From owner-svn-src-head@freebsd.org Fri Jul 14 14:55:36 2017
Return-Path: `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
- `dstCapacity` is an upper bound of originalSize.
+ `dstCapacity` is an upper bound of originalSize to regenerate.
If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
@return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
or an errorCode if it fails (which can be tested using ZSTD_isError()).
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.
+ 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.
- 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.
-
'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),
@@ -96,7 +93,7 @@
note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
Always ensure result fits within application's authorized limits.
Each application can set its own limits.
- note 5 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameParams() to know more.
+ note 5 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameHeader() to know more.
Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()).
Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()).
+ Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx())
Compression using a predefined Dictionary (see dictBuilder/zdict.h).
- Note : This function loads the dictionary, resulting in significant startup delay.
- Note : When `dict == NULL || dictSize < 8` no dictionary is used.
+ Compression using a predefined Dictionary (see dictBuilder/zdict.h).
+ Note : This function loads the dictionary, resulting in significant startup delay.
+ Note : When `dict == NULL || dictSize < 8` no dictionary is used.
Decompression using a predefined Dictionary (see dictBuilder/zdict.h).
- Dictionary must be identical to the one used during compression.
- Note : This function loads the dictionary, resulting in significant startup delay.
- Note : When `dict == NULL || dictSize < 8` no dictionary is used.
+ Decompression using a predefined Dictionary (see dictBuilder/zdict.h).
+ Dictionary must be identical to the one used during compression.
+ Note : This function loads the dictionary, resulting in significant startup delay.
+ Note : When `dict == NULL || dictSize < 8` no dictionary is used.
When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once.
- 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
+ When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once.
+ ZSTD_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay.
+ ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
+ `dictBuffer` can be released after ZSTD_CDict creation, since its content is copied within CDict
Function frees memory allocated by ZSTD_createCDict().
+ Function frees memory allocated by ZSTD_createCDict().
zstd 1.2.0 Manual
+zstd 1.3.0 Manual
Contents
@@ -13,14 +13,14 @@
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)
- a single step, reusing a context (described as Explicit memory management)
- unbounded multiple steps (described as Streaming compression)
- The compression ratio achievable on small data can be highly improved using compression with a dictionary in:
+ The compression ratio achievable on small data can be highly improved using a dictionary in:
- a single step (described as Simple dictionary API)
- a single step, reusing a dictionary (described as Fast dictionary API)
Advanced experimental functions can be accessed using #define ZSTD_STATIC_LINKING_ONLY before including zstd.h.
- These APIs shall never be used with a dynamic library.
+ Advanced experimental APIs shall never be used with a dynamic library.
They are not "stable", their definition may change in the future. Only static linking is allowed.
Version
-unsigned ZSTD_versionNumber(void); /**< library version number; to be used when checking dll version */
+
unsigned ZSTD_versionNumber(void); /**< useful to check dll version */
Simple API
@@ -66,28 +67,24 @@
size_t ZSTD_decompress( void* dst, size_t dstCapacity,
const void* src, size_t compressedSize);
unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
-
Helper functions
int ZSTD_maxCLevel(void);
/*!< maximum compression level available */
@@ -114,20 +111,26 @@ const char* ZSTD_getErrorName(size_t code); /*
ZSTD_CCtx* ZSTD_createCCtx(void);
size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx);
-size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, int compressionLevel);
+
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;
ZSTD_DCtx* ZSTD_createDCtx(void);
size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
-size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
-
size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx,
+ void* dst, size_t dstCapacity,
+ const void* src, size_t srcSize);
+
Simple dictionary API
@@ -137,32 +140,33 @@ size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
const void* src, size_t srcSize,
const void* dict,size_t dictSize,
int compressionLevel);
-
size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
void* dst, size_t dstCapacity,
const void* src, size_t srcSize,
const void* dict,size_t dictSize);
-
-Fast dictionary API
+Bulk processing dictionary API
-ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, int compressionLevel);
-
ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
+ int compressionLevel);
+
size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
-
size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
@@ -176,20 +180,20 @@ size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx);
ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize); -Create a digested dictionary, ready to start decompression operation without startup delay. - dictBuffer can be released after DDict creation, as its content is copied inside DDict +
Create a digested dictionary, ready to start decompression operation without startup delay. + dictBuffer can be released after DDict creation, as its content is copied inside DDict
size_t ZSTD_freeDDict(ZSTD_DDict* ddict); -Function frees memory allocated with ZSTD_createDDict() +
Function frees memory allocated with ZSTD_createDDict()
size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, const ZSTD_DDict* ddict); -Decompression using a digested Dictionary. - Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times. +
Decompression using a digested Dictionary. + Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times.
