zstd/lib/zstd.h

/**
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#ifndef ZSTD_H_235446
#define ZSTD_H_235446

#if defined (__cplusplus)
extern "C" {
#endif

/*======   Dependency   ======*/
#include <stddef.h>   /* size_t */


/*======  Export for Windows  ======*/
/*!
*  ZSTD_DLL_EXPORT :
*  Enable exporting of functions when building a Windows DLL
*/
#if defined(_WIN32) && defined(ZSTD_DLL_EXPORT) && (ZSTD_DLL_EXPORT==1)
#  define ZSTDLIB_API __declspec(dllexport)
#else
#  define ZSTDLIB_API
#endif


/*=======   Version   =======*/
#define ZSTD_VERSION_MAJOR    1
#define ZSTD_VERSION_MINOR    0
#define ZSTD_VERSION_RELEASE  1

#define ZSTD_LIB_VERSION ZSTD_VERSION_MAJOR.ZSTD_VERSION_MINOR.ZSTD_VERSION_RELEASE
#define ZSTD_QUOTE(str) #str
#define ZSTD_EXPAND_AND_QUOTE(str) ZSTD_QUOTE(str)
#define ZSTD_VERSION_STRING ZSTD_EXPAND_AND_QUOTE(ZSTD_LIB_VERSION)

#define ZSTD_VERSION_NUMBER  (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
ZSTDLIB_API unsigned ZSTD_versionNumber (void);


/* *************************************
*  Simple API
***************************************/
/*! ZSTD_compress() :
    Compresses `src` buffer into already allocated `dst`.
    Hint : compression runs faster if `dstCapacity` >=  `ZSTD_compressBound(srcSize)`.
    @return : the number of bytes written into `dst` (<= `dstCapacity),
              or an error code if it fails (which can be tested using ZSTD_isError()) */
ZSTDLIB_API size_t ZSTD_compress( void* dst, size_t dstCapacity,
                            const void* src, size_t srcSize,
                                  int compressionLevel);

/*! ZSTD_getDecompressedSize() :
*   @return : decompressed size as a 64-bits value _if known_, 0 otherwise.
*    note 1 : 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 2 : decompressed size is an optional field, that may not be present.
*             When `return==0`, data to decompress can have any size.
*             In which case, it's necessary to use streaming mode to decompress data.
*             Optionally, application may rely on its own implied limits.
*             (For example, application data could be necessarily cut into blocks <= 16 KB).
*    note 3 : 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 4 : when `return==0`, if precise failure cause is needed, use ZSTD_getFrameParams() to know more. */
ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);

/*! ZSTD_decompress() :
    `compressedSize` : must be the _exact_ size of compressed input, otherwise decompression will fail.
    `dstCapacity` must be equal or larger than originalSize (see ZSTD_getDecompressedSize() ).
    If originalSize is unknown, and if there is no implied application-specific limitations,
    it's preferable 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()) */
ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
                              const void* src, size_t compressedSize);


/*======  Helper functions  ======*/
ZSTDLIB_API int         ZSTD_maxCLevel(void);               /*!< maximum compression level available */
ZSTDLIB_API size_t      ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case scenario */
ZSTDLIB_API unsigned    ZSTD_isError(size_t code);          /*!< tells if a `size_t` function result is an error code */
ZSTDLIB_API const char* ZSTD_getErrorName(size_t code);     /*!< provides readable string from an error code */


/*-*************************************
*  Explicit memory management
***************************************/
/** Compression context */
typedef struct ZSTD_CCtx_s ZSTD_CCtx;
ZSTDLIB_API ZSTD_CCtx* ZSTD_createCCtx(void);
ZSTDLIB_API size_t     ZSTD_freeCCtx(ZSTD_CCtx* cctx);

/** ZSTD_compressCCtx() :
    Same as ZSTD_compress(), requires an allocated ZSTD_CCtx (see ZSTD_createCCtx()) */
ZSTDLIB_API size_t ZSTD_compressCCtx(ZSTD_CCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, int compressionLevel);

/** Decompression context */
typedef struct ZSTD_DCtx_s ZSTD_DCtx;
ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx(void);
ZSTDLIB_API size_t     ZSTD_freeDCtx(ZSTD_DCtx* dctx);

/** ZSTD_decompressDCtx() :
*   Same as ZSTD_decompress(), requires an allocated ZSTD_DCtx (see ZSTD_createDCtx()) */
ZSTDLIB_API size_t ZSTD_decompressDCtx(ZSTD_DCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);


