717 lines
34 KiB
C++
717 lines
34 KiB
C++
/* ******************************************************************
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* FSE : Finite State Entropy codec
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* Public Prototypes declaration
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* Copyright (c) Yann Collet, Facebook, Inc.
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*
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* You can contact the author at :
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* - Source repository : https://github.com/Cyan4973/FiniteStateEntropy
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*
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* This source code is licensed under both the BSD-style license (found in the
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* LICENSE file in the root directory of this source tree) and the GPLv2 (found
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* in the COPYING file in the root directory of this source tree).
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* You may select, at your option, one of the above-listed licenses.
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****************************************************************** */
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#if defined (__cplusplus)
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extern "C" {
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#endif
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#ifndef FSE_H
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#define FSE_H
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/*-*****************************************
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* Dependencies
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******************************************/
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#include "zstd_deps.h" /* size_t, ptrdiff_t */
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/*-*****************************************
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* FSE_PUBLIC_API : control library symbols visibility
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******************************************/
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#if defined(FSE_DLL_EXPORT) && (FSE_DLL_EXPORT==1) && defined(__GNUC__) && (__GNUC__ >= 4)
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# define FSE_PUBLIC_API __attribute__ ((visibility ("default")))
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#elif defined(FSE_DLL_EXPORT) && (FSE_DLL_EXPORT==1) /* Visual expected */
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# define FSE_PUBLIC_API __declspec(dllexport)
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#elif defined(FSE_DLL_IMPORT) && (FSE_DLL_IMPORT==1)
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# define FSE_PUBLIC_API __declspec(dllimport) /* It isn't required but allows to generate better code, saving a function pointer load from the IAT and an indirect jump.*/
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#else
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# define FSE_PUBLIC_API
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#endif
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/*------ Version ------*/
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#define FSE_VERSION_MAJOR 0
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#define FSE_VERSION_MINOR 9
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#define FSE_VERSION_RELEASE 0
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#define FSE_LIB_VERSION FSE_VERSION_MAJOR.FSE_VERSION_MINOR.FSE_VERSION_RELEASE
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#define FSE_QUOTE(str) #str
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#define FSE_EXPAND_AND_QUOTE(str) FSE_QUOTE(str)
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#define FSE_VERSION_STRING FSE_EXPAND_AND_QUOTE(FSE_LIB_VERSION)
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#define FSE_VERSION_NUMBER (FSE_VERSION_MAJOR *100*100 + FSE_VERSION_MINOR *100 + FSE_VERSION_RELEASE)
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FSE_PUBLIC_API unsigned FSE_versionNumber(void); /**< library version number; to be used when checking dll version */
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/*-****************************************
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* FSE simple functions
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******************************************/
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/*! FSE_compress() :
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Compress content of buffer 'src', of size 'srcSize', into destination buffer 'dst'.
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'dst' buffer must be already allocated. Compression runs faster is dstCapacity >= FSE_compressBound(srcSize).
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@return : size of compressed data (<= dstCapacity).
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Special values : if return == 0, srcData is not compressible => Nothing is stored within dst !!!
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if return == 1, srcData is a single byte symbol * srcSize times. Use RLE compression instead.
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if FSE_isError(return), compression failed (more details using FSE_getErrorName())
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*/
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FSE_PUBLIC_API size_t FSE_compress(void* dst, size_t dstCapacity,
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const void* src, size_t srcSize);
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/*! FSE_decompress():
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Decompress FSE data from buffer 'cSrc', of size 'cSrcSize',
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into already allocated destination buffer 'dst', of size 'dstCapacity'.
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@return : size of regenerated data (<= maxDstSize),
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or an error code, which can be tested using FSE_isError() .
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** Important ** : FSE_decompress() does not decompress non-compressible nor RLE data !!!
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Why ? : making this distinction requires a header.
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Header management is intentionally delegated to the user layer, which can better manage special cases.
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*/
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FSE_PUBLIC_API size_t FSE_decompress(void* dst, size_t dstCapacity,
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const void* cSrc, size_t cSrcSize);
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/*-*****************************************
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* Tool functions
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******************************************/
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FSE_PUBLIC_API size_t FSE_compressBound(size_t size); /* maximum compressed size */
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/* Error Management */
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FSE_PUBLIC_API unsigned FSE_isError(size_t code); /* tells if a return value is an error code */
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FSE_PUBLIC_API const char* FSE_getErrorName(size_t code); /* provides error code string (useful for debugging) */
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/*-*****************************************
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* FSE advanced functions
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******************************************/
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/*! FSE_compress2() :
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Same as FSE_compress(), but allows the selection of 'maxSymbolValue' and 'tableLog'
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Both parameters can be defined as '0' to mean : use default value
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@return : size of compressed data
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Special values : if return == 0, srcData is not compressible => Nothing is stored within cSrc !!!