typedef ZSTD_CCtx ZSTD_CStream; /**< CCtx and CStream are now effectively same object (>= v1.3.0) */ +
ZSTD_CStream* ZSTD_createCStream(void); size_t ZSTD_freeCStream(ZSTD_CStream* zcs);
typedef ZSTD_DCtx ZSTD_DStream; /**< DCtx and DStream are now effectively same object (>= v1.3.0) */ +
ZSTD_DStream* ZSTD_createDStream(void); size_t ZSTD_freeDStream(ZSTD_DStream* zds);
typedef enum { ZSTD_fast, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2, ZSTD_btlazy2, ZSTD_btopt, ZSTD_btopt2 } 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 */ @@ -319,68 +330,141 @@ size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_o ZSTD_frameParameters fParams; } ZSTD_parameters;
+typedef struct { + unsigned long long frameContentSize; + size_t windowSize; + unsigned dictID; + unsigned checksumFlag; +} ZSTD_frameHeader; +
Custom memory allocation functions
typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size); typedef void (*ZSTD_freeFunction) (void* opaque, void* address); typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem; +/* use this constant to defer to stdlib's functions */ +static const ZSTD_customMem ZSTD_defaultCMem = { NULL, NULL, NULL };
size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);`src` should point to the start of a ZSTD encoded frame or skippable frame `srcSize` must be at least as large as the frame - @return : the compressed size of the frame pointed to by `src`, suitable to pass to - `ZSTD_decompress` or similar, or an error code if given invalid input. + @return : the compressed size of the frame pointed to by `src`, + suitable to pass to `ZSTD_decompress` or similar, + or an error code if given invalid input.
unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize); -`src` should point to the start of a ZSTD encoded frame - `srcSize` must be at least as large as the frame header. A value greater than or equal - to `ZSTD_frameHeaderSize_max` is guaranteed to be large enough in all cases. - @return : decompressed size of the frame pointed to be `src` if known, otherwise - - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined - - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) +
#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1) +#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2) +unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize); +`src` should point to the start of a ZSTD encoded frame. + `srcSize` must be at least as large as the frame header. + A value >= `ZSTD_frameHeaderSize_max` is guaranteed to be large enough. + @return : - decompressed size of the frame pointed to be `src` if known + - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined + - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize); -`src` should point the start of a series of ZSTD encoded and/or skippable frames - `srcSize` must be the _exact_ size of this series +
`src` should point the start of a series of ZSTD encoded and/or skippable frames + `srcSize` must be the _exact_ size of this series (i.e. there should be a frame boundary exactly `srcSize` bytes after `src`) - @return : the decompressed size of all data in the contained frames, as a 64-bit value _if known_ - - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN - - if an error occurred: ZSTD_CONTENTSIZE_ERROR + @return : - decompressed size of all data in all successive frames + - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN + - if an error occurred: ZSTD_CONTENTSIZE_ERROR - note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. - When `return==ZSTD_CONTENTSIZE_UNKNOWN`, 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. - (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), - 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. - note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified. - Always ensure result fits within application's authorized limits. - Each application can set its own limits. - note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to - read each contained frame header. This is efficient as most of the data is skipped, - however it does mean that all frame data must be present and valid. + note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. + When `return==ZSTD_CONTENTSIZE_UNKNOWN`, 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. + (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), + 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. + note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified. + Always ensure result fits within application's authorized limits. + Each application can set its own limits. + note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to + read each contained frame header. This is efficient as most of the data is skipped, + however it does mean that all frame data must be present and valid.
