
 const char               *name,            /*   pass-thru param for above.                */
 UErrorCode               *nonFatalErr,     /* Error code if this data was not acceptable  */
                                            /*   but openChoice should continue with       */
                                            /*   trying to get data from fallback path.    */
 UErrorCode               *fatalErr         /* Bad error, caller should return immediately */
 )
{
    UDataMemory  *rDataMem = NULL;          /* the new UDataMemory, to be returned.        */

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

    if(pHeader->dataHeader.magic1==0xda &&
        pHeader->dataHeader.magic2==0x27 &&
        pHeader->info.isBigEndian==U_IS_BIG_ENDIAN &&
        (isAcceptable==NULL || isAcceptable(context, type, name, &pHeader->info))
        ) {
        rDataMem=UDataMemory_createNewInstance(fatalErr);
        if (U_FAILURE(*fatalErr)) {
            return NULL;
        }
        rDataMem->pHeader = pHeader;
    } else {
        /* the data is not acceptable, look further */
        /* If we eventually find something good, this errorcode will be */
        /*    cleared out.                                              */
        *nonFatalErr=U_INVALID_FORMAT_ERROR;
    }
    return rDataMem;
}


/*
 *  A note on the ownership of Mapped Memory
 *
 *  For common format files, ownership resides with the UDataMemory object
 *    that lives in the cache of opened common data.  These UDataMemorys are private
 *    to the udata implementation, and are never seen directly by users.
 *
 *    The UDataMemory objects returned to users will have the address of some desired
 *    data within the mapped region, but they wont have the mapping info itself, and thus
 *    won't cause anything to be removed from memory when they are closed.
 *
 *  For individual data files, the UDataMemory returned to the user holds the
 *  information necessary to unmap the data on close.  If the user independently
 *  opens the same data file twice, two completely independent mappings will be made.
 *  (There is no cache of opened data items from individual files, only a cache of
 *   opened Common Data files, that is, files containing a collection of data items.)
 *
 *  For common data passed in from the user via udata_setAppData() or
 *  udata_setCommonData(), ownership remains with the user.
 *
 *  UDataMemory objects themselves, as opposed to the memory they describe,
 *  can be anywhere - heap, stack/local or global.
 *  They have a flag to indicate when they're heap allocated and thus
 *  must be deleted when closed.
 */


/*----------------------------------------------------------------------------*
 *                                                                            *
 * main data loading functions                                                *
 *                                                                            *
 *----------------------------------------------------------------------------*/
static UDataMemory *
doOpenChoice(const char *path, const char *type, const char *name,
             UDataMemoryIsAcceptable *isAcceptable, void *context,
             UErrorCode *pErrorCode)
{
    UDataPathIterator iter;
    const char *pathBuffer;
    int32_t pathLen;

    char                tocEntryName[100];
    char                oldStylePath[1024];
    char                oldStylePathBasename[100];
    const char         *dataPath;

    const char         *tocEntrySuffix;
    UDataMemory         dataMemory;
    UDataMemory        *pCommonData;
    UDataMemory        *pEntryData;
    const DataHeader   *pHeader;
    const char         *inBasename;
    UErrorCode          errorCode=U_ZERO_ERROR;
    UBool               isICUData= (UBool)(path==NULL);
    /* Make up a full mame by appending the type to the supplied
     *  name, assuming that a type was supplied.
     */

    /* prepend the package */
    uprv_strcpy(tocEntryName, packageNameFromPath(path));

    tocEntrySuffix = tocEntryName+uprv_strlen(tocEntryName); /* suffix starts here */

    uprv_strcat(tocEntryName, "_");

    uprv_strcat(tocEntryName, name);
    if(type!=NULL && *type!=0) {
        uprv_strcat(tocEntryName, ".");
        uprv_strcat(tocEntryName, type);
    }

#ifdef UDATA_DEBUG
    fprintf(stderr, " tocEntryName = %s\n", tocEntryName);
#endif    


    /* the data was not found in the common data,  look further, */
    /* try to get an individual data file */
    /* === basename=uprv_computeDirPath(path, pathBuffer); === */
    if(path == NULL) {
        path = COMMON_DATA_NAME;
        inBasename = COMMON_DATA_NAME;
    } else {
        if(isICUData) {
            inBasename=COMMON_DATA_NAME;
        } else {
            inBasename=findBasename(path);
        }
    }

    /************************ Begin loop looking for ind. files ***************/
#ifdef UDATA_DEBUG
    fprintf(stderr, "IND: inBasename = %s\n", inBasename);
#endif

    /* Deal with a null basename */
    if( (*inBasename==0) && (uprv_strlen(path) > 3) ) {
        /* the purpose of this exercise is to turn  /tmp/foo/bar/  into
           path=  /tmp/foo/bar/bar   and basename= bar 
           (i.e. /tmp/foo/bar/bar.dat  or /tmp/foo/bar/bar_en_US.res )
        */

        char *rightSlash;
        uprv_strcpy(oldStylePath, path);
        oldStylePath[uprv_strlen(path)-1]=0; /* chop off trailing slash */
        
        rightSlash = (char*)uprv_strrchr(oldStylePath, U_FILE_SEP_CHAR);
        if(rightSlash != NULL) {
            rightSlash++;
            inBasename = uprv_strcpy(oldStylePathBasename, rightSlash);
            uprv_strcat(oldStylePath, U_FILE_SEP_STRING);
            uprv_strcat(oldStylePath, inBasename);  /* one more time, for the base name */
            path = oldStylePath;
        } else {
            *pErrorCode = U_FILE_ACCESS_ERROR;  /* hopelessly bad case */
            return NULL;
        }
    }
    /* End of dealing with a null basename */

    dataPath = u_getDataDirectory();