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if return == 1, srcData is a single byte symbol * srcSize times. Use RLE compression.
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if FSE_isError(return), it's an error code.
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*/
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FSE_PUBLIC_API size_t FSE_compress2 (void* dst, size_t dstSize, const void* src, size_t srcSize, unsigned maxSymbolValue, unsigned tableLog);
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/*-*****************************************
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* FSE detailed API
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******************************************/
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/*!
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FSE_compress() does the following:
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1. count symbol occurrence from source[] into table count[] (see hist.h)
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2. normalize counters so that sum(count[]) == Power_of_2 (2^tableLog)
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3. save normalized counters to memory buffer using writeNCount()
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4. build encoding table 'CTable' from normalized counters
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5. encode the data stream using encoding table 'CTable'
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FSE_decompress() does the following:
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1. read normalized counters with readNCount()
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2. build decoding table 'DTable' from normalized counters
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3. decode the data stream using decoding table 'DTable'
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The following API allows targeting specific sub-functions for advanced tasks.
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For example, it's possible to compress several blocks using the same 'CTable',
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or to save and provide normalized distribution using external method.
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*/
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/* *** COMPRESSION *** */
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/*! FSE_optimalTableLog():
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dynamically downsize 'tableLog' when conditions are met.
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It saves CPU time, by using smaller tables, while preserving or even improving compression ratio.
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@return : recommended tableLog (necessarily <= 'maxTableLog') */
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FSE_PUBLIC_API unsigned FSE_optimalTableLog(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue);
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/*! FSE_normalizeCount():
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normalize counts so that sum(count[]) == Power_of_2 (2^tableLog)
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'normalizedCounter' is a table of short, of minimum size (maxSymbolValue+1).
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useLowProbCount is a boolean parameter which trades off compressed size for
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faster header decoding. When it is set to 1, the compressed data will be slightly
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smaller. And when it is set to 0, FSE_readNCount() and FSE_buildDTable() will be
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faster. If you are compressing a small amount of data (< 2 KB) then useLowProbCount=0
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is a good default, since header deserialization makes a big speed difference.
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Otherwise, useLowProbCount=1 is a good default, since the speed difference is small.
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@return : tableLog,
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or an errorCode, which can be tested using FSE_isError() */
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FSE_PUBLIC_API size_t FSE_normalizeCount(short* normalizedCounter, unsigned tableLog,
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const unsigned* count, size_t srcSize, unsigned maxSymbolValue, unsigned useLowProbCount);
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/*! FSE_NCountWriteBound():
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Provides the maximum possible size of an FSE normalized table, given 'maxSymbolValue' and 'tableLog'.
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Typically useful for allocation purpose. */
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FSE_PUBLIC_API size_t FSE_NCountWriteBound(unsigned maxSymbolValue, unsigned tableLog);
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/*! FSE_writeNCount():
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Compactly save 'normalizedCounter' into 'buffer'.
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@return : size of the compressed table,
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or an errorCode, which can be tested using FSE_isError(). */
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FSE_PUBLIC_API size_t FSE_writeNCount (void* buffer, size_t bufferSize,
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const short* normalizedCounter,
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unsigned maxSymbolValue, unsigned tableLog);
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/*! Constructor and Destructor of FSE_CTable.
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Note that FSE_CTable size depends on 'tableLog' and 'maxSymbolValue' */
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typedef unsigned FSE_CTable; /* don't allocate that. It's only meant to be more restrictive than void* */
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FSE_PUBLIC_API FSE_CTable* FSE_createCTable (unsigned maxSymbolValue, unsigned tableLog);
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FSE_PUBLIC_API void FSE_freeCTable (FSE_CTable* ct);
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/*! FSE_buildCTable():
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Builds `ct`, which must be already allocated, using FSE_createCTable().
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@return : 0, or an errorCode, which can be tested using FSE_isError() */
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FSE_PUBLIC_API size_t FSE_buildCTable(FSE_CTable* ct, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog);
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/*! FSE_compress_usingCTable():
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Compress `src` using `ct` into `dst` which must be already allocated.
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@return : size of compressed data (<= `dstCapacity`),
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or 0 if compressed data could not fit into `dst`,
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or an errorCode, which can be tested using FSE_isError() */
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FSE_PUBLIC_API size_t FSE_compress_usingCTable (void* dst, size_t dstCapacity, const void* src, size_t srcSize, const FSE_CTable* ct);
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/*!
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Tutorial :
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----------
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The first step is to count all symbols. FSE_count() does this job very fast.
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Result will be saved into 'count', a table of unsigned int, which must be already allocated, and have 'maxSymbolValuePtr[0]+1' cells.
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'src' is a table of bytes of size 'srcSize'. All values within 'src' MUST be <= maxSymbolValuePtr[0]
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maxSymbolValuePtr[0] will be updated, with its real value (necessarily <= original value)
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FSE_count() will return the number of occurrence of the most frequent symbol.
