<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">Buffer-less and synchronous inner streaming functions</a></li>
-<li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li>
-<li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li>
-<li><a href="#Chapter23">Block level API</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">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>
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
int compressionLevel);
-</b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx
- The function will compress at requested compression level,
- ignoring any other parameter
+</b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
+ Important : in order to behave similarly to `ZSTD_compress()`,
+ this function compresses at requested compression level,
+ __ignoring any other parameter__ .
+ If any advanced parameter was set using the advanced API,
+ they will all be reset. Only `compressionLevel` remains.
+
</p></pre><BR>
<h3>Decompression context</h3><pre> When decompressing many times,
</b>/* compression parameters<b>
* Note: When compressing with a ZSTD_CDict these parameters are superseded
- * by the parameters used to construct the ZSTD_CDict. See ZSTD_CCtx_refCDict()
- * for more info (superseded-by-cdict). */
- ZSTD_c_compressionLevel=100, </b>/* Update all compression parameters according to pre-defined cLevel table<b>
+ * by the parameters used to construct the ZSTD_CDict.
+ * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
+ ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b>
+ * Note that exact compression parameters are dynamically determined,
+ * depending on both compression level and srcSize (when known).
* Default level is ZSTD_CLEVEL_DEFAULT==3.
* Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
* Note 1 : it's possible to pass a negative compression level.
- * Note 2 : setting a level sets all default values of other compression parameters */
+ * Note 2 : setting a level resets all other compression parameters to default */
+ </b>/* Advanced compression parameters :<b>
+ * It's possible to pin down compression parameters to some specific values.
+ * In which case, these values are no longer dynamically selected by the compressor */
ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
+ * This will set a memory budget for streaming decompression,
+ * with larger values requiring more memory
+ * and typically compressing more.
* Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
* Special: value 0 means "use default windowLog".
* Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
- * requires explicitly allowing such window size at decompression stage if using streaming. */
+ * requires explicitly allowing such size at streaming decompression stage. */
ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b>
* Resulting memory usage is (1 << (hashLog+2)).
* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
* Resulting memory usage is (1 << (chainLog+2)).
* Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
* Larger tables result in better and slower compression.
- * This parameter is useless when using "fast" strategy.
+ * This parameter is useless for "fast" strategy.
* It's still useful when using "dfast" strategy,
* in which case it defines a secondary probe table.
* Special: value 0 means "use default chainLog". */
ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b>
* More attempts result in better and slower compression.
- * This parameter is useless when using "fast" and "dFast" strategies.
+ * This parameter is useless for "fast" and "dFast" strategies.
* Special: value 0 means "use default searchLog". */
ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b>
* Note that Zstandard can still find matches of smaller size,
ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
* Content size must be known at the beginning of compression.
* This is automatically the case when using ZSTD_compress2(),
- * For streaming variants, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
+ * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default: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.
* Job size must be a minimum of overlap size, or 1 MB, whichever is largest.
- * The minimum size is automatically and transparently enforced */
+ * The minimum size is automatically and transparently enforced. */
ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b>
* The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
* It helps preserve compression ratio, while each job is compressed in parallel.
ZSTD_c_experimentalParam4=1001,
ZSTD_c_experimentalParam5=1002,
ZSTD_c_experimentalParam6=1003,
- ZSTD_c_experimentalParam7=1004,
+ ZSTD_c_experimentalParam7=1004
} ZSTD_cParameter;
</b></pre><BR>
<pre><b>typedef struct {
</b></pre><BR>
<pre><b>typedef enum {
ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
- ZSTD_dlm_byRef = 1, </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
+ ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
} ZSTD_dictLoadMethod_e;
</b></pre><BR>
<pre><b>typedef enum {
- </b>/* Opened question : should we have a format ZSTD_f_auto ?<b>
- * Today, it would mean exactly the same as ZSTD_f_zstd1.
- * But, in the future, should several formats become supported,
- * on the compression side, it would mean "default format".
