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ZSTD_estimateCCtx_advanced()

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ZSTD_estimateCCtx() is now a "simple" function,
taking int compressionLevel as single argument.

ZSTD_estimateCCtx_advanced() takes a CParams argument,
which is both more complete and more complex to generate.
This commit is contained in:
Yann Collet
2017-06-26 15:52:39 -07:00
parent 379f9d874d
commit 31af8290d1
4 changed files with 31 additions and 13 deletions
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doc/zstd_manual.html
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@ -389,6 +389,12 @@ unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
however it does mean that all frame data must be present and valid.
</p></pre><BR>
<pre><b>size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
</b><p> `src` should point to the start of a ZSTD frame
`srcSize` must be >= ZSTD_frameHeaderSize_prefix.
@return : size of the Frame Header
</p></pre><BR>
<a name="Chapter13"></a><h2>Context memory usage</h2><pre></pre>
<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
@ -401,12 +407,15 @@ size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
Object memory usage can evolve if it's re-used multiple times.
</p></pre><BR>
<pre><b>size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams);
<pre><b>size_t ZSTD_estimateCCtxSize(int compressionLevel);
size_t ZSTD_estimateCCtxSize_advanced(ZSTD_compressionParameters cParams);
size_t ZSTD_estimateDCtxSize(void);
</b><p> These functions make it possible to estimate memory usage
of a future target object, before its allocation,
given a set of parameters, which vary depending on target object.
of a future {D,C}Ctx, before its creation.
The objective is to guide decision before allocation.
ZSTD_estimateCCtxSize() will consider src size to be arbitrarily "large".
If srcSize is known to be small, ZSTD_estimateCCtxSize_advanced() will provide a better (smaller) estimation.
ZSTD_estimateCCtxSize_advanced() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
Note : CCtx estimation is only correct for single-threaded compression
</p></pre><BR>