size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs, int compressionLevel, unsigned maxChunkSize);
+Seekable compression functions
size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs, int compressionLevel, int checksumFlag, unsigned maxChunkSize);
size_t ZSTD_seekable_compressStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
size_t ZSTD_seekable_endChunk(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output);
size_t ZSTD_seekable_endStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output);
diff --git a/examples/seekable_compression.c b/examples/seekable_compression.c
index 5ab36c3c..f4bceb10 100644
--- a/examples/seekable_compression.c
+++ b/examples/seekable_compression.c
@@ -68,7 +68,7 @@ static void compressFile_orDie(const char* fname, const char* outName, int cLeve
ZSTD_seekable_CStream* const cstream = ZSTD_seekable_createCStream();
if (cstream==NULL) { fprintf(stderr, "ZSTD_seekable_createCStream() error \n"); exit(10); }
- size_t const initResult = ZSTD_seekable_initCStream(cstream, cLevel, chunkSize);
+ size_t const initResult = ZSTD_seekable_initCStream(cstream, cLevel, 1, chunkSize);
if (ZSTD_isError(initResult)) { fprintf(stderr, "ZSTD_seekable_initCStream() error : %s \n", ZSTD_getErrorName(initResult)); exit(11); }
size_t read, toRead = buffInSize;
@@ -77,15 +77,16 @@ static void compressFile_orDie(const char* fname, const char* outName, int cLeve
while (input.pos < input.size) {
ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
toRead = ZSTD_seekable_compressStream(cstream, &output , &input); /* toRead is guaranteed to be <= ZSTD_CStreamInSize() */
- if (ZSTD_isError(toRead)) { fprintf(stderr, "ZSTD_compressStream() error : %s \n", ZSTD_getErrorName(toRead)); exit(12); }
+ if (ZSTD_isError(toRead)) { fprintf(stderr, "ZSTD_seekable_compressStream() error : %s \n", ZSTD_getErrorName(toRead)); exit(12); }
if (toRead > buffInSize) toRead = buffInSize; /* Safely handle case when `buffInSize` is manually changed to a value < ZSTD_CStreamInSize()*/
fwrite_orDie(buffOut, output.pos, fout);
}
}
- ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
while (1) {
+ ZSTD_outBuffer output = { buffOut, buffOutSize, 0 };
size_t const remainingToFlush = ZSTD_seekable_endStream(cstream, &output); /* close stream */
+ if (ZSTD_isError(remainingToFlush)) { fprintf(stderr, "ZSTD_seekable_endStream() error : %s \n", ZSTD_getErrorName(remainingToFlush)); exit(13); }
fwrite_orDie(buffOut, output.pos, fout);
if (!remainingToFlush) break;
}
@@ -123,4 +124,6 @@ int main(int argc, const char** argv) {
const char* const outFileName = createOutFilename_orDie(inFileName);
compressFile_orDie(inFileName, outFileName, 5, chunkSize);
}
+
+ return 0;
}
diff --git a/examples/seekable_decompression.c b/examples/seekable_decompression.c
index 97563c3d..641e0429 100644
--- a/examples/seekable_decompression.c
+++ b/examples/seekable_decompression.c
@@ -143,6 +143,7 @@ static void decompressFile_orDie(const char* fname, unsigned startOffset, unsign
toRead = result;
}
fwrite_orDie(buffOut, output.pos, fout);
+ if (toRead > buffInSize) toRead = buffInSize;
}
} while (result > 0);
@@ -171,5 +172,6 @@ int main(int argc, const char** argv)
unsigned const endOffset = (unsigned) atoi(argv[3]);
decompressFile_orDie(inFilename, startOffset, endOffset);
}
+
return 0;
}
diff --git a/lib/compress/zstdseek_compress.c b/lib/compress/zstdseek_compress.c
index 284724e5..f9e108af 100644
--- a/lib/compress/zstdseek_compress.c
+++ b/lib/compress/zstdseek_compress.c
@@ -39,6 +39,8 @@ struct ZSTD_seekable_CStream_s {
U32 maxChunkSize;
int checksumFlag;
+
+ int writingSeekTable;
};
ZSTD_seekable_CStream* ZSTD_seekable_createCStream()