- * On the decompression side, it would mean "automatic format detection",
- * so that ZSTD_f_zstd1 would mean "accept *only* zstd frames".
- * Since meaning is a little different, another option could be to define different enums for compression and decompression.
- * This question could be kept for later, when there are actually multiple formats to support,
- * but there is also the question of pinning enum values, and pinning value `0` is especially important */
ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
- ZSTD_f_zstd1_magicless = 1, </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
+ ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
* Useful to save 4 bytes per generated frame.
* Decoder cannot recognise automatically this format, requiring this instruction. */
} ZSTD_format_e;
*/
ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b>
ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b>
- ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b>
+ ZSTD_dictForceCopy = 2 </b>/* Always copy the dictionary. */<b>
} ZSTD_dictAttachPref_e;
</b></pre><BR>
<pre><b>typedef enum {
* levels will be compressed. */
ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b>
* emitted if Huffman compression is not profitable. */
- ZSTD_lcm_uncompressed = 2, </b>/**< Always emit uncompressed literals. */<b>
+ ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b>
} ZSTD_literalCompressionMode_e;
</b></pre><BR>
<a name="Chapter15"></a><h2>Frame size functions</h2><pre></pre>
</b><p> Create a digested dictionary for compression
Dictionary content is just referenced, not duplicated.
As a consequence, `dictBuffer` **must** outlive CDict,
- and its content must remain unmodified throughout the lifetime of CDict.
+ and its content must remain unmodified throughout the lifetime of CDict.
+ note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef
</p></pre><BR>
<pre><b>ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
const void* src, size_t srcSize,
const void* dict,size_t dictSize,
ZSTD_parameters params);
-</b><p> Same as ZSTD_compress_usingDict(), with fine-tune control over compression parameters (by structure)
+</b><p> Note : this function is now DEPRECATED.
+ It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
+ This prototype will be marked as deprecated and generate compilation warning on reaching v1.5.x
</p></pre><BR>
<pre><b>size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
const void* src, size_t srcSize,
const ZSTD_CDict* cdict,
ZSTD_frameParameters fParams);
-</b><p> Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters
+</b><p> Note : this function is now REDUNDANT.
+ It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
+ This prototype will be marked as deprecated and generate compilation warning in some future version
</p></pre><BR>
<pre><b>size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
* pledgedSrcSize must be correct. If it is not known at init time, use
* ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
* "0" also disables frame content size field. It may be enabled in the future.
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
-size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize);
-</b>/**! ZSTD_initCStream_usingDict() :<b>
- * 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);
- *
- * Creates of an internal CDict (incompatible with static CCtx), except if
- * dict == NULL or dictSize < 8, in which case no dict is used.
- * Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
- * it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
- */
-size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel);
-</b>/**! ZSTD_initCStream_advanced() :<b>
- * 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) {
- * ZSTD_CCtx_setParameter(zcs, param, value);
- * }
- * ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
- * ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
- *
- * pledgedSrcSize must be correct. If srcSize is not known at init time, use
- * value ZSTD_CONTENTSIZE_UNKNOWN. dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
- */
-size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
- ZSTD_parameters params, unsigned long long pledgedSrcSize);
-</b>/**! ZSTD_initCStream_usingCDict() :<b>
- * This function is deprecated, and equivalent to:
- * ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
- * ZSTD_CCtx_refCDict(zcs, cdict);
- *
- * note : cdict will just be referenced, and must outlive compression session
- */
-size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
-</b>/**! ZSTD_initCStream_usingCDict_advanced() :<b>
- * 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) {
- * ZSTD_CCtx_setParameter(zcs, fParam, value);
- * }
- * ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
- * ZSTD_CCtx_refCDict(zcs, cdict);
- *
- * same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
- * pledgedSrcSize must be correct. If srcSize is not known at init time, use
- * value ZSTD_CONTENTSIZE_UNKNOWN.
