From 483eb2f56657e8e7f419ab1a4fab8dce9ade8609 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 20:24:20 +0200 Subject: Adding upstream version 14.2.21. Signed-off-by: Daniel Baumann --- src/zstd/doc/zstd_manual.html | 1200 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1200 insertions(+) create mode 100644 src/zstd/doc/zstd_manual.html (limited to 'src/zstd/doc/zstd_manual.html') diff --git a/src/zstd/doc/zstd_manual.html b/src/zstd/doc/zstd_manual.html new file mode 100644 index 00000000..b4720ada --- /dev/null +++ b/src/zstd/doc/zstd_manual.html @@ -0,0 +1,1200 @@ + + + +zstd 1.3.2 Manual + + +

zstd 1.3.2 Manual

Introduction
Version
Simple API
Explicit memory management
Simple dictionary API
Bulk processing dictionary API
Streaming
Streaming compression - HowTo
Streaming decompression - HowTo
START OF ADVANCED AND EXPERIMENTAL FUNCTIONS
Advanced types
Frame size functions
Context memory usage
Advanced compression functions
Advanced decompression functions
Advanced streaming functions
Buffer-less and synchronous inner streaming functions
Buffer-less streaming compression (synchronous mode)
Buffer-less streaming decompression (synchronous mode)
New advanced API (experimental)
Block level API

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 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 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.
+  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);   /**< useful to check dll version */
+

Simple API

+ +

size_t ZSTD_compress( void* dst, size_t dstCapacity,
+                const void* src, size_t srcSize,
+                      int compressionLevel);
+  Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
+  Hint : compression runs faster if `dstCapacity` >=  `ZSTD_compressBound(srcSize)`.
+  @return : compressed size written into `dst` (<= `dstCapacity),
+            or an error code if it fails (which can be tested using ZSTD_isError()). 
+

+ +

size_t ZSTD_decompress( void* dst, size_t dstCapacity,
+                  const void* src, size_t compressedSize);
+  `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
+  `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()). 
+

+ +

#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.
+            hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
+  @return : - decompressed size of the frame in `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)
+   note 1 : a 0 return value means the frame is valid but "empty".
+   note 2 : decompressed size is an optional field, it may not be present, typically 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 rely on some implicit limit,
+            as ZSTD_decompress() only needs an upper bound of decompressed size.
+            (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 4 : 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 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
+            Always ensure return value fits within application's authorized limits.
+            Each application can set its own limits.
+   note 6 : This function replaces ZSTD_getDecompressedSize() 
+

+ +

unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
+  NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
+  Both functions work the same way,
+  but ZSTD_getDecompressedSize() blends
+  "empty", "unknown" and "error" results in the same return value (0),
+  while ZSTD_getFrameContentSize() distinguishes them.
+
+  'src' is the start of a zstd compressed frame.
+  @return : content size to be decompressed, as a 64-bits value _if known and not empty_, 0 otherwise. 
+

+ +

Helper functions

#define ZSTD_COMPRESSBOUND(srcSize)   ((srcSize) + ((srcSize)>>8) + (((srcSize) < 128 KB) ? ((128 KB - (srcSize)) >> 11) /* margin, from 64 to 0 */ : 0))  /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */
+size_t      ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case scenario */
+unsigned    ZSTD_isError(size_t code);          /*!< tells if a `size_t` function result is an error code */
+const char* ZSTD_getErrorName(size_t code);     /*!< provides readable string from an error code */
+int         ZSTD_maxCLevel(void);               /*!< maximum compression level available */
+

Explicit memory management

+ +

Compression context

  When compressing many times,
+  it is recommended to allocate a context just 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. 
+

typedef struct ZSTD_CCtx_s ZSTD_CCtx; +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);
+  Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()). 
+

+ +

Decompression context

  When decompressing many times,
+  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. 
+

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);
+  Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()) 
+

+ +

Simple dictionary API

+ +

size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
+                               void* dst, size_t dstCapacity,
+                         const void* src, size_t srcSize,
+                         const void* dict,size_t dictSize,
+                               int compressionLevel);
+  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. 
+

+ +

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);
+  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. 
+

