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.
 */

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

#ifndef ZSTD_H_235446
#define ZSTD_H_235446

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


/* =====   ZSTDLIB_API : control library symbols visibility   ===== */
#ifndef ZSTDLIB_VISIBILITY
#  if defined(__GNUC__) && (__GNUC__ >= 4)
#    define ZSTDLIB_VISIBILITY __attribute__ ((visibility ("default")))
#  else
#    define ZSTDLIB_VISIBILITY
#  endif
#endif
#if defined(ZSTD_DLL_EXPORT) && (ZSTD_DLL_EXPORT==1)
#  define ZSTDLIB_API __declspec(dllexport) ZSTDLIB_VISIBILITY
#elif defined(ZSTD_DLL_IMPORT) && (ZSTD_DLL_IMPORT==1)
#  define ZSTDLIB_API __declspec(dllimport) ZSTDLIB_VISIBILITY /* It isn't required but allows to generate better code, saving a function pointer load from the IAT and an indirect jump.*/
#else
#  define ZSTDLIB_API ZSTDLIB_VISIBILITY
#endif


/*******************************************************************************************************
  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   ------*/
#define ZSTD_VERSION_MAJOR    1
#define ZSTD_VERSION_MINOR    3
#define ZSTD_VERSION_RELEASE  1

#define ZSTD_VERSION_NUMBER  (ZSTD_VERSION_MAJOR *100*100 + ZSTD_VERSION_MINOR *100 + ZSTD_VERSION_RELEASE)
ZSTDLIB_API unsigned ZSTD_versionNumber(void);   /**< useful to check dll version */

#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)
ZSTDLIB_API const char* ZSTD_versionString(void);   /* v1.3.0 */


/***************************************
*  Simple API
***************************************/
/*! ZSTD_compress() :
 *  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()). */
ZSTDLIB_API size_t ZSTD_compress( void* dst, size_t dstCapacity,
                            const void* src, size_t srcSize,
                                  int compressionLevel);

/*! ZSTD_decompress() :
 *  `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()). */
ZSTDLIB_API size_t ZSTD_decompress( void* dst, size_t dstCapacity,
                              const void* src, size_t compressedSize);

/*! ZSTD_getFrameContentSize() : v1.3.0
 *  `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() */
#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
#define ZSTD_CONTENTSIZE_ERROR   (0ULL - 2)
ZSTDLIB_API unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);

/*! ZSTD_getDecompressedSize() :
 *  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. */
ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);


/*======  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
 *  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;
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
 *  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;
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 loads the dictionary, resulting in significant startup delay.
 *  Note : When `dict == NULL || dictSize < 8` no dictionary is used. */
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 loads the dictionary, resulting in significant startup delay.
 *  Note : When `dict == NULL || dictSize < 8` no dictionary is used. */
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);


/**********************************
 *  Bulk processing dictionary API
 *********************************/
typedef struct ZSTD_CDict_s ZSTD_CDict;

/*! ZSTD_createCDict() :
 *  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 */
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
                                         int compressionLevel);

/*! ZSTD_freeCDict() :
 *  Function frees memory allocated by ZSTD_createCDict(). */
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.
 *  Frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) */
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);


typedef struct ZSTD_DDict_s ZSTD_DDict;

/*! ZSTD_createDDict() :
 *  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 */
ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);

/*! ZSTD_freeDDict() :
 *  Function frees memory allocated with ZSTD_createDDict() */
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 - 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) */
                                 /* Continue to distinguish them for compatibility with versions <= v1.2.0 */
/*===== ZSTD_CStream management functions =====*/
ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream(void);
ZSTDLIB_API size_t ZSTD_freeCStream(ZSTD_CStream* zcs);

/*===== Streaming compression functions =====*/
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);

ZSTDLIB_API size_t ZSTD_CStreamInSize(void);    /**< recommended size for input buffer */
ZSTDLIB_API 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) */
                                 /* Continue to distinguish them for compatibility with versions <= v1.2.0 */
/*===== ZSTD_DStream management functions =====*/
ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream(void);
ZSTDLIB_API size_t ZSTD_freeDStream(ZSTD_DStream* zds);

