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decompress: decode legacy frames whose header is split across calls #4812

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13 changes: 11 additions & 2 deletions lib/decompress/zstd_decompress.c
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Original file line number Diff line number Diff line change
Expand Up @@ -465,6 +465,9 @@ size_t ZSTD_getFrameHeader_advanced(ZSTD_FrameHeader* zfhPtr, const void* src, s
assert(src != NULL);
ZSTD_memcpy(hbuf, src, toCopy);
if ( MEM_readLE32(hbuf) != ZSTD_MAGICNUMBER ) {
#if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT>=1)
if (ZSTD_isLegacy(hbuf, 4)) return minInputSize; /* legacy frames are supported too */
#endif
/* not a zstd frame : let's check if it's a skippable frame */
MEM_writeLE32(hbuf, ZSTD_MAGIC_SKIPPABLE_START);
ZSTD_memcpy(hbuf, src, toCopy);
Expand Down Expand Up @@ -2140,7 +2143,7 @@ size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inB
}
if (ZSTD_isError(hSize)) {
#if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT>=1)
U32 const legacyVersion = ZSTD_isLegacy(istart, iend-istart);
U32 const legacyVersion = ZSTD_isLegacy(zds->headerBuffer, zds->lhSize);
if (legacyVersion) {
ZSTD_DDict const* const ddict = ZSTD_getDDict(zds);
const void* const dict = ddict ? ZSTD_DDict_dictContent(ddict) : NULL;
Expand All @@ -2152,7 +2155,13 @@ size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inB
zds->previousLegacyVersion, legacyVersion,
dict, dictSize), "");
zds->legacyVersion = zds->previousLegacyVersion = legacyVersion;
{ size_t const hint = ZSTD_decompressLegacyStream(zds->legacyContext, legacyVersion, output, input);
{ /* the frame header may have been buffered by previous calls : replay it first */
ZSTD_inBuffer header;
size_t hint;
header.src = zds->headerBuffer; header.size = zds->lhSize; header.pos = 0;
FORWARD_IF_ERROR(ZSTD_decompressLegacyStream(zds->legacyContext, legacyVersion, output, &header), "");
input->pos = (size_t)(ip - (const char*)(input->src));
hint = ZSTD_decompressLegacyStream(zds->legacyContext, legacyVersion, output, input);
if (hint==0) zds->streamStage = zdss_init; /* or stay in stage zdss_loadHeader */
return hint;
} }
Expand Down
17 changes: 12 additions & 5 deletions tests/legacy.c
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Original file line number Diff line number Diff line change
Expand Up @@ -156,8 +156,10 @@ static int testSimpleAPI(const char* compressed, size_t compressedSize,
}


/* @maxChunk : nb of bytes given to each ZSTD_decompressStream() call */
static int testStreamingAPI(const char* compressed, size_t compressedSize,
const char* expected, size_t expectedSize)
const char* expected, size_t expectedSize,
size_t maxChunk)
{
int error_code = 0;
size_t const outBuffSize = ZSTD_DStreamOutSize();
Expand All @@ -168,7 +170,6 @@ static int testStreamingAPI(const char* compressed, size_t compressedSize,
int needsInit = 1;

input.src = compressed;
input.size = compressedSize;

if (outBuff == NULL) {
DISPLAY("ERROR: Could not allocate memory\n");
Expand All @@ -182,13 +183,16 @@ static int testStreamingAPI(const char* compressed, size_t compressedSize,

while (1) {
ZSTD_outBuffer output = {outBuff, outBuffSize, 0};
input.size = (compressedSize - input.pos > maxChunk) ? input.pos + maxChunk : compressedSize;
if (needsInit) {
size_t const ret = ZSTD_initDStream(stream);
if (ZSTD_isError(ret)) {
DISPLAY("ERROR: ZSTD_initDStream: %s\n", ZSTD_getErrorName(ret));
error_code = 1;
break;
} }
}
needsInit = 0;
}

{ size_t const ret = ZSTD_decompressStream(stream, &output, &input);
if (ZSTD_isError(ret)) {
Expand All @@ -212,7 +216,7 @@ static int testStreamingAPI(const char* compressed, size_t compressedSize,
break;
}
outputPos += output.pos;
if (input.pos == input.size && output.pos < output.size) {
if (input.pos == compressedSize && output.pos < output.size) {
break;
}
}
Expand Down Expand Up @@ -297,7 +301,10 @@ int main(void)
/* all blocks being identical, the first @nbStreamFrames ones
* are what the streaming subset must decode to */
if (testStreamingAPI(streamable, streamableSize,
expected, blockSize * nbStreamFrames)) break;
expected, blockSize * nbStreamFrames, streamableSize)) break;
/* one byte at a time : frame headers arrive split across calls */
if (testStreamingAPI(streamable, streamableSize,
expected, blockSize * nbStreamFrames, 1)) break;
result = 0;
} while (0);

Expand Down