+ +

Bulk processing dictionary API

+ +

ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
+                             int compressionLevel);
+  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 
+

+ +

size_t      ZSTD_freeCDict(ZSTD_CDict* CDict);
+  Function frees memory allocated by ZSTD_createCDict(). 
+

+ +

size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
+                                void* dst, size_t dstCapacity,
+                          const void* src, size_t srcSize,
+                          const ZSTD_CDict* cdict);
+  Compression using a digested Dictionary.
+  Faster startup than ZSTD_compress_usingDict(), recommended when same dictionary is used multiple times.
+  Note that compression level is decided during dictionary creation.
+  Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) 
+

+ +

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 
+

+ +

size_t      ZSTD_freeDDict(ZSTD_DDict* ddict);
+  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. 
+

+ +

Streaming

+ +

typedef struct ZSTD_inBuffer_s {
+  const void* src;    /**< start of input buffer */
+  size_t size;        /**< size of input buffer */
+  size_t pos;         /**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */
+} ZSTD_inBuffer;
+

typedef struct ZSTD_outBuffer_s {
+  void*  dst;         /**< start of output buffer */
+  size_t size;        /**< size of output buffer */
+  size_t pos;         /**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */
+} ZSTD_outBuffer;
+

Streaming compression - HowTo

+  A ZSTD_CStream object is required to track streaming operation.
+  Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
+  ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
+  It is recommended to re-use ZSTD_CStream in situations where many streaming operations will be achieved consecutively,
+  since it will play nicer with system's memory, by re-using already allocated memory.
+  Use one separate ZSTD_CStream per thread for parallel execution.
+
+  Start a new compression by initializing ZSTD_CStream.
+  Use ZSTD_initCStream() to start a new compression operation.
+  Use ZSTD_initCStream_usingDict() or ZSTD_initCStream_usingCDict() for a compression which requires a dictionary (experimental section)
+
+  Use ZSTD_compressStream() repetitively to consume input stream.
+  The function will automatically update both `pos` fields.
+  Note that it may not consume the entire input, in which case `pos < size`,
+  and it's up to the caller to present again remaining data.
+  @return : a size hint, preferred nb of bytes to use as input for next function call
+            or an error code, which can be tested using ZSTD_isError().
+            Note 1 : it's just a hint, to help latency a little, any other value will work fine.
+            Note 2 : size hint is guaranteed to be <= ZSTD_CStreamInSize()
+
+  At any moment, it's possible to flush whatever data remains within internal buffer, using ZSTD_flushStream().
+  `output->pos` will be updated.
+  Note that some content might still be left within internal buffer if `output->size` is too small.
+  @return : nb of bytes still present within internal buffer (0 if it's empty)
+            or an error code, which can be tested using ZSTD_isError().
+
+  ZSTD_endStream() instructs to finish a frame.
+  It will perform a flush and write frame epilogue.
+  The epilogue is required for decoders to consider a frame completed.
+  ZSTD_endStream() may not be able to flush full data if `output->size` is too small.
+  In which case, call again ZSTD_endStream() to complete the flush.
+  @return : 0 if frame fully completed and fully flushed,
+             or >0 if some data is still present within internal buffer
+                  (value is minimum size estimation for remaining data to flush, but it could be more)
+            or an error code, which can be tested using ZSTD_isError().
+
+ 
+

+ +

typedef ZSTD_CCtx ZSTD_CStream;  /**< CCtx and CStream are now effectively same object (>= v1.3.0) */
+

ZSTD_CStream management functions

ZSTD_CStream* ZSTD_createCStream(void); +size_t ZSTD_freeCStream(ZSTD_CStream* zcs); +

+

Streaming compression functions

size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel); +size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input); +size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); +size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); +

+

size_t ZSTD_CStreamInSize(void);    /**< recommended size for input buffer */
+

size_t ZSTD_CStreamOutSize(void);   /**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block in all circumstances. */
+