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This can be used to know if there is a single symbol within 'src', and to quickly evaluate its compressibility.
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If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError()).
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The next step is to normalize the frequencies.
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FSE_normalizeCount() will ensure that sum of frequencies is == 2 ^'tableLog'.
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It also guarantees a minimum of 1 to any Symbol with frequency >= 1.
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You can use 'tableLog'==0 to mean "use default tableLog value".
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If you are unsure of which tableLog value to use, you can ask FSE_optimalTableLog(),
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which will provide the optimal valid tableLog given sourceSize, maxSymbolValue, and a user-defined maximum (0 means "default").
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The result of FSE_normalizeCount() will be saved into a table,
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called 'normalizedCounter', which is a table of signed short.
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'normalizedCounter' must be already allocated, and have at least 'maxSymbolValue+1' cells.
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The return value is tableLog if everything proceeded as expected.
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It is 0 if there is a single symbol within distribution.
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If there is an error (ex: invalid tableLog value), the function will return an ErrorCode (which can be tested using FSE_isError()).
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'normalizedCounter' can be saved in a compact manner to a memory area using FSE_writeNCount().
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'buffer' must be already allocated.
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For guaranteed success, buffer size must be at least FSE_headerBound().
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The result of the function is the number of bytes written into 'buffer'.
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If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError(); ex : buffer size too small).
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'normalizedCounter' can then be used to create the compression table 'CTable'.
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The space required by 'CTable' must be already allocated, using FSE_createCTable().
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You can then use FSE_buildCTable() to fill 'CTable'.
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If there is an error, both functions will return an ErrorCode (which can be tested using FSE_isError()).
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'CTable' can then be used to compress 'src', with FSE_compress_usingCTable().
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Similar to FSE_count(), the convention is that 'src' is assumed to be a table of char of size 'srcSize'
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The function returns the size of compressed data (without header), necessarily <= `dstCapacity`.
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If it returns '0', compressed data could not fit into 'dst'.
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If there is an error, the function will return an ErrorCode (which can be tested using FSE_isError()).
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*/
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/* *** DECOMPRESSION *** */
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/*! FSE_readNCount():
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Read compactly saved 'normalizedCounter' from 'rBuffer'.
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@return : size read from 'rBuffer',
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or an errorCode, which can be tested using FSE_isError().
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maxSymbolValuePtr[0] and tableLogPtr[0] will also be updated with their respective values */
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FSE_PUBLIC_API size_t FSE_readNCount (short* normalizedCounter,
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unsigned* maxSymbolValuePtr, unsigned* tableLogPtr,
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const void* rBuffer, size_t rBuffSize);
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/*! FSE_readNCount_bmi2():
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* Same as FSE_readNCount() but pass bmi2=1 when your CPU supports BMI2 and 0 otherwise.
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*/
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FSE_PUBLIC_API size_t FSE_readNCount_bmi2(short* normalizedCounter,
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unsigned* maxSymbolValuePtr, unsigned* tableLogPtr,
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const void* rBuffer, size_t rBuffSize, int bmi2);
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/*! Constructor and Destructor of FSE_DTable.
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Note that its size depends on 'tableLog' */
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typedef unsigned FSE_DTable; /* don't allocate that. It's just a way to be more restrictive than void* */
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FSE_PUBLIC_API FSE_DTable* FSE_createDTable(unsigned tableLog);
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FSE_PUBLIC_API void FSE_freeDTable(FSE_DTable* dt);
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/*! FSE_buildDTable():
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Builds 'dt', which must be already allocated, using FSE_createDTable().
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return : 0, or an errorCode, which can be tested using FSE_isError() */
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FSE_PUBLIC_API size_t FSE_buildDTable (FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog);
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/*! FSE_decompress_usingDTable():
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Decompress compressed source `cSrc` of size `cSrcSize` using `dt`
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into `dst` which must be already allocated.
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@return : size of regenerated data (necessarily <= `dstCapacity`),
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or an errorCode, which can be tested using FSE_isError() */
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FSE_PUBLIC_API size_t FSE_decompress_usingDTable(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, const FSE_DTable* dt);
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/*!
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Tutorial :
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----------
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(Note : these functions only decompress FSE-compressed blocks.
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If block is uncompressed, use memcpy() instead
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If block is a single repeated byte, use memset() instead )
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The first step is to obtain the normalized frequencies of symbols.
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This can be performed by FSE_readNCount() if it was saved using FSE_writeNCount().
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'normalizedCounter' must be already allocated, and have at least 'maxSymbolValuePtr[0]+1' cells of signed short.
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In practice, that means it's necessary to know 'maxSymbolValue' beforehand,
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or size the table to handle worst case situations (typically 256).
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FSE_readNCount() will provide 'tableLog' and 'maxSymbolValue'.