-Advanced compression functions
+size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize); +`src` should point to the start of a ZSTD frame + `srcSize` must be >= ZSTD_frameHeaderSize_prefix. + @return : size of the Frame Header +
-size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams); -Gives the amount of memory allocated for a ZSTD_CCtx given a set of compression parameters. - `frameContentSize` is an optional parameter, provide `0` if unknown +
Context memory usage
+ +size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); +size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); +size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); +size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); +size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); +size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); +These functions give the current memory usage of selected object. + Object memory usage can evolve if it's re-used multiple times.
+size_t ZSTD_estimateCCtxSize(int compressionLevel); +size_t ZSTD_estimateCCtxSize_advanced(ZSTD_compressionParameters cParams); +size_t ZSTD_estimateDCtxSize(void); +These functions make it possible to estimate memory usage + of a future {D,C}Ctx, before its creation. + ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one. + It will also consider src size to be arbitrarily "large", which is worst case. + If srcSize is known to always be small, ZSTD_estimateCCtxSize_advanced() can provide a tighter estimation. + ZSTD_estimateCCtxSize_advanced() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. + Note : CCtx estimation is only correct for single-threaded compression +
+ +size_t ZSTD_estimateCStreamSize(int compressionLevel); +size_t ZSTD_estimateCStreamSize_advanced(ZSTD_compressionParameters cParams); +size_t ZSTD_estimateDStreamSize(size_t windowSize); +size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize); +ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one. + It will also consider src size to be arbitrarily "large", which is worst case. + If srcSize is known to always be small, ZSTD_estimateCStreamSize_advanced() can provide a tighter estimation. + ZSTD_estimateCStreamSize_advanced() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. + Note : CStream estimation is only correct for single-threaded compression. + ZSTD_DStream memory budget depends on window Size. + This information can be passed manually, using ZSTD_estimateDStreamSize, + or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame(); + Note : if streaming is init with function ZSTD_init?Stream_usingDict(), + an internal ?Dict will be created, which additional size is not estimated here. + In this case, get total size by adding ZSTD_estimate?DictSize +
+ +size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel); +size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, unsigned byReference); +size_t ZSTD_estimateDDictSize(size_t dictSize, unsigned byReference); +ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict(). + ZSTD_estimateCStreamSize_advanced() makes it possible to control precisely compression parameters, like ZSTD_createCDict_advanced(). + Note : dictionary created "byReference" are smaller +
+ +Advanced compression functions
+ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);Create a ZSTD compression context using external alloc and free functions
-size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); -Gives the amount of memory used by a given ZSTD_CCtx +
ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize); +workspace: The memory area to emplace the context into. + Provided pointer must 8-bytes aligned. + It must outlive context usage. + workspaceSize: Use ZSTD_estimateCCtxSize() or ZSTD_estimateCStreamSize() + to determine how large workspace must be to support scenario. + @return : pointer to ZSTD_CCtx*, or NULL if error (size too small) + Note : zstd will never resize nor malloc() when using a static cctx. + If it needs more memory than available, it will simply error out. + Note 2 : there is no corresponding "free" function. + Since workspace was allocated externally, it must be freed externally too. + Limitation 1 : currently not compatible with internal CDict creation, such as + ZSTD_CCtx_loadDictionary() or ZSTD_initCStream_usingDict(). + Limitation 2 : currently not compatible with multi-threading +
typedef enum { @@ -399,13 +483,34 @@ typedef struct { ZSTD_allocFunction customAlloc; ZSTD_ It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict
-ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize, unsigned byReference, +typedef enum { ZSTD_dm_auto=0, /* dictionary is "full" if it starts with ZSTD_MAGIC_DICTIONARY, rawContent otherwize */ + ZSTD_dm_rawContent, /* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */ + ZSTD_dm_fullDict /* refuses to load a dictionary if it does not respect Zstandard's specification */ +} ZSTD_dictMode_e; +
+ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize, + unsigned byReference, ZSTD_dictMode_e dictMode, ZSTD_compressionParameters cParams, ZSTD_customMem customMem);Create a ZSTD_CDict using external alloc and free, and customized compression parameters
-size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); -Gives the amount of memory used by a given ZSTD_sizeof_CDict +
ZSTD_CDict* ZSTD_initStaticCDict( + void* workspace, size_t workspaceSize, + const void* dict, size_t dictSize, + unsigned byReference, ZSTD_dictMode_e dictMode, + ZSTD_compressionParameters cParams); +Generate a digested dictionary in provided memory area. + workspace: The memory area to emplace the dictionary into. + Provided pointer must 8-bytes aligned. + It must outlive dictionary usage. + workspaceSize: Use ZSTD_estimateCDictSize() + to determine how large workspace must be. + cParams : use ZSTD_getCParams() to transform a compression level + into its relevants cParams. + @return : pointer to ZSTD_CDict*, or NULL if error (size too small) + Note : there is no corresponding "free" function. + Since workspace was allocated externally, it must be freed externally. +
ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); @@ -423,8 +528,8 @@ typedef struct { ZSTD_allocFunction customAlloc; ZSTD_
ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); -optimize params for a given `srcSize` and `dictSize`. - both values are optional, select `0` if unknown. +
optimize params for a given `srcSize` and `dictSize`. + both values are optional, select `0` if unknown.
