AuroraMiddleware/zstd
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final parameter tuning

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This commit is contained in:
Yann Collet 2018-09-12 16:54:57 -07:00
parent 419dfd4ea3
commit 674dd21bd0
2 changed files with 7 additions and 3 deletions
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7
doc/zstd_manual.html
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@ -181,7 +181,8 @@ size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
</b><p> When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once.
ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay.
ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
`dictBuffer` can be released after ZSTD_CDict creation, since its content is copied within CDict
`dictBuffer` can be released after ZSTD_CDict creation, since its content is copied within CDict
Note : A ZSTD_CDict can be created with an empty dictionary, but it is inefficient for small data.
</p></pre><BR>
<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
@ -195,7 +196,9 @@ size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
</b><p> Compression using a digested Dictionary.
Faster startup than ZSTD_compress_usingDict(), recommended when same dictionary is used multiple times.
Note that compression level is decided during dictionary creation.
Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
Note : ZSTD_compress_usingCDict() can be used with a ZSTD_CDict created from an empty dictionary.
But it is inefficient for small data, and it is recommended to use ZSTD_compressCCtx().
</p></pre><BR>
<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);

3
lib/decompress/zstd_decompress.c
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@ -1039,7 +1039,8 @@ size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx* dctx, int* nbSeqPtr,
/* prefetch dictionary content */
if (dctx->ddictIsCold) {
size_t const dictSize = (const char*)dctx->prefixStart - (const char*)dctx->virtualStart;
size_t const pSize = MIN(dictSize, (size_t)(64*nbSeq));
size_t const psmin = MIN(dictSize, (size_t)(64*nbSeq) /* heuristic */ );
size_t const pSize = MIN(psmin, 128 KB /* protection */ );
const void* const pStart = (const char*)dctx->dictEnd - pSize;
PREFETCH_AREA(pStart, pSize);
dctx->ddictIsCold = 0;