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Merge pull request #1806 from felixhandte/estimate-cctx-doc

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Update Comment on `ZSTD_estimateCCtxSize()`
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Felix Handte
2019-09-20 15:36:00 -04:00
committed by GitHub
parent 0e76000dee f7d9b36835
commit c047fcf7bf
2 changed files with 20 additions and 11 deletions
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lib/zstd.h
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@@ -1221,14 +1221,23 @@ ZSTDLIB_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
***************************************/
/*! ZSTD_estimate*() :
* These functions make it possible to estimate memory usage
* of a future {D,C}Ctx, before its creation.
* ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one.
* It will also consider src size to be arbitrarily "large", which is worst case.
* If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
* ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
* ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1.
* Note : CCtx size estimation is only correct for single-threaded compression. */
* These functions make it possible to estimate memory usage of a future
* {D,C}Ctx, before its creation.
*
* ZSTD_estimateCCtxSize() will provide a budget large enough for any
* compression level up to selected one. Unlike ZSTD_estimateCStreamSize*(),
* this estimate does not include space for a window buffer, so this estimate
* is guaranteed to be enough for single-shot compressions, but not streaming
* compressions. It will however assume the input may be arbitrarily large,
* which is the worst case. If srcSize is known to always be small,
* ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
* ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with
* ZSTD_getCParams() to create cParams from compressionLevel.
* ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with
* ZSTD_CCtxParams_setParameter().
*
* Note: only single-threaded compression is supported. This function will
* return an error code if ZSTD_c_nbWorkers is >= 1. */
ZSTDLIB_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);