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added documentation for LDM + dictionary compatibility #3553

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Mar 16, 2023
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added documentation for LDM + dictionary compatibility #3553

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15 changes: 11 additions & 4 deletions lib/zstd.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1020,9 +1020,11 @@ ZSTDLIB_API unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
* Advanced dictionary and prefix API (Requires v1.4.0+)
*
* This API allows dictionaries to be used with ZSTD_compress2(),
* ZSTD_compressStream2(), and ZSTD_decompressDCtx(). Dictionaries are sticky, and
* only reset with the context is reset with ZSTD_reset_parameters or
* ZSTD_reset_session_and_parameters. Prefixes are single-use.
* ZSTD_compressStream2(), and ZSTD_decompressDCtx().
* Dictionaries are sticky, they remain valid when same context is re-used,
* they only reset when the context is reset
* with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters.
* In contrast, Prefixes are single-use.
******************************************************************************/


Expand All @@ -1043,7 +1045,11 @@ ZSTDLIB_API unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
* Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference 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. */
* to precisely select how dictionary content must be interpreted.
* Note 5 : This method does not benefit from LDM (long distance mode).
* If you want to employ LDM on some large dictionary content,
* prefer employing ZSTD_CCtx_refPrefix() described below.
*/
ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);

/*! ZSTD_CCtx_refCDict() : Requires v1.4.0+
Expand All @@ -1066,6 +1072,7 @@ ZSTDLIB_API size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
* Decompression will need same prefix to properly regenerate data.
* Compressing with a prefix is similar in outcome as performing a diff and compressing it,
* but performs much faster, especially during decompression (compression speed is tunable with compression level).
* This method is compatible with LDM (long distance mode).
* @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
* Note 1 : Prefix buffer is referenced. It **must** outlive compression.
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