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ZSTD_decompress_usingDDict() compatible with Legacy mode

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Yann Collet
2016-07-06 20:32:27 +02:00
parent a3d03a3973
commit f246cf5423
3 changed files with 26 additions and 3 deletions
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lib/common/zstd.h
+9 -3
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@@ -408,12 +408,14 @@ ZSTDLIB_API size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t ds
* Block functions
****************************************/
/*! Block functions produce and decode raw zstd blocks, without frame metadata.
Frame metadata cost is typically ~18 bytes, which is non-negligible on very small blocks.
User will have to take in charge required information to regenerate data, such as compressed and content sizes.
A few rules to respect :
- Uncompressed block size must be <= ZSTD_BLOCKSIZE_MAX (128 KB)
+ If you need to compress more, it's recommended to use ZSTD_compress() instead, since frame metadata costs become negligible.
- Compressing or decompressing requires a context structure
+ If you need to compress more, cut data into multiple blocks
+ Consider using the regular ZSTD_compress() instead, as frame metadata costs become negligible when source size is large.
- Compressing and decompressing require a context structure
+ Use ZSTD_createCCtx() and ZSTD_createDCtx()
- It is necessary to init context before starting
+ compression : ZSTD_compressBegin()
@@ -423,12 +425,16 @@ ZSTDLIB_API size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t ds
- When a block is considered not compressible enough, ZSTD_compressBlock() result will be zero.
In which case, nothing is produced into `dst`.
+ User must test for such outcome and deal directly with uncompressed data
+ ZSTD_decompressBlock() doesn't accept uncompressed data as input !!
+ ZSTD_decompressBlock() doesn't accept uncompressed data as input !!!
+ In case of multiple successive blocks, decoder must be informed of uncompressed block existence to follow proper history.
Use ZSTD_insertBlock() in such a case.
Insert block once it's copied into its final position.
*/
#define ZSTD_BLOCKSIZE_MAX (128 * 1024) /* define, for static allocation */
ZSTDLIB_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
ZSTDLIB_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
ZSTDLIB_API size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); /**< insert block into `dctx` history. Useful to track uncompressed blocks */
/*-*************************************