size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx, @@ -451,22 +556,32 @@ typedef struct { ZSTD_allocFunction customAlloc; ZSTD_ Note 3 : Skippable Frame Identifiers are considered valid.
-size_t ZSTD_estimateDCtxSize(void); -Gives the potential amount of memory allocated to create a ZSTD_DCtx -
-ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);Create a ZSTD decompression context using external alloc and free functions
-size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); -Gives the amount of memory used by a given ZSTD_DCtx +
ZSTD_DCtx* ZSTD_initStaticDCtx(void* workspace, size_t workspaceSize); +workspace: The memory area to emplace the context into. + Provided pointer must 8-bytes aligned. + It must outlive context usage. + workspaceSize: Use ZSTD_estimateDCtxSize() or ZSTD_estimateDStreamSize() + to determine how large workspace must be to support scenario. + @return : pointer to ZSTD_DCtx*, or NULL if error (size too small) + Note : zstd will never resize nor malloc() when using a static dctx. + If it needs more memory than available, it will simply error out. + Note 2 : static dctx is incompatible with legacy support + Note 3 : there is no corresponding "free" function. + Since workspace was allocated externally, it must be freed externally. + Limitation : currently not compatible with internal DDict creation, + such as ZSTD_initDStream_usingDict(). +
ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);Create a digested dictionary, ready to start decompression operation without startup delay. - Dictionary content is simply referenced, and therefore stays in dictBuffer. - It is important that dictBuffer outlives DDict, it must remain read accessible throughout the lifetime of DDict + Dictionary content is referenced, and therefore stays in dictBuffer. + It is important that dictBuffer outlives DDict, + it must remain read accessible throughout the lifetime of DDict
ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize, @@ -474,8 +589,19 @@ typedef struct { ZSTD_allocFunction customAlloc; ZSTD_Create a ZSTD_DDict using external alloc and free, optionally by reference
-size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); -Gives the amount of memory used by a given ZSTD_DDict +
ZSTD_DDict* ZSTD_initStaticDDict(void* workspace, size_t workspaceSize, + const void* dict, size_t dictSize, + unsigned byReference); +Generate a digested dictionary in provided memory area. + workspace: The memory area to emplace the dictionary into. + Provided pointer must 8-bytes aligned. + It must outlive dictionary usage. + workspaceSize: Use ZSTD_estimateDDictSize() + to determine how large workspace must be. + @return : pointer to ZSTD_DDict*, or NULL if error (size too small) + Note : there is no corresponding "free" function. + Since workspace was allocated externally, it must be freed externally. +
unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize); @@ -499,19 +625,19 @@ typedef struct { ZSTD_allocFunction customAlloc; ZSTD_ Note : this use case also happens when using a non-conformant dictionary. - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`). - This is not a Zstandard frame. - When identifying the exact failure cause, it's possible to use ZSTD_getFrameParams(), which will provide a more precise error code. + When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
Advanced streaming functions
Advanced Streaming compression functions
ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem); -size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);/**< size of CStream is variable, depending primarily on compression level */ +ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); /**< same as ZSTD_initStaticCCtx() */ size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, int compressionLevel, unsigned long long pledgedSrcSize); /**< pledgedSrcSize must be correct, a size of 0 means unknown. for a frame size of 0 use initCStream_advanced */ -size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); /**< note: a dict will not be used if dict == NULL or dictSize < 8 */ +size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel); /**< creates of an internal CDict (incompatible with static CCtx), except if dict == NULL or dictSize < 8, in which case no dict is used. */ size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); /**< pledgedSrcSize is optional and can be 0 (meaning unknown). note: if the contentSizeFlag is set, pledgedSrcSize == 0 means the source size is actually 0 */ size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); /**< note : cdict will just be referenced, and must outlive compression session */ -size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, unsigned long long pledgedSrcSize, ZSTD_frameParameters fParams); /**< same as ZSTD_initCStream_usingCDict(), with control over frame parameters */ +size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, const ZSTD_CDict* cdict, ZSTD_frameParameters fParams, unsigned long long pledgedSrcSize); /**< same as ZSTD_initCStream_usingCDict(), with control over frame parameters */