/*===== Streaming decompression functions =====*/
ZSTDLIB_API size_t ZSTD_initDStream(ZSTD_DStream* zds);
ZSTDLIB_API size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);

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

#endif  /* ZSTD_H_235446 */



/****************************************************************************************
 * 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.
 * ***************************************************************************************/

#if defined(ZSTD_STATIC_LINKING_ONLY) && !defined(ZSTD_H_ZSTD_STATIC_LINKING_ONLY)
#define ZSTD_H_ZSTD_STATIC_LINKING_ONLY

/* --- Constants ---*/
#define ZSTD_MAGICNUMBER            0xFD2FB528   /* >= v0.8.0 */
#define ZSTD_MAGIC_SKIPPABLE_START  0x184D2A50U
#define ZSTD_MAGIC_DICTIONARY       0xEC30A437   /* v0.7+ */

#define ZSTD_WINDOWLOG_MAX_32  27
#define ZSTD_WINDOWLOG_MAX_64  27
#define ZSTD_WINDOWLOG_MAX    ((unsigned)(sizeof(size_t) == 4 ? ZSTD_WINDOWLOG_MAX_32 : ZSTD_WINDOWLOG_MAX_64))
#define ZSTD_WINDOWLOG_MIN     10
#define ZSTD_HASHLOG_MAX       ZSTD_WINDOWLOG_MAX
#define ZSTD_HASHLOG_MIN        6
#define ZSTD_CHAINLOG_MAX     (ZSTD_WINDOWLOG_MAX+1)
#define ZSTD_CHAINLOG_MIN      ZSTD_HASHLOG_MIN
#define ZSTD_HASHLOG3_MAX      17
#define ZSTD_SEARCHLOG_MAX    (ZSTD_WINDOWLOG_MAX-1)
#define ZSTD_SEARCHLOG_MIN      1
#define ZSTD_SEARCHLENGTH_MAX   7   /* only for ZSTD_fast, other strategies are limited to 6 */
#define ZSTD_SEARCHLENGTH_MIN   3   /* only for ZSTD_btopt, other strategies are limited to 4 */
#define ZSTD_TARGETLENGTH_MIN   4
#define ZSTD_TARGETLENGTH_MAX 999

#define ZSTD_FRAMEHEADERSIZE_MAX 18    /* for static allocation */
#define ZSTD_FRAMEHEADERSIZE_MIN  6
static const size_t ZSTD_frameHeaderSize_prefix = 5;  /* minimum input size to know frame header size */
static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
static const size_t ZSTD_frameHeaderSize_min = ZSTD_FRAMEHEADERSIZE_MIN;
static const size_t ZSTD_skippableHeaderSize = 8;  /* magic number + skippable frame length */


/*--- 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;

typedef struct ZSTD_CCtx_params_s ZSTD_CCtx_params;

/*= 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
***************************************/

/*! ZSTD_findFrameCompressedSize() :
 *  `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 */
ZSTDLIB_API size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);

/*! ZSTD_findDecompressedSize() :
 *  `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. */
ZSTDLIB_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);

/*! ZSTD_frameHeaderSize() :
*   `src` should point to the start of a ZSTD frame
*   `srcSize` must be >= ZSTD_frameHeaderSize_prefix.
*   @return : size of the Frame Header */
ZSTDLIB_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);


/***************************************
*  Context memory usage
***************************************/

/*! ZSTD_sizeof_*() :
 *  These functions give the current memory usage of selected object.
 *  Object memory usage can evolve if it's re-used multiple times. */
ZSTDLIB_API size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
ZSTDLIB_API size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
ZSTDLIB_API size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
ZSTDLIB_API size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
ZSTDLIB_API size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
ZSTDLIB_API size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);