Streaming decompression - HowTo

+  A ZSTD_DStream object is required to track streaming operations.
+  Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
+  ZSTD_DStream objects can be re-used multiple times.
+
+  Use ZSTD_initDStream() to start a new decompression operation,
+   or ZSTD_initDStream_usingDict() if decompression requires a dictionary.
+   @return : recommended first input size
+
+  Use ZSTD_decompressStream() repetitively to consume your input.
+  The function will update both `pos` fields.
+  If `input.pos < input.size`, some input has not been consumed.
+  It's up to the caller to present again remaining data.
+  If `output.pos < output.size`, decoder has flushed everything it could.
+  @return : 0 when a frame is completely decoded and fully flushed,
+            an error code, which can be tested using ZSTD_isError(),
+            any other value > 0, which means there is still some decoding to do to complete current frame.
+            The return value is a suggested next input size (a hint to improve latency) that will never load more than the current frame.
+ 
+

+ +

typedef ZSTD_DCtx ZSTD_DStream;  /**< DCtx and DStream are now effectively same object (>= v1.3.0) */
+

ZSTD_DStream management functions

ZSTD_DStream* ZSTD_createDStream(void); +size_t ZSTD_freeDStream(ZSTD_DStream* zds); +

+

Streaming decompression functions

size_t ZSTD_initDStream(ZSTD_DStream* zds); +size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); +

+

size_t ZSTD_DStreamInSize(void);    /*!< recommended size for input buffer */
+

size_t ZSTD_DStreamOutSize(void);   /*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */
+

START OF ADVANCED AND EXPERIMENTAL FUNCTIONS

 The definitions in this section are considered experimental.
+ They should never be used with a dynamic library, as prototypes may change in the future.
+ They are provided for advanced scenarios.
+ Use them only in association with static linking.
+ 
+

+ +

Advanced types

+ +

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 */
+    unsigned chainLog;       /**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */
+    unsigned hashLog;        /**< dispatch table : larger == faster, more memory */
+    unsigned searchLog;      /**< nb of searches : larger == more compression, slower */
+    unsigned searchLength;   /**< match length searched : larger == faster decompression, sometimes less compression */
+    unsigned targetLength;   /**< acceptable match size for optimal parser (only) : larger == more compression, slower */
+    ZSTD_strategy strategy;
+} ZSTD_compressionParameters;
+

typedef struct {
+    unsigned contentSizeFlag; /**< 1: content size will be in frame header (when known) */
+    unsigned checksumFlag;    /**< 1: generate a 32-bits checksum at end of frame, for error detection */
+    unsigned noDictIDFlag;    /**< 1: no dictID will be saved into frame header (if dictionary compression) */
+} ZSTD_frameParameters;
+

typedef struct {
+    ZSTD_compressionParameters cParams;
+    ZSTD_frameParameters fParams;
+} ZSTD_parameters;
+

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 };
+

Frame size functions

+ +

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 first frame starting at `src`,
+            suitable to pass to `ZSTD_decompress` or similar,
+            or an error code if input is invalid 
+

+ +

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
+       (i.e. there should be a frame boundary exactly at `srcSize` bytes after `src`)
+  @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.
+   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 fast as most of the data is skipped,
+            however it does mean that all frame data must be present and valid. 
+

+ +

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 
+

+ +

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 when re-used multiple times. 
+

+ +

size_t ZSTD_estimateCCtxSize(int compressionLevel);
+size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
+size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
+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_usingCParams() can provide a tighter estimation.
+  ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
+  ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbThreads is > 1.
+  Note : CCtx estimation is only correct for single-threaded compression 
+

+ +

size_t ZSTD_estimateCStreamSize(int compressionLevel);
+size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
+size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
+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_usingCParams() can provide a tighter estimation.
+  ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
+  ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbThreads is set to a value > 1.
+  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 
+

+ +

typedef enum {
+    ZSTD_dlm_byCopy = 0,     /**< Copy dictionary content internally */
+    ZSTD_dlm_byRef,          /**< Reference dictionary content -- the dictionary buffer must outlive its users. */
+} ZSTD_dictLoadMethod_e;
+

size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
+size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
+size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
+  ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
+  ZSTD_estimateCStreamSize_advanced_usingCParams() makes it possible to control precisely compression parameters, like ZSTD_createCDict_advanced().
+  Note : dictionary created by reference using ZSTD_dlm_byRef are smaller
+ 
+