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The result of FSE_readNCount() is the number of bytes read from 'rBuffer'.
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Note that 'rBufferSize' must be at least 4 bytes, even if useful information is less than that.
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If there is an error, the function will return an error code, which can be tested using FSE_isError().
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The next step is to build the decompression tables 'FSE_DTable' from 'normalizedCounter'.
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This is performed by the function FSE_buildDTable().
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The space required by 'FSE_DTable' must be already allocated using FSE_createDTable().
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If there is an error, the function will return an error code, which can be tested using FSE_isError().
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`FSE_DTable` can then be used to decompress `cSrc`, with FSE_decompress_usingDTable().
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`cSrcSize` must be strictly correct, otherwise decompression will fail.
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FSE_decompress_usingDTable() result will tell how many bytes were regenerated (<=`dstCapacity`).
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If there is an error, the function will return an error code, which can be tested using FSE_isError(). (ex: dst buffer too small)
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*/
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#endif /* FSE_H */
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#if defined(FSE_STATIC_LINKING_ONLY) && !defined(FSE_H_FSE_STATIC_LINKING_ONLY)
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#define FSE_H_FSE_STATIC_LINKING_ONLY
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/* *** Dependency *** */
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#include "bitstream.h"
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/* *****************************************
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* Static allocation
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*******************************************/
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/* FSE buffer bounds */
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#define FSE_NCOUNTBOUND 512
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#define FSE_BLOCKBOUND(size) ((size) + ((size)>>7) + 4 /* fse states */ + sizeof(size_t) /* bitContainer */)
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#define FSE_COMPRESSBOUND(size) (FSE_NCOUNTBOUND + FSE_BLOCKBOUND(size)) /* Macro version, useful for static allocation */
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/* It is possible to statically allocate FSE CTable/DTable as a table of FSE_CTable/FSE_DTable using below macros */
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#define FSE_CTABLE_SIZE_U32(maxTableLog, maxSymbolValue) (1 + (1<<((maxTableLog)-1)) + (((maxSymbolValue)+1)*2))
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#define FSE_DTABLE_SIZE_U32(maxTableLog) (1 + (1<<(maxTableLog)))
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/* or use the size to malloc() space directly. Pay attention to alignment restrictions though */
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#define FSE_CTABLE_SIZE(maxTableLog, maxSymbolValue) (FSE_CTABLE_SIZE_U32(maxTableLog, maxSymbolValue) * sizeof(FSE_CTable))
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#define FSE_DTABLE_SIZE(maxTableLog) (FSE_DTABLE_SIZE_U32(maxTableLog) * sizeof(FSE_DTable))
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/* *****************************************
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* FSE advanced API
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***************************************** */
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unsigned FSE_optimalTableLog_internal(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue, unsigned minus);
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/**< same as FSE_optimalTableLog(), which used `minus==2` */
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/* FSE_compress_wksp() :
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* Same as FSE_compress2(), but using an externally allocated scratch buffer (`workSpace`).
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* FSE_COMPRESS_WKSP_SIZE_U32() provides the minimum size required for `workSpace` as a table of FSE_CTable.
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*/
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#define FSE_COMPRESS_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) ( FSE_CTABLE_SIZE_U32(maxTableLog, maxSymbolValue) + ((maxTableLog > 12) ? (1 << (maxTableLog - 2)) : 1024) )
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size_t FSE_compress_wksp (void* dst, size_t dstSize, const void* src, size_t srcSize, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize);
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size_t FSE_buildCTable_raw (FSE_CTable* ct, unsigned nbBits);
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/**< build a fake FSE_CTable, designed for a flat distribution, where each symbol uses nbBits */
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size_t FSE_buildCTable_rle (FSE_CTable* ct, unsigned char symbolValue);
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/**< build a fake FSE_CTable, designed to compress always the same symbolValue */
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/* FSE_buildCTable_wksp() :
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* Same as FSE_buildCTable(), but using an externally allocated scratch buffer (`workSpace`).
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* `wkspSize` must be >= `FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog)` of `unsigned`.
