Skip to content

Commit

Permalink
ZSTD_frameHeaderSize_prefix (#340), as result of ZSTD_initStream
Browse files Browse the repository at this point in the history
  • Loading branch information
@Cyan4973
Cyan4973 committed Sep 5, 2016
1 parent 7bdfcea commit 7c83dfd
Show file tree
Hide file tree
Showing 2 changed files with 23 additions and 22 deletions.
41 changes: 20 additions & 21 deletions lib/decompress/zstd_decompress.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -136,7 +136,7 @@ size_t ZSTD_estimateDCtxSize(void) { return sizeof(ZSTD_DCtx); }

size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx)
{
dctx->expected = ZSTD_frameHeaderSize_min;
dctx->expected = ZSTD_frameHeaderSize_prefix;
dctx->stage = ZSTDds_getFrameHeaderSize;
dctx->previousDstEnd = NULL;
dctx->base = NULL;
Expand Down Expand Up @@ -190,16 +190,16 @@ void ZSTD_copyDCtx(ZSTD_DCtx* dstDCtx, const ZSTD_DCtx* srcDCtx)
/* See compression format details in : zstd_compression_format.md */

/** ZSTD_frameHeaderSize() :
* srcSize must be >= ZSTD_frameHeaderSize_min.
* srcSize must be >= ZSTD_frameHeaderSize_prefix.
* @return : size of the Frame Header */
static size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize)
{
if (srcSize < ZSTD_frameHeaderSize_min) return ERROR(srcSize_wrong);
if (srcSize < ZSTD_frameHeaderSize_prefix) return ERROR(srcSize_wrong);
{ BYTE const fhd = ((const BYTE*)src)[4];
U32 const dictID= fhd & 3;
U32 const singleSegment = (fhd >> 5) & 1;
U32 const fcsId = fhd >> 6;
return ZSTD_frameHeaderSize_min + !singleSegment + ZSTD_did_fieldSize[dictID] + ZSTD_fcs_fieldSize[fcsId]
return ZSTD_frameHeaderSize_prefix + !singleSegment + ZSTD_did_fieldSize[dictID] + ZSTD_fcs_fieldSize[fcsId]
+ (singleSegment && !fcsId);
}
}
Expand All @@ -214,7 +214,7 @@ size_t ZSTD_getFrameParams(ZSTD_frameParams* fparamsPtr, const void* src, size_t
{
const BYTE* ip = (const BYTE*)src;

if (srcSize < ZSTD_frameHeaderSize_min) return ZSTD_frameHeaderSize_min;
if (srcSize < ZSTD_frameHeaderSize_prefix) return ZSTD_frameHeaderSize_prefix;
if (MEM_readLE32(src) != ZSTD_MAGICNUMBER) {
if ((MEM_readLE32(src) & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) {
if (srcSize < ZSTD_skippableHeaderSize) return ZSTD_skippableHeaderSize; /* magic number + skippable frame length */
Expand Down Expand Up @@ -863,7 +863,7 @@ static size_t ZSTD_decompressFrame(ZSTD_DCtx* dctx,
if (srcSize < ZSTD_frameHeaderSize_min+ZSTD_blockHeaderSize) return ERROR(srcSize_wrong);

/* Frame Header */
{ size_t const frameHeaderSize = ZSTD_frameHeaderSize(src, ZSTD_frameHeaderSize_min);
{ size_t const frameHeaderSize = ZSTD_frameHeaderSize(src, ZSTD_frameHeaderSize_prefix);
size_t result;
if (ZSTD_isError(frameHeaderSize)) return frameHeaderSize;
if (srcSize < frameHeaderSize+ZSTD_blockHeaderSize) return ERROR(srcSize_wrong);
Expand Down Expand Up @@ -1013,26 +1013,26 @@ size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, c
switch (dctx->stage)
{
case ZSTDds_getFrameHeaderSize :
if (srcSize != ZSTD_frameHeaderSize_min) return ERROR(srcSize_wrong); /* impossible */
if ((MEM_readLE32(src) & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) {
memcpy(dctx->headerBuffer, src, ZSTD_frameHeaderSize_min);
dctx->expected = ZSTD_skippableHeaderSize - ZSTD_frameHeaderSize_min; /* magic number + skippable frame length */
if (srcSize != ZSTD_frameHeaderSize_prefix) return ERROR(srcSize_wrong); /* impossible */
if ((MEM_readLE32(src) & 0xFFFFFFF0U) == ZSTD_MAGIC_SKIPPABLE_START) { /* skippable frame */
memcpy(dctx->headerBuffer, src, ZSTD_frameHeaderSize_prefix);
dctx->expected = ZSTD_skippableHeaderSize - ZSTD_frameHeaderSize_prefix; /* magic number + skippable frame length */
dctx->stage = ZSTDds_decodeSkippableHeader;
return 0;
}
dctx->headerSize = ZSTD_frameHeaderSize(src, ZSTD_frameHeaderSize_min);
dctx->headerSize = ZSTD_frameHeaderSize(src, ZSTD_frameHeaderSize_prefix);
if (ZSTD_isError(dctx->headerSize)) return dctx->headerSize;
memcpy(dctx->headerBuffer, src, ZSTD_frameHeaderSize_min);
if (dctx->headerSize > ZSTD_frameHeaderSize_min) {
dctx->expected = dctx->headerSize - ZSTD_frameHeaderSize_min;
memcpy(dctx->headerBuffer, src, ZSTD_frameHeaderSize_prefix);
if (dctx->headerSize > ZSTD_frameHeaderSize_prefix) {
dctx->expected = dctx->headerSize - ZSTD_frameHeaderSize_prefix;
dctx->stage = ZSTDds_decodeFrameHeader;
return 0;
}
dctx->expected = 0; /* not necessary to copy more */

