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added unit tests for compressBound()

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and rephrased the code documentation, as suggested by @terrelln
This commit is contained in:
Yann Collet
2022-12-16 12:35:14 -08:00
parent 45ed0df18a
commit 97f63ce2b5
2 changed files with 109 additions and 89 deletions
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lib/zstd.h
+5 -6
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@@ -204,11 +204,10 @@ ZSTDLIB_API size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize)
/* ZSTD_compressBound() :
* maximum compressed size in worst case single-pass scenario.
* When invoking `ZSTD_compress()` or any other one-pass compression function,
* providing @dstCapacity >= ZSTD_compressBound(srcSize) guarantees success.
* Note that it's still allowed to provide a smaller @dstCapacity value,
* in which case, the caller must inspect the return value with ZSTD_isError(),
* to detect any potential compression failure.
* Note : ZSTD_compressBound() itself can fail, if @srcSize is too large.
* it's recommended to provide @dstCapacity >= ZSTD_compressBound(srcSize)
* as it eliminates one potential failure scenario,
* aka not enough room in dst buffer to write the compressed frame.
* Note : ZSTD_compressBound() itself can fail, if @srcSize > ZSTD_MAX_INPUT_SIZE .
* In which case, ZSTD_compressBound() will return an error code
* which can be tested using ZSTD_isError().
*
@@ -219,7 +218,7 @@ ZSTDLIB_API size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize)
* Will produce constant value 0 if srcSize too large.
*/
#define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00LLU : 0xFF00FF00U)
#define ZSTD_COMPRESSBOUND(srcSize) (((unsigned long long)(srcSize) > ZSTD_MAX_INPUT_SIZE) ? 0 : (srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) /* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */
#define ZSTD_COMPRESSBOUND(srcSize) (((size_t)(srcSize) > ZSTD_MAX_INPUT_SIZE) ? 0 : (srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) /* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */
ZSTDLIB_API size_t ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case single-pass scenario */
/* ZSTD_isError() :
* Most ZSTD_* functions returning a size_t value can be tested for error,