</b>/* compression parameters */<b>
ZSTD_p_compressionLevel=100, </b>/* Update all compression parameters according to pre-defined cLevel table<b>
* Default level is ZSTD_CLEVEL_DEFAULT==3.
- * Special: value 0 means "do not change cLevel". */
+ * Special: value 0 means "do not change cLevel".
+ * Note 1 : it's possible to pass a negative compression level by casting it to unsigned type.
+ * Note 2 : setting compressionLevel automatically updates ZSTD_p_literalCompression. */
ZSTD_p_windowLog, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
* Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
* Special: value 0 means "do not change windowLog".
* Note that currently, for all strategies < btopt, effective minimum is 4.
* Note that currently, for all strategies > fast, effective maximum is 6.
* Special: value 0 means "do not change minMatchLength". */
- ZSTD_p_targetLength, </b>/* Only useful for strategies >= btopt.<b>
- * Length of Match considered "good enough" to stop search.
- * Larger values make compression stronger and slower.
+ ZSTD_p_targetLength, </b>/* Impact of this field depends on strategy.<b>
+ * For strategies btopt & btultra:
+ * Length of Match considered "good enough" to stop search.
+ * Larger values make compression stronger, and slower.
+ * For strategy fast:
+ * Distance between match sampling.
+ * Larger values make compression faster, and weaker.
* Special: value 0 means "do not change targetLength". */
ZSTD_p_compressionStrategy, </b>/* See ZSTD_strategy enum definition.<b>
* Cast selected strategy as unsigned for ZSTD_CCtx_setParameter() compatibility.
* (note : a strong exception to this rule is when first invocation sets ZSTD_e_end : it becomes 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, all invocations are blocking */
- ZSTD_p_jobSize, </b>/* Size of a compression job. This value is only enforced in streaming (non-blocking) mode.<b>
- * Each compression job is completed in parallel, so indirectly controls the nb of active threads.
+ ZSTD_p_jobSize, </b>/* Size of a compression job. This value is enforced only in non-blocking mode.<b>
+ * Each compression job is completed in parallel, so this value indirectly controls the nb of active threads.
* 0 means default, which is dynamically determined based on compression parameters.
- * Job size must be a minimum of overlapSize, or 1 KB, whichever is largest
+ * Job size must be a minimum of overlapSize, or 1 MB, whichever is largest.
* The minimum size is automatically and transparently enforced */
ZSTD_p_overlapSizeLog, </b>/* Size of previous input reloaded at the beginning of each job.<b>
* 0 => no overlap, 6(default) => use 1/8th of windowSize, >=9 => use full windowSize */
</b>/* advanced parameters - may not remain available after API update */<b>
+
+ ZSTD_p_literalCompression=1000, </b>/* control huffman compression of literals (enabled) by default.<b>
+ * disabling it improves speed and decreases compression ratio by a large amount.
+ * note : this setting is updated when changing compression level.
+ * positive compression levels set literalCompression to 1.
+ * negative compression levels set literalCompression to 0. */
+
ZSTD_p_forceMaxWindow=1100, </b>/* Force back-reference distances to remain < windowSize,<b>
* even when referencing into Dictionary content (default:0) */
+
ZSTD_p_enableLongDistanceMatching=1200, </b>/* Enable long distance matching.<b>
* This parameter is designed to improve the compression
* ratio for large inputs with long distance matches.
<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictMode_e dictMode);
-</b><p> Create an internal CDict from dict buffer.
- Decompression will have to use same buffer.
+</b><p> Create an internal CDict from `dict` buffer.
+ Decompression will have to use same dictionary.
@result : 0, or an error code (which can be tested with ZSTD_isError()).
- Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
- meaning "return to no-dictionary mode".
- Note 1 : `dict` content will be copied internally. Use
- ZSTD_CCtx_loadDictionary_byReference() to reference dictionary
- content instead. The dictionary buffer must then outlive its
- users.
+ Special: Adding a NULL (or 0-size) dictionary invalidates previous dictionary,
+ meaning "return to no-dictionary mode".
+ Note 1 : Dictionary will be used for all future compression jobs.
+ To return to "no-dictionary" situation, load a NULL dictionary
Note 2 : Loading a dictionary involves building tables, which are dependent on compression parameters.
For this reason, compression parameters cannot be changed anymore after loading a dictionary.
- It's also a CPU-heavy operation, with non-negligible impact on latency.
- Note 3 : Dictionary will be used for all future compression jobs.
- To return to "no-dictionary" situation, load a NULL dictionary
- Note 5 : Use ZSTD_CCtx_loadDictionary_advanced() to select how dictionary
- content will be interpreted.
-
+ It's also a CPU consuming operation, with non-negligible impact on latency.
+ Note 3 :`dict` content will be copied internally.
+ Use ZSTD_CCtx_loadDictionary_byReference() to reference dictionary content instead.
+ In such a case, dictionary buffer must outlive its users.
+ Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
+ to precisely select how dictionary content must be interpreted.
</p></pre><BR>
<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
Special : adding a NULL CDict means "return to no-dictionary mode".
Note 1 : Currently, only one dictionary can be managed.
Adding a new dictionary effectively "discards" any previous one.
- Note 2 : CDict is just referenced, its lifetime must outlive CCtx.
-
+ Note 2 : CDict is just referenced, its lifetime must outlive CCtx.
</p></pre><BR>
<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize);
Subsequent compression jobs will be done without prefix (if none is explicitly referenced).
If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict instead.
@result : 0, or an error code (which can be tested with ZSTD_isError()).
- Special : Adding any prefix (including NULL) invalidates any previous prefix or dictionary
+ Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
Note 1 : Prefix buffer is referenced. It must outlive compression job.
Note 2 : Referencing a prefix involves building tables, which are dependent on compression parameters.
- It's a CPU-heavy operation, with non-negligible impact on latency.
- Note 3 : By default, the prefix is treated as raw content
- (ZSTD_dm_rawContent). Use ZSTD_CCtx_refPrefix_advanced() to alter
- dictMode.
+ It's a CPU consuming operation, with non-negligible impact on latency.
+ Note 3 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent).
+ Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode.
</p></pre><BR>
<pre><b>typedef enum {
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