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-<title>zstd 1.4.6 Manual</title>
+<title>zstd 1.4.5 Manual</title>
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<body>
-<h1>zstd 1.4.6 Manual</h1>
+<h1>zstd 1.4.5 Manual</h1>
<hr>
<a name="Contents"></a><h2>Contents</h2>
<ol>
<li><a href="#Chapter14">experimental API (static linking only)</a></li>
<li><a href="#Chapter15">Frame size functions</a></li>
<li><a href="#Chapter16">Memory management</a></li>
-<li><a href="#Chapter17">This API is temporary and is expected to change or disappear in the future!</a></li>
-<li><a href="#Chapter18">Advanced compression functions</a></li>
-<li><a href="#Chapter19">Advanced decompression functions</a></li>
-<li><a href="#Chapter20">Advanced streaming functions</a></li>
-<li><a href="#Chapter21">! ZSTD_initCStream_usingDict() :</a></li>
-<li><a href="#Chapter22">! ZSTD_initCStream_advanced() :</a></li>
-<li><a href="#Chapter23">! ZSTD_initCStream_usingCDict() :</a></li>
-<li><a href="#Chapter24">! ZSTD_initCStream_usingCDict_advanced() :</a></li>
+<li><a href="#Chapter17">Advanced compression functions</a></li>
+<li><a href="#Chapter18">Advanced decompression functions</a></li>
+<li><a href="#Chapter19">Advanced streaming functions</a></li>
+<li><a href="#Chapter20">! ZSTD_initCStream_usingDict() :</a></li>
+<li><a href="#Chapter21">! ZSTD_initCStream_advanced() :</a></li>
+<li><a href="#Chapter22">! ZSTD_initCStream_usingCDict() :</a></li>
+<li><a href="#Chapter23">! ZSTD_initCStream_usingCDict_advanced() :</a></li>
+<li><a href="#Chapter24">This function is deprecated, and is equivalent to:</a></li>
<li><a href="#Chapter25">This function is deprecated, and is equivalent to:</a></li>
-<li><a href="#Chapter26">This function is deprecated, and is equivalent to:</a></li>
-<li><a href="#Chapter27">Buffer-less and synchronous inner streaming functions</a></li>
-<li><a href="#Chapter28">Buffer-less streaming compression (synchronous mode)</a></li>
-<li><a href="#Chapter29">Buffer-less streaming decompression (synchronous mode)</a></li>
-<li><a href="#Chapter30">Block level API</a></li>
+<li><a href="#Chapter26">Buffer-less and synchronous inner streaming functions</a></li>
+<li><a href="#Chapter27">Buffer-less streaming compression (synchronous mode)</a></li>
+<li><a href="#Chapter28">Buffer-less streaming decompression (synchronous mode)</a></li>
+<li><a href="#Chapter29">Block level API</a></li>
</ol>
<hr>
<a name="Chapter1"></a><h2>Introduction</h2><pre>
<a name="Chapter2"></a><h2>Version</h2><pre></pre>
-<pre><b>unsigned ZSTD_versionNumber(void);
-</b><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE).
-</p></pre><BR>
-
-<pre><b>const char* ZSTD_versionString(void);
-</b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+.
-</p></pre><BR>
-
+<pre><b>unsigned ZSTD_versionNumber(void); </b>/**< to check runtime library version */<b>
+</b></pre><BR>
<a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
</b>/* multi-threading parameters */<b>
- </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
- * Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
- * In a situation where it's unknown if the linked library supports multi-threading or not,
- * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
- */
+ </b>/* These parameters are only useful if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
+ * They return an error otherwise. */
ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b>
- * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
+ * When nbWorkers >= 1, triggers asynchronous mode when used with ZSTD_compressStream*() :
* ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
- * while compression is performed in parallel, within worker thread(s).
+ * while compression work is performed in parallel, within worker threads.
* (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
* in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
* More workers improve speed, but also increase memory usage.
- * Default value is `0`, aka "single-threaded mode" : no worker is spawned,
- * compression is performed inside Caller's thread, and all invocations are blocking */
+ * Default value is `0`, aka "single-threaded mode" : no worker is spawned, compression is performed inside Caller's thread, all invocations are blocking */
ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b>
* Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
* 0 means default, which is dynamically determined based on compression parameters.
* ZSTD_c_literalCompressionMode
* ZSTD_c_targetCBlockSize
* ZSTD_c_srcSizeHint
- * ZSTD_c_enableDedicatedDictSearch
* Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
* note : never ever use experimentalParam? names directly;
* also, the enums values themselves are unstable and can still change.
