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Merge branch 'dev' of github.com:facebook/zstd into dev

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Yann Collet
2018-11-13 15:54:05 -08:00
parent 092c4abd4c f28af025d9
commit 768a264200
5 changed files with 82 additions and 53 deletions
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59
doc/zstd_manual.html
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@ -798,6 +798,38 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
* Decoder cannot recognise automatically this format, requiring instructions. */
} ZSTD_format_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
* to evolve and should be considered only in the context of extremely
* advanced performance tuning.
*
* Zstd currently supports the use of a CDict in two ways:
*
* - The contents of the CDict can be copied into the working context. This
* means that the compression can search both the dictionary and input
* while operating on a single set of internal tables. This makes
* the compression faster per-byte of input. However, the initial copy of
* the CDict's tables incurs a fixed cost at the beginning of the
* compression. For small compressions (< 8 KB), that copy can dominate
* the cost of the compression.
*
* - The CDict's tables can be used in-place. In this model, compression is
* slower per input byte, because the compressor has to search two sets of
* tables. However, this model incurs no start-up cost (as long as the
* working context's tables can be reused). For small inputs, this can be
* faster than copying the CDict's tables.
*
* Zstd has a simple internal heuristic that selects which strategy to use
* at the beginning of a compression. However, if experimentation shows that
* Zstd is making poor choices, it is possible to override that choice with
* this enum.
*/
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_dictAttachPref_e;
</b></pre><BR>
<pre><b>typedef enum {
</b>/* compression format */<b>
ZSTD_p_format = 10, </b>/* See ZSTD_format_e enum definition.<b>
@ -911,29 +943,14 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
ZSTD_p_forceMaxWindow=1100, </b>/* Force back-reference distances to remain < windowSize,<b>
* even when referencing into Dictionary content (default:0) */
ZSTD_p_forceAttachDict, </b>/* ZSTD supports usage of a CDict in-place<b>
* (avoiding having to copy the compression tables
* from the CDict into the working context). Using
* a CDict in this way saves an initial setup step,
* but comes at the cost of more work per byte of
* input. ZSTD has a simple internal heuristic that
* guesses which strategy will be faster. You can
* use this flag to override that guess.
ZSTD_p_forceAttachDict, </b>/* Controls whether the contents of a CDict are<b>
* used in place, or whether they are copied into
* the working context.
*
* Note that the by-reference, in-place strategy is
* only used when reusing a compression context
* with compatible compression parameters. (If
* incompatible / uninitialized, the working
* context needs to be cleared anyways, which is
* about as expensive as overwriting it with the
* dictionary context, so there's no savings in
* using the CDict by-ref.)
*
* Values greater than 0 force attaching the dict.
* Values less than 0 force copying the dict.
* 0 selects the default heuristic-guided behavior.
* Accepts values from the ZSTD_dictAttachPref_e
* enum. See the comments on that enum for an
* explanation of the feature.
*/
} ZSTD_cParameter;
</b></pre><BR>
<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned value);