ddidderr/zstd-rs
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pushed enum values for strategy by one (ZSTD_fast==1)

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this makes it possible to use `0` to mean:
"do not change strategy"
This commit is contained in:
Yann Collet
2017-05-12 16:29:19 -07:00
parent add66f816d
commit a5ffe3d370
6 changed files with 71 additions and 55 deletions
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lib/compress/zstd_compress.c
+8 -4
View File
@@ -273,7 +273,8 @@ size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned v
return 0;
case ZSTD_p_compressionStrategy :
if (value > (unsigned)ZSTD_btultra) return ERROR(compressionParameter_unsupported);
if (value == 0) return 0; /* special value : 0 means "don't change anything" */
CLAMPCHECK(value, (unsigned)ZSTD_fast, (unsigned)ZSTD_btultra);
ZSTD_cLevelToCParams(cctx);
cctx->params.cParams.strategy = (ZSTD_strategy)value;
return 0;
@@ -2575,14 +2576,17 @@ typedef void (*ZSTD_blockCompressor) (ZSTD_CCtx* ctx, const void* src, size_t sr
static ZSTD_blockCompressor ZSTD_selectBlockCompressor(ZSTD_strategy strat, int extDict)
{
static const ZSTD_blockCompressor blockCompressor[2][8] = {
{ ZSTD_compressBlock_fast, ZSTD_compressBlock_doubleFast, ZSTD_compressBlock_greedy,
static const ZSTD_blockCompressor blockCompressor[2][(unsigned)ZSTD_btultra+1] = {
{ NULL,
ZSTD_compressBlock_fast, ZSTD_compressBlock_doubleFast, ZSTD_compressBlock_greedy,
ZSTD_compressBlock_lazy, ZSTD_compressBlock_lazy2, ZSTD_compressBlock_btlazy2,
ZSTD_compressBlock_btopt, ZSTD_compressBlock_btultra },
{ ZSTD_compressBlock_fast_extDict, ZSTD_compressBlock_doubleFast_extDict, ZSTD_compressBlock_greedy_extDict,
{ NULL,
ZSTD_compressBlock_fast_extDict, ZSTD_compressBlock_doubleFast_extDict, ZSTD_compressBlock_greedy_extDict,
ZSTD_compressBlock_lazy_extDict,ZSTD_compressBlock_lazy2_extDict, ZSTD_compressBlock_btlazy2_extDict,
ZSTD_compressBlock_btopt_extDict, ZSTD_compressBlock_btultra_extDict }
};
ZSTD_STATIC_ASSERT((unsigned)ZSTD_fast == 1);
return blockCompressor[extDict][(U32)strat];
}
lib/zstd.h
+27 -21
View File
@@ -36,9 +36,10 @@ extern "C" {
/*******************************************************************************************************
Introduction
zstd, short for Zstandard, is a fast lossless compression algorithm, targeting real-time compression scenarios
at zlib-level and better compression ratios. The zstd compression library provides in-memory compression and
decompression functions. The library supports compression levels from 1 up to ZSTD_maxCLevel() which is 22.
zstd, short for Zstandard, is a fast lossless compression algorithm,
targeting real-time compression scenarios at zlib-level and better compression ratios.
The zstd compression library provides in-memory compression and decompression functions.
The library supports compression levels from 1 up to ZSTD_maxCLevel() which is currently 22.
Levels >= 20, labeled `--ultra`, should be used with caution, as they require more memory.
Compression can be done in:
- a single step (described as Simple API)
@@ -89,21 +90,17 @@ ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
const void* src, size_t compressedSize);
/*! ZSTD_getDecompressedSize() :
* NOTE: This function is planned to be obsolete, in favour of ZSTD_getFrameContentSize.
* ZSTD_getFrameContentSize functions the same way, returning the decompressed size of a single
* frame, but distinguishes empty frames from frames with an unknown size, or errors.
*
* Additionally, ZSTD_findDecompressedSize can be used instead. It can handle multiple
* concatenated frames in one buffer, and so is more general.
* As a result however, it requires more computation and entire frames to be passed to it,
* as opposed to ZSTD_getFrameContentSize which requires only a single frame's header.
* NOTE: This function is planned to be obsolete, in favor of ZSTD_getFrameContentSize().
* ZSTD_getFrameContentSize() works the same way,
* returning the decompressed size of a single frame,
* but distinguishes empty frames from frames with an unknown size, or errors.
*
* 'src' is the start of a zstd compressed frame.
* @return : content size to be decompressed, as a 64-bits value _if known_, 0 otherwise.
* note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
* note 1 : decompressed size is an optional field, it may not be present, typically in streaming mode.
* When `return==0`, data to decompress could be any size.
* In which case, it's necessary to use streaming mode to decompress data.
* Optionally, application can still use ZSTD_decompress() while relying on implied limits.
* Optionally, application can use ZSTD_decompress() while relying on implied limits.
* (For example, data may be necessarily cut into blocks <= 16 KB).
* note 2 : decompressed size is always present when compression is done with ZSTD_compress()
* note 3 : decompressed size can be very large (64-bits value),
@@ -137,20 +134,26 @@ ZSTDLIB_API size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
/*! ZSTD_compressCCtx() :
* Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()). */
ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, int compressionLevel);
ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
int compressionLevel);
/*= Decompression context
* When decompressing many times,
* it is recommended to allocate a context just once, and re-use it for each successive compression operation.
* it is recommended to allocate a context only once,
* and re-use it for each successive compression operation.
* This will make workload friendlier for system's memory.
* Use one context per thread for parallel execution in multi-threaded environments. */
* Use one context per thread for parallel execution. */
typedef struct ZSTD_DCtx_s ZSTD_DCtx;
ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx(void);
ZSTDLIB_API size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
/*! ZSTD_decompressDCtx() :
* Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()). */
ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
* Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()) */
ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize);
/**************************
@@ -187,7 +190,8 @@ typedef struct ZSTD_CDict_s ZSTD_CDict;
* ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay.
* ZSTD_CDict can be created once and used by multiple threads concurrently, as its usage is read-only.
* `dictBuffer` can be released after ZSTD_CDict creation, as its content is copied within CDict */
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, int compressionLevel);
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
int compressionLevel);
/*! ZSTD_freeCDict() :
* Function frees memory allocated by ZSTD_createCDict(). */
@@ -375,7 +379,8 @@ static const size_t ZSTD_skippableHeaderSize = 8; /* magic number + skippable f
/*--- Advanced types ---*/
typedef enum { ZSTD_fast, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2, ZSTD_btlazy2, ZSTD_btopt, ZSTD_btultra } ZSTD_strategy; /* from faster to stronger */
typedef enum { ZSTD_fast=1, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2,
ZSTD_btlazy2, ZSTD_btopt, ZSTD_btultra } ZSTD_strategy; /* from faster to stronger */
typedef struct {
unsigned windowLog; /**< largest match distance : larger == more compression, more memory needed during decompression */
@@ -623,7 +628,8 @@ typedef enum {
ZSTD_p_compressionStrategy, /* See ZSTD_strategy enum definition.
* Cast selected strategy as unsigned for ZSTD_CCtx_setParameter() compatibility.
* The higher the value of selected strategy, the more complex it is,
* resulting in stronger and slower compression. */
* resulting in stronger and slower compression.
* Special: value 0 means "do not change strategy". */
#if 0
ZSTD_p_windowSize, /* Maximum allowed back-reference distance.
* Can be set to a more precise value than windowLog.