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*/
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#define FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog) (maxSymbolValue + 2 + (1ull << (tableLog - 2)))
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#define FSE_BUILD_CTABLE_WORKSPACE_SIZE(maxSymbolValue, tableLog) (sizeof(unsigned) * FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog))
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size_t FSE_buildCTable_wksp(FSE_CTable* ct, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize);
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#define FSE_BUILD_DTABLE_WKSP_SIZE(maxTableLog, maxSymbolValue) (sizeof(short) * (maxSymbolValue + 1) + (1ULL << maxTableLog) + 8)
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#define FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) ((FSE_BUILD_DTABLE_WKSP_SIZE(maxTableLog, maxSymbolValue) + sizeof(unsigned) - 1) / sizeof(unsigned))
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FSE_PUBLIC_API size_t FSE_buildDTable_wksp(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize);
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/**< Same as FSE_buildDTable(), using an externally allocated `workspace` produced with `FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxSymbolValue)` */
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size_t FSE_buildDTable_raw (FSE_DTable* dt, unsigned nbBits);
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/**< build a fake FSE_DTable, designed to read a flat distribution where each symbol uses nbBits */
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size_t FSE_buildDTable_rle (FSE_DTable* dt, unsigned char symbolValue);
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/**< build a fake FSE_DTable, designed to always generate the same symbolValue */
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#define FSE_DECOMPRESS_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) (FSE_DTABLE_SIZE_U32(maxTableLog) + FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) + (FSE_MAX_SYMBOL_VALUE + 1) / 2 + 1)
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#define FSE_DECOMPRESS_WKSP_SIZE(maxTableLog, maxSymbolValue) (FSE_DECOMPRESS_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) * sizeof(unsigned))
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size_t FSE_decompress_wksp(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize);
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/**< same as FSE_decompress(), using an externally allocated `workSpace` produced with `FSE_DECOMPRESS_WKSP_SIZE_U32(maxLog, maxSymbolValue)` */
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size_t FSE_decompress_wksp_bmi2(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize, int bmi2);
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/**< Same as FSE_decompress_wksp() but with dynamic BMI2 support. Pass 1 if your CPU supports BMI2 or 0 if it doesn't. */
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typedef enum {
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FSE_repeat_none, /**< Cannot use the previous table */
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FSE_repeat_check, /**< Can use the previous table but it must be checked */
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FSE_repeat_valid /**< Can use the previous table and it is assumed to be valid */
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} FSE_repeat;
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/* *****************************************
|
|
* FSE symbol compression API
|
|
*******************************************/
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/*!
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This API consists of small unitary functions, which highly benefit from being inlined.
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|
Hence their body are included in next section.
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|
*/
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typedef struct {
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ptrdiff_t value;
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const void* stateTable;
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const void* symbolTT;
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unsigned stateLog;
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} FSE_CState_t;
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static void FSE_initCState(FSE_CState_t* CStatePtr, const FSE_CTable* ct);
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static void FSE_encodeSymbol(BIT_CStream_t* bitC, FSE_CState_t* CStatePtr, unsigned symbol);
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static void FSE_flushCState(BIT_CStream_t* bitC, const FSE_CState_t* CStatePtr);
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|
|
/**<
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These functions are inner components of FSE_compress_usingCTable().
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They allow the creation of custom streams, mixing multiple tables and bit sources.
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A key property to keep in mind is that encoding and decoding are done **in reverse direction**.
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So the first symbol you will encode is the last you will decode, like a LIFO stack.
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|
|
You will need a few variables to track your CStream. They are :
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|
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FSE_CTable ct; // Provided by FSE_buildCTable()
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BIT_CStream_t bitStream; // bitStream tracking structure
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FSE_CState_t state; // State tracking structure (can have several)
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|
The first thing to do is to init bitStream and state.
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size_t errorCode = BIT_initCStream(&bitStream, dstBuffer, maxDstSize);
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FSE_initCState(&state, ct);
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Note that BIT_initCStream() can produce an error code, so its result should be tested, using FSE_isError();
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You can then encode your input data, byte after byte.
|
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FSE_encodeSymbol() outputs a maximum of 'tableLog' bits at a time.
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Remember decoding will be done in reverse direction.
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|
FSE_encodeByte(&bitStream, &state, symbol);
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|
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At any time, you can also add any bit sequence.
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Note : maximum allowed nbBits is 25, for compatibility with 32-bits decoders
|
|
BIT_addBits(&bitStream, bitField, nbBits);
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|
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The above methods don't commit data to memory, they just store it into local register, for speed.
|
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Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t).
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|
Writing data to memory is a manual operation, performed by the flushBits function.
|
|
BIT_flushBits(&bitStream);
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|
|
Your last FSE encoding operation shall be to flush your last state value(s).
|
|
FSE_flushState(&bitStream, &state);
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|
|
Finally, you must close the bitStream.
|
|
The function returns the size of CStream in bytes.
|
|
If data couldn't fit into dstBuffer, it will return a 0 ( == not compressible)
|
|
If there is an error, it returns an errorCode (which can be tested using FSE_isError()).
|
|
size_t size = BIT_closeCStream(&bitStream);
|
|
*/
|
|
|
|
|
|
/* *****************************************
|
|
* FSE symbol decompression API
|
|
*******************************************/
|
|
typedef struct {
|
|
size_t state;
|
|
const void* table; /* precise table may vary, depending on U16 */
|
|
} FSE_DState_t;
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|
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|
|
static void FSE_initDState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD, const FSE_DTable* dt);
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|
|
static unsigned char FSE_decodeSymbol(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD);
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|
|
|
static unsigned FSE_endOfDState(const FSE_DState_t* DStatePtr);
|
|
|
|
/**<
|
|
Let's now decompose FSE_decompress_usingDTable() into its unitary components.