@@ -52,6 +54,7 @@ ZSTD_seekable_CStream* ZSTD_seekable_createCStream()
zcs->cstream = ZSTD_createCStream();
if (zcs->cstream == NULL) goto failed1;
+ /* allocate some initial space */
{ size_t const CHUNKLOG_STARTING_CAPACITY = 16;
zcs->chunklog.entries =
malloc(sizeof(chunklogEntry_t) * CHUNKLOG_STARTING_CAPACITY);
@@ -70,7 +73,7 @@ failed1:
size_t ZSTD_seekable_freeCStream(ZSTD_seekable_CStream* zcs)
{
- if (zcs == NULL) return 0; /* support free on NULL */
+ if (zcs == NULL) return 0; /* support free on null */
ZSTD_freeCStream(zcs->cstream);
free(zcs->chunklog.entries);
free(zcs);
@@ -80,12 +83,14 @@ size_t ZSTD_seekable_freeCStream(ZSTD_seekable_CStream* zcs)
size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs,
int compressionLevel,
+ int checksumFlag,
U32 maxChunkSize)
{
zcs->chunklog.size = 0;
zcs->chunkCSize = 0;
zcs->chunkDSize = 0;
+ /* make sure maxChunkSize has a reasonable value */
if (maxChunkSize > ZSTD_SEEKABLE_MAX_CHUNK_DECOMPRESSED_SIZE) {
return ERROR(compressionParameter_unsupported);
}
@@ -94,11 +99,13 @@ size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs,
? maxChunkSize
: ZSTD_SEEKABLE_MAX_CHUNK_DECOMPRESSED_SIZE;
- zcs->checksumFlag = 0;
+ zcs->checksumFlag = checksumFlag;
if (zcs->checksumFlag) {
XXH64_reset(&zcs->xxhState, 0);
}
+ zcs->writingSeekTable = 0;
+
return ZSTD_initCStream(zcs->cstream, compressionLevel);
}
@@ -114,10 +121,13 @@ static size_t ZSTD_seekable_logChunk(ZSTD_seekable_CStream* zcs)
};
if (zcs->checksumFlag)
zcs->chunklog.entries[zcs->chunklog.size].checksum =
+ /* take lower 32 bits of digest */
XXH64_digest(&zcs->xxhState) & 0xFFFFFFFFU;
zcs->chunklog.size++;
+ /* grow the buffer if required */
if (zcs->chunklog.size == zcs->chunklog.capacity) {
+ /* exponential size increase for constant amortized runtime */
size_t const newCapacity = zcs->chunklog.capacity * 2;
chunklogEntry_t* const newEntries = realloc(zcs->chunklog.entries,
sizeof(chunklogEntry_t) * newCapacity);
@@ -134,6 +144,7 @@ static size_t ZSTD_seekable_logChunk(ZSTD_seekable_CStream* zcs)
size_t ZSTD_seekable_endChunk(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output)
{
size_t const prevOutPos = output->pos;
+ /* end the frame */
size_t ret = ZSTD_endStream(zcs->cstream, output);
zcs->chunkCSize += output->pos - prevOutPos;
@@ -165,6 +176,7 @@ size_t ZSTD_seekable_compressStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer*
inLen = MIN(inLen, (size_t)(zcs->maxChunkSize - zcs->chunkDSize));
+ /* if we haven't finished flushing the last chunk, don't start writing a new one */
if (inLen > 0) {
ZSTD_inBuffer inTmp = { inBase, inLen, 0 };
size_t const prevOutPos = output->pos;
@@ -184,8 +196,12 @@ size_t ZSTD_seekable_compressStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer*
}
if (zcs->maxChunkSize == zcs->chunkDSize) {
+ /* log the chunk and start over */
size_t const ret = ZSTD_seekable_endChunk(zcs, output);
if (ZSTD_isError(ret)) return ret;
+
+ /* get the client ready for the next chunk */
+ return (size_t)zcs->maxChunkSize;
}
return (size_t)(zcs->maxChunkSize - zcs->chunkDSize);
@@ -204,62 +220,78 @@ static size_t ZSTD_seekable_seekTableSize(ZSTD_seekable_CStream* zcs)
static size_t ZSTD_seekable_writeSeekTable(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output)
{
BYTE* op = (BYTE*) output->dst;
+ BYTE tmp[4]; /* so that we can work with buffers too small to write a whole word to */
/* repurpose
* zcs->chunkDSize: the current index in the table and
- * zcs->chunkCSize: the amount of the table written so far */
+ * zcs->chunkCSize: the amount of the table written so far
+ *
+ * This function is written this way so that if it has to return early
+ * because of a small buffer, it can keep going where it left off.