+ +

Advanced compression functions

+ +

ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem); +

Create a ZSTD compression context using external alloc and free functions +

+ +

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
+ 
+

+ +

ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
+  Create a digested dictionary for compression
+  Dictionary content is simply referenced, and therefore stays in dictBuffer.
+  It is important that dictBuffer outlives CDict, it must remain read accessible throughout the lifetime of CDict 
+

+ +

typedef enum { ZSTD_dm_auto=0,        /* dictionary is "full" if it starts with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */
+               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,
+                                      ZSTD_dictLoadMethod_e dictLoadMethod,
+                                      ZSTD_dictMode_e dictMode,
+                                      ZSTD_compressionParameters cParams,
+                                      ZSTD_customMem customMem);
+  Create a ZSTD_CDict using external alloc and free, and customized compression parameters 
+

+ +

ZSTD_CDict* ZSTD_initStaticCDict(
+                void* workspace, size_t workspaceSize,
+          const void* dict, size_t dictSize,
+                ZSTD_dictLoadMethod_e dictLoadMethod, 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);
+   @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
+   `estimatedSrcSize` value is optional, select 0 if not known 
+

+ +

ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
+   same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
+   All fields of `ZSTD_frameParameters` are set to default (0) 
+

+ +

size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
+   Ensure param values remain within authorized range 
+

+ +

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. +

+ +

size_t ZSTD_compress_advanced (ZSTD_CCtx* cctx,
+                      void* dst, size_t dstCapacity,
+                const void* src, size_t srcSize,
+                const void* dict,size_t dictSize,
+                      ZSTD_parameters params);
+   Same as ZSTD_compress_usingDict(), with fine-tune control over each compression parameter 
+

+ +

size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
+                      void* dst, size_t dstCapacity,
+                const void* src, size_t srcSize,
+                const ZSTD_CDict* cdict, ZSTD_frameParameters fParams);
+   Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters 
+

+ +

Advanced decompression functions

+ +

unsigned ZSTD_isFrame(const void* buffer, size_t size);
+  Tells if the content of `buffer` starts with a valid Frame Identifier.
+  Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
+  Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
+  Note 3 : Skippable Frame Identifiers are considered valid. 
+

+ +

ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem); +

Create a ZSTD decompression context using external alloc and free functions +

+ +

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 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,
+                                      ZSTD_dictLoadMethod_e dictLoadMethod,
+                                      ZSTD_customMem customMem);
+  Create a ZSTD_DDict using external alloc and free, optionally by reference 
+

+ +

ZSTD_DDict* ZSTD_initStaticDDict(void* workspace, size_t workspaceSize,
+                                 const void* dict, size_t dictSize,
+                                 ZSTD_dictLoadMethod_e dictLoadMethod);
+  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);
+  Provides the dictID stored within dictionary.
+  if @return == 0, the dictionary is not conformant with Zstandard specification.
+  It can still be loaded, but as a content-only dictionary. 
+

+ +

unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
+  Provides the dictID of the dictionary loaded into `ddict`.
+  If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
+  Non-conformant dictionaries can still be loaded, but as content-only dictionaries. 
+

+ +

unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
+  Provides the dictID required to decompressed the frame stored within `src`.
+  If @return == 0, the dictID could not be decoded.
+  This could for one of the following reasons :
+  - The frame does not require a dictionary to be decoded (most common case).
+  - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden information.
+    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_getFrameHeader(), which will provide a more precise error code. 
+

+ +

Advanced streaming functions

+ +

Advanced Streaming compression functions

ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
+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); /**< creates of an internal CDict (incompatible with static CCtx), except if dict == NULL or dictSize < 8, in which case no dict is used. Note: dict is loaded with ZSTD_dm_auto (treated as a full zstd dictionary if it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.*/
+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. dict is loaded with ZSTD_dm_auto and ZSTD_dlm_byCopy. */
+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, 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.
+  This is typically useful to skip dictionary loading stage, since it will re-use it in-place..
+  Note that zcs must be init at least once before using ZSTD_resetCStream().
+  pledgedSrcSize==0 means "srcSize unknown".
+  If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
+  @return : 0, or an error code (which can be tested using ZSTD_isError()) 
+