/*-************************
*  Simple dictionary API
***************************/
/*! ZSTD_compress_usingDict() :
*   Compression using a predefined Dictionary (see dictBuilder/zdict.h).
*   Note : This function load the dictionary, resulting in significant startup delay. */
ZSTDLIB_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);

/*! ZSTD_decompress_usingDict() :
*   Decompression using a predefined Dictionary (see dictBuilder/zdict.h).
*   Dictionary must be identical to the one used during compression.
*   Note : This function load the dictionary, resulting in significant startup delay */
ZSTDLIB_API 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
****************************/
/*! ZSTD_createCDict() :
*   Create a digested dictionary, ready to start compression operation without startup delay.
*   `dict` can be released after ZSTD_CDict creation */
typedef struct ZSTD_CDict_s ZSTD_CDict;
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dict, size_t dictSize, int compressionLevel);
ZSTDLIB_API size_t      ZSTD_freeCDict(ZSTD_CDict* CDict);

/*! ZSTD_compress_usingCDict() :
*   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 */
ZSTDLIB_API size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
                                            void* dst, size_t dstCapacity,
                                      const void* src, size_t srcSize,
                                      const ZSTD_CDict* cdict);

/*! ZSTD_createDDict() :
*   Create a digested dictionary, ready to start decompression operation without startup delay.
*   `dict` can be released after creation */
typedef struct ZSTD_DDict_s ZSTD_DDict;
ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict(const void* dict, size_t dictSize);
ZSTDLIB_API size_t      ZSTD_freeDDict(ZSTD_DDict* ddict);

/*! ZSTD_decompress_usingDDict() :
*   Decompression using a digested Dictionary
*   Faster startup than ZSTD_decompress_usingDict(), recommended when same dictionary is used multiple times. */
ZSTDLIB_API size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
                                              void* dst, size_t dstCapacity,
                                        const void* src, size_t srcSize,
                                        const ZSTD_DDict* ddict);


/*-**************************
*  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   ======*/

/*-***********************************************************************
*  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.
*
*  Start by initializing ZSTD_CStream.
*  Use ZSTD_initCStream() to start a new compression operation.
*  Use ZSTD_initCStream_usingDict() for a compression which requires a dictionary.
*
*  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
*           (it's just a hint, to help latency a little, any other value will work fine)
*           (note : the size hint is guaranteed to be <= ZSTD_CStreamInSize() )
*            or an error code, which can be tested using ZSTD_isError().
*
*  At any moment, it's possible to flush whatever data remains within buffer, using ZSTD_flushStream().
*  `output->pos` will be updated.
*  Note 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.
*  Similar to ZSTD_flushStream(), it may not be able to flush the full content if `output->size` is too small.
*  In which case, call again ZSTD_endStream() to complete the flush.
*  @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().
*
* *******************************************************************/

typedef struct ZSTD_CStream_s ZSTD_CStream;
ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream(void);
ZSTDLIB_API size_t ZSTD_freeCStream(ZSTD_CStream* zcs);

ZSTDLIB_API size_t ZSTD_CStreamInSize(void);    /**< recommended size for input buffer */
ZSTDLIB_API size_t ZSTD_CStreamOutSize(void);   /**< recommended size for output buffer */

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


/*======   decompression   ======*/

/*-***************************************************************************
*  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 is not consumed.
*  It's up to the caller to present again remaining data.
*  If `output.pos == output.size`, there is probably some more data to flush, still stored inside internal buffers.
*  @return : 0 when a frame is completely decoded and fully flushed,
*            an error code, which can be tested using ZSTD_isError(),
*            any value > 0, which means there is still some work to do to complete the frame.
*            In general, the return value is a suggested next input size (merely a hint, to help latency).
*            1 is a special value, which means either "there is still some data to flush", or "need 1 more byte as input".
*            In which case, start by flushing. When flush is completed, if return value is still `1`, it means "need 1 more byte".
* *******************************************************************************/

typedef struct ZSTD_DStream_s ZSTD_DStream;
ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream(void);
ZSTDLIB_API size_t ZSTD_freeDStream(ZSTD_DStream* zds);

ZSTDLIB_API size_t ZSTD_DStreamInSize(void);    /*!< recommended size for input buffer */
ZSTDLIB_API size_t ZSTD_DStreamOutSize(void);   /*!< recommended size for output buffer */

