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minor : improved API code comment

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Extend guarantee that ZSTD_getFrameContentSize() will delivering the decompressed size
to any single-pass compression function.

Answer #1156
This commit is contained in:
Yann Collet 2018-05-31 11:12:18 -07:00
parent ac4f7ead3b
commit 9b979d0e33
1 changed files with 4 additions and 4 deletions
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8
lib/zstd.h
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@ -96,7 +96,7 @@ ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
* `src` should point to the start of a ZSTD encoded frame. * `src` should point to the start of a ZSTD encoded frame.
* `srcSize` must be at least as large as the frame header. * `srcSize` must be at least as large as the frame header.
* hint : any size >= `ZSTD_frameHeaderSize_max` is large enough. * hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
* @return : - decompressed size of the frame in `src`, if known * @return : - decompressed size of `src` frame content, if known
* - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined * - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
* - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) * - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
* note 1 : a 0 return value means the frame is valid but "empty". * note 1 : a 0 return value means the frame is valid but "empty".
@ -106,7 +106,8 @@ ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
* Optionally, application can rely on some implicit limit, * Optionally, application can rely on some implicit limit,
* as ZSTD_decompress() only needs an upper bound of decompressed size. * as ZSTD_decompress() only needs an upper bound of decompressed size.
* (For example, data could be necessarily cut into blocks <= 16 KB). * (For example, data could be necessarily cut into blocks <= 16 KB).
* note 3 : decompressed size is always present when compression is done with ZSTD_compress() * note 3 : decompressed size is always present when compression is completed using single-pass functions,
* such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
* note 4 : decompressed size can be very large (64-bits value), * note 4 : decompressed size can be very large (64-bits value),
* potentially larger than what local system can handle as a single memory segment. * potentially larger than what local system can handle as a single memory segment.
* In which case, it's necessary to use streaming mode to decompress data. * In which case, it's necessary to use streaming mode to decompress data.
@ -123,8 +124,7 @@ ZSTDLIB_API unsigned long long ZSTD_getFrameContentSize(const void *src, size_t
* Both functions work the same way, but ZSTD_getDecompressedSize() blends * Both functions work the same way, but ZSTD_getDecompressedSize() blends
* "empty", "unknown" and "error" results to the same return value (0), * "empty", "unknown" and "error" results to the same return value (0),
* while ZSTD_getFrameContentSize() gives them separate return values. * while ZSTD_getFrameContentSize() gives them separate return values.
* `src` is the start of a zstd compressed frame. * @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. */
* @return : content size to be decompressed, as a 64-bits value _if known and not empty_, 0 otherwise. */
ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);