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Merge pull request #2974 from facebook/fix2966_part3

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Lazy parameters adaptation (part 1 - ZSTD_c_stableInBuffer)
This commit is contained in:
Yann Collet
2022-01-27 06:14:04 -08:00
committed by GitHub
parent 7543085013 f2d9652ad8
commit bad7f82300
7 changed files with 208 additions and 99 deletions
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lib/zstd.h
+15 -15
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@@ -1834,13 +1834,16 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo
* Experimental parameter.
* Default is 0 == disabled. Set to 1 to enable.
*
* Tells the compressor that the ZSTD_inBuffer will ALWAYS be the same
* between calls, except for the modifications that zstd makes to pos (the
* caller must not modify pos). This is checked by the compressor, and
* compression will fail if it ever changes. This means the only flush
* mode that makes sense is ZSTD_e_end, so zstd will error if ZSTD_e_end
* is not used. The data in the ZSTD_inBuffer in the range [src, src + pos)
* MUST not be modified during compression or you will get data corruption.
* Tells the compressor that input data presented with ZSTD_inBuffer
* will ALWAYS be the same between calls.
* Technically, the @src pointer must never be changed,
* and the @pos field can only be updated by zstd.
* However, it's possible to increase the @size field,
* allowing scenarios where more data can be appended after compressions starts.
* These conditions are checked by the compressor,
* and compression will fail if they are not respected.
* Also, data in the ZSTD_inBuffer within the range [src, src + pos)
* MUST not be modified during compression or it will result in data corruption.
*
* When this flag is enabled zstd won't allocate an input window buffer,
* because the user guarantees it can reference the ZSTD_inBuffer until
@@ -1848,18 +1851,15 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo
* large enough to fit a block (see ZSTD_c_stableOutBuffer). This will also
* avoid the memcpy() from the input buffer to the input window buffer.
*
* NOTE: ZSTD_compressStream2() will error if ZSTD_e_end is not used.
* That means this flag cannot be used with ZSTD_compressStream().
*
* NOTE: So long as the ZSTD_inBuffer always points to valid memory, using
* this flag is ALWAYS memory safe, and will never access out-of-bounds
* memory. However, compression WILL fail if you violate the preconditions.
* memory. However, compression WILL fail if conditions are not respected.
*
* WARNING: The data in the ZSTD_inBuffer in the range [dst, dst + pos) MUST
* not be modified during compression or you will get data corruption. This
* is because zstd needs to reference data in the ZSTD_inBuffer to find
* WARNING: The data in the ZSTD_inBuffer in the range [src, src + pos) MUST
* not be modified during compression or it will result in data corruption.
* This is because zstd needs to reference data in the ZSTD_inBuffer to find
* matches. Normally zstd maintains its own window buffer for this purpose,
* but passing this flag tells zstd to use the user provided buffer.
* but passing this flag tells zstd to rely on user provided buffer instead.
*/
#define ZSTD_c_stableInBuffer ZSTD_c_experimentalParam9