+ +

Advanced Streaming decompression functions

ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
+ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize);    /**< same as ZSTD_initStaticDCtx() */
+typedef enum { DStream_p_maxWindowSize } ZSTD_DStreamParameter_e;
+size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);   /* obsolete : this API will be removed in a future version */
+size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); /**< note: no dictionary will be used if dict == NULL or dictSize < 8 */
+size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);  /**< note : ddict is referenced, it must outlive decompression session */
+size_t ZSTD_resetDStream(ZSTD_DStream* zds);  /**< re-use decompression parameters from previous init; saves dictionary loading */
+

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.
+  But it's also a complex one, with several restrictions, documented below.
+  Prefer normal streaming API for an easier experience.
+ 
+

+ +

Buffer-less streaming compression (synchronous mode)

+  A ZSTD_CCtx object is required to track streaming operations.
+  Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
+  ZSTD_CCtx object can be re-used multiple times within successive compression operations.
+
+  Start by initializing a context.
+  Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression,
+  or ZSTD_compressBegin_advanced(), for finer parameter control.
+  It's also possible to duplicate a reference context which has already been initialized, using ZSTD_copyCCtx()
+
+  Then, consume your input using ZSTD_compressContinue().
+  There are some important considerations to keep in mind when using this advanced function :
+  - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
+  - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
+  - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
+    Worst case evaluation is provided by ZSTD_compressBound().
+    ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
+  - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
+    It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
+  - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
+    In which case, it will "discard" the relevant memory section from its history.
+
+  Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
+  It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
+  Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
+
+  `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress again.
+

+ +

Buffer-less streaming compression functions

size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
+size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
+size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, 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_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); /**< note: fails if cdict==NULL */
+size_t ZSTD_compressBegin_usingCDict_advanced(ZSTD_CCtx* const cctx, const ZSTD_CDict* const cdict, ZSTD_frameParameters const fParams, unsigned long long const pledgedSrcSize);   /* compression parameters are already set within cdict. pledgedSrcSize=0 means null-size */
+size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); /**<  note: if pledgedSrcSize can be 0, indicating unknown size.  if it is non-zero, it must be accurate.  for 0 size frames, use compressBegin_advanced */
+

Buffer-less streaming decompression (synchronous mode)

+ A ZSTD_DCtx object is required to track streaming operations.
+ 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_getFrameHeader().
+ 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().
+
+ It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
+ such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
+ Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
+ As a consequence, check that values remain within valid application range.
+ For example, do not allocate memory blindly, check that `windowSize` is within expectation.
+ Each application can set its own limits, depending on local restrictions.
+ For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
+
+ ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
+ ZSTD_decompressContinue() is very sensitive to contiguity,
+ if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
+ or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
+ There are multiple ways to guarantee this condition.
+
+ The most memory efficient way is to use a round buffer of sufficient size.
+ Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
+ which can @return an error code if required value is too large for current system (in 32-bits mode).
+ In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
+ up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
+ which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
+ At which point, decoding can resume from the beginning of the buffer.
+ Note that already decoded data stored in the buffer should be flushed before being overwritten.
+
+ There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
+
+ Finally, if you control the compression process, you can also ignore all buffer size rules,
+ as long as the encoder and decoder progress in "lock-step",
+ aka use exactly the same buffer sizes, break contiguity at the same place, etc.
+
+ Once buffers are setup, start decompression, with ZSTD_decompressBegin().
+ If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
+
+ Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
+ ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
+ ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
+
+ @result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
+ It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
+ It can also be an error code, which can be tested with ZSTD_isError().
+
+ A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
+ Context can then be reset to start a new decompression.
+
+ Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
+ This information is not required to properly decode a frame.
+
+ == Special case : skippable frames
+
+ Skippable frames allow integration of user-defined data into a flow of concatenated frames.
+ Skippable frames will be ignored (skipped) by decompressor.
+ The format of skippable frames is as follows :
+ a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
+ 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_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
+ For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
+