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



#ifdef ZSTD_STATIC_LINKING_ONLY

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

/*--- Constants ---*/
#define ZSTD_MAGICNUMBER            0xFD2FB528   /* v0.8 */
#define ZSTD_MAGIC_SKIPPABLE_START  0x184D2A50U

#define ZSTD_WINDOWLOG_MAX_32  25
#define ZSTD_WINDOWLOG_MAX_64  27
#define ZSTD_WINDOWLOG_MAX    ((U32)(MEM_32bits() ? ZSTD_WINDOWLOG_MAX_32 : ZSTD_WINDOWLOG_MAX_64))
#define ZSTD_WINDOWLOG_MIN     18
#define ZSTD_CHAINLOG_MAX     (ZSTD_WINDOWLOG_MAX+1)
#define ZSTD_CHAINLOG_MIN       4
#define ZSTD_HASHLOG_MAX       ZSTD_WINDOWLOG_MAX
#define ZSTD_HASHLOG_MIN       12
#define ZSTD_HASHLOG3_MAX      17
#define ZSTD_SEARCHLOG_MAX    (ZSTD_WINDOWLOG_MAX-1)
#define ZSTD_SEARCHLOG_MIN      1
#define ZSTD_SEARCHLENGTH_MAX   7
#define ZSTD_SEARCHLENGTH_MIN   3
#define ZSTD_TARGETLENGTH_MIN   4
#define ZSTD_TARGETLENGTH_MAX 999

#define ZSTD_FRAMEHEADERSIZE_MAX 18    /* for static allocation */
static const size_t ZSTD_frameHeaderSize_prefix = 5;
static const size_t ZSTD_frameHeaderSize_min = 6;
static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
static const size_t ZSTD_skippableHeaderSize = 8;  /* magic number + skippable frame length */


/*--- Types ---*/
typedef enum { ZSTD_fast, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2, ZSTD_btlazy2, ZSTD_btopt } 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 (if known). */
    unsigned checksumFlag;    /**< 1: will generate a 22-bits checksum at end of frame, to be used for error detection by decompressor */
    unsigned noDictIDFlag;    /**< 1: no dict ID 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;


/*-*************************************
*  Advanced compression functions
***************************************/
/*! ZSTD_estimateCCtxSize() :
 *  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 */
ZSTDLIB_API size_t ZSTD_estimateCCtxSize(ZSTD_compressionParameters cParams);

/*! ZSTD_createCCtx_advanced() :
 *  Create a ZSTD compression context using external alloc and free functions */
ZSTDLIB_API ZSTD_CCtx* ZSTD_createCCtx_advanced(ZSTD_customMem customMem);

/*! ZSTD_createCDict_advanced() :
 *  Create a ZSTD_CDict using external alloc and free, and customized compression parameters */
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_advanced(const void* dict, size_t dictSize,
                                                  ZSTD_parameters params, ZSTD_customMem customMem);

/*! ZSTD_sizeofCCtx() :
 *  Gives the amount of memory used by a given ZSTD_CCtx */
ZSTDLIB_API size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);

/*! ZSTD_getParams() :
*   same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of a `ZSTD_compressionParameters`.
*   All fields of `ZSTD_frameParameters` are set to default (0) */
ZSTDLIB_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long srcSize, size_t dictSize);

/*! ZSTD_getCParams() :
*   @return ZSTD_compressionParameters structure for a selected compression level and srcSize.
*   `srcSize` value is optional, select 0 if not known */
ZSTDLIB_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long srcSize, size_t dictSize);

/*! ZSTD_checkCParams() :
*   Ensure param values remain within authorized range */
ZSTDLIB_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params);

/*! ZSTD_adjustCParams() :
*   optimize params for a given `srcSize` and `dictSize`.
*   both values are optional, select `0` if unknown. */
ZSTDLIB_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);

/*! ZSTD_compress_advanced() :
*   Same as ZSTD_compress_usingDict(), with fine-tune control of each compression parameter */
ZSTDLIB_API size_t ZSTD_compress_advanced (ZSTD_CCtx* ctx,
                                           void* dst, size_t dstCapacity,
                                     const void* src, size_t srcSize,
                                     const void* dict,size_t dictSize,
                                           ZSTD_parameters params);


/*--- Advanced Decompression functions ---*/

/*! ZSTD_estimateDCtxSize() :
 *  Gives the potential amount of memory allocated to create a ZSTD_DCtx */
ZSTDLIB_API size_t ZSTD_estimateDCtxSize(void);

