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implemented ZSTD_refPrefix()

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This commit is contained in:
Yann Collet
2017-06-27 15:49:12 -07:00
parent 7d3816183f
commit b7372933b8
4 changed files with 61 additions and 57 deletions
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doc/zstd_manual.html
+12 -17
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@@ -348,7 +348,7 @@ static const ZSTD_customMem ZSTD_defaultCMem = { NULL, NULL, NULL };
<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
</b><p> `src` should point to the start of a ZSTD encoded frame or skippable frame
`srcSize` must be at least as large as the frame
@return : the compressed size of the frame pointed to by `src`,FUZ_rand(&lseed) & 1)
@return : the compressed size of the frame pointed to by `src`,
suitable to pass to `ZSTD_decompress` or similar,
or an error code if given invalid input.
</p></pre><BR>
@@ -806,20 +806,13 @@ void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
* The higher the value of selected strategy, the more complex it is,
* resulting in stronger and slower compression.
* Special: value 0 means "do not change strategy". */
#if 0
ZSTD_p_windowSize, </b>/* Maximum allowed back-reference distance.<b>
* Can be set to a more precise value than windowLog.
* Will be transparently reduced to closest possible inferior value
* (see Zstandard compression format) */
</b>/* Not ready yet ! */<b>
#endif
</b>/* frame parameters */<b>
ZSTD_p_contentSizeFlag=200, </b>/* Content size is written into frame header _whenever known_ (default:1) */<b>
ZSTD_p_checksumFlag, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
ZSTD_p_dictIDFlag, </b>/* When applicable, dictID of dictionary is provided in frame header (default:1) */<b>
</b>/* dictionary parameters (must be set before loading) */<b>
</b>/* dictionary parameters (must be set before ZSTD_CCtx_loadDictionary) */<b>
ZSTD_p_dictMode=300, </b>/* Select how dictionary content must be interpreted. Value must be from type ZSTD_dictMode_e.<b>
* default : 0==auto : dictionary will be "full" if it respects specification, otherwise it will be "rawContent" */
ZSTD_p_refDictContent, </b>/* Dictionary content will be referenced, instead of copied (default:0==byCopy).<b>
@@ -876,7 +869,7 @@ void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
</p></pre><BR>
<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
</b><p> Ref a prepared dictionary, to be used for all next compression jobs.
</b><p> Reference a prepared dictionary, to be used for all next compression jobs.
Note that compression parameters are enforced from within CDict,
and supercede any compression parameter previously set within CCtx.
The dictionary will remain valid for future compression jobs using same CCtx.
@@ -888,16 +881,18 @@ void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);
</p></pre><BR>
<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize); </b>/* Not ready yet ! <===================================== */<b>
</b><p> Reference a prefix (raw-content dictionary) for next compression job.
Decompression will have to use same prefix.
Prefix is only used once. Tables are discarded at end of compression job.
If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict.
<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize);
</b><p> Reference a prefix (single-usage dictionary) for next compression job.
Decompression need same prefix to properly regenerate data.
Prefix is **only used once**. Tables are discarded at end of compression job.
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 a NULL (or 0-size) dictionary invalidates any previous prefix, meaning "return to no-dictionary mode".
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.
It's a CPU-heavy operation, with non-negligible impact on latency.
Note 3 : it's possible to alter ZSTD_p_dictMode using ZSTD_CCtx_setParameter()
</p></pre><BR>
<pre><b>typedef enum {