ZSTD_c_experimentalParam4=1001,
ZSTD_c_experimentalParam5=1002,
ZSTD_c_experimentalParam6=1003,
- ZSTD_c_experimentalParam7=1004,
- ZSTD_c_experimentalParam8=1005
+ ZSTD_c_experimentalParam7=1004
} ZSTD_cParameter;
</b></pre><BR>
<pre><b>typedef struct {
* At the time of this writing, they include :
* ZSTD_d_format
* ZSTD_d_stableOutBuffer
- * ZSTD_d_forceIgnoreChecksum
* Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
* note : never ever use experimentalParam? names directly
*/
ZSTD_d_experimentalParam1=1000,
- ZSTD_d_experimentalParam2=1001,
- ZSTD_d_experimentalParam3=1002
+ ZSTD_d_experimentalParam2=1001
} ZSTD_dParameter;
</b></pre><BR>
- Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
- output->pos must be <= dstCapacity, input->pos must be <= srcSize
- output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
- - endOp must be a valid directive
- When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
- - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available,
+ - When nbWorkers>=1, function is non-blocking : it just acquires a copy of input, and distributes jobs to internal worker threads, flush whatever is available,
and then immediately returns, just indicating that there is some data remaining to be flushed.
The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
- Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking.
* Decoder cannot recognise automatically this format, requiring this instruction. */
} ZSTD_format_e;
</b></pre><BR>
-<pre><b>typedef enum {
- </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b>
- ZSTD_d_validateChecksum = 0,
- ZSTD_d_ignoreChecksum = 1
-} ZSTD_forceIgnoreChecksum_e;
-</b></pre><BR>
<pre><b>typedef enum {
</b>/* Note: this enum and the behavior it controls are effectively internal<b>
* implementation details of the compressor. They are expected to continue
</p></pre><BR>
-<a name="Chapter17"></a><h2>This API is temporary and is expected to change or disappear in the future!</h2><pre>
-<BR></pre>
-
-<a name="Chapter18"></a><h2>Advanced compression functions</h2><pre></pre>
+<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
<pre><b>ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
</b><p> Create a digested dictionary for compression
<pre><b>size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
</b><p> Similar to ZSTD_CCtx_setParameter.
Set one compression parameter, selected by enum ZSTD_cParameter.
- Parameters must be applied to a ZSTD_CCtx using
- ZSTD_CCtx_setParametersUsingCCtxParams().
- @result : a code representing success or failure (which can be tested with
- ZSTD_isError()).
+ Parameters must be applied to a ZSTD_CCtx using ZSTD_CCtx_setParametersUsingCCtxParams().
+ @result : 0, or an error code (which can be tested with ZSTD_isError()).
</p></pre><BR>
</p></pre><BR>
-<a name="Chapter1
9"></a><h2>Advanced decompression functions</h2><pre></pre>
+<a name="Chapter1
8"></a><h2>Advanced decompression functions</h2><pre></pre>
<pre><b>unsigned ZSTD_isFrame(const void* buffer, size_t size);
</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
</p></pre><BR>
-<a name="Chapter
20"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API.
+<a name="Chapter
19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API.
Once Advanced API reaches "stable" status,
redundant functions will be deprecated, and then at some point removed.
<BR></pre>
int compressionLevel,
unsigned long long pledgedSrcSize);
</pre></b><BR>
-<a name="Chapter2
1"></a><h2>! ZSTD_initCStream_usingDict() :</h2><pre> This function is deprecated, and is equivalent to:
+<a name="Chapter2
0"></a><h2>! ZSTD_initCStream_usingDict() :</h2><pre> This function is deprecated, and is equivalent to:
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
<BR></pre>
-<a name="Chapter2
2"></a><h2>! ZSTD_initCStream_advanced() :</h2><pre> This function is deprecated, and is approximately equivalent to:
+<a name="Chapter2
1"></a><h2>! ZSTD_initCStream_advanced() :</h2><pre> This function is deprecated, and is approximately equivalent to:
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
// Pseudocode: Set each zstd parameter and leave the rest as-is.
for ((param, value) : params) {
<BR></pre>
-<a name="Chapter2
3"></a><h2>! ZSTD_initCStream_usingCDict() :</h2><pre> This function is deprecated, and equivalent to:
+<a name="Chapter2
2"></a><h2>! ZSTD_initCStream_usingCDict() :</h2><pre> This function is deprecated, and equivalent to:
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
ZSTD_CCtx_refCDict(zcs, cdict);
<BR></pre>
-<a name="Chapter2
4"></a><h2>! ZSTD_initCStream_usingCDict_advanced() :</h2><pre> This function is DEPRECATED, and is approximately equivalent to:
+<a name="Chapter2
3"></a><h2>! ZSTD_initCStream_usingCDict_advanced() :</h2><pre> This function is DEPRECATED, and is approximately equivalent to:
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
// Pseudocode: Set each zstd frame parameter and leave the rest as-is.
for ((fParam, value) : fParams) {
*/
size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
</pre></b><BR>
-<a name="Chapter2
5"></a><h2>This function is deprecated, and is equivalent to:</h2><pre>
+<a name="Chapter2
4"></a><h2>This function is deprecated, and is equivalent to:</h2><pre>
ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
ZSTD_DCtx_refDDict(zds, ddict);
<BR></pre>
-<a name="Chapter2
6"></a><h2>This function is deprecated, and is equivalent to:</h2><pre>
+<a name="Chapter2
5"></a><h2>This function is deprecated, and is equivalent to:</h2><pre>
ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
re-use decompression parameters from previous init; saves dictionary loading
<BR></pre>
-<a name="Chapter2
7"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
+<a name="Chapter2
6"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
This is an advanced API, giving full control over buffer management, for users which need direct control over memory.