case ZSTDds_decodeFrameHeader:
{ size_t result;
memcpy(dctx->headerBuffer + ZSTD_frameHeaderSize_min, src, dctx->expected);
memcpy(dctx->headerBuffer + ZSTD_frameHeaderSize_prefix, src, dctx->expected);
result = ZSTD_decodeFrameHeader(dctx, dctx->headerBuffer, dctx->headerSize);
if (ZSTD_isError(result)) return result;
dctx->expected = ZSTD_blockHeaderSize;
Expand Down Expand Up @@ -1110,7 +1110,7 @@ size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, c
return 0;
}
case ZSTDds_decodeSkippableHeader:
{ memcpy(dctx->headerBuffer + ZSTD_frameHeaderSize_min, src, dctx->expected);
{ memcpy(dctx->headerBuffer + ZSTD_frameHeaderSize_prefix, src, dctx->expected);
dctx->expected = MEM_readLE32(dctx->headerBuffer + 4);
dctx->stage = ZSTDds_skipFrame;
return 0;
Expand Down Expand Up @@ -1387,7 +1387,7 @@ size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t di
zds->dictSize = dictSize;
}
zds->legacyVersion = 0;
return 0;
return ZSTD_frameHeaderSize_prefix;
}

size_t ZSTD_initDStream(ZSTD_DStream* zds)
Expand Down Expand Up @@ -1468,19 +1468,18 @@ size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inB
memcpy(zds->headerBuffer + zds->lhSize, ip, iend-ip);
zds->lhSize += iend-ip;
input->pos = input->size;
return (hSize - zds->lhSize) + ZSTD_blockHeaderSize; /* remaining header bytes + next block header */
return (MAX(ZSTD_frameHeaderSize_min, hSize) - zds->lhSize) + ZSTD_blockHeaderSize; /* remaining header bytes + next block header */
}
memcpy(zds->headerBuffer + zds->lhSize, ip, toLoad); zds->lhSize = hSize; ip += toLoad;
break;
} }

/* Consume header */
ZSTD_decompressBegin_usingDict(zds->zd, zds->dictContent, zds->dictSize);
{ size_t const h1Size = ZSTD_nextSrcSizeToDecompress(zds->zd); /* == ZSTD_frameHeaderSize_min */
{ size_t const h1Size = ZSTD_nextSrcSizeToDecompress(zds->zd); /* == ZSTD_frameHeaderSize_prefix */
size_t const h1Result = ZSTD_decompressContinue(zds->zd, NULL, 0, zds->headerBuffer, h1Size);
if (ZSTD_isError(h1Result)) return h1Result; /* should not happen : already checked */
if (h1Size < zds->lhSize) { /* long header */
size_t const h2Size = ZSTD_nextSrcSizeToDecompress(zds->zd);
{ size_t const h2Size = ZSTD_nextSrcSizeToDecompress(zds->zd);
size_t const h2Result = ZSTD_decompressContinue(zds->zd, NULL, 0, zds->headerBuffer+h1Size, h2Size);
if (ZSTD_isError(h2Result)) return h2Result;
} }
Expand Down
4 changes: 3 additions & 1 deletion lib/zstd.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -248,6 +248,7 @@ ZSTDLIB_API size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
*
* Use ZSTD_initDStream() to start a new decompression operation,
* or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
* @return : recommended first input size
*
* Use ZSTD_decompressStream() repetitively to consume your input.
* The function will update both `pos` fields.
Expand Down Expand Up @@ -303,7 +304,8 @@ ZSTDLIB_API size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* outp
#define ZSTD_TARGETLENGTH_MAX 999

#define ZSTD_FRAMEHEADERSIZE_MAX 18 /* for static allocation */
static const size_t ZSTD_frameHeaderSize_min = 5;
static const size_t ZSTD_frameHeaderSize_prefix = 5;
static const size_t ZSTD_frameHeaderSize_min = 6;
static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
static const size_t ZSTD_skippableHeaderSize = 8; /* magic number + skippable frame length */

Expand Down

0 comments on commit 7c83dfd

Please sign in to comment.