facebook/zstd
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

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

Browse Source 
Update Comment on `ZSTD_estimateCCtxSize()`
This commit is contained in:
Felix Handte 2019-09-20 15:36:00 -04:00 committed by GitHub
commit c047fcf7bf
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 20 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
lib/zstd.h
View File

@ -1221,14 +1221,23 @@ ZSTDLIB_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
***************************************/ ***************************************/
/*! ZSTD_estimate*() : /*! ZSTD_estimate*() :
* These functions make it possible to estimate memory usage * These functions make it possible to estimate memory usage of a future
* of a future {D,C}Ctx, before its creation. * {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. * ZSTD_estimateCCtxSize() will provide a budget large enough for any
* If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation. * compression level up to selected one. Unlike ZSTD_estimateCStreamSize*(),
* ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. * this estimate does not include space for a window buffer, so this estimate
* 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. * is guaranteed to be enough for single-shot compressions, but not streaming
* Note : CCtx size estimation is only correct for single-threaded compression. */ * 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(int compressionLevel);
ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams); ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params); ZSTDLIB_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);

6
tests/fuzzer.c
View File

@ -2156,9 +2156,9 @@ static int basicUnitTests(U32 const seed, double compressibility)
size_t approxIndex = 0; size_t approxIndex = 0;
size_t maxIndex = ((3U << 29) + (1U << ZSTD_WINDOWLOG_MAX)); /* ZSTD_CURRENT_MAX from zstd_compress_internal.h */ size_t maxIndex = ((3U << 29) + (1U << ZSTD_WINDOWLOG_MAX)); /* ZSTD_CURRENT_MAX from zstd_compress_internal.h */
/* vastly overprovision space in a static context so that we can do all /* Provision enough space in a static context so that we can do all
* this without ever reallocating, which would reset the indices */ * this without ever reallocating, which would reset the indices. */
size_t const staticCCtxSize = 2 * ZSTD_estimateCCtxSize(22); size_t const staticCCtxSize = ZSTD_estimateCStreamSize(22);
void* const staticCCtxBuffer = malloc(staticCCtxSize); void* const staticCCtxBuffer = malloc(staticCCtxSize);
ZSTD_CCtx* cctx = ZSTD_initStaticCCtx(staticCCtxBuffer, staticCCtxSize); ZSTD_CCtx* cctx = ZSTD_initStaticCCtx(staticCCtxBuffer, staticCCtxSize);