zstd/contrib/linux-kernel/include/linux/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

/* ======   Dependency   ======*/
#include <linux/types.h>   /* size_t */


/* =====   ZSTDLIB_API : control library symbols visibility   ===== */
#define ZSTDLIB_API


/*******************************************************************************************************
  Introduction

  zstd, short for Zstandard, is a fast lossless compression algorithm, targeting real-time compression scenarios
  at zlib-level and better compression ratios. The zstd compression library provides in-memory compression and
  decompression functions. The library supports compression levels from 1 up to ZSTD_maxCLevel() which is 22.
  Levels >= 20, labeled `--ultra`, should be used with caution, as they require more memory.
  Compression can be done in:
	- a single step (described as Simple API)
	- a single step, reusing a context (described as Explicit memory management)
	- unbounded multiple steps (described as Streaming compression)
  The compression ratio achievable on small data can be highly improved using compression with a dictionary in:
	- a single step (described as Simple dictionary API)
	- a single step, reusing a dictionary (described as Fast dictionary API)

  Advanced experimental functions can be accessed using #define ZSTD_STATIC_LINKING_ONLY before including zstd.h.
  These APIs shall never be used with a dynamic library.
  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    1
#define ZSTD_VERSION_RELEASE  5

#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)


/*======  Helper functions  ======*/
typedef enum {
  ZSTD_error_no_error,
  ZSTD_error_GENERIC,
  ZSTD_error_prefix_unknown,
  ZSTD_error_version_unsupported,
  ZSTD_error_parameter_unknown,
  ZSTD_error_frameParameter_unsupported,
  ZSTD_error_frameParameter_unsupportedBy32bits,
  ZSTD_error_frameParameter_windowTooLarge,
  ZSTD_error_compressionParameter_unsupported,
  ZSTD_error_init_missing,
  ZSTD_error_memory_allocation,
  ZSTD_error_stage_wrong,
  ZSTD_error_dstSize_tooSmall,
  ZSTD_error_srcSize_wrong,
  ZSTD_error_corruption_detected,
  ZSTD_error_checksum_wrong,
  ZSTD_error_tableLog_tooLarge,
  ZSTD_error_maxSymbolValue_tooLarge,
  ZSTD_error_maxSymbolValue_tooSmall,
  ZSTD_error_dictionary_corrupted,
  ZSTD_error_dictionary_wrong,
  ZSTD_error_dictionaryCreation_failed,
  ZSTD_error_maxCode
} ZSTD_ErrorCode;

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 */
/*! ZSTD_isError() :
*   tells if a `size_t` function result is an error code */
ZSTDLIB_API static __attribute__((unused)) unsigned ZSTD_isError(size_t code) {
	return code > (size_t)-ZSTD_error_maxCode;
}
/*! ZSTD_getErrorCode() :
*   convert a `size_t` function result into a proper ZSTD_errorCode enum */
ZSTDLIB_API static __attribute__((unused)) ZSTD_ErrorCode ZSTD_getErrorCode(size_t functionResult) {
	if (!ZSTD_isError(functionResult)) {
		return (ZSTD_ErrorCode)0;
	}
	return (ZSTD_ErrorCode)(0 - functionResult);
}

/***************************************
*  Explicit memory management
***************************************/

typedef enum { ZSTD_fast, ZSTD_dfast, ZSTD_greedy, ZSTD_lazy, ZSTD_lazy2, ZSTD_btlazy2, ZSTD_btopt, ZSTD_btopt2 } ZSTD_strategy;   /* from faster to stronger */

typedef 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;

size_t ZSTD_CCtxWorkspaceBound(ZSTD_compressionParameters params);

/*= 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* workspace, size_t workspaceSize);

/*! 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, ZSTD_parameters params);

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, ZSTD_parameters params);

size_t ZSTD_DCtxWorkspaceBound(void);

/*= Decompression context
*   When decompressing 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_DCtx_s ZSTD_DCtx;
ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx(void* workspace, size_t workspaceSize);

/*! 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);

ZSTDLIB_API size_t ZSTD_decompress_usingDict(ZSTD_DCtx* ctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, const void *dict, size_t dictSize);

/****************************
*  Fast dictionary API
****************************/
size_t ZSTD_CDictWorkspaceBound(ZSTD_compressionParameters params);

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 used by multiple threads concurrently, as its usage is read-only.
*   `dictBuffer` content is referenced, and it must remain accessible throughout the lifetime of the CDict */
ZSTDLIB_API ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, ZSTD_parameters params, void* workspace, size_t workspaceSize);

/*! 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);


size_t ZSTD_DDictWorkspaceBound(void);

typedef struct ZSTD_DDict_s ZSTD_DDict;