    /* #1 look in ind. files ================================== */
    /* init path iterator for individual files */
    udata_pathiter_init(&iter, u_getDataDirectory(), path, tocEntrySuffix, FALSE);
    
    while((pathBuffer = udata_pathiter_next(&iter, &pathLen)))
    {
#ifdef UDATA_DEBUG
        fprintf(stderr, "UDATA: trying individual file %s\n", pathBuffer);
#endif
        if( uprv_mapFile(&dataMemory, pathBuffer) ||
            (inBasename!=pathBuffer && uprv_mapFile(&dataMemory, inBasename)))
        {
            pEntryData = checkDataItem(dataMemory.pHeader, isAcceptable, context, type, name, &errorCode, pErrorCode);
            if (pEntryData != NULL) {
                /* Data is good.
                 *  Hand off ownership of the backing memory to the user's UDataMemory.
                 *  and return it.   */
                pEntryData->mapAddr = dataMemory.mapAddr;
                pEntryData->map     = dataMemory.map;
                
#ifdef UDATA_DEBUG
                fprintf(stderr, "** Mapped file: %s\n", pathBuffer);
#endif
                return pEntryData;
            }
            
            /* the data is not acceptable, or some error occured.  Either way, unmap the memory */
            udata_close(&dataMemory);
            
            /* If we had a nasty error, bail out completely.  */
            if (U_FAILURE(*pErrorCode)) {
                return NULL;
            }
            
            /* Otherwise remember that we found data but didn't like it for some reason  */
            errorCode=U_INVALID_FORMAT_ERROR;
        }
#ifdef UDATA_DEBUG
        fprintf(stderr, "%s\n", UDataMemory_isLoaded(&dataMemory)?"LOADED":"not loaded");
#endif
    }

    /* #2 */

    /* try to get common data.  The loop is for platforms such as the 390 that do
     *  not initially load the full set of ICU data.  If the lookup of an ICU data item
     *  fails, the full (but slower to load) set is loaded, the and the loop repeats,
     *  trying the lookup again.  Once the full set of ICU data is loaded, the loop wont
     *  repeat because the full set will be checked the first time through.
     *
     *  The loop also handles the fallback to a .dat file if the application linked
     *   to the stub data library rather than a real library.
     */
    for (;;) {
        pCommonData=openCommonData(path, isICUData, &errorCode); /** search for pkg **/

        if(U_SUCCESS(errorCode)) {
            /* look up the data piece in the common data */
            pHeader=pCommonData->vFuncs->Lookup(pCommonData, tocEntryName, &errorCode);
#ifdef UDATA_DEBUG
            fprintf(stderr, "pHeader=%p\n", pHeader);
#endif
            if(pHeader!=NULL) {
                pEntryData = checkDataItem(pHeader, isAcceptable, context, type, name, &errorCode, pErrorCode);
#ifdef UDATA_DEBUG
            fprintf(stderr, "pEntryData=%p\n", pEntryData);
#endif
                if (U_FAILURE(*pErrorCode)) {
                    return NULL;
                }
                if (pEntryData != NULL) {
                    return pEntryData;
                }
            }
        }
        /* Data wasn't found.  If we were looking for an ICUData item and there is
         * more data available, load it and try again,
         * otherwise break out of this loop. */
        if (!(isICUData && pCommonData && extendICUData(pCommonData, &errorCode))) {
            break;
        }
    };

    /* data not found */
    if(U_SUCCESS(*pErrorCode)) {
        if(U_SUCCESS(errorCode)) {
            /* file not found */
            *pErrorCode=U_FILE_ACCESS_ERROR;
        } else {
            /* entry point not found or rejected */
            *pErrorCode=errorCode;
        }
    }
    return NULL;
}


/* API ---------------------------------------------------------------------- */

U_CAPI UDataMemory * U_EXPORT2
udata_open(const char *path, const char *type, const char *name,
           UErrorCode *pErrorCode) {
#ifdef UDATA_DEBUG
    fprintf(stderr, "udata_open(): Opening: %s . %s\n", name, type);
    fflush(stderr);
#endif

    if(pErrorCode==NULL || U_FAILURE(*pErrorCode)) {
        return NULL;
    } else if(name==NULL || *name==0) {
        *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
        return NULL;
    } else {
        return doOpenChoice(path, type, name, NULL, NULL, pErrorCode);
    }
}


U_CAPI UDataMemory * U_EXPORT2
udata_openChoice(const char *path, const char *type, const char *name,
                 UDataMemoryIsAcceptable *isAcceptable, void *context,
                 UErrorCode *pErrorCode) {
#ifdef UDATA_DEBUG
  fprintf(stderr, "udata_openChoice(): Opening: %s . %s\n", name, type);fflush(stderr);
#endif

    if(pErrorCode==NULL || U_FAILURE(*pErrorCode)) {
        return NULL;
    } else if(name==NULL || *name==0 || isAcceptable==NULL) {
        *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
        return NULL;
    } else {
        return doOpenChoice(path, type, name, isAcceptable, context, pErrorCode);
    }
}


U_CAPI void U_EXPORT2
udata_getInfo(UDataMemory *pData, UDataInfo *pInfo) {
    if(pInfo!=NULL) {
        if(pData!=NULL && pData->pHeader!=NULL) {
            const UDataInfo *info=&pData->pHeader->info;
            if(pInfo->size>info->size) {
                pInfo->size=info->size;
            }
            uprv_memcpy((uint16_t *)pInfo+1, (uint16_t *)info+1, pInfo->size-2);
        } else {
            pInfo->size=0;
        }
    }
}