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/* ******************************************************************
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* FSE : Finite State Entropy codec
* Public Prototypes declaration
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* Copyright ( c ) Yann Collet , Facebook , Inc .
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*
* You can contact the author at :
* - Source repository : https : //github.com/Cyan4973/FiniteStateEntropy
*
* This source code is licensed under both the BSD - style license ( found in the
* LICENSE file in the root directory of this source tree ) and the GPLv2 ( found
* in the COPYING file in the root directory of this source tree ) .
* You may select , at your option , one of the above - listed licenses .
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
# if defined (__cplusplus)
extern " C " {
# endif
# ifndef FSE_H
# define FSE_H
/*-*****************************************
* Dependencies
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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# include "zstd_deps.h" /* size_t, ptrdiff_t */
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/*-*****************************************
* FSE_PUBLIC_API : control library symbols visibility
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
# if defined(FSE_DLL_EXPORT) && (FSE_DLL_EXPORT==1) && defined(__GNUC__) && (__GNUC__ >= 4)
# define FSE_PUBLIC_API __attribute__ ((visibility ("default")))
# elif defined(FSE_DLL_EXPORT) && (FSE_DLL_EXPORT==1) /* Visual expected */
# define FSE_PUBLIC_API __declspec(dllexport)
# elif defined(FSE_DLL_IMPORT) && (FSE_DLL_IMPORT==1)
# 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.*/
# else
# define FSE_PUBLIC_API
# endif
/*------ Version ------*/
# define FSE_VERSION_MAJOR 0
# define FSE_VERSION_MINOR 9
# define FSE_VERSION_RELEASE 0
# define FSE_LIB_VERSION FSE_VERSION_MAJOR.FSE_VERSION_MINOR.FSE_VERSION_RELEASE
# define FSE_QUOTE(str) #str
# define FSE_EXPAND_AND_QUOTE(str) FSE_QUOTE(str)
# define FSE_VERSION_STRING FSE_EXPAND_AND_QUOTE(FSE_LIB_VERSION)
# define FSE_VERSION_NUMBER (FSE_VERSION_MAJOR *100*100 + FSE_VERSION_MINOR *100 + FSE_VERSION_RELEASE)
FSE_PUBLIC_API unsigned FSE_versionNumber ( void ) ; /**< library version number; to be used when checking dll version */
/*-****************************************
* FSE simple functions
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*! FSE_compress() :
Compress content of buffer ' src ' , of size ' srcSize ' , into destination buffer ' dst ' .
' dst ' buffer must be already allocated . Compression runs faster is dstCapacity > = FSE_compressBound ( srcSize ) .
@ return : size of compressed data ( < = dstCapacity ) .
Special values : if return = = 0 , srcData is not compressible = > Nothing is stored within dst ! ! !
if return = = 1 , srcData is a single byte symbol * srcSize times . Use RLE compression instead .
if FSE_isError ( return ) , compression failed ( more details using FSE_getErrorName ( ) )
*/
FSE_PUBLIC_API size_t FSE_compress ( void * dst , size_t dstCapacity ,
const void * src , size_t srcSize ) ;
/*! FSE_decompress():
Decompress FSE data from buffer ' cSrc ' , of size ' cSrcSize ' ,
into already allocated destination buffer ' dst ' , of size ' dstCapacity ' .
@ return : size of regenerated data ( < = maxDstSize ) ,
or an error code , which can be tested using FSE_isError ( ) .
* * Important * * : FSE_decompress ( ) does not decompress non - compressible nor RLE data ! ! !
Why ? : making this distinction requires a header .
Header management is intentionally delegated to the user layer , which can better manage special cases .
*/
FSE_PUBLIC_API size_t FSE_decompress ( void * dst , size_t dstCapacity ,
const void * cSrc , size_t cSrcSize ) ;
/*-*****************************************
* Tool functions
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
FSE_PUBLIC_API size_t FSE_compressBound ( size_t size ) ; /* maximum compressed size */
/* Error Management */
FSE_PUBLIC_API unsigned FSE_isError ( size_t code ) ; /* tells if a return value is an error code */
FSE_PUBLIC_API const char * FSE_getErrorName ( size_t code ) ; /* provides error code string (useful for debugging) */
/*-*****************************************
* FSE advanced functions
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*! FSE_compress2() :
Same as FSE_compress ( ) , but allows the selection of ' maxSymbolValue ' and ' tableLog '
Both parameters can be defined as ' 0 ' to mean : use default value
@ return : size of compressed data
Special values : if return = = 0 , srcData is not compressible = > Nothing is stored within cSrc ! ! !
if return = = 1 , srcData is a single byte symbol * srcSize times . Use RLE compression .
if FSE_isError ( return ) , it ' s an error code .