size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);start a new compression job, using same parameters from previous job. @@ -524,11 +650,11 @@ size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStre
Advanced Streaming decompression functions
typedef enum { DStream_p_maxWindowSize } ZSTD_DStreamParameter_e; ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem); -size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);/**< note: a dict will not be used if dict == NULL or dictSize < 8 */ +ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); /**< same as ZSTD_initStaticDCtx() */ size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue); +size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); /**< note: a dict will not be used if dict == NULL or dictSize < 8 */ size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); /**< note : ddict will just be referenced, and must outlive decompression session */ size_t ZSTD_resetDStream(ZSTD_DStream* zds); /**< re-use decompression parameters from previous init; saves dictionary loading */ -size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
Buffer-less and synchronous inner streaming functions
This is an advanced API, giving full control over buffer management, for users which need direct control over memory. @@ -578,21 +704,24 @@ size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it. A ZSTD_DCtx object can be re-used multiple times. - First typical operation is to retrieve frame parameters, using ZSTD_getFrameParams(). - It fills a ZSTD_frameParams structure which provide important information to correctly decode the frame, - such as the minimum rolling buffer size to allocate to decompress data (`windowSize`), - and the dictionary ID used. + First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader(). + It fills a ZSTD_frameHeader structure with important information to correctly decode the frame, + such as minimum rolling buffer size to allocate to decompress data (`windowSize`), + and the dictionary ID in use. (Note : content size is optional, it may not be present. 0 means : content size unknown). Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information. As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation. - Each application can set its own limit, depending on local restrictions. For extended interoperability, it is recommended to support at least 8 MB. - Frame parameters are extracted from the beginning of the compressed frame. - Data fragment must be large enough to ensure successful decoding, typically `ZSTD_frameHeaderSize_max` bytes. - @result : 0 : successful decoding, the `ZSTD_frameParams` structure is correctly filled. + Each application can set its own limit, depending on local restrictions. + For extended interoperability, it is recommended to support windowSize of at least 8 MB. + Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough. + Data fragment must be large enough to ensure successful decoding. + `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough. + @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled. >0 : `srcSize` is too small, please provide at least @result bytes on next attempt. errorCode, which can be tested using ZSTD_isError(). - Start decompression, with ZSTD_decompressBegin() or ZSTD_decompressBegin_usingDict(). + Start decompression, with ZSTD_decompressBegin(). + If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict(). Alternatively, you can copy a prepared context, using ZSTD_copyDCtx(). Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively. @@ -624,29 +753,196 @@ size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits c) Frame Content - any content (User Data) of length equal to Frame Size For skippable frames ZSTD_decompressContinue() always returns 0. - For skippable frames ZSTD_getFrameParams() returns fparamsPtr->windowLog==0 what means that a frame is skippable. + For skippable frames ZSTD_getFrameHeader() returns fparamsPtr->windowLog==0 what means that a frame is skippable. Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content. For purposes of decompression, it is valid in both cases to skip the frame using ZSTD_findFrameCompressedSize to find its size in bytes. It also returns Frame Size as fparamsPtr->frameContentSize.-typedef struct { - unsigned long long frameContentSize; - unsigned windowSize; - unsigned dictID; - unsigned checksumFlag; -} ZSTD_frameParams; -
-Buffer-less streaming decompression functions
