it's an unsupported scenario.
<a name="Chapter23"></a><h2>Block level API</h2><pre></pre>
<pre><b></b><p> Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
- User will have to take in charge required information to regenerate data, such as compressed and content sizes.
+ But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
A few rules to respect :
- Compressing and decompressing require a context structure
+ copyCCtx() and copyDCtx() can be used too
- Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
+ If input is larger than a block size, it's necessary to split input data into multiple blocks
- + For inputs larger than a single block, really consider using regular ZSTD_compress() instead.
- Frame metadata is not that costly, and quickly becomes negligible as source size grows larger.
- - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
- In which case, nothing is produced into `dst` !
- + User must test for such outcome and deal directly with uncompressed data
- + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
+ + For inputs larger than a single block, consider using regular ZSTD_compress() instead.
+ Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
+ - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
+ ===> In which case, nothing is produced into `dst` !
+ + User __must__ test for such outcome and deal directly with uncompressed data
+ + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
+ Doing so would mess up with statistics history, leading to potential data corruption.
+ + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
+ In case of multiple successive blocks, should some of them be uncompressed,
decoder must be informed of their existence in order to follow proper history.
Use ZSTD_insertBlock() for such a case.
/**
* Return the specified error if the condition evaluates to true.
*
- * In debug modes, prints additional information. In order to do that
- * (particularly, printing the conditional that failed), this can't just wrap
- * RETURN_ERROR().
+ * In debug modes, prints additional information.
+ * In order to do that (particularly, printing the conditional that failed),
+ * this can't just wrap RETURN_ERROR().
*/
#define RETURN_ERROR_IF(cond, err, ...) \
if (cond) { \
BYTE* const ostart = (BYTE*)dst;
BYTE* const oend = ostart + dstCapacity;
BYTE* op = ostart;
- size_t const nbSeq = seqStorePtr->sequences - seqStorePtr->sequencesStart;
+ size_t const nbSeq = (size_t)(seqStorePtr->sequences - seqStorePtr->sequencesStart);
BYTE* seqHead;
BYTE* lastNCount = NULL;
/* Compress literals */
{ const BYTE* const literals = seqStorePtr->litStart;
- size_t const litSize = seqStorePtr->lit - literals;
+ size_t const litSize = (size_t)(seqStorePtr->lit - literals);
size_t const cSize = ZSTD_compressLiterals(
&prevEntropy->huf, &nextEntropy->huf,
cctxParams->cParams.strategy,
if (nbSeq==0) {
/* Copy the old tables over as if we repeated them */
memcpy(&nextEntropy->fse, &prevEntropy->fse, sizeof(prevEntropy->fse));
- return op - ostart;
+ return (size_t)(op - ostart);
}
/* seqHead : flags for FSE encoding type */
ZSTD_defaultAllowed, strategy);
assert(set_basic < set_compressed && set_rle < set_compressed);
assert(!(LLtype < set_compressed && nextEntropy->fse.litlength_repeatMode != FSE_repeat_none)); /* We don't copy tables */
- { size_t const countSize = ZSTD_buildCTable(op, oend - op, CTable_LitLength, LLFSELog, (symbolEncodingType_e)LLtype,
+ { size_t const countSize = ZSTD_buildCTable(op, (size_t)(oend - op), CTable_LitLength, LLFSELog, (symbolEncodingType_e)LLtype,
count, max, llCodeTable, nbSeq, LL_defaultNorm, LL_defaultNormLog, MaxLL,
prevEntropy->fse.litlengthCTable, sizeof(prevEntropy->fse.litlengthCTable),
workspace, wkspSize);
OF_defaultNorm, OF_defaultNormLog,