- */
-size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize);
+size_t
+ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
+ int compressionLevel,
+ unsigned long long pledgedSrcSize);
</pre></b><BR>
+<a name="Chapter20"></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);
+
+ Creates of an internal CDict (incompatible with static CCtx), except if
+ dict == NULL or dictSize < 8, in which case no dict is used.
+ Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
+ it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
+ Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
+
+<BR></pre>
+
+<a name="Chapter21"></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) {
+ ZSTD_CCtx_setParameter(zcs, param, value);
+ }
+ ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
+ ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
+
+ dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
+ pledgedSrcSize must be correct.
+ If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
+ Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
+
+<BR></pre>
+
+<a name="Chapter22"></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);
+
+ note : cdict will just be referenced, and must outlive compression session
+ Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
+
+<BR></pre>
+
+<a name="Chapter23"></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) {
+ ZSTD_CCtx_setParameter(zcs, fParam, value);
+ }
+ ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
+ ZSTD_CCtx_refCDict(zcs, cdict);
+
+ same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
+ pledgedSrcSize must be correct. If srcSize is not known at init time, use
+ value ZSTD_CONTENTSIZE_UNKNOWN.
+ Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
+
+<BR></pre>
+
<pre><b>size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
</b><p> This function is deprecated, and is equivalent to:
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
@return : 0, or an error code (which can be tested using ZSTD_isError())
+ Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
</p></pre><BR>
* ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
*
* note: no dictionary will be used if dict == NULL or dictSize < 8
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
-</b>/**<b>
- * This function is deprecated, and is equivalent to:
- *
- * ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
- * ZSTD_DCtx_refDDict(zds, ddict);
- *
- * note : ddict is referenced, it must outlive decompression session
- */
-size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
-</b>/**<b>
- * This function is deprecated, and is equivalent to:
- *
- * ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
- *
- * re-use decompression parameters from previous init; saves dictionary loading
- */
-size_t ZSTD_resetDStream(ZSTD_DStream* zds);
</pre></b><BR>
-<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions</h2><pre>
+<a name="Chapter24"></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);
+
+ note : ddict is referenced, it must outlive decompression session
+ Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
+
+<BR></pre>
+
+<a name="Chapter25"></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
+ Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
+
+<BR></pre>
+
+<a name="Chapter26"></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
1"></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
2"></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="Chapter2
3"></a><h2>Block level API</h2><pre></pre>
+<a name="Chapter2
9"></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).
+<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.
A few rules to respect :
ZSTDLIB_API size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
/*! ZSTD_compressCCtx() :
- * Same as ZSTD_compress(), using an explicit ZSTD_CCtx
- * The function will compress at requested compression level,
- * ignoring any other parameter */
+ * Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
+ * Important : in order to behave similarly to `ZSTD_compress()`,
+ * this function compresses at requested compression level,
+ * __ignoring any other parameter__ .
+ * If any advanced parameter was set using the advanced API,
+ * they will all be reset. Only `compressionLevel` remains.
+ */
ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
* using ZSTD_CCtx_set*() functions.
* Pushed parameters are sticky : they are valid for next compressed frame, and any subsequent frame.
* "sticky" parameters are applicable to `ZSTD_compress2()` and `ZSTD_compressStream*()` !
- * They do not apply to "simple" one-shot variants such as ZSTD_compressCCtx()
+ * __They do not apply to "simple" one-shot variants such as ZSTD_compressCCtx()__ .
*
* It's possible to reset all parameters to "default" using ZSTD_CCtx_reset().
*
/* compression parameters
* Note: When compressing with a ZSTD_CDict these parameters are superseded
- * by the parameters used to construct the ZSTD_CDict. See ZSTD_CCtx_refCDict()
- * for more info (superseded-by-cdict). */
- ZSTD_c_compressionLevel=100, /* Update all compression parameters according to pre-defined cLevel table
+ * by the parameters used to construct the ZSTD_CDict.
+ * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
+ ZSTD_c_compressionLevel=100, /* Set compression parameters according to pre-defined cLevel table.
+ * Note that exact compression parameters are dynamically determined,
+ * depending on both compression level and srcSize (when known).
* Default level is ZSTD_CLEVEL_DEFAULT==3.
* Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
* Note 1 : it's possible to pass a negative compression level.
- * Note 2 : setting a level sets all default values of other compression parameters */
+ * Note 2 : setting a level resets all other compression parameters to default */
+ /* Advanced compression parameters :
+ * It's possible to pin down compression parameters to some specific values.
+ * In which case, these values are no longer dynamically selected by the compressor */
ZSTD_c_windowLog=101, /* Maximum allowed back-reference distance, expressed as power of 2.
+ * This will set a memory budget for streaming decompression,
+ * with larger values requiring more memory
+ * and typically compressing more.
* Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
* Special: value 0 means "use default windowLog".
* Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
- * requires explicitly allowing such window size at decompression stage if using streaming. */
+ * requires explicitly allowing such size at streaming decompression stage. */
ZSTD_c_hashLog=102, /* Size of the initial probe table, as a power of 2.
* Resulting memory usage is (1 << (hashLog+2)).
* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
* Resulting memory usage is (1 << (chainLog+2)).
* Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
* Larger tables result in better and slower compression.
- * This parameter is useless when using "fast" strategy.
+ * This parameter is useless for "fast" strategy.
* It's still useful when using "dfast" strategy,
* in which case it defines a secondary probe table.
* Special: value 0 means "use default chainLog". */
ZSTD_c_searchLog=104, /* Number of search attempts, as a power of 2.
* More attempts result in better and slower compression.
- * This parameter is useless when using "fast" and "dFast" strategies.
+ * This parameter is useless for "fast" and "dFast" strategies.
* Special: value 0 means "use default searchLog". */
ZSTD_c_minMatch=105, /* Minimum size of searched matches.
* Note that Zstandard can still find matches of smaller size,
ZSTD_c_contentSizeFlag=200, /* Content size will be written into frame header _whenever known_ (default:1)
* Content size must be known at the beginning of compression.
* This is automatically the case when using ZSTD_compress2(),
- * For streaming variants, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
+ * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
ZSTD_c_checksumFlag=201, /* A 32-bits checksum of content is written at end of frame (default:0) */
ZSTD_c_dictIDFlag=202, /* When applicable, dictionary's ID is written into frame header (default:1) */
* 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.
* Job size must be a minimum of overlap size, or 1 MB, whichever is largest.
- * The minimum size is automatically and transparently enforced */
+ * The minimum size is automatically and transparently enforced. */
ZSTD_c_overlapLog=402, /* Control the overlap size, as a fraction of window size.
* The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
* It helps preserve compression ratio, while each job is compressed in parallel.
} ZSTD_dictLoadMethod_e;
typedef enum {
- /* Opened question : should we have a format ZSTD_f_auto ?
- * Today, it would mean exactly the same as ZSTD_f_zstd1.
- * But, in the future, should several formats become supported,
- * on the compression side, it would mean "default format".
- * On the decompression side, it would mean "automatic format detection",
- * so that ZSTD_f_zstd1 would mean "accept *only* zstd frames".
- * Since meaning is a little different, another option could be to define different enums for compression and decompression.
- * This question could be kept for later, when there are actually multiple formats to support,
- * but there is also the question of pinning enum values, and pinning value `0` is especially important */
ZSTD_f_zstd1 = 0, /* zstd frame format, specified in zstd_compression_format.md (default) */
ZSTD_f_zstd1_magicless = 1 /* Variant of zstd frame format, without initial 4-bytes magic number.
* Useful to save 4 bytes per generated frame.
* Create a digested dictionary for compression
* Dictionary content is just referenced, not duplicated.
* As a consequence, `dictBuffer` **must** outlive CDict,
- * and its content must remain unmodified throughout the lifetime of CDict. */
+ * and its content must remain unmodified throughout the lifetime of CDict.