/*! ZSTD_estimate*() :
 *  These functions make it possible to estimate memory usage
 *  of a future {D,C}Ctx, before its creation.
 *  ZSTD_estimateCCtxSize() will provide a budget large enough for any compression level up to selected one.
 *  It will also consider src size to be arbitrarily "large", which is worst case.
 *  If srcSize is known to always be small, ZSTD_estimateCCtxSize_advanced_usingCParams() can provide a tighter estimation.
 *  ZSTD_estimateCCtxSize_advanced_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
 *  ZSTD_estimateCCtxSize_advanced_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return 0 if ZSTD_p_nbThreads is set to a value > 1.
 *  Note : CCtx estimation is only correct for single-threaded compression */
ZSTDLIB_API size_t ZSTD_estimateCCtxSize(int compressionLevel);
ZSTDLIB_API size_t ZSTD_estimateCCtxSize_advanced_usingCParams(ZSTD_compressionParameters cParams);
ZSTDLIB_API size_t ZSTD_estimateCCtxSize_advanced_usingCCtxParams(const ZSTD_CCtx_params* params);
ZSTDLIB_API size_t ZSTD_estimateDCtxSize(void);

/*! ZSTD_estimateCStreamSize() :
 *  ZSTD_estimateCStreamSize() will provide a budget large enough for any compression level up to selected one.
 *  It will also consider src size to be arbitrarily "large", which is worst case.
 *  If srcSize is known to always be small, ZSTD_estimateCStreamSize_advanced_usingCParams() can provide a tighter estimation.
 *  ZSTD_estimateCStreamSize_advanced_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
 *  ZSTD_estimateCStreamSize_advanced_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return 0 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 */
ZSTDLIB_API size_t ZSTD_estimateCStreamSize(int compressionLevel);
ZSTDLIB_API size_t ZSTD_estimateCStreamSize_advanced_usingCParams(ZSTD_compressionParameters cParams);
ZSTDLIB_API size_t ZSTD_estimateCStreamSize_advanced_usingCCtxParams(const ZSTD_CCtx_params* params);
ZSTDLIB_API size_t ZSTD_estimateDStreamSize(size_t windowSize);
ZSTDLIB_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);

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

/*! ZSTD_estimate?DictSize() :
 *  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
 */
ZSTDLIB_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
ZSTDLIB_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
ZSTDLIB_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);


/***************************************
*  Advanced compression functions
***************************************/
/*! 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_initStaticCCtx() : initialize a fixed-size zstd compression context
 *  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
 */
ZSTDLIB_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);


/*! ZSTD_createCDict_byReference() :
 *  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 */
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);

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_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_dictLoadMethod_e dictLoadMethod,
                                                  ZSTD_dictMode_e dictMode,
                                                  ZSTD_compressionParameters cParams,
                                                  ZSTD_customMem customMem);

/*! ZSTD_initStaticCDict_advanced() :
 *  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.
 */
ZSTDLIB_API 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);

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

/*! ZSTD_getParams() :
*   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) */
ZSTDLIB_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, 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 over each compression parameter */
ZSTDLIB_API 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);

/*! ZSTD_compress_usingCDict_advanced() :
*   Same as ZSTD_compress_usingCDict(), with fine-tune control over frame parameters */
ZSTDLIB_API 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);


/*--- Advanced decompression functions ---*/

/*! ZSTD_isFrame() :
 *  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. */
ZSTDLIB_API unsigned ZSTD_isFrame(const void* buffer, size_t size);

/*! 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_initStaticDCtx() : initialize a fixed-size zstd decompression context
 *  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().
 */
ZSTDLIB_API ZSTD_DCtx* ZSTD_initStaticDCtx(void* workspace, size_t workspaceSize);

/*! ZSTD_createDDict_byReference() :
 *  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 */
ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);

/*! ZSTD_createDDict_advanced() :
 *  Create a ZSTD_DDict using external alloc and free, optionally by reference */
ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict_advanced(const void* dict, size_t dictSize,
                                                  ZSTD_dictLoadMethod_e dictLoadMethod,
                                                  ZSTD_customMem customMem);

/*! ZSTD_initStaticDDict() :
 *  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.
 */
ZSTDLIB_API ZSTD_DDict* ZSTD_initStaticDDict(void* workspace, size_t workspaceSize,
                                             const void* dict, size_t dictSize,
                                             ZSTD_dictLoadMethod_e dictLoadMethod);