+ +

Buffer-less streaming decompression functions

typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
+typedef struct {
+    unsigned long long frameContentSize; /* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */
+    unsigned long long windowSize;       /* can be very large, up to <= frameContentSize */
+    unsigned blockSizeMax;
+    ZSTD_frameType_e frameType;          /* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */
+    unsigned headerSize;
+    unsigned dictID;
+    unsigned checksumFlag;
+} ZSTD_frameHeader;
+size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize);   /**< doesn't consume input */
+size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize);  /**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */
+

typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
+

New advanced API (experimental)

+ +

typedef enum {
+    /* Question : should we have a format ZSTD_f_auto ?
+     * For the time being, it would mean exactly the same as ZSTD_f_zstd1.
+     * But, in the future, should several formats be supported,
+     * on the compression side, it would mean "default format".
+     * On the decompression side, it would mean "multi format",
+     * and ZSTD_f_zstd1 could be reserved to mean "accept *only* zstd frames".
+     * Since meaning is a little different, another option could be to define different enums for compression and decompression.
+     * This question could be kept for later, when there are actually multiple formats to support,
+     * but there is also the question of pinning enum values, and pinning value `0` is especially important */
+    ZSTD_f_zstd1 = 0,        /* zstd frame format, specified in zstd_compression_format.md (default) */
+    ZSTD_f_zstd1_magicless,  /* Variant of zstd frame format, without initial 4-bytes magic number.
+                              * Useful to save 4 bytes per generated frame.
+                              * Decoder cannot recognise automatically this format, requiring instructions. */
+} ZSTD_format_e;
+

typedef enum {
+    /* compression format */
+    ZSTD_p_format = 10,      /* See ZSTD_format_e enum definition.
+                              * Cast selected format as unsigned for ZSTD_CCtx_setParameter() compatibility. */
+
+    /* 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".
+                              * Note: Using a window size greater than ZSTD_MAXWINDOWSIZE_DEFAULT (default: 2^27)
+                              * requires setting the maximum window size at least as large during decompression. */
+    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)
+                              * note that content size must be known at the beginning,
+                              * it is sent using ZSTD_CCtx_setPledgedSrcSize() */
+    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) */
+
+    /* 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_p_enableLongDistanceMatching=1200,  /* Enable long distance matching.
+                                         * This parameter is designed to improve the compression
+                                         * ratio for large inputs with long distance matches.
+                                         * This increases the memory usage as well as window size.
+                                         * Note: setting this parameter sets all the LDM parameters
+                                         * as well as ZSTD_p_windowLog. It should be set after
+                                         * ZSTD_p_compressionLevel and before ZSTD_p_windowLog and
+                                         * other LDM parameters. Setting the compression level
+                                         * after this parameter overrides the window log, though LDM
+                                         * will remain enabled until explicitly disabled. */
+    ZSTD_p_ldmHashLog,   /* Size of the table for long distance matching, as a power of 2.
+                          * Larger values increase memory usage and compression ratio, but decrease
+                          * compression speed.
+                          * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
+                          * (default: windowlog - 7). */
+    ZSTD_p_ldmMinMatch,  /* Minimum size of searched matches for long distance matcher.
+                          * Larger/too small values usually decrease compression ratio.
+                          * Must be clamped between ZSTD_LDM_MINMATCH_MIN
+                          * and ZSTD_LDM_MINMATCH_MAX (default: 64). */
+    ZSTD_p_ldmBucketSizeLog,  /* Log size of each bucket in the LDM hash table for collision resolution.
+                               * Larger values usually improve collision resolution but may decrease
+                               * compression speed.
+                               * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX (default: 3). */
+    ZSTD_p_ldmHashEveryLog,  /* Frequency of inserting/looking up entries in the LDM hash table.
+                              * The default is MAX(0, (windowLog - ldmHashLog)) to
+                              * optimize hash table usage.
+                              * Larger values improve compression speed. Deviating far from the
+                              * default value will likely result in a decrease in compression ratio.
+                              * Must be clamped between 0 and ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN. */
+
+} 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);
+size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
+size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictMode_e dictMode);
+  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. Use
+            ZSTD_CCtx_loadDictionary_byReference() to reference dictionary
+            content instead. The dictionary buffer must then outlive its
+            users.
+  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
+  Note 5 : Use ZSTD_CCtx_loadDictionary_advanced() to select how dictionary
+           content will be interpreted.
+ 
+