*/
FSE_PUBLIC_API size_t FSE_compress2 ( void * dst , size_t dstSize , const void * src , size_t srcSize , unsigned maxSymbolValue , unsigned tableLog ) ;
/*-*****************************************
* FSE detailed API
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*!
FSE_compress ( ) does the following :
1. count symbol occurrence from source [ ] into table count [ ] ( see hist . h )
2. normalize counters so that sum ( count [ ] ) = = Power_of_2 ( 2 ^ tableLog )
3. save normalized counters to memory buffer using writeNCount ( )
4. build encoding table ' CTable ' from normalized counters
5. encode the data stream using encoding table ' CTable '
FSE_decompress ( ) does the following :
1. read normalized counters with readNCount ( )
2. build decoding table ' DTable ' from normalized counters
3. decode the data stream using decoding table ' DTable '
The following API allows targeting specific sub - functions for advanced tasks .
For example , it ' s possible to compress several blocks using the same ' CTable ' ,
or to save and provide normalized distribution using external method .
*/
/* *** COMPRESSION *** */
/*! FSE_optimalTableLog():
dynamically downsize ' tableLog ' when conditions are met .
It saves CPU time , by using smaller tables , while preserving or even improving compression ratio .
@ return : recommended tableLog ( necessarily < = ' maxTableLog ' ) */
FSE_PUBLIC_API unsigned FSE_optimalTableLog ( unsigned maxTableLog , size_t srcSize , unsigned maxSymbolValue ) ;
/*! FSE_normalizeCount():
normalize counts so that sum ( count [ ] ) = = Power_of_2 ( 2 ^ tableLog )
' 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
faster header decoding . When it is set to 1 , the compressed data will be slightly
smaller . And when it is set to 0 , FSE_readNCount ( ) and FSE_buildDTable ( ) will be
faster . If you are compressing a small amount of data ( < 2 KB ) then useLowProbCount = 0
is a good default , since header deserialization makes a big speed difference .
Otherwise , useLowProbCount = 1 is a good default , since the speed difference is small .
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@ return : tableLog ,
or an errorCode , which can be tested using FSE_isError ( ) */
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():
Provides the maximum possible size of an FSE normalized table , given ' maxSymbolValue ' and ' tableLog ' .
Typically useful for allocation purpose . */
FSE_PUBLIC_API size_t FSE_NCountWriteBound ( unsigned maxSymbolValue , unsigned tableLog ) ;
/*! FSE_writeNCount():
Compactly save ' normalizedCounter ' into ' buffer ' .
@ return : size of the compressed table ,
or an errorCode , which can be tested using FSE_isError ( ) . */
FSE_PUBLIC_API size_t FSE_writeNCount ( void * buffer , size_t bufferSize ,
const short * normalizedCounter ,
unsigned maxSymbolValue , unsigned tableLog ) ;
/*! Constructor and Destructor of FSE_CTable.
Note that FSE_CTable size depends on ' tableLog ' and ' maxSymbolValue ' */
typedef unsigned FSE_CTable ; /* don't allocate that. It's only meant to be more restrictive than void* */
FSE_PUBLIC_API FSE_CTable * FSE_createCTable ( unsigned maxSymbolValue , unsigned tableLog ) ;
FSE_PUBLIC_API void FSE_freeCTable ( FSE_CTable * ct ) ;
/*! FSE_buildCTable():
Builds ` ct ` , which must be already allocated , using FSE_createCTable ( ) .
@ return : 0 , or an errorCode , which can be tested using FSE_isError ( ) */
FSE_PUBLIC_API size_t FSE_buildCTable ( FSE_CTable * ct , const short * normalizedCounter , unsigned maxSymbolValue , unsigned tableLog ) ;
/*! FSE_compress_usingCTable():
Compress ` src ` using ` ct ` into ` dst ` which must be already allocated .
@ return : size of compressed data ( < = ` dstCapacity ` ) ,
or 0 if compressed data could not fit into ` dst ` ,
or an errorCode , which can be tested using FSE_isError ( ) */
FSE_PUBLIC_API size_t FSE_compress_usingCTable ( void * dst , size_t dstCapacity , const void * src , size_t srcSize , const FSE_CTable * ct ) ;
/*!
Tutorial :
- - - - - - - - - -
The first step is to count all symbols . FSE_count ( ) does this job very fast .
Result will be saved into ' count ' , a table of unsigned int , which must be already allocated , and have ' maxSymbolValuePtr [ 0 ] + 1 ' cells .