+ */
size_t const sizePerChunk = 8 + (zcs->checksumFlag?4:0);
- size_t const seekTableLen = ZSD_seekable_seekTableSize(zcs);
+ size_t const seekTableLen = ZSTD_seekable_seekTableSize(zcs);
- if (zcs->chunkCSize == 0) {
- if (output->size - output->pos < 4) return seekTableLen - zcs->chunkCSize;
- MEM_writeLE32(op + output->pos, ZSTD_MAGIC_SKIPPABLE_START);
- output->pos += 4;
- zcs->chunkCSize += 4;
- }
- if (zcs->chunkCSize == 4) {
- if (output->size - output->pos < 4) return seekTableLen - zcs->chunkCSize;
- MEM_writeLE32(op + output->pos, seekTableLen - ZSTD_skippableHeaderSize);
- output->pos += 4;
- zcs->chunkCSize += 4;
- }
+#define st_write32(x, o) \
+ do { \
+ if (zcs->chunkCSize < (o) + 4) { \
+ size_t const lenWrite = MIN(output->size - output->pos, \
+ (o) + 4 - zcs->chunkCSize); \
+ MEM_writeLE32(tmp, (x)); \
+ memcpy(op + output->pos, tmp + (zcs->chunkCSize - (o)), lenWrite); \
+ zcs->chunkCSize += lenWrite; \
+ output->pos += lenWrite; \
+ if (lenWrite < 4) return seekTableLen - zcs->chunkCSize; \
+ } \
+ } while (0)
+
+ st_write32(ZSTD_MAGIC_SKIPPABLE_START, 0);
+ st_write32(seekTableLen - ZSTD_skippableHeaderSize, 4);
while (zcs->chunkDSize < zcs->chunklog.size) {
- if (output->size - output->pos < sizePerChunk) return seekTableLen - zcs->chunkCSize;
- MEM_writeLE32(op + output->pos + 0, zcs->chunklog.entries[zcs->chunkDSize].cSize);
- MEM_writeLE32(op + output->pos + 4, zcs->chunklog.entries[zcs->chunkDSize].dSize);
+ st_write32(zcs->chunklog.entries[zcs->chunkDSize].cSize,
+ ZSTD_skippableHeaderSize + sizePerChunk * zcs->chunkDSize);
+ st_write32(zcs->chunklog.entries[zcs->chunkDSize].dSize,
+ ZSTD_skippableHeaderSize + sizePerChunk * zcs->chunkDSize + 4);
if (zcs->checksumFlag) {
- MEM_writeLE32(op + output->pos + 8, zcs->chunklog.entries[zcs->chunkDSize].checksum);
+ st_write32(zcs->chunklog.entries[zcs->chunkDSize].checksum,
+ ZSTD_skippableHeaderSize + sizePerChunk * zcs->chunkDSize + 8);
}
- output->pos += sizePerChunk;
- zcs->chunkCSize += sizePerChunk;
+
zcs->chunkDSize++;
}
- if (output->size - output->pos < ZSTD_seekTableFooterSize) return seekTableLen - zcs->chunkCSize;
- MEM_writeLE32(op + output->pos, zcs->chunklog.size);
- { BYTE sfd = 0;
+ st_write32(zcs->chunklog.size, seekTableLen - ZSTD_seekTableFooterSize);
+
+ if (output->size - output->pos < 1) return seekTableLen - zcs->chunkCSize;
+ if (zcs->chunkCSize < seekTableLen - 4) {
+ BYTE sfd = 0;
sfd |= (zcs->checksumFlag) << 7;
- op[output->pos + 4] = sfd;
+ op[output->pos] = sfd;
+ output->pos++;
+ zcs->chunkCSize++;
}
- MEM_writeLE32(op + output->pos + 5, ZSTD_SEEKABLE_MAGICNUMBER);
- output->pos += ZSTD_seekTableFooterSize;
- zcs->chunkCSize += ZSTD_seekTableFooterSize;
+ st_write32(ZSTD_SEEKABLE_MAGICNUMBER, seekTableLen - 4);
if (zcs->chunkCSize != seekTableLen) return ERROR(GENERIC);
return 0;
+
+#undef st_write32
}
size_t ZSTD_seekable_endStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output)
{
- if (zcs->chunkDSize) {
+ if (!zcs->writingSeekTable && zcs->chunkDSize) {
const size_t endChunk = ZSTD_seekable_endChunk(zcs, output);
+ if (ZSTD_isError(endChunk)) return endChunk;
/* return an accurate size hint */
- if (endChunk) return endChunk + ZSTD_seekable_seekTableLen(zcs);
+ if (endChunk) return endChunk + ZSTD_seekable_seekTableSize(zcs);
}
+ zcs->writingSeekTable = 1;
+
return ZSTD_seekable_writeSeekTable(zcs, output);
}
diff --git a/lib/decompress/zstdseek_decompress.c b/lib/decompress/zstdseek_decompress.c
index e76b4c61..5e303f26 100644