+ +

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);
+size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictMode_e dictMode);
+  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 : By default, the prefix is treated as raw content
+           (ZSTD_dm_rawContent). Use ZSTD_CCtx_refPrefix_advanced() to alter
+           dictMode. 
+

+ +

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 close current frame. Any additional data 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.
+  - outpot->pos must be <= dstCapacity, input->pos must be <= srcSize
+  - outpot->pos and input->pos 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.
+ 
+

+ +

void ZSTD_CCtx_reset(ZSTD_CCtx* cctx);   /* Not ready yet ! */
+  Return a CCtx to clean state.
+  Useful after an error, or to interrupt an ongoing compression job and start a new one.
+  Any internal data not yet flushed is cancelled.
+  Dictionary (if any) is dropped.
+  All parameters are back to default values.
+  It's possible to modify compression parameters after a reset.
+ 
+

+ +

size_t ZSTD_compress_generic_simpleArgs (
+                ZSTD_CCtx* cctx,
+                void* dst, size_t dstCapacity, size_t* dstPos,
+          const void* src, size_t srcSize, size_t* srcPos,
+                ZSTD_EndDirective endOp);
+  Same as ZSTD_compress_generic(),
+  but using only integral types as arguments.
+  Argument list is larger than ZSTD_{in,out}Buffer,
+  but can be helpful for binders from dynamic languages
+  which have troubles handling structures containing memory pointers.
+ 
+

+ +

ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
+  Quick howto :
+  - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
+  - ZSTD_CCtxParam_setParameter() : Push parameters one by one into
+                                    an existing ZSTD_CCtx_params structure.
+                                    This is similar to
+                                    ZSTD_CCtx_setParameter().
+  - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
+                                    an existing CCtx.
+                                    These parameters will be applied to
+                                    all subsequent compression jobs.
+  - ZSTD_compress_generic() : Do compression using the CCtx.
+  - ZSTD_freeCCtxParams() : Free the memory.
+
+  This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
+  for static allocation for single-threaded compression.
+ 
+

+ +

size_t ZSTD_resetCCtxParams(ZSTD_CCtx_params* params); +

Reset params to default, with the default compression level. + +

+ +

size_t ZSTD_initCCtxParams(ZSTD_CCtx_params* cctxParams, int compressionLevel); +

Initializes the compression parameters of cctxParams according to + compression level. All other parameters are reset to their default values. + +

+ +

size_t ZSTD_initCCtxParams_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params); +

Initializes the compression and frame parameters of cctxParams according to + params. All other parameters are reset to their default values. + +

+ +

size_t ZSTD_CCtxParam_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, unsigned value); +

Similar to ZSTD_CCtx_setParameter. + Set one compression parameter, selected by enum ZSTD_cParameter. + Parameters must be applied to a ZSTD_CCtx using ZSTD_CCtx_setParametersUsingCCtxParams(). + 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_setParametersUsingCCtxParams(
+        ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
+  Apply a set of ZSTD_CCtx_params to the compression context.
+  This must be done before the dictionary is loaded.
+  The pledgedSrcSize is treated as unknown.
+  Multithreading parameters are applied only if nbThreads > 1.
+ 
+

+ +

Advanced parameters for decompression API

size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);   /* not implemented */
+size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);   /* not implemented */
+size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictMode_e dictMode);   /* not implemented */
+  Create an internal DDict from dict buffer,
+  to be used to decompress next frames.
+ @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.
+            Use ZSTD_DCtx_loadDictionary_byReference()
+            to reference dictionary content instead.
+            In which case, the dictionary buffer must outlive its users.
+  Note 2 : Loading a dictionary involves building tables,
+           which has a non-negligible impact on CPU usage and latency.
+  Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to select
+           how dictionary content will be interpreted and loaded.
+ 
+

