mirror of
https://github.com/facebook/zstd.git
synced 2024-12-15 06:57:21 +08:00
296 lines
14 KiB
C
296 lines
14 KiB
C
/* ******************************************************************
|
|
FSE : Finite State Entropy coder
|
|
header file
|
|
Copyright (C) 2013-2015, Yann Collet.
|
|
|
|
BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
|
|
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, are permitted provided that the following conditions are
|
|
met:
|
|
|
|
* Redistributions of source code must retain the above copyright
|
|
notice, this list of conditions and the following disclaimer.
|
|
* Redistributions in binary form must reproduce the above
|
|
copyright notice, this list of conditions and the following disclaimer
|
|
in the documentation and/or other materials provided with the
|
|
distribution.
|
|
|
|
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
|
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
|
|
You can contact the author at :
|
|
- Source repository : https://github.com/Cyan4973/FiniteStateEntropy
|
|
- Public forum : https://groups.google.com/forum/#!forum/lz4c
|
|
****************************************************************** */
|
|
#ifndef FSE_H
|
|
#define FSE_H
|
|
|
|
#if defined (__cplusplus)
|
|
extern "C" {
|
|
#endif
|
|
|
|
|
|
/* *****************************************
|
|
* Includes
|
|
******************************************/
|
|
#include <stddef.h> /* size_t, ptrdiff_t */
|
|
|
|
|
|
/*-****************************************
|
|
* FSE simple functions
|
|
******************************************/
|
|
size_t FSE_compress(void* dst, size_t maxDstSize,
|
|
const void* src, size_t srcSize);
|
|
size_t FSE_decompress(void* dst, size_t maxDstSize,
|
|
const void* cSrc, size_t cSrcSize);
|
|
/*!
|
|
FSE_compress():
|
|
Compress content of buffer 'src', of size 'srcSize', into destination buffer 'dst'.
|
|
'dst' buffer must be already allocated. Compression runs faster is maxDstSize >= FSE_compressBound(srcSize)
|
|
return : size of compressed data (<= maxDstSize)
|
|
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_decompress():
|
|
Decompress FSE data from buffer 'cSrc', of size 'cSrcSize',
|
|
into already allocated destination buffer 'dst', of size 'maxDstSize'.
|
|
return : size of regenerated data (<= maxDstSize)
|
|
or an error code, which can be tested using FSE_isError()
|
|
|
|
** Important ** : FSE_decompress() doesn't 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.
|
|
*/
|
|
|
|
|
|
/* *****************************************
|
|
* Tool functions
|
|
******************************************/
|
|
size_t FSE_compressBound(size_t size); /* maximum compressed size */
|
|
|
|
/* Error Management */
|
|
unsigned FSE_isError(size_t code); /* tells if a return value is an error code */
|
|
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.
|
|
*/
|
|
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[]
|
|
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_count():
|
|
Provides the precise count of each byte within a table 'count'
|
|
'count' is a table of unsigned int, of minimum size (*maxSymbolValuePtr+1).
|
|
*maxSymbolValuePtr will be updated if detected smaller than initial value.
|
|
@return : the count of the most frequent symbol (which is not identified)
|
|
if return == srcSize, there is only one symbol.
|
|
Can also return an error code, which can be tested with FSE_isError() */
|
|
size_t FSE