' src ' is a table of bytes of size ' srcSize ' . All values within ' src ' MUST be < = maxSymbolValuePtr [ 0 ]
maxSymbolValuePtr [ 0 ] will be updated , with its real value ( necessarily < = original value )
FSE_count ( ) will return the number of occurrence of the most frequent symbol .
This can be used to know if there is a single symbol within ' src ' , and to quickly evaluate its compressibility .
If there is an error , the function will return an ErrorCode ( which can be tested using FSE_isError ( ) ) .
The next step is to normalize the frequencies .
FSE_normalizeCount ( ) will ensure that sum of frequencies is = = 2 ^ ' tableLog ' .
It also guarantees a minimum of 1 to any Symbol with frequency > = 1.
You can use ' tableLog ' = = 0 to mean " use default tableLog value " .
If you are unsure of which tableLog value to use , you can ask FSE_optimalTableLog ( ) ,
which will provide the optimal valid tableLog given sourceSize , maxSymbolValue , and a user - defined maximum ( 0 means " default " ) .
The result of FSE_normalizeCount ( ) will be saved into a table ,
called ' normalizedCounter ' , which is a table of signed short .
' normalizedCounter ' must be already allocated , and have at least ' maxSymbolValue + 1 ' cells .
The return value is tableLog if everything proceeded as expected .
It is 0 if there is a single symbol within distribution .
If there is an error ( ex : invalid tableLog value ) , the function will return an ErrorCode ( which can be tested using FSE_isError ( ) ) .
' normalizedCounter ' can be saved in a compact manner to a memory area using FSE_writeNCount ( ) .
' buffer ' must be already allocated .
For guaranteed success , buffer size must be at least FSE_headerBound ( ) .
The result of the function is the number of bytes written into ' buffer ' .
If there is an error , the function will return an ErrorCode ( which can be tested using FSE_isError ( ) ; ex : buffer size too small ) .
' normalizedCounter ' can then be used to create the compression table ' CTable ' .
The space required by ' CTable ' must be already allocated , using FSE_createCTable ( ) .
You can then use FSE_buildCTable ( ) to fill ' CTable ' .
If there is an error , both functions will return an ErrorCode ( which can be tested using FSE_isError ( ) ) .
' CTable ' can then be used to compress ' src ' , with FSE_compress_usingCTable ( ) .
Similar to FSE_count ( ) , the convention is that ' src ' is assumed to be a table of char of size ' srcSize '
The function returns the size of compressed data ( without header ) , necessarily < = ` dstCapacity ` .
If it returns ' 0 ' , compressed data could not fit into ' dst ' .
If there is an error , the function will return an ErrorCode ( which can be tested using FSE_isError ( ) ) .
*/
/* *** DECOMPRESSION *** */
/*! FSE_readNCount():
Read compactly saved ' normalizedCounter ' from ' rBuffer ' .
@ return : size read from ' rBuffer ' ,
or an errorCode , which can be tested using FSE_isError ( ) .
maxSymbolValuePtr [ 0 ] and tableLogPtr [ 0 ] will also be updated with their respective values */
FSE_PUBLIC_API size_t FSE_readNCount ( short * normalizedCounter ,
unsigned * maxSymbolValuePtr , unsigned * tableLogPtr ,
const void * rBuffer , size_t rBuffSize ) ;
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/*! FSE_readNCount_bmi2():
* Same as FSE_readNCount ( ) but pass bmi2 = 1 when your CPU supports BMI2 and 0 otherwise .
*/
FSE_PUBLIC_API size_t FSE_readNCount_bmi2 ( short * normalizedCounter ,
unsigned * maxSymbolValuePtr , unsigned * tableLogPtr ,
const void * rBuffer , size_t rBuffSize , int bmi2 ) ;
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/*! Constructor and Destructor of FSE_DTable.
Note that its size depends on ' tableLog ' */
typedef unsigned FSE_DTable ; /* don't allocate that. It's just a way to be more restrictive than void* */
FSE_PUBLIC_API FSE_DTable * FSE_createDTable ( unsigned tableLog ) ;
FSE_PUBLIC_API void FSE_freeDTable ( FSE_DTable * dt ) ;
/*! FSE_buildDTable():
Builds ' dt ' , which must be already allocated , using FSE_createDTable ( ) .
return : 0 , or an errorCode , which can be tested using FSE_isError ( ) */
FSE_PUBLIC_API size_t FSE_buildDTable ( FSE_DTable * dt , const short * normalizedCounter , unsigned maxSymbolValue , unsigned tableLog ) ;
/*! FSE_decompress_usingDTable():
Decompress compressed source ` cSrc ` of size ` cSrcSize ` using ` dt `
into ` dst ` which must be already allocated .