|
|
You will decode FSE-encoded symbols from the bitStream,
|
|
and also any other bitFields you put in, **in reverse order**.
|
|
|
|
You will need a few variables to track your bitStream. They are :
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|
|
|
BIT_DStream_t DStream; // Stream context
|
|
FSE_DState_t DState; // State context. Multiple ones are possible
|
|
FSE_DTable* DTablePtr; // Decoding table, provided by FSE_buildDTable()
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|
|
|
The first thing to do is to init the bitStream.
|
|
errorCode = BIT_initDStream(&DStream, srcBuffer, srcSize);
|
|
|
|
You should then retrieve your initial state(s)
|
|
(in reverse flushing order if you have several ones) :
|
|
errorCode = FSE_initDState(&DState, &DStream, DTablePtr);
|
|
|
|
You can then decode your data, symbol after symbol.
|
|
For information the maximum number of bits read by FSE_decodeSymbol() is 'tableLog'.
|
|
Keep in mind that symbols are decoded in reverse order, like a LIFO stack (last in, first out).
|
|
unsigned char symbol = FSE_decodeSymbol(&DState, &DStream);
|
|
|
|
You can retrieve any bitfield you eventually stored into the bitStream (in reverse order)
|
|
Note : maximum allowed nbBits is 25, for 32-bits compatibility
|
|
size_t bitField = BIT_readBits(&DStream, nbBits);
|
|
|
|
All above operations only read from local register (which size depends on size_t).
|
|
Refueling the register from memory is manually performed by the reload method.
|
|
endSignal = FSE_reloadDStream(&DStream);
|
|
|
|
BIT_reloadDStream() result tells if there is still some more data to read from DStream.
|
|
BIT_DStream_unfinished : there is still some data left into the DStream.
|
|
BIT_DStream_endOfBuffer : Dstream reached end of buffer. Its container may no longer be completely filled.
|
|
BIT_DStream_completed : Dstream reached its exact end, corresponding in general to decompression completed.
|
|
BIT_DStream_tooFar : Dstream went too far. Decompression result is corrupted.
|
|
|
|
When reaching end of buffer (BIT_DStream_endOfBuffer), progress slowly, notably if you decode multiple symbols per loop,
|
|
to properly detect the exact end of stream.
|
|
After each decoded symbol, check if DStream is fully consumed using this simple test :
|
|
BIT_reloadDStream(&DStream) >= BIT_DStream_completed
|
|
|
|
When it's done, verify decompression is fully completed, by checking both DStream and the relevant states.
|
|
Checking if DStream has reached its end is performed by :
|
|
BIT_endOfDStream(&DStream);
|
|
Check also the states. There might be some symbols left there, if some high probability ones (>50%) are possible.
|
|
FSE_endOfDState(&DState);
|
|
*/
|
|
|
|
|
|
/* *****************************************
|
|
* FSE unsafe API
|
|
*******************************************/
|
|
static unsigned char FSE_decodeSymbolFast(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD);
|
|
/* faster, but works only if nbBits is always >= 1 (otherwise, result will be corrupted) */
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|
|
|
|
|
/* *****************************************
|
|
* Implementation of inlined functions
|
|
*******************************************/
|
|
typedef struct {
|
|
int deltaFindState;
|
|
U32 deltaNbBits;
|
|
} FSE_symbolCompressionTransform; /* total 8 bytes */
|
|
|
|
MEM_STATIC void FSE_initCState(FSE_CState_t* statePtr, const FSE_CTable* ct)
|
|
{
|
|
const void* ptr = ct;
|
|
const U16* u16ptr = (const U16*) ptr;
|
|
const U32 tableLog = MEM_read16(ptr);
|
|
statePtr->value = (ptrdiff_t)1<<tableLog;
|
|
statePtr->stateTable = u16ptr+2;
|
|
statePtr->symbolTT = ct + 1 + (tableLog ? (1<<(tableLog-1)) : 1);
|
|
statePtr->stateLog = tableLog;
|
|
}
|
|
|
|
|
|
/*! FSE_initCState2() :
|
|