/*! ZSTD_createDDict() :
*   Create a digested dictionary, ready to start decompression operation without startup delay.
*   `dictBuffer` content is referenced, and it must remain accessible throughout the lifetime of the DDict */
ZSTDLIB_API ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize, void* workspace, size_t workspaceSize);

/*! 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.
*  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, hence compression completed)
*            or an error code, which can be tested using ZSTD_isError().
*
* *******************************************************************/

size_t ZSTD_CStreamWorkspaceBound(ZSTD_compressionParameters params);

typedef struct ZSTD_CStream_s ZSTD_CStream;
/*===== ZSTD_CStream management functions =====*/
ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream(ZSTD_parameters params, unsigned long long pledgedSrcSize, void* workspace, size_t workspaceSize);
ZSTDLIB_API ZSTD_CStream* ZSTD_createCStream_usingCDict(const ZSTD_CDict* cdict, unsigned long long pledgedSrcSize, void* workspace, size_t workspaceSize);

/*===== Streaming compression functions =====*/
ZSTDLIB_API size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);  /**< re-use compression parameters from previous init; skip dictionary loading stage; zcs must be init at least once before. note: pledgedSrcSize must be correct, a size of 0 means unknown.  for a frame size of 0 use initCStream_advanced */
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.
* *******************************************************************************/

size_t ZSTD_DStreamWorkspaceBound(size_t maxWindowSize);

typedef struct ZSTD_DStream_s ZSTD_DStream;
/*===== ZSTD_DStream management functions =====*/
ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream(size_t maxWindowSize, void* workspace, size_t workspaceSize);
ZSTDLIB_API ZSTD_DStream* ZSTD_createDStream_usingDDict(size_t maxWindowSize, const ZSTD_DDict* ddict, void* workspace, size_t workspaceSize);

/*===== Streaming decompression functions =====*/
ZSTDLIB_API size_t ZSTD_resetDStream(ZSTD_DStream* zds);  /**< re-use decompression parameters from previous init; saves dictionary loading */
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. */


/****************************************************************************************
 * START OF ADVANCED AND EXPERIMENTAL FUNCTIONS
 * 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   /* >= v0.8.0 */
#define ZSTD_MAGIC_SKIPPABLE_START  0x184D2A50U

#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
#define ZSTD_CONTENTSIZE_ERROR   (0ULL - 2)

#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;
static const size_t ZSTD_frameHeaderSize_min = ZSTD_FRAMEHEADERSIZE_MIN;
static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
static const size_t ZSTD_skippableHeaderSize = 8;  /* magic number + skippable frame length */


/***************************************
*  Compressed 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 frame pointed to by `src`, suitable to pass to
 *      `ZSTD_decompress` or similar, or an error code if given invalid input. */
ZSTDLIB_API size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);

/***************************************
*  Decompressed size functions
***************************************/
/*! ZSTD_getFrameContentSize() :
*   `src` should point to the start of a ZSTD encoded frame
*   `srcSize` must be at least as large as the frame header.  A value greater than or equal
*       to `ZSTD_frameHeaderSize_max` is guaranteed to be large enough in all cases.
*   @return : decompressed size of the frame pointed to be `src` if known, otherwise
*             - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
*             - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) */
ZSTDLIB_API unsigned long long ZSTD_getFrameContentSize(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 `srcSize` bytes after `src`)
*   @return : the decompressed size of all data in the contained frames, as a 64-bit value _if known_
*             - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
*             - if an error occurred: ZSTD_CONTENTSIZE_ERROR
*
*    note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
*             When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
*             In which case, it's necessary to use streaming mode to decompress data.
*             Optionally, application can still use ZSTD_decompress() while relying on implied limits.
*             (For example, data may be necessarily cut into blocks <= 16 KB).
*    note 2 : decompressed size is always present when compression is done with ZSTD_compress()
*    note 3 : decompressed size can be very large (64-bits value),
*             potentially larger than what local system can handle as a single memory segment.
*             In which case, it's necessary to use streaming mode to decompress data.
*    note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
*             Always ensure result fits within application's authorized limits.
*             Each application can set its own limits.
*    note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
*             read each contained frame header.  This is efficient as most of the data is skipped,
*             however it does mean that all frame data must be present and valid. */
ZSTDLIB_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);

/***************************************
*  Advanced compression functions
***************************************/
/*! 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);

/*--- 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_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 used ZSTD_getFrameParams(), which will provide a more precise error code. */
ZSTDLIB_API unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);


/*********************************************************************
*  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_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_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict, 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_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.
	Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
		   For purposes of decompression, it is valid in both cases to skip the frame using
		   ZSTD_findFrameCompressedSize to find its size in bytes.
  It also returns Frame Size as fparamsPtr->frameContentSize.
*/

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

/*=====   Buffer-less streaming decompression functions  =====*/
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);

/**
	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 */
/*=====   Raw zstd block functions  =====*/
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_H_235446 */