+ +

size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);   /* not implemented */
+  Reference a prepared dictionary, to be used to decompress next frames.
+  The dictionary remains active for decompression of future frames using same DCtx.
+ @result : 0, or an error code (which can be tested with ZSTD_isError()).
+  Note 1 : Currently, only one dictionary can be managed.
+           Referencing a new dictionary effectively "discards" any previous one.
+  Special : adding a NULL DDict means "return to no-dictionary mode".
+  Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
+ 
+

+ +

size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize);   /* not implemented */
+size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictMode_e dictMode);   /* not implemented */
+  Reference a prefix (single-usage dictionary) for next compression job.
+  Prefix is **only used once**. It must be explicitly referenced before each frame.
+  If there is a need to use same prefix multiple times, consider embedding it into a ZSTD_DDict instead.
+ @result : 0, or an error code (which can be tested with ZSTD_isError()).
+  Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
+  Note 2 : Prefix buffer is referenced. It must outlive compression job.
+  Note 3 : By default, the prefix is treated as raw content (ZSTD_dm_rawContent).
+           Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode.
+  Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
+ 
+

+ +

size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
+  Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
+  This is useful to prevent a decoder context from reserving too much memory for itself (potential attack scenario).
+  This parameter is only useful in streaming mode, since no internal buffer is allocated in direct mode.
+  By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_MAX)
+ @return : 0, or an error code (which can be tested using ZSTD_isError()).
+ 
+

+ +

size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
+  Instruct the decoder context about what kind of data to decode next.
+  This instruction is mandatory to decode data without a fully-formed header,
+  such ZSTD_f_zstd1_magicless for example.
+ @return : 0, or an error code (which can be tested using ZSTD_isError()).
+ 
+

+ +

size_t ZSTD_decompress_generic(ZSTD_DCtx* dctx,
+                               ZSTD_outBuffer* output,
+                               ZSTD_inBuffer* input);
+  Behave the same as ZSTD_decompressStream.
+  Decompression parameters cannot be changed once decompression is started.
+ @return : an error code, which can be tested using ZSTD_isError()
+           if >0, a hint, nb of expected input bytes for next invocation.
+           `0` means : a frame has just been fully decoded and flushed.
+ 
+

+ +

size_t ZSTD_decompress_generic_simpleArgs (
+                ZSTD_DCtx* dctx,
+                void* dst, size_t dstCapacity, size_t* dstPos,
+          const void* src, size_t srcSize, size_t* srcPos);
+  Same as ZSTD_decompress_generic(),
+  but using only integral types as arguments.
+  Argument list is larger than ZSTD_{in,out}Buffer,
+  but can be helpful for binders from dynamic languages
+  which have troubles handling structures containing memory pointers.
+ 
+

+ +

void ZSTD_DCtx_reset(ZSTD_DCtx* dctx);
+  Return a DCtx to clean state.
+  If a decompression was ongoing, any internal data not yet flushed is cancelled.
+  All parameters are back to default values, including sticky ones.
+  Dictionary (if any) is dropped.
+  Parameters can be modified again after a reset.
+ 
+

+ +

Block level API

+ +

Frame metadata cost is typically ~18 bytes, which can be non-negligible for very small blocks (< 100 bytes). + User will have to take in charge required information to regenerate data, such as compressed and content sizes. + + A few rules to respect : + - Compressing and decompressing require a context structure + + Use ZSTD_createCCtx() and ZSTD_createDCtx() + - It is necessary to init context before starting + + compression : any ZSTD_compressBegin*() variant, including with dictionary + + decompression : any ZSTD_decompressBegin*() variant, including with dictionary + + copyCCtx() and copyDCtx() can be used too + - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB + + If input is larger than a block size, it's necessary to split input data into multiple blocks + + For inputs larger than a single block size, consider using the regular ZSTD_compress() instead. + Frame metadata is not that costly, and quickly becomes negligible as source size grows larger. + - 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 !!! + + In case of multiple successive blocks, should some of them be uncompressed, + decoder must be informed of their existence in order to follow proper history. + Use ZSTD_insertBlock() for such a case. +

+ +

Raw zstd block functions

size_t ZSTD_getBlockSize   (const ZSTD_CCtx* cctx);
+size_t ZSTD_compressBlock  (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
+size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
+size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize);  /**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression */
+

+ + -- cgit v1.2.3