* Same as FSE_initCState(), but the first symbol to include (which will be the last to be read)
|
|
* uses the smallest state value possible, saving the cost of this symbol */
|
|
MEM_STATIC void FSE_initCState2(FSE_CState_t* statePtr, const FSE_CTable* ct, U32 symbol)
|
|
{
|
|
FSE_initCState(statePtr, ct);
|
|
{ const FSE_symbolCompressionTransform symbolTT = ((const FSE_symbolCompressionTransform*)(statePtr->symbolTT))[symbol];
|
|
const U16* stateTable = (const U16*)(statePtr->stateTable);
|
|
U32 nbBitsOut = (U32)((symbolTT.deltaNbBits + (1<<15)) >> 16);
|
|
statePtr->value = (nbBitsOut << 16) - symbolTT.deltaNbBits;
|
|
statePtr->value = stateTable[(statePtr->value >> nbBitsOut) + symbolTT.deltaFindState];
|
|
}
|
|
}
|
|
|
|
MEM_STATIC void FSE_encodeSymbol(BIT_CStream_t* bitC, FSE_CState_t* statePtr, unsigned symbol)
|
|
{
|
|
FSE_symbolCompressionTransform const symbolTT = ((const FSE_symbolCompressionTransform*)(statePtr->symbolTT))[symbol];
|
|
const U16* const stateTable = (const U16*)(statePtr->stateTable);
|
|
U32 const nbBitsOut = (U32)((statePtr->value + symbolTT.deltaNbBits) >> 16);
|
|
BIT_addBits(bitC, statePtr->value, nbBitsOut);
|
|
statePtr->value = stateTable[ (statePtr->value >> nbBitsOut) + symbolTT.deltaFindState];
|
|
}
|
|
|
|
MEM_STATIC void FSE_flushCState(BIT_CStream_t* bitC, const FSE_CState_t* statePtr)
|
|
{
|
|
BIT_addBits(bitC, statePtr->value, statePtr->stateLog);
|
|
BIT_flushBits(bitC);
|
|
}
|
|
|
|
|
|
/* FSE_getMaxNbBits() :
|
|
* Approximate maximum cost of a symbol, in bits.
|
|
* Fractional get rounded up (i.e : a symbol with a normalized frequency of 3 gives the same result as a frequency of 2)
|
|
* note 1 : assume symbolValue is valid (<= maxSymbolValue)
|
|
* note 2 : if freq[symbolValue]==0, @return a fake cost of tableLog+1 bits */
|
|
MEM_STATIC U32 FSE_getMaxNbBits(const void* symbolTTPtr, U32 symbolValue)
|
|
{
|
|
const FSE_symbolCompressionTransform* symbolTT = (const FSE_symbolCompressionTransform*) symbolTTPtr;
|
|
return (symbolTT[symbolValue].deltaNbBits + ((1<<16)-1)) >> 16;
|
|
}
|
|
|
|
/* FSE_bitCost() :
|
|
* Approximate symbol cost, as fractional value, using fixed-point format (accuracyLog fractional bits)
|
|
* note 1 : assume symbolValue is valid (<= maxSymbolValue)
|
|
* note 2 : if freq[symbolValue]==0, @return a fake cost of tableLog+1 bits */
|
|
MEM_STATIC U32 FSE_bitCost(const void* symbolTTPtr, U32 tableLog, U32 symbolValue, U32 accuracyLog)
|
|
{
|
|
const FSE_symbolCompressionTransform* symbolTT = (const FSE_symbolCompressionTransform*) symbolTTPtr;
|
|
U32 const minNbBits = symbolTT[symbolValue].deltaNbBits >> 16;
|
|
U32 const threshold = (minNbBits+1) << 16;
|
|
assert(tableLog < 16);
|
|
assert(accuracyLog < 31-tableLog); /* ensure enough room for renormalization double shift */
|
|
{ U32 const tableSize = 1 << tableLog;
|
|
U32 const deltaFromThreshold = threshold - (symbolTT[symbolValue].deltaNbBits + tableSize);
|
|
U32 const normalizedDeltaFromThreshold = (deltaFromThreshold << accuracyLog) >> tableLog; /* linear interpolation (very approximate) */
|
|
U32 const bitMultiplier = 1 << accuracyLog;
|
|
assert(symbolTT[symbolValue].deltaNbBits + tableSize <= threshold);
|
|
assert(normalizedDeltaFromThreshold <= bitMultiplier);
|
|
return (minNbBits+1)*bitMultiplier - normalizedDeltaFromThreshold;
|
|
}
|
|
}
|
|
|
|
|
|
/* ====== Decompression ====== */
|
|
|
|
typedef struct {
|
|
U16 tableLog;
|
|
U16 fastMode;
|
|
} FSE_DTableHeader; /* sizeof U32 */
|
|
|
|
typedef struct
|
|
{
|
|
unsigned short newState;
|
|
unsigned char symbol;
|
|
unsigned char nbBits;
|
|
} FSE_decode_t; /* size == U32 */
|
|
|
|
MEM_STATIC void FSE_initDState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD, const FSE_DTable* dt)
|
|
{
|
|
const void* ptr = dt;
|
|