/*! ZSTD_getDictID_fromDict() :
 *  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. */
ZSTDLIB_API unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);

/*! ZSTD_getDictID_fromDDict() :
 *  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. */
ZSTDLIB_API unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);

/*! ZSTD_getDictID_fromFrame() :
 *  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. */
ZSTDLIB_API unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);


/********************************************************************
*  Advanced streaming functions
********************************************************************/

/*=====   Advanced Streaming compression functions  =====*/
ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream_advanced(ZSTD_customMem customMem);
ZSTDLIB_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize);    /**< same as ZSTD_initStaticCCtx() */
ZSTDLIB_API 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 */
ZSTDLIB_API 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. */
ZSTDLIB_API 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 */
ZSTDLIB_API size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);  /**< note : cdict will just be referenced, and must outlive compression session */
ZSTDLIB_API 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 */

/*! ZSTD_resetCStream() :
 *  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()) */
ZSTDLIB_API size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);


/*=====   Advanced Streaming decompression functions  =====*/
typedef enum { DStream_p_maxWindowSize } ZSTD_DStreamParameter_e;
ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem);
ZSTDLIB_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize);    /**< same as ZSTD_initStaticDCtx() */
ZSTDLIB_API size_t ZSTD_setDStreamParameter(ZSTD_DStream* zds, ZSTD_DStreamParameter_e paramType, unsigned paramValue);
ZSTDLIB_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); /**< note: a dict will not be used if dict == NULL or dictSize < 8 */
ZSTDLIB_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);  /**< note : ddict will just be referenced, and must outlive decompression session */
ZSTDLIB_API 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 many restrictions (documented below).
*  Prefer using 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 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 srcSize==0, in which case, it will write a final empty block to end the frame.
  Without last block mark, frames will be considered unfinished (corrupted) by decoders.

  `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress some new frame.
*/

/*=====   Buffer-less streaming compression functions  =====*/
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); /**< pledgedSrcSize is optional and can be 0 (meaning unknown). note: if the contentSizeFlag is set, pledgedSrcSize == 0 means the source size is actually 0 */
ZSTDLIB_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); /**< note: fails if cdict==NULL */
ZSTDLIB_API 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 */
ZSTDLIB_API 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 */

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);



/*-
  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().
  It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
  such as minimum rolling buffer size to allocate to decompress data (`windowSize`),
  and the dictionary ID in use.
  (Note : content size is optional, it may not be present. 0 means : content size unknown).
  Note that these values could be wrong, either because of data malformation, or because an attacker is spoofing deliberate false information.
  As a consequence, check that values remain within valid application range, especially `windowSize`, before allocation.
  Each application can set its own limit, depending on local restrictions.
  For extended interoperability, it is recommended to support windowSize of at least 8 MB.
  Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
  Data fragment must be large enough to ensure successful decoding.
  `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
  @result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
           >0 : `srcSize` is too small, please provide at least @result bytes on next attempt.
           errorCode, which can be tested using ZSTD_isError().

  Start decompression, with ZSTD_decompressBegin().
  If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
  Alternatively, you can copy a prepared context, using ZSTD_copyDCtx().

  Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
  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_getFrameHeader() returns fparamsPtr->windowLog==0 what means that a frame is skippable.
    Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
           For purposes of decompression, it is valid in both cases to skip the frame using
           ZSTD_findFrameCompressedSize to find its size in bytes.
  It also returns Frame Size as fparamsPtr->frameContentSize.
*/

/*=====   Buffer-less streaming decompression functions  =====*/
typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
typedef struct {
    unsigned long long frameContentSize; /* ZSTD_CONTENTSIZE_UNKNOWN means this field is not available. 0 means "empty" */
    unsigned long long windowSize;       /* can be very large, up to <= frameContentSize */
    ZSTD_frameType_e frameType;          /* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */
    unsigned headerSize;
    unsigned dictID;
    unsigned checksumFlag;
} ZSTD_frameHeader;
ZSTDLIB_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize);   /**< doesn't consume input */
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 size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
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);



