int LZ4_compress_fast_continue()

in lz4.cpp [1707:1783]

• 56 lines of code
• 17 McCabe index (conditional complexity)

int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream,
                                const char* source, char* dest,
                                int inputSize, int maxOutputSize,
                                int acceleration)
{
    const tableType_t tableType = byU32;
    LZ4_stream_t_internal* const streamPtr = &LZ4_stream->internal_donotuse;
    const char* dictEnd = streamPtr->dictSize ? (const char*)streamPtr->dictionary + streamPtr->dictSize : NULL;

    DEBUGLOG(5, "LZ4_compress_fast_continue (inputSize=%i, dictSize=%u)", inputSize, streamPtr->dictSize);

    LZ4_renormDictT(streamPtr, inputSize);   /* fix index overflow */
    if (acceleration < 1) acceleration = LZ4_ACCELERATION_DEFAULT;
    if (acceleration > LZ4_ACCELERATION_MAX) acceleration = LZ4_ACCELERATION_MAX;

    /* invalidate tiny dictionaries */
    if ( (streamPtr->dictSize < 4)     /* tiny dictionary : not enough for a hash */
      && (dictEnd != source)           /* prefix mode */
      && (inputSize > 0)               /* tolerance : don't lose history, in case next invocation would use prefix mode */
      && (streamPtr->dictCtx == NULL)  /* usingDictCtx */
      ) {
        DEBUGLOG(5, "LZ4_compress_fast_continue: dictSize(%u) at addr:%p is too small", streamPtr->dictSize, streamPtr->dictionary);
        /* remove dictionary existence from history, to employ faster prefix mode */
        streamPtr->dictSize = 0;
        streamPtr->dictionary = (const BYTE*)source;
        dictEnd = source;
    }

    /* Check overlapping input/dictionary space */
    {   const char* const sourceEnd = source + inputSize;
        if ((sourceEnd > (const char*)streamPtr->dictionary) && (sourceEnd < dictEnd)) {
            streamPtr->dictSize = (U32)(dictEnd - sourceEnd);
            if (streamPtr->dictSize > 64 KB) streamPtr->dictSize = 64 KB;
            if (streamPtr->dictSize < 4) streamPtr->dictSize = 0;
            streamPtr->dictionary = (const BYTE*)dictEnd - streamPtr->dictSize;
        }
    }

    /* prefix mode : source data follows dictionary */
    if (dictEnd == source) {
        if ((streamPtr->dictSize < 64 KB) && (streamPtr->dictSize < streamPtr->currentOffset))
            return LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, withPrefix64k, dictSmall, acceleration);
        else
            return LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, withPrefix64k, noDictIssue, acceleration);
    }

    /* external dictionary mode */
    {   int result;
        if (streamPtr->dictCtx) {
            /* We depend here on the fact that dictCtx'es (produced by
             * LZ4_loadDict) guarantee that their tables contain no references
             * to offsets between dictCtx->currentOffset - 64 KB and
             * dictCtx->currentOffset - dictCtx->dictSize. This makes it safe
             * to use noDictIssue even when the dict isn't a full 64 KB.
             */
            if (inputSize > 4 KB) {
                /* For compressing large blobs, it is faster to pay the setup
                 * cost to copy the dictionary's tables into the active context,
                 * so that the compression loop is only looking into one table.
                 */
                LZ4_memcpy(streamPtr, streamPtr->dictCtx, sizeof(*streamPtr));
                result = LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, usingExtDict, noDictIssue, acceleration);
            } else {
                result = LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, usingDictCtx, noDictIssue, acceleration);
            }
        } else {  /* small data <= 4 KB */
            if ((streamPtr->dictSize < 64 KB) && (streamPtr->dictSize < streamPtr->currentOffset)) {
                result = LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, usingExtDict, dictSmall, acceleration);
            } else {
                result = LZ4_compress_generic(streamPtr, source, dest, inputSize, NULL, maxOutputSize, limitedOutput, tableType, usingExtDict, noDictIssue, acceleration);
            }
        }
        streamPtr->dictionary = (const BYTE*)source;
        streamPtr->dictSize = (U32)inputSize;
        return result;
    }
}