--- a/lib/decompress/zstdseek_decompress.c
+++ b/lib/decompress/zstdseek_decompress.c
@@ -28,6 +28,10 @@ typedef struct {
int checksumFlag;
} seekTable_t;
+/** ZSTD_seekable_offsetToChunk() :
+ * Performs a binary search to find the last chunk with a decompressed offset
+ * <= pos
+ * @return : the chunk's index */
static U32 ZSTD_seekable_offsetToChunk(const seekTable_t* table, U64 pos)
{
U32 lo = 0;
@@ -44,8 +48,9 @@ static U32 ZSTD_seekable_offsetToChunk(const seekTable_t* table, U64 pos)
return lo;
}
+/* Stream decompressor state machine stages */
enum ZSTD_seekable_DStream_stage {
- zsds_init,
+ zsds_init = 0,
zsds_seek,
zsds_decompress,
zsds_done,
@@ -75,6 +80,7 @@ ZSTD_seekable_DStream* ZSTD_seekable_createDStream(void)
if (zds == NULL) return NULL;
+ /* also initializes stage to zsds_init */
memset(zds, 0, sizeof(*zds));
zds->dstream = ZSTD_createDStream();
@@ -88,7 +94,7 @@ ZSTD_seekable_DStream* ZSTD_seekable_createDStream(void)
size_t ZSTD_seekable_freeDStream(ZSTD_seekable_DStream* zds)
{
- if (zds == NULL) return 0;
+ if (zds == NULL) return 0; /* support free on null */
ZSTD_freeDStream(zds->dstream);
free(zds->seekTable.entries);
free(zds);
@@ -105,6 +111,7 @@ size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable_DStream* zds, const void* src,
U32 sizePerEntry;
+ /* footer is fixed size */
if (srcSize < ZSTD_seekTableFooterSize)
return ZSTD_seekTableFooterSize;
@@ -112,15 +119,13 @@ size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable_DStream* zds, const void* src,
return ERROR(prefix_unknown);
}
- {
- BYTE const sfd = ip[-5];
+ { BYTE const sfd = ip[-5];
checksumFlag = sfd >> 7;
-
- numChunks = MEM_readLE32(ip-9);
-
- sizePerEntry = 8 + (checksumFlag?4:0);
}
+ numChunks = MEM_readLE32(ip-9);
+ sizePerEntry = 8 + (checksumFlag?4:0);
+
{ U32 const tableSize = sizePerEntry * numChunks;
U32 const frameSize = tableSize + ZSTD_seekTableFooterSize + ZSTD_skippableHeaderSize;
@@ -151,6 +156,7 @@ size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable_DStream* zds, const void* src,
return ERROR(memory_allocation);
}
+ /* compute cumulative positions */
for (idx = 0, pos = 0; idx < numChunks; idx++) {
entries[idx].cOffset = cOffset;
entries[idx].dOffset = dOffset;
@@ -175,7 +181,8 @@ size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable_DStream* zds, const void* src,
size_t ZSTD_seekable_initDStream(ZSTD_seekable_DStream* zds, U64 rangeStart, U64 rangeEnd)
{
- /* restrict range to the end of the file, and not before the range start */
+ /* restrict range to the end of the file, of non-negative size */
+ rangeStart = MIN(rangeStart, zds->seekTable.entries[zds->seekTable.tableLen].dOffset);
rangeEnd = MIN(rangeEnd, zds->seekTable.entries[zds->seekTable.tableLen].dOffset);
rangeEnd = MAX(rangeEnd, rangeStart);
@@ -192,6 +199,8 @@ size_t ZSTD_seekable_initDStream(ZSTD_seekable_DStream* zds, U64 rangeStart, U64
XXH64_reset(&zds->xxhState, 0);
}
+ if (rangeStart == rangeEnd) zds->stage = zsds_done;
+
{ const size_t ret = ZSTD_initDStream(zds->dstream);
if (ZSTD_isError(ret)) return ret; }
return 0;
@@ -222,7 +231,7 @@ size_t ZSTD_seekable_decompressStream(ZSTD_seekable_DStream* zds, ZSTD_outBuffer
while (1) {
switch (zds->stage) {
case zsds_init:
- return ERROR(init_missing);
+ return ERROR(init_missing); /* ZSTD_seekable_initDStream should be called first */
case zsds_decompress: {
BYTE* const outBase = (BYTE*)output->dst + output->pos;
size_t const outLen = output->size - output->pos;