size_t ZSTD_getFrameParams(ZSTD_frameParams* fparamsPtr, const void* src, size_t srcSize);/**< doesn't consume input, see details below */ +Buffer-less streaming decompression functions
size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize);/**< doesn't consume input */ size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx); size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); +size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict); void ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx); -size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx); -size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); -typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; -ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);
+typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; +
+New advanced API (experimental, and compression only)
+typedef enum { + /* compression parameters */ + ZSTD_p_compressionLevel=100, /* Update all compression parameters according to pre-defined cLevel table + * Default level is ZSTD_CLEVEL_DEFAULT==3. + * Special: value 0 means "do not change cLevel". */ + ZSTD_p_windowLog, /* Maximum allowed back-reference distance, expressed as power of 2. + * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX. + * Special: value 0 means "do not change windowLog". */ + ZSTD_p_hashLog, /* Size of the probe table, as a power of 2. + * Resulting table size is (1 << (hashLog+2)). + * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX. + * Larger tables improve compression ratio of strategies <= dFast, + * and improve speed of strategies > dFast. + * Special: value 0 means "do not change hashLog". */ + ZSTD_p_chainLog, /* Size of the full-search table, as a power of 2. + * Resulting table size is (1 << (chainLog+2)). + * Larger tables result in better and slower compression. + * This parameter is useless when using "fast" strategy. + * Special: value 0 means "do not change chainLog". */ + ZSTD_p_searchLog, /* Number of search attempts, as a power of 2. + * More attempts result in better and slower compression. + * This parameter is useless when using "fast" and "dFast" strategies. + * Special: value 0 means "do not change searchLog". */ + ZSTD_p_minMatch, /* Minimum size of searched matches (note : repCode matches can be smaller). + * Larger values make faster compression and decompression, but decrease ratio. + * Must be clamped between ZSTD_SEARCHLENGTH_MIN and ZSTD_SEARCHLENGTH_MAX. + * Note that currently, for all strategies < btopt, effective minimum is 4. + * Note that currently, for all strategies > fast, effective maximum is 6. + * Special: value 0 means "do not change minMatchLength". */ + ZSTD_p_targetLength, /* Only useful for strategies >= btopt. + * Length of Match considered "good enough" to stop search. + * Larger values make compression stronger and slower. + * Special: value 0 means "do not change targetLength". */ + 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. + * Special: value 0 means "do not change strategy". */ + + /* frame parameters */ + ZSTD_p_contentSizeFlag=200, /* Content size is written into frame header _whenever known_ (default:1) */ + ZSTD_p_checksumFlag, /* A 32-bits checksum of content is written at end of frame (default:0) */ + ZSTD_p_dictIDFlag, /* When applicable, dictID of dictionary is provided in frame header (default:1) */ + + /* dictionary parameters (must be set before ZSTD_CCtx_loadDictionary) */ + ZSTD_p_dictMode=300, /* Select how dictionary content must be interpreted. Value must be from type ZSTD_dictMode_e. + * default : 0==auto : dictionary will be "full" if it respects specification, otherwise it will be "rawContent" */ + ZSTD_p_refDictContent, /* Dictionary content will be referenced, instead of copied (default:0==byCopy). + * It requires that dictionary buffer outlives its users */ + + /* multi-threading parameters */ + ZSTD_p_nbThreads=400, /* Select how many threads a compression job can spawn (default:1) + * More threads improve speed, but also increase memory usage. + * Can only receive a value > 1 if ZSTD_MULTITHREAD is enabled. + * Special: value 0 means "do not change nbThreads" */ + ZSTD_p_jobSize, /* Size of a compression job. Each compression job is completed in parallel. + * 0 means default, which is dynamically determined based on compression parameters. + * Job size must be a minimum of overlapSize, or 1 KB, whichever is largest + * The minimum size is automatically and transparently enforced */ + ZSTD_p_overlapSizeLog, /* Size of previous input reloaded at the beginning of each job. + * 0 => no overlap, 6(default) => use 1/8th of windowSize, >=9 => use full windowSize */ + + /* advanced parameters - may not remain available after API update */ + ZSTD_p_forceMaxWindow=1100, /* Force back-reference distances to remain < windowSize, + * even when referencing into Dictionary content (default:0) */ + +} ZSTD_cParameter; +