@ return : size of regenerated data ( necessarily < = ` dstCapacity ` ) ,
or an errorCode , which can be tested using FSE_isError ( ) */
FSE_PUBLIC_API size_t FSE_decompress_usingDTable ( void * dst , size_t dstCapacity , const void * cSrc , size_t cSrcSize , const FSE_DTable * dt ) ;
/*!
Tutorial :
- - - - - - - - - -
( Note : these functions only decompress FSE - compressed blocks .
If block is uncompressed , use memcpy ( ) instead
If block is a single repeated byte , use memset ( ) instead )
The first step is to obtain the normalized frequencies of symbols .
This can be performed by FSE_readNCount ( ) if it was saved using FSE_writeNCount ( ) .
' normalizedCounter ' must be already allocated , and have at least ' maxSymbolValuePtr [ 0 ] + 1 ' cells of signed short .
In practice , that means it ' s necessary to know ' maxSymbolValue ' beforehand ,
or size the table to handle worst case situations ( typically 256 ) .
FSE_readNCount ( ) will provide ' tableLog ' and ' maxSymbolValue ' .
The result of FSE_readNCount ( ) is the number of bytes read from ' rBuffer ' .
Note that ' rBufferSize ' must be at least 4 bytes , even if useful information is less than that .
If there is an error , the function will return an error code , which can be tested using FSE_isError ( ) .
The next step is to build the decompression tables ' FSE_DTable ' from ' normalizedCounter ' .
This is performed by the function FSE_buildDTable ( ) .
The space required by ' FSE_DTable ' must be already allocated using FSE_createDTable ( ) .
If there is an error , the function will return an error code , which can be tested using FSE_isError ( ) .
` FSE_DTable ` can then be used to decompress ` cSrc ` , with FSE_decompress_usingDTable ( ) .
` cSrcSize ` must be strictly correct , otherwise decompression will fail .
FSE_decompress_usingDTable ( ) result will tell how many bytes were regenerated ( < = ` dstCapacity ` ) .
If there is an error , the function will return an error code , which can be tested using FSE_isError ( ) . ( ex : dst buffer too small )
*/
# endif /* FSE_H */
# if defined(FSE_STATIC_LINKING_ONLY) && !defined(FSE_H_FSE_STATIC_LINKING_ONLY)
# define FSE_H_FSE_STATIC_LINKING_ONLY
/* *** Dependency *** */
# include "bitstream.h"
/* *****************************************
* Static allocation
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/* FSE buffer bounds */
# 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 */
/* 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))
# 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 */
# define FSE_CTABLE_SIZE(maxTableLog, maxSymbolValue) (FSE_CTABLE_SIZE_U32(maxTableLog, maxSymbolValue) * sizeof(FSE_CTable))
# define FSE_DTABLE_SIZE(maxTableLog) (FSE_DTABLE_SIZE_U32(maxTableLog) * sizeof(FSE_DTable))
/* *****************************************
* FSE advanced API
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
unsigned FSE_optimalTableLog_internal ( unsigned maxTableLog , size_t srcSize , unsigned maxSymbolValue , unsigned minus ) ;
/**< same as FSE_optimalTableLog(), which used `minus==2` */
/* FSE_compress_wksp() :
* 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 ) ;
size_t FSE_buildCTable_raw ( FSE_CTable * ct , unsigned nbBits ) ;
/**< build a fake FSE_CTable, designed for a flat distribution, where each symbol uses nbBits */
size_t FSE_buildCTable_rle ( FSE_CTable * ct , unsigned char symbolValue ) ;
/**< build a fake FSE_CTable, designed to compress always the same symbolValue */
/* FSE_buildCTable_wksp() :
* 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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* See FSE_buildCTable_wksp ( ) for breakdown of workspace usage .