+ * note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef */
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
/*! ZSTD_getCParams() :
ZSTDLIB_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
/*! ZSTD_compress_advanced() :
- * Same as ZSTD_compress_usingDict(), with fine-tune control over compression parameters (by structure) */
+ * Note : this function is now DEPRECATED.
+ * It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
+ * This prototype will be marked as deprecated and generate compilation warning on reaching v1.5.x */
ZSTDLIB_API size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
ZSTD_parameters params);
/*! ZSTD_compress_usingCDict_advanced() :
- * Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters */
+ * Note : this function is now REDUNDANT.
+ * It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
+ * This prototype will be marked as deprecated and generate compilation warning in some future version */
ZSTDLIB_API size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
* pledgedSrcSize must be correct. If it is not known at init time, use
* ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
* "0" also disables frame content size field. It may be enabled in the future.
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
-ZSTDLIB_API size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize);
+ZSTDLIB_API size_t
+ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
+ int compressionLevel,
+ unsigned long long pledgedSrcSize);
+
/**! ZSTD_initCStream_usingDict() :
* This function is deprecated, and is equivalent to:
* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
* dict == NULL or dictSize < 8, in which case no dict is used.
* Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
* it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
-ZSTDLIB_API size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel);
+ZSTDLIB_API size_t
+ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
+ const void* dict, size_t dictSize,
+ int compressionLevel);
+
/**! ZSTD_initCStream_advanced() :
* This function is deprecated, and is approximately equivalent to:
* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
* ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
* ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
*
- * pledgedSrcSize must be correct. If srcSize is not known at init time, use
- * value ZSTD_CONTENTSIZE_UNKNOWN. dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
+ * dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
+ * pledgedSrcSize must be correct.
+ * If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
-ZSTDLIB_API size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
- ZSTD_parameters params, unsigned long long pledgedSrcSize);
+ZSTDLIB_API size_t
+ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
+ const void* dict, size_t dictSize,
+ ZSTD_parameters params,
+ unsigned long long pledgedSrcSize);
+
/**! ZSTD_initCStream_usingCDict() :
* This function is deprecated, and equivalent to:
* ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
* ZSTD_CCtx_refCDict(zcs, cdict);
*
* note : cdict will just be referenced, and must outlive compression session
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
ZSTDLIB_API size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
+
/**! ZSTD_initCStream_usingCDict_advanced() :
- * This function is deprecated, and is approximately equivalent to:
+ * 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) {
* same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
* pledgedSrcSize must be correct. If srcSize is not known at init time, use
* value ZSTD_CONTENTSIZE_UNKNOWN.
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
-ZSTDLIB_API size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize);
+ZSTDLIB_API size_t
+ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
+ const ZSTD_CDict* cdict,
+ ZSTD_frameParameters fParams,
+ unsigned long long pledgedSrcSize);
/*! ZSTD_resetCStream() :
* This function is deprecated, and is equivalent to:
* For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
* but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
* @return : 0, or an error code (which can be tested using ZSTD_isError())
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
ZSTDLIB_API size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
* ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
*
* note: no dictionary will be used if dict == NULL or dictSize < 8
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
ZSTDLIB_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
+
/**
* This function is deprecated, and is equivalent to:
*
* ZSTD_DCtx_refDDict(zds, ddict);
*
* note : ddict is referenced, it must outlive decompression session
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
ZSTDLIB_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
+
/**
* This function is deprecated, and is equivalent to:
*
* ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
*
* re-use decompression parameters from previous init; saves dictionary loading
+ * Note : this prototype will be marked as deprecated and generate compilation warnings on reaching v1.5.x
*/
ZSTDLIB_API size_t ZSTD_resetDStream(ZSTD_DStream* zds);
/*!
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).
+ 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.
A few rules to respect :
projects / thirdparty / zstd.git / commitdiff