/*===   New advanced API (experimental, and compression only)  ===*/

/* notes on API design :
 *   In this proposal, parameters are pushed one by one into an existing CCtx,
 *   and then applied on all subsequent compression jobs.
 *   When no parameter is ever provided, CCtx is created with compression level ZSTD_CLEVEL_DEFAULT.
 *
 *   This API is intended to replace all others experimental API.
 *   It can basically do all other use cases, and even new ones.
 *   It stands a good chance to become "stable",
 *   after a reasonable testing period.
 */

/* note on naming convention :
 *   Initially, the API favored names like ZSTD_setCCtxParameter() .
 *   In this proposal, convention is changed towards ZSTD_CCtx_setParameter() .
 *   The main driver is that it identifies more clearly the target object type.
 *   It feels clearer in light of potential variants :
 *   ZSTD_CDict_setParameter() (rather than ZSTD_setCDictParameter())
 *   ZSTD_DCtx_setParameter()  (rather than ZSTD_setDCtxParameter() )
 *   Left variant feels easier to distinguish.
 */

/* note on enum design :
 * All enum will be manually set to explicit values before reaching "stable API" status */

typedef enum {
    /* compression parameters */
    ZSTD_p_compressionLevel=100, /* Update all compression parameters according to pre-defined cLevel table
                              * Default level is ZSTD_CLEVEL_DEFAULT==3.
                              * Special: value 0 means "do not change cLevel". */
    ZSTD_p_windowLog,        /* Maximum allowed back-reference distance, expressed as power of 2.
                              * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
                              * Special: value 0 means "do not change windowLog". */
    ZSTD_p_hashLog,          /* Size of the probe table, as a power of 2.
                              * Resulting table size is (1 << (hashLog+2)).
                              * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
                              * Larger tables improve compression ratio of strategies <= dFast,
                              * and improve speed of strategies > dFast.
                              * Special: value 0 means "do not change hashLog". */
    ZSTD_p_chainLog,         /* Size of the full-search table, as a power of 2.
                              * Resulting table size is (1 << (chainLog+2)).
                              * Larger tables result in better and slower compression.
                              * This parameter is useless when using "fast" strategy.
                              * Special: value 0 means "do not change chainLog". */
    ZSTD_p_searchLog,        /* Number of search attempts, as a power of 2.
                              * More attempts result in better and slower compression.
                              * This parameter is useless when using "fast" and "dFast" strategies.
                              * Special: value 0 means "do not change searchLog". */
    ZSTD_p_minMatch,         /* Minimum size of searched matches (note : repCode matches can be smaller).
                              * Larger values make faster compression and decompression, but decrease ratio.
                              * Must be clamped between ZSTD_SEARCHLENGTH_MIN and ZSTD_SEARCHLENGTH_MAX.
                              * Note that currently, for all strategies < btopt, effective minimum is 4.
                              * Note that currently, for all strategies > fast, effective maximum is 6.
                              * Special: value 0 means "do not change minMatchLength". */
    ZSTD_p_targetLength,     /* Only useful for strategies >= btopt.
                              * Length of Match considered "good enough" to stop search.
                              * Larger values make compression stronger and slower.
                              * Special: value 0 means "do not change targetLength". */
    ZSTD_p_compressionStrategy, /* See ZSTD_strategy enum definition.
                              * Cast selected strategy as unsigned for ZSTD_CCtx_setParameter() compatibility.
                              * The higher the value of selected strategy, the more complex it is,
                              * resulting in stronger and slower compression.
                              * Special: value 0 means "do not change strategy". */

    /* frame parameters */
    ZSTD_p_contentSizeFlag=200, /* Content size is written into frame header _whenever known_ (default:1)
                              * 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_cParameter;


/*! ZSTD_CCtx_setParameter() :
 *  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()). */
ZSTDLIB_API size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned value);

/*! ZSTD_CCtx_setPledgedSrcSize() :
 *  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. */
ZSTDLIB_API size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);