defaultPolicy, strategy);
assert(!(Offtype < set_compressed && nextEntropy->fse.offcode_repeatMode != FSE_repeat_none)); /* We don't copy tables */
- { size_t const countSize = ZSTD_buildCTable(op, oend - op, CTable_OffsetBits, OffFSELog, (symbolEncodingType_e)Offtype,
+ { size_t const countSize = ZSTD_buildCTable(op, (size_t)(oend - op), CTable_OffsetBits, OffFSELog, (symbolEncodingType_e)Offtype,
count, max, ofCodeTable, nbSeq, OF_defaultNorm, OF_defaultNormLog, DefaultMaxOff,
prevEntropy->fse.offcodeCTable, sizeof(prevEntropy->fse.offcodeCTable),
workspace, wkspSize);
ML_defaultNorm, ML_defaultNormLog,
ZSTD_defaultAllowed, strategy);
assert(!(MLtype < set_compressed && nextEntropy->fse.matchlength_repeatMode != FSE_repeat_none)); /* We don't copy tables */
- { size_t const countSize = ZSTD_buildCTable(op, oend - op, CTable_MatchLength, MLFSELog, (symbolEncodingType_e)MLtype,
+ { size_t const countSize = ZSTD_buildCTable(op, (size_t)(oend - op), CTable_MatchLength, MLFSELog, (symbolEncodingType_e)MLtype,
count, max, mlCodeTable, nbSeq, ML_defaultNorm, ML_defaultNormLog, MaxML,
prevEntropy->fse.matchlengthCTable, sizeof(prevEntropy->fse.matchlengthCTable),
workspace, wkspSize);
*seqHead = (BYTE)((LLtype<<6) + (Offtype<<4) + (MLtype<<2));
{ size_t const bitstreamSize = ZSTD_encodeSequences(
- op, oend - op,
+ op, (size_t)(oend - op),
CTable_MatchLength, mlCodeTable,
CTable_OffsetBits, ofCodeTable,
CTable_LitLength, llCodeTable,
}
DEBUGLOG(5, "compressed block size : %u", (unsigned)(op - ostart));
- return op - ostart;
+ return (size_t)(op - ostart);
}
MEM_STATIC size_t
size_t ZSTD_compressBlock(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize)
{
- size_t const blockSizeMax = ZSTD_getBlockSize(cctx);
- RETURN_ERROR_IF(srcSize > blockSizeMax, srcSize_wrong);
+ DEBUGLOG(5, "ZSTD_compressBlock: srcSize = %u", (unsigned)srcSize);
+ { size_t const blockSizeMax = ZSTD_getBlockSize(cctx);
+ RETURN_ERROR_IF(srcSize > blockSizeMax, srcSize_wrong); }
return ZSTD_compressContinue_internal(cctx, dst, dstCapacity, src, srcSize, 0 /* frame mode */, 0 /* last chunk */);
}
if (srcSize <= HASH_READ_SIZE) return 0;
while (iend - ip > HASH_READ_SIZE) {
- size_t const remaining = iend - ip;
+ size_t const remaining = (size_t)(iend - ip);
size_t const chunk = MIN(remaining, ZSTD_CHUNKSIZE_MAX);
const BYTE* const ichunk = ip + chunk;
}
/** ZSTD_insertBlock() :
- insert `src` block into `dctx` history. Useful to track uncompressed blocks. */
+ * insert `src` block into `dctx` history. Useful to track uncompressed blocks. */
size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize)
{
+ DEBUGLOG(5, "ZSTD_insertBlock: %u bytes", (unsigned)blockSize);
ZSTD_checkContinuity(dctx, blockStart);
dctx->previousDstEnd = (const char*)blockStart + blockSize;
return blockSize;
size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
const void* src, size_t srcSize) /* note : srcSize < BLOCKSIZE */
{
+ DEBUGLOG(5, "ZSTD_decodeLiteralsBlock");
RETURN_ERROR_IF(srcSize < MIN_CBLOCK_SIZE, corruption_detected);
{ const BYTE* const istart = (const BYTE*) src;
switch(litEncType)
{
case set_repeat:
+ DEBUGLOG(5, "set_repeat flag : re-using stats from previous compressed literals block");
RETURN_ERROR_IF(dctx->litEntropy==0, dictionary_corrupted);
/* fall-through */
/* 2 - 2 - 18 - 18 */
lhSize = 5;
litSize = (lhc >> 4) & 0x3FFFF;
- litCSize = (lhc >> 22) + (istart[4] << 10);
+ litCSize = (lhc >> 22) + ((size_t)istart[4] << 10);
break;
}
RETURN_ERROR_IF(litSize > ZSTD_BLOCKSIZE_MAX, corruption_detected);
symbolNext[s] = 1;
} else {
if (normalizedCounter[s] >= largeLimit) DTableH.fastMode=0;
- symbolNext[s] = normalizedCounter[s];
+ assert(normalizedCounter[s]>=0);
+ symbolNext[s] = (U16)normalizedCounter[s];
} } }
memcpy(dt, &DTableH, sizeof(DTableH));
}
/*!
