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Avoid DictSmall Checks By Strategically Bumping CurrentOffset

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This commit is contained in:
W. Felix Handte 2018-03-05 11:59:22 -05:00
parent 1c4601d643
commit d571d0cdba
1 changed files with 23 additions and 22 deletions
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45
lib/lz4.c
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@ -546,7 +546,10 @@ LZ4_FORCE_INLINE void LZ4_resetTable(
cctx->currentOffset = 0;
cctx->tableType = unusedTable;
}
if (dictDirective == usingExtDictCtx && cctx->currentOffset == 0) {
if (dictDirective == usingExtDictCtx &&
tableType != byPtr &&
cctx->currentOffset == 0)
{
cctx->currentOffset = 1;
}
}
@ -842,11 +845,8 @@ int LZ4_compress_fast_safeExtState(void* state, const char* source, char* dest,
} else {
const tableType_t tableType = (sizeof(void*)==8) ? byU32 : byPtr;
LZ4_resetTable(ctx, inputSize, tableType, noDict);
if (ctx->currentOffset) {
return LZ4_compress_generic(ctx, source, dest, inputSize, 0, notLimited, tableType, noDict, dictSmall, acceleration);
} else {
return LZ4_compress_generic(ctx, source, dest, inputSize, 0, notLimited, tableType, noDict, noDictIssue, acceleration);
}
ctx->currentOffset += 64 KB;
return LZ4_compress_generic(ctx, source, dest, inputSize, 0, notLimited, tableType, noDict, noDictIssue, acceleration);
}
} else {
if (inputSize < LZ4_64Klimit) {
@ -860,11 +860,8 @@ int LZ4_compress_fast_safeExtState(void* state, const char* source, char* dest,
} else {
const tableType_t tableType = (sizeof(void*)==8) ? byU32 : byPtr;
LZ4_resetTable(ctx, inputSize, tableType, noDict);
if (ctx->currentOffset) {
return LZ4_compress_generic(ctx, source, dest, inputSize, maxOutputSize, limitedOutput, tableType, noDict, dictSmall, acceleration);
} else {
return LZ4_compress_generic(ctx, source, dest, inputSize, maxOutputSize, limitedOutput, tableType, noDict, noDictIssue, acceleration);
}
ctx->currentOffset += 64 KB;
return LZ4_compress_generic(ctx, source, dest, inputSize, maxOutputSize, limitedOutput, tableType, noDict, noDictIssue, acceleration);
}
}
}
@ -1222,21 +1219,25 @@ int LZ4_compress_fast_continue (LZ4_stream_t* LZ4_stream, const char* source, ch
/* external dictionary mode */
{ int result;
if (streamPtr->dictCtx && inputSize < 2 KB) {
LZ4_resetTable(streamPtr, inputSize, tableType, usingExtDictCtx);
if ((streamPtr->dictCtx->dictSize < 64 KB) && (streamPtr->dictCtx->dictSize < streamPtr->currentOffset)) {
result = LZ4_compress_generic(streamPtr, source, dest, inputSize, maxOutputSize, limitedOutput, tableType, usingExtDictCtx, dictSmall, acceleration);
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 > 2 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 in one table.
*/
memcpy(streamPtr, streamPtr->dictCtx, sizeof(LZ4_stream_t));
result = LZ4_compress_generic(streamPtr, source, dest, inputSize, maxOutputSize, limitedOutput, tableType, usingExtDict, noDictIssue, acceleration);
} else {
LZ4_resetTable(streamPtr, inputSize, tableType, usingExtDictCtx);
result = LZ4_compress_generic(streamPtr, source, dest, inputSize, maxOutputSize, limitedOutput, tableType, usingExtDictCtx, noDictIssue, acceleration);
}
} else {
if (streamPtr->dictCtx) {
/* 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 in one table.
*/
memcpy(streamPtr, streamPtr->dictCtx, sizeof(LZ4_stream_t));
}
LZ4_resetTable(streamPtr, inputSize, tableType, usingExtDict);
if ((streamPtr->dictSize < 64 KB) && (streamPtr->dictSize < streamPtr->currentOffset)) {
result = LZ4_compress_generic(streamPtr, source, dest, inputSize, maxOutputSize, limitedOutput, tableType, usingExtDict, dictSmall, acceleration);