/*! ZSTD_CCtx_loadDictionary() :
 *  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.
 */
ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictMode_e dictMode);


/*! ZSTD_CCtx_refCDict() :
 *  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.
 */
ZSTDLIB_API size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);

/*! ZSTD_CCtx_refPrefix() :
 *  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. */
ZSTDLIB_API size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize);
ZSTDLIB_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictMode_e 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 ends current frame. Any future compression starts a new frame. */
} ZSTD_EndDirective;

/*! ZSTD_compress_generic() :
 *  Behave about the same as ZSTD_compressStream. To note :
 *  - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_setParameter()
 *  - Compression parameters cannot be changed once compression is started.
 *  - *dstPos must be <= dstCapacity, *srcPos must be <= srcSize
 *  - *dspPos and *srcPos will be updated. They are guaranteed to remain below their respective limit.
 *  - @return provides the minimum amount of data still to flush from internal buffers
 *            or an error code, which can be tested using ZSTD_isError().
 *            if @return != 0, flush is not fully completed, there is some data left within internal buffers.
 *  - after a ZSTD_e_end directive, if internal buffer is not fully flushed,
 *            only ZSTD_e_end or ZSTD_e_flush operations are allowed.
 *            It is necessary to fully flush internal buffers
 *            before starting a new compression job, or changing compression parameters.
 */
ZSTDLIB_API size_t ZSTD_compress_generic (ZSTD_CCtx* cctx,
                                          ZSTD_outBuffer* output,
                                          ZSTD_inBuffer* input,
                                          ZSTD_EndDirective endOp);

/*! ZSTD_CCtx_reset() :
 *  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.
 *  It's possible to modify compression parameters after a reset.
 */
ZSTDLIB_API void ZSTD_CCtx_reset(ZSTD_CCtx* cctx);   /* Not ready yet ! */


/*! ZSTD_compress_generic_simpleArgs() :
 *  Same as ZSTD_compress_generic(),
 *  but using only integral types as arguments.
 *  Argument list is larger and less expressive than ZSTD_{in,out}Buffer,
 *  but can be helpful for binders from dynamic languages
 *  which have troubles handling structures containing memory pointers.
 */
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);


/** ZSTD_CCtx_params
 *
 *  - 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_opaque() for static allocation
 *  for single-threaded compression.
 */
ZSTDLIB_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void);

/*! ZSTD_resetCCtxParams() :
 *  Reset params to default, with the default compression level.
 */
ZSTDLIB_API size_t ZSTD_resetCCtxParams(ZSTD_CCtx_params* params);

/*! ZSTD_initCCtxParams() :
 *  Initializes the compression parameters of cctxParams according to
 *  compression level. All other parameters are reset to their default values.
 */
ZSTDLIB_API size_t ZSTD_initCCtxParams(ZSTD_CCtx_params* cctxParams, int compressionLevel);

/*! ZSTD_initCCtxParams_advanced() :
 *  Initializes the compression and frame parameters of cctxParams according to
 *  params. All other parameters are reset to their default values.
 */
ZSTDLIB_API size_t ZSTD_initCCtxParams_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);

ZSTDLIB_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params);

/*! ZSTD_CCtxParam_setParameter() :
 *  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()).
 */
ZSTDLIB_API size_t ZSTD_CCtxParam_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, unsigned value);

/*! ZSTD_CCtx_setParametersUsingCCtxParams() :
 * 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.
 */
ZSTDLIB_API size_t ZSTD_CCtx_setParametersUsingCCtxParams(
        ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);

/**
    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 : 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
      + 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.
*/

#define ZSTD_BLOCKSIZELOG_MAX 17
#define ZSTD_BLOCKSIZE_MAX   (1<<ZSTD_BLOCKSIZELOG_MAX)   /* define, for static allocation */
/*=====   Raw zstd block functions  =====*/
ZSTDLIB_API size_t ZSTD_getBlockSize   (const 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_H_ZSTD_STATIC_LINKING_ONLY */

#if defined (__cplusplus)
}
#endif