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*/
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# define FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(maxSymbolValue, tableLog) (((maxSymbolValue + 2) + (1ull << (tableLog))) / 2 + sizeof(U64) / sizeof(U32) /* additional 8 bytes for potential table overwrite */ )
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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)
# define FSE_BUILD_DTABLE_WKSP_SIZE_U32(maxTableLog, maxSymbolValue) ((FSE_BUILD_DTABLE_WKSP_SIZE(maxTableLog, maxSymbolValue) + sizeof(unsigned) - 1) / sizeof(unsigned))
FSE_PUBLIC_API size_t FSE_buildDTable_wksp ( FSE_DTable * dt , const short * normalizedCounter , unsigned maxSymbolValue , unsigned tableLog , void * workSpace , size_t wkspSize ) ;
/**< 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 ) ;
/**< build a fake FSE_DTable, designed to read a flat distribution where each symbol uses nbBits */
size_t FSE_buildDTable_rle ( FSE_DTable * dt , unsigned char symbolValue ) ;
/**< 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))
size_t FSE_decompress_wksp ( void * dst , size_t dstCapacity , const void * cSrc , size_t cSrcSize , unsigned maxLog , void * workSpace , size_t wkspSize ) ;
/**< same as FSE_decompress(), using an externally allocated `workSpace` produced with `FSE_DECOMPRESS_WKSP_SIZE_U32(maxLog, maxSymbolValue)` */
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 ) ;
/**< 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 {
FSE_repeat_none , /**< Cannot use the previous table */
FSE_repeat_check , /**< Can use the previous table but it must be checked */
FSE_repeat_valid /**< Can use the previous table and it is assumed to be valid */
} FSE_repeat ;
/* *****************************************
* FSE symbol compression API
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*!
This API consists of small unitary functions , which highly benefit from being inlined .
Hence their body are included in next section .
*/
typedef struct {
ptrdiff_t value ;
const void * stateTable ;
const void * symbolTT ;
unsigned stateLog ;
} FSE_CState_t ;
static void FSE_initCState ( FSE_CState_t * CStatePtr , const FSE_CTable * ct ) ;
static void FSE_encodeSymbol ( BIT_CStream_t * bitC , FSE_CState_t * CStatePtr , unsigned symbol ) ;
static void FSE_flushCState ( BIT_CStream_t * bitC , const FSE_CState_t * CStatePtr ) ;
/**<
These functions are inner components of FSE_compress_usingCTable ( ) .
They allow the creation of custom streams , mixing multiple tables and bit sources .
A key property to keep in mind is that encoding and decoding are done * * in reverse direction * * .
So the first symbol you will encode is the last you will decode , like a LIFO stack .
You will need a few variables to track your CStream . They are :
FSE_CTable ct ; // Provided by FSE_buildCTable()
BIT_CStream_t bitStream ; // bitStream tracking structure
FSE_CState_t state ; // State tracking structure (can have several)
The first thing to do is to init bitStream and state .
size_t errorCode = BIT_initCStream ( & bitStream , dstBuffer , maxDstSize ) ;
FSE_initCState ( & state , ct ) ;
Note that BIT_initCStream ( ) can produce an error code , so its result should be tested , using FSE_isError ( ) ;
You can then encode your input data , byte after byte .
FSE_encodeSymbol ( ) outputs a maximum of ' tableLog ' bits at a time .
Remember decoding will be done in reverse direction .
FSE_encodeByte ( & bitStream , & state , symbol ) ;
At any time , you can also add any bit sequence .
Note : maximum allowed nbBits is 25 , for compatibility with 32 - bits decoders
BIT_addBits ( & bitStream , bitField , nbBits ) ;
The above methods don ' t commit data to memory , they just store it into local register , for speed .
Local register size is 64 - bits on 64 - bits systems , 32 - bits on 32 - bits systems ( size_t ) .
Writing data to memory is a manual operation , performed by the flushBits function .
BIT_flushBits ( & bitStream ) ;
Your last FSE encoding operation shall be to flush your last state value ( s ) .
FSE_flushState ( & bitStream , & state ) ;
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 ;
static void FSE_initDState ( FSE_DState_t * DStatePtr , BIT_DStream_t * bitD , const FSE_DTable * dt ) ;
static unsigned char FSE_decodeSymbol ( FSE_DState_t * DStatePtr , BIT_DStream_t * bitD ) ;
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 :
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()
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) */
/* *****************************************
* 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 - > 1 KB ; 12 - > 4 KB ; 16 - > 64 KB ; 20 - > 1 MB ; etc . )
* Increasing memory usage improves compression ratio
* Reduced memory usage can improve speed , due to cache effect
* Recommended max value is 14 , for 16 KB , 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
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# if (FSE_DEFAULT_MEMORY_USAGE > FSE_MAX_MEMORY_USAGE)
# error "FSE_DEFAULT_MEMORY_USAGE must be <= FSE_MAX_MEMORY_USAGE"
# endif
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/*!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
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# define FSE_TABLESTEP(tableSize) (((tableSize)>>1) + ((tableSize)>>3) + 3)
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# endif /* FSE_STATIC_LINKING_ONLY */
# if defined (__cplusplus)
}
# endif