Block functions produce and decode raw zstd blocks, without frame metadata.
Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes).
- User will have to take in charge required information to regenerate data, such as compressed and content sizes.
+ But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
A few rules to respect :
- Compressing and decompressing require a context structure
+ copyCCtx() and copyDCtx() can be used too
- Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
+ If input is larger than a block size, it's necessary to split input data into multiple blocks
- + For inputs larger than a single block, really consider using regular ZSTD_compress() instead.
- Frame metadata is not that costly, and quickly becomes negligible as source size grows larger.
- - When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
- In which case, nothing is produced into `dst` !
- + User must test for such outcome and deal directly with uncompressed data
- + ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
+ + For inputs larger than a single block, consider using regular ZSTD_compress() instead.
+ Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
+ - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
+ ===> In which case, nothing is produced into `dst` !
+ + User __must__ test for such outcome and deal directly with uncompressed data
+ + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
+ Doing so would mess up with statistics history, leading to potential data corruption.
+ + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
+ In case of multiple successive blocks, should some of them be uncompressed,
decoder must be informed of their existence in order to follow proper history.
Use ZSTD_insertBlock() for such a case.
DISPLAYLEVEL(3, "test%3i : Dictionary Block compression test : ", testNb++);
CHECK( ZSTD_compressBegin_usingDict(cctx, CNBuffer, dictSize, 5) );
CHECK_VAR(cSize, ZSTD_compressBlock(cctx, compressedBuffer, ZSTD_compressBound(blockSize), (char*)CNBuffer+dictSize, blockSize));
- CHECK( ZSTD_compressBlock(cctx, (char*)compressedBuffer+cSize, ZSTD_compressBound(blockSize), (char*)CNBuffer+dictSize+blockSize, blockSize) ); /* just to ensure cctx history consistency */
- memcpy((char*)compressedBuffer+cSize, (char*)CNBuffer+dictSize+blockSize, blockSize); /* fake non-compressed block (without header) */
+ RDG_genBuffer((char*)CNBuffer+dictSize+blockSize, blockSize, 0.0, 0.0, seed); /* create a non-compressible second block */
+ { CHECK_NEWV(r, ZSTD_compressBlock(cctx, (char*)compressedBuffer+cSize, ZSTD_compressBound(blockSize), (char*)CNBuffer+dictSize+blockSize, blockSize) ); /* for cctx history consistency */
+ assert(r == 0); /* non-compressible block */ }
+ memcpy((char*)compressedBuffer+cSize, (char*)CNBuffer+dictSize+blockSize, blockSize); /* send non-compressed block (without header) */
CHECK_VAR(cSize2, ZSTD_compressBlock(cctx, (char*)compressedBuffer+cSize+blockSize, ZSTD_compressBound(blockSize),
(char*)CNBuffer+dictSize+2*blockSize, blockSize));
DISPLAYLEVEL(3, "OK \n");
DISPLAYLEVEL(1, "ZSTD_decompressBlock() with _usingDict() and after insertBlock() fails : %u, instead of %u expected \n", (unsigned)r, (unsigned)blockSize);
goto _output_error;
} }
+ assert(memcpy((char*)CNBuffer+dictSize, decodedBuffer, blockSize*3)); /* ensure regenerated content is identical to origin */
DISPLAYLEVEL(3, "OK \n");
DISPLAYLEVEL(3, "test%3i : Block compression with CDict : ", testNb++);
projects / thirdparty / zstd.git / commitdiff