/*! ZSTD_createDCtx_advanced() :
 *  Create a ZSTD decompression context using external alloc and free functions */
ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);

/*! ZSTD_sizeofDCtx() :
 *  Gives the amount of memory used by a given ZSTD_DCtx */
ZSTDLIB_API size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);


/* ******************************************************************
*  Advanced Streaming functions
********************************************************************/

/*======   compression   ======*/

ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
ZSTDLIB_API size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, const void* dict, size_t dictSize, int compressionLevel);
ZSTDLIB_API size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, const void* dict, size_t dictSize,
                                 ZSTD_parameters params, unsigned long long pledgedSrcSize);
ZSTDLIB_API size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);


/*======   decompression   ======*/

typedef enum { ZSTDdsp_maxWindowSize } ZSTD_DStreamParameter_e;

ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
ZSTDLIB_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
ZSTDLIB_API size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);
ZSTDLIB_API 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.
*  But it's also a complex one, with many restrictions (documented below).
*  Prefer using normal streaming API for an easier experience */

ZSTDLIB_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
ZSTDLIB_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
ZSTDLIB_API size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize);
ZSTDLIB_API size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx);

ZSTDLIB_API size_t ZSTD_compressContinue(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
ZSTDLIB_API size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);

/*
  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 buffer only.
  - Interface is synchronous : input is consumed entirely and produce 1+ (or more) 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 a NULL,0 src content, in which case, it will write a final empty block to end the frame,
  Without last block mark, frames will be considered unfinished (broken) by decoders.

  You can then reuse `ZSTD_CCtx` (ZSTD_compressBegin()) to compress some new frame.
*/

typedef struct {
    unsigned long long frameContentSize;
    unsigned windowSize;
    unsigned dictID;
    unsigned checksumFlag;
} ZSTD_frameParams;

ZSTDLIB_API size_t ZSTD_getFrameParams(ZSTD_frameParams* fparamsPtr, const void* src, size_t srcSize);   /**< doesn't consume input, see details below */

ZSTDLIB_API size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx);
ZSTDLIB_API size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
ZSTDLIB_API void   ZSTD_copyDCtx(ZSTD_DCtx* dctx, const ZSTD_DCtx* preparedDCtx);

ZSTDLIB_API size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx);
ZSTDLIB_API 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;
ZSTDLIB_API ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx);

/*
  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_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.
  (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.
           >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().
  Alternatively, you can copy a prepared context, using ZSTD_copyDCtx().

  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, which is not an error; it just means ZSTD_decompressContinue() has decoded some metadata item.
  It can also be an error code, which can be tested with ZSTD_isError().

  ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize`.
  They should preferably be located contiguously, prior to current block.
  Alternatively, a round buffer of sufficient size is also possible. Sufficient size is determined by frame parameters.
  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.

  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 a 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_decompressContinue() always returns 0.
  For skippable frames ZSTD_getFrameParams() returns fparamsPtr->windowLog==0 what means that a frame is skippable.
  It also returns Frame Size as fparamsPtr->frameContentSize.
*/


/* **************************************
*  Block functions
****************************************/
/*! Block functions produce and decode raw zstd blocks, without frame metadata.
    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 : ZSTD_compressBegin()
      + decompression : ZSTD_decompressBegin()
      + variants _usingDict() are also allowed
      + copyCCtx() and copyDCtx() work too
    - Block size is limited, it must be <= ZSTD_getBlockSizeMax()
      + If you need to compress more, cut data into multiple blocks
      + Consider using the regular ZSTD_compress() instead, as frame metadata costs become negligible when source size is large.
    - 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, decoder must be informed of uncompressed block existence to follow proper history.
        Use ZSTD_insertBlock() in such a case.
*/

#define ZSTD_BLOCKSIZE_ABSOLUTEMAX (128 * 1024)   /* define, for static allocation */
ZSTDLIB_API size_t ZSTD_getBlockSizeMax(ZSTD_CCtx* cctx);
ZSTDLIB_API size_t ZSTD_compressBlock  (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
ZSTDLIB_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
ZSTDLIB_API size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize);  /**< insert block into `dctx` history. Useful for uncompressed blocks */


#endif   /* ZSTD_STATIC_LINKING_ONLY */

#if defined (__cplusplus)
}
#endif

#endif  /* ZSTD_H_235446 */