+size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned value); +Set one compression parameter, selected by enum ZSTD_cParameter. + Note : when `value` is an enum, cast it to unsigned for proper type checking. + @result : 0, or an error code (which can be tested with ZSTD_isError()). +
+ +size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize); +Total input data size to be compressed as a single frame. + This value will be controlled at the end, and result in error if not respected. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Note 1 : 0 means zero, empty. + In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN. + Note that ZSTD_CONTENTSIZE_UNKNOWN is default value for new compression jobs. + Note 2 : If all data is provided and consumed in a single round, + this value is overriden by srcSize instead. +
+ +size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); +Create an internal CDict from dict buffer. + Decompression will have to use same buffer. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, + meaning "return to no-dictionary mode". + Note 1 : `dict` content will be copied internally, + except if ZSTD_p_refDictContent is set before loading. + Note 2 : Loading a dictionary involves building tables, which are dependent on compression parameters. + For this reason, compression parameters cannot be changed anymore after loading a dictionary. + It's also a CPU-heavy operation, with non-negligible impact on latency. + Note 3 : Dictionary will be used for all future compression jobs. + To return to "no-dictionary" situation, load a NULL dictionary +
+ +size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); +Reference a prepared dictionary, to be used for all next compression jobs. + Note that compression parameters are enforced from within CDict, + and supercede any compression parameter previously set within CCtx. + The dictionary will remain valid for future compression jobs using same CCtx. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : adding a NULL CDict means "return to no-dictionary mode". + Note 1 : Currently, only one dictionary can be managed. + Adding a new dictionary effectively "discards" any previous one. + Note 2 : CDict is just referenced, its lifetime must outlive CCtx. + +
+ +size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize); +Reference a prefix (single-usage dictionary) for next compression job. + Decompression need same prefix to properly regenerate data. + Prefix is **only used once**. Tables are discarded at end of compression job. + Subsequent compression jobs will be done without prefix (if none is explicitly referenced). + If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_CDict instead. + @result : 0, or an error code (which can be tested with ZSTD_isError()). + Special : Adding any prefix (including NULL) invalidates any previous prefix or dictionary + Note 1 : Prefix buffer is referenced. It must outlive compression job. + Note 2 : Referencing a prefix involves building tables, which are dependent on compression parameters. + It's a CPU-heavy operation, with non-negligible impact on latency. + Note 3 : it's possible to alter ZSTD_p_dictMode using ZSTD_CCtx_setParameter() +
+ +typedef enum { + ZSTD_e_continue=0, /* collect more data, encoder transparently decides when to output result, for optimal conditions */ + ZSTD_e_flush, /* flush any data provided so far - frame will continue, future data can still reference previous data for better compression */ + ZSTD_e_end /* flush any remaining data and ends current frame. Any future compression starts a new frame. */ +} ZSTD_EndDirective; +
+size_t ZSTD_compress_generic (ZSTD_CCtx* cctx, + ZSTD_outBuffer* output, + ZSTD_inBuffer* input, + ZSTD_EndDirective endOp); +Behave about the same as ZSTD_compressStream. To note : + - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_setParameter() + - Compression parameters cannot be changed once compression is started. + - *dstPos must be <= dstCapacity, *srcPos must be <= srcSize + - *dspPos and *srcPos will be updated. They are guaranteed to remain below their respective limit. + - @return provides the minimum amount of data still to flush from internal buffers + or an error code, which can be tested using ZSTD_isError(). + if @return != 0, flush is not fully completed, there is some data left within internal buffers. + - after a ZSTD_e_end directive, if internal buffer is not fully flushed, + only ZSTD_e_end or ZSTD_e_flush operations are allowed. + It is necessary to fully flush internal buffers + before starting a new compression job, or changing compression parameters. *** DIFF OUTPUT TRUNCATED AT 1000 LINES ***