But it's also a complex one, with several restrictions, documented below.
Prefer normal streaming API for an easier experience.
<BR></pre>
-<a name="Chapter2
8"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
+<a name="Chapter2
7"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
A ZSTD_CCtx object is required to track streaming operations.
Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
ZSTD_CCtx object can be re-used multiple times within successive compression operations.
size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize); </b>/* compression parameters are already set within cdict. pledgedSrcSize must be correct. If srcSize is not known, use macro ZSTD_CONTENTSIZE_UNKNOWN */<b>
size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
</pre></b><BR>
-<a name="Chapter2
9"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
+<a name="Chapter2
8"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
A ZSTD_DCtx object is required to track streaming operations.
Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
A ZSTD_DCtx object can be re-used multiple times.
<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
</b></pre><BR>
-<a name="Chapter
30"></a><h2>Block level API</h2><pre></pre>
+<a name="Chapter
29"></a><h2>Block level API</h2><pre></pre>
<pre><b></b><p> Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
/* Struct containing info needed to make decision about ldm inclusion */
typedef struct {
- rawSeqStore_t seqStore; /* External match candidates store for this block */
- U32 startPosInBlock; /* Start position of the current match candidate */
- U32 endPosInBlock; /* End position of the current match candidate */
- U32 offset; /* Offset of the match candidate */
+ rawSeqStore_t seqStore; /* External match candidates store for this block */
+ U32 startPosInBlock; /* Start position of the current match candidate */
+ U32 endPosInBlock; /* End position of the current match candidate */
+ U32 offset; /* Offset of the match candidate */
} ZSTD_optLdm_t;
/* ZSTD_optLdm_skipRawSeqStoreBytes():
if (currPos == 0 || rawSeqStore->pos == rawSeqStore->size) {
rawSeqStore->posInSequence = 0;
}
- assert(rawSeqStore->posInSequence <=
- rawSeqStore->seq[rawSeqStore->pos].litLength + rawSeqStore->seq[rawSeqStore->pos].matchLength);
}
/* ZSTD_opt_getNextMatchAndUpdateSeqStore():
U32 matchBytesRemaining;
/* Setting match end position to MAX to ensure we never use an LDM during this block */
- if (optLdm->seqStore.pos >= optLdm->seqStore.size || optLdm->seqStore.size == 0) {
+ if (optLdm->seqStore.size == 0 || optLdm->seqStore.pos >= optLdm->seqStore.size) {
optLdm->startPosInBlock = UINT_MAX;
optLdm->endPosInBlock = UINT_MAX;
return;
*/
static void ZSTD_optLdm_processMatchCandidate(ZSTD_optLdm_t* optLdm, ZSTD_match_t* matches, U32* nbMatches,
U32 currPosInBlock, U32 remainingBytes) {
- if (optLdm->seqStore.size == 0 && optLdm->seqStore.pos >= optLdm->seqStore.size) {
+ if (optLdm->seqStore.size == 0 || optLdm->seqStore.pos >= optLdm->seqStore.size) {
return;
}
ZSTD_optimal_t* const opt = optStatePtr->priceTable;
ZSTD_match_t* const matches = optStatePtr->matchTable;
ZSTD_optimal_t lastSequence;
- ZSTD_optLdm_t optLdm = {ms->ldmSeqStore, 0, 0, 0}; /* ms->ldmSeqStore itself is immutable in this function */
+ ZSTD_optLdm_t optLdm;
+
+ if (ms->ldmSeqStore) {
+ optLdm.seqStore = *ms->ldmSeqStore;
+ optLdm.endPosInBlock = optLdm.startPosInBlock = optLdm.offset = 0;
+ } else {
+ optLdm.seqStore.size = optLdm.seqStore.pos = 0;
+ }
/* Get first match from ldm seq store if long mode is enabled */
ZSTD_opt_getNextMatchAndUpdateSeqStore(&optLdm, (U32)(ip-istart), (U32)(iend-ip));
ZSTD_setBasePrices(optStatePtr, optLevel);
}
} /* while (ip < ilimit) */
-
+
/* Return the last literals size */
return (size_t)(iend - anchor);
}
const void* src, size_t srcSize)
{
U32 tmpRep[ZSTD_REP_NUM]; /* updated rep codes will sink here */
- rawSeqStore_t tmpSeqStore = ms->ldmSeqStore;
ZSTD_memcpy(tmpRep, rep, sizeof(tmpRep));
DEBUGLOG(4, "ZSTD_initStats_ultra (srcSize=%zu)", srcSize);
ms->window.dictLimit += (U32)srcSize;
ms->window.lowLimit = ms->window.dictLimit;
ms->nextToUpdate = ms->window.dictLimit;
- ms->ldmSeqStore = tmpSeqStore;
/* re-inforce weight of collected statistics */
ZSTD_upscaleStats(&ms->opt);
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