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Reduce streaming decompression memory by (128KB - blockSizeMax) #3616

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Apr 17, 2023
Merged

Reduce streaming decompression memory by (128KB - blockSizeMax) #3616

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21 changes: 16 additions & 5 deletions lib/decompress/zstd_decompress.c
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Original file line number Diff line number Diff line change
Expand Up @@ -265,6 +265,7 @@ static void ZSTD_initDCtx_internal(ZSTD_DCtx* dctx)
#endif
dctx->noForwardProgress = 0;
dctx->oversizedDuration = 0;
dctx->isFrameDecompression = 1;
#if DYNAMIC_BMI2
dctx->bmi2 = ZSTD_cpuSupportsBmi2();
#endif
Expand Down Expand Up @@ -1003,7 +1004,8 @@ static size_t ZSTD_decompressFrame(ZSTD_DCtx* dctx,
switch(blockProperties.blockType)
{
case bt_compressed:
decodedSize = ZSTD_decompressBlock_internal(dctx, op, (size_t)(oBlockEnd-op), ip, cBlockSize, /* frame */ 1, not_streaming);
assert(dctx->isFrameDecompression == 1);
decodedSize = ZSTD_decompressBlock_internal(dctx, op, (size_t)(oBlockEnd-op), ip, cBlockSize, not_streaming);
break;
case bt_raw :
/* Use oend instead of oBlockEnd because this function is safe to overlap. It uses memmove. */
Expand Down Expand Up @@ -1319,7 +1321,8 @@ size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, c
{
case bt_compressed:
DEBUGLOG(5, "ZSTD_decompressContinue: case bt_compressed");
rSize = ZSTD_decompressBlock_internal(dctx, dst, dstCapacity, src, srcSize, /* frame */ 1, is_streaming);
assert(dctx->isFrameDecompression == 1);
rSize = ZSTD_decompressBlock_internal(dctx, dst, dstCapacity, src, srcSize, is_streaming);
dctx->expected = 0; /* Streaming not supported */
break;
case bt_raw :
Expand Down Expand Up @@ -1548,6 +1551,7 @@ size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx)
dctx->litEntropy = dctx->fseEntropy = 0;
dctx->dictID = 0;
dctx->bType = bt_reserved;
dctx->isFrameDecompression = 1;
ZSTD_STATIC_ASSERT(sizeof(dctx->entropy.rep) == sizeof(repStartValue));
ZSTD_memcpy(dctx->entropy.rep, repStartValue, sizeof(repStartValue)); /* initial repcodes */
dctx->LLTptr = dctx->entropy.LLTable;
Expand Down Expand Up @@ -1911,6 +1915,7 @@ size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset)
|| (reset == ZSTD_reset_session_and_parameters) ) {
dctx->streamStage = zdss_init;
dctx->noForwardProgress = 0;
dctx->isFrameDecompression = 1;
}
if ( (reset == ZSTD_reset_parameters)
|| (reset == ZSTD_reset_session_and_parameters) ) {
Expand All @@ -1929,9 +1934,15 @@ size_t ZSTD_sizeof_DStream(const ZSTD_DStream* dctx)

size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize)
{
size_t const blockSize = (size_t) MIN(windowSize, ZSTD_BLOCKSIZE_MAX);
/* space is needed to store the litbuffer after the output of a given block without stomping the extDict of a previous run, as well as to cover both windows against wildcopy*/
unsigned long long const neededRBSize = windowSize + blockSize + ZSTD_BLOCKSIZE_MAX + (WILDCOPY_OVERLENGTH * 2);
size_t const blockSize = (size_t)MIN(windowSize, ZSTD_BLOCKSIZE_MAX);
/* We need blockSize + WILDCOPY_OVERLENGTH worth of buffer so that if a block
* ends at windowSize + WILDCOPY_OVERLENGTH + 1 bytes, we can start writing
* the block at the beginning of the output buffer, and maintain a full window.
*
* We need another blockSize worth of buffer so that we can store split
* literals at the end of the block without overwriting the extDict window.
*/
unsigned long long const neededRBSize = windowSize + (blockSize * 2) + (WILDCOPY_OVERLENGTH * 2);
unsigned long long const neededSize = MIN(frameContentSize, neededRBSize);
size_t const minRBSize = (size_t) neededSize;
RETURN_ERROR_IF((unsigned long long)minRBSize != neededSize,
Expand Down
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