@@ -248,7 +257,7 @@ size_t ZSTD_seekable_decompressStream(ZSTD_seekable_DStream* zds, ZSTD_outBuffer
zds->compressedOffset += input->pos - prevInputPos;
zds->decompressedOffset += outTmp.pos;
- if (zds->seekTable.checksumFlag) {
+ if (jt->checksumFlag) {
XXH64_update(&zds->xxhState, outTmp.dst, outTmp.pos);
}
@@ -256,7 +265,7 @@ size_t ZSTD_seekable_decompressStream(ZSTD_seekable_DStream* zds, ZSTD_outBuffer
/* need more input */
return MIN(
ZSTD_DStreamInSize(),
- (size_t)(zds->seekTable.entries[zds->curChunk + 1]
+ (size_t)(jt->entries[zds->curChunk + 1]
.cOffset -
zds->compressedOffset));
}
@@ -285,11 +294,11 @@ size_t ZSTD_seekable_decompressStream(ZSTD_seekable_DStream* zds, ZSTD_outBuffer
output->pos += outTmp.pos;
- if (zds->seekTable.checksumFlag) {
+ if (jt->checksumFlag) {
XXH64_update(&zds->xxhState, outTmp.dst, outTmp.pos);
if (ret == 0) {
/* verify the checksum */
- U32 const digest = XXH64_digest(&zds->xxhState);
+ U32 const digest = XXH64_digest(&zds->xxhState) & 0xFFFFFFFFU;
if (digest != jt->entries[zds->curChunk].checksum) {
return ERROR(checksum_wrong);
}
@@ -306,17 +315,21 @@ size_t ZSTD_seekable_decompressStream(ZSTD_seekable_DStream* zds, ZSTD_outBuffer
if (ret == 0) {
/* frame is done */
+ /* make sure this lines up with the expected frame border */
+ if (zds->decompressedOffset !=
+ jt->entries[zds->curChunk + 1].dOffset ||
+ zds->compressedOffset !=
+ jt->entries[zds->curChunk + 1].cOffset)
+ return ERROR(corruption_detected);
ZSTD_resetDStream(zds->dstream);
zds->stage = zsds_seek;
break;
}
/* need more input */
- return MIN(
- ZSTD_DStreamInSize(),
- (size_t)(zds->seekTable.entries[zds->curChunk + 1]
- .cOffset -
- zds->compressedOffset));
+ return MIN(ZSTD_DStreamInSize(), (size_t)(
+ jt->entries[zds->curChunk + 1].cOffset -
+ zds->compressedOffset));
}
}
case zsds_seek: {
@@ -338,6 +351,7 @@ size_t ZSTD_seekable_decompressStream(ZSTD_seekable_DStream* zds, ZSTD_outBuffer
zds->nextSeek = jt->entries[targetChunk].cOffset;
zds->decompressedOffset = jt->entries[targetChunk].dOffset;
+ /* signal to user that a seek is required */
return ERROR(needSeek);
}
case zsds_done:
diff --git a/lib/zstd.h b/lib/zstd.h
index 5bbd1b74..748a9827 100644
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -807,6 +807,8 @@ typedef struct ZSTD_seekable_DStream_s ZSTD_seekable_DStream;
* for a new compression operation.
* `maxChunkSize` indicates the size at which to automatically start a new
* seekable frame. `maxChunkSize == 0` implies the default maximum size.
+* `checksumFlag` indicates whether or not the seek table should include chunk
+* checksums on the uncompressed data for verification.
* @return : a size hint for input to provide for compression, or an error code
* checkable with ZSTD_isError()
*
@@ -836,7 +838,7 @@ ZSTDLIB_API ZSTD_seekable_CStream* ZSTD_seekable_createCStream(void);
ZSTDLIB_API size_t ZSTD_seekable_freeCStream(ZSTD_seekable_CStream* zcs);
/*===== Seekable compression functions =====*/
-ZSTDLIB_API size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs, int compressionLevel, unsigned maxChunkSize);
+ZSTDLIB_API size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs, int compressionLevel, int checksumFlag, unsigned maxChunkSize);
ZSTDLIB_API size_t ZSTD_seekable_compressStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
ZSTDLIB_API size_t ZSTD_seekable_endChunk(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output);
ZSTDLIB_API size_t ZSTD_seekable_endStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output);