const FSE_DTableHeader* const DTableH = (const FSE_DTableHeader*)ptr;
|
|
DStatePtr->state = BIT_readBits(bitD, DTableH->tableLog);
|
|
BIT_reloadDStream(bitD);
|
|
DStatePtr->table = dt + 1;
|
|
}
|
|
|
|
MEM_STATIC BYTE FSE_peekSymbol(const FSE_DState_t* DStatePtr)
|
|
{
|
|
FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
|
|
return DInfo.symbol;
|
|
}
|
|
|
|
MEM_STATIC void FSE_updateState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
|
|
{
|
|
FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
|
|
U32 const nbBits = DInfo.nbBits;
|
|
size_t const lowBits = BIT_readBits(bitD, nbBits);
|
|
DStatePtr->state = DInfo.newState + lowBits;
|
|
}
|
|
|
|
MEM_STATIC BYTE FSE_decodeSymbol(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
|
|
{
|
|
FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
|
|
U32 const nbBits = DInfo.nbBits;
|
|
BYTE const symbol = DInfo.symbol;
|
|
size_t const lowBits = BIT_readBits(bitD, nbBits);
|
|
|
|
DStatePtr->state = DInfo.newState + lowBits;
|
|
return symbol;
|
|
}
|
|
|
|
/*! FSE_decodeSymbolFast() :
|
|
unsafe, only works if no symbol has a probability > 50% */
|
|
MEM_STATIC BYTE FSE_decodeSymbolFast(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
|
|
{
|
|
FSE_decode_t const DInfo = ((const FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
|
|
U32 const nbBits = DInfo.nbBits;
|
|
BYTE const symbol = DInfo.symbol;
|
|
size_t const lowBits = BIT_readBitsFast(bitD, nbBits);
|
|
|
|
DStatePtr->state = DInfo.newState + lowBits;
|
|
return symbol;
|
|
}
|
|
|
|
MEM_STATIC unsigned FSE_endOfDState(const FSE_DState_t* DStatePtr)
|
|
{
|
|
return DStatePtr->state == 0;
|
|
}
|
|
|
|
|
|
|
|
#ifndef FSE_COMMONDEFS_ONLY
|
|
|
|
/* **************************************************************
|
|
* Tuning parameters
|
|
****************************************************************/
|
|
/*!MEMORY_USAGE :
|
|
* Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.)
|
|
* Increasing memory usage improves compression ratio
|
|
* Reduced memory usage can improve speed, due to cache effect
|
|
* Recommended max value is 14, for 16KB, which nicely fits into Intel x86 L1 cache */
|
|
#ifndef FSE_MAX_MEMORY_USAGE
|
|
# define FSE_MAX_MEMORY_USAGE 14
|
|
#endif
|
|
#ifndef FSE_DEFAULT_MEMORY_USAGE
|
|
# define FSE_DEFAULT_MEMORY_USAGE 13
|
|
#endif
|
|
#if (FSE_DEFAULT_MEMORY_USAGE > FSE_MAX_MEMORY_USAGE)
|
|
# error "FSE_DEFAULT_MEMORY_USAGE must be <= FSE_MAX_MEMORY_USAGE"
|
|
#endif
|
|
|
|
/*!FSE_MAX_SYMBOL_VALUE :
|
|
* Maximum symbol value authorized.
|
|
* Required for proper stack allocation */
|
|
#ifndef FSE_MAX_SYMBOL_VALUE
|
|
# define FSE_MAX_SYMBOL_VALUE 255
|
|
#endif
|
|
|
|
/* **************************************************************
|
|
* template functions type & suffix
|
|
****************************************************************/
|
|
#define FSE_FUNCTION_TYPE BYTE
|
|
#define FSE_FUNCTION_EXTENSION
|
|
#define FSE_DECODE_TYPE FSE_decode_t
|
|
|
|
|
|
#endif /* !FSE_COMMONDEFS_ONLY */
|
|
|
|
|
|
/* ***************************************************************
|
|
* Constants
|
|
*****************************************************************/
|
|
#define FSE_MAX_TABLELOG (FSE_MAX_MEMORY_USAGE-2)
|
|
#define FSE_MAX_TABLESIZE (1U<<FSE_MAX_TABLELOG)
|
|
#define FSE_MAXTABLESIZE_MASK (FSE_MAX_TABLESIZE-1)
|
|
#define FSE_DEFAULT_TABLELOG (FSE_DEFAULT_MEMORY_USAGE-2)
|
|
#define FSE_MIN_TABLELOG 5
|
|
|
|
#define FSE_TABLELOG_ABSOLUTE_MAX 15
|
|
#if FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX
|
|
# error "FSE_MAX_TABLELOG > FSE_TABLELOG_ABSOLUTE_MAX is not supported"
|
|
#endif
|
|
|
|
#define FSE_TABLESTEP(tableSize) (((tableSize)>>1) + ((tableSize)>>3) + 3)
|
|
|
|
|
|
#endif /* FSE_STATIC_LINKING_ONLY */
|
|
|
|
|
|
#if defined (__cplusplus)
|
|
}
|
|
#endif
|