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Add a forward progress requirement bound to seekable streaming decompression

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This commit is contained in:
senhuang42 2020-12-02 12:24:16 -05:00
parent 6112b82526
commit 9db49a3989
1 changed files with 11 additions and 1 deletions
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12
contrib/seekable_format/zstdseek_decompress.c
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@ -79,6 +79,8 @@
#define MIN(a, b) ((a) < (b) ? (a) : (b)) #define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b)) #define MAX(a, b) ((a) > (b) ? (a) : (b))
#define ZSTD_SEEKABLE_NO_OUTPUT_PROGRESS_MAX 16
/* Special-case callbacks for FILE* and in-memory modes, so that we can treat /* Special-case callbacks for FILE* and in-memory modes, so that we can treat
* them the same way as the advanced API */ * them the same way as the advanced API */
static int ZSTD_seekable_read_FILE(void* opaque, void* buffer, size_t n) static int ZSTD_seekable_read_FILE(void* opaque, void* buffer, size_t n)
@ -380,6 +382,7 @@ size_t ZSTD_seekable_initAdvanced(ZSTD_seekable* zs, ZSTD_seekable_customFile sr
size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t len, unsigned long long offset) size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t len, unsigned long long offset)
{ {
U32 targetFrame = ZSTD_seekable_offsetToFrameIndex(zs, offset); U32 targetFrame = ZSTD_seekable_offsetToFrameIndex(zs, offset);
U32 noOutputProgressCount = 0;
do { do {
/* check if we can continue from a previous decompress job */ /* check if we can continue from a previous decompress job */
if (targetFrame != zs->curFrame || offset != zs->decompressedOffset) { if (targetFrame != zs->curFrame || offset != zs->decompressedOffset) {
@ -398,6 +401,7 @@ size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t len, unsign
size_t toRead; size_t toRead;
ZSTD_outBuffer outTmp; ZSTD_outBuffer outTmp;
size_t prevOutPos; size_t prevOutPos;
size_t forwardProgress;
if (zs->decompressedOffset < offset) { if (zs->decompressedOffset < offset) {
/* dummy decompressions until we get to the target offset */ /* dummy decompressions until we get to the target offset */
outTmp = (ZSTD_outBuffer){zs->outBuff, MIN(SEEKABLE_BUFF_SIZE, offset - zs->decompressedOffset), 0}; outTmp = (ZSTD_outBuffer){zs->outBuff, MIN(SEEKABLE_BUFF_SIZE, offset - zs->decompressedOffset), 0};
@ -415,7 +419,13 @@ size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t len, unsign
XXH64_update(&zs->xxhState, (BYTE*)outTmp.dst + prevOutPos, XXH64_update(&zs->xxhState, (BYTE*)outTmp.dst + prevOutPos,
outTmp.pos - prevOutPos); outTmp.pos - prevOutPos);
} }
zs->decompressedOffset += outTmp.pos - prevOutPos; forwardProgress = outTmp.pos - prevOutPos;
if (!forwardProgress && noOutputProgressCount++ > ZSTD_SEEKABLE_NO_OUTPUT_PROGRESS_MAX) {
return ERROR(seekableIO);
} else {
noOutputProgressCount = 0;
}
zs->decompressedOffset += forwardProgress;
if (toRead == 0) { if (toRead == 0) {
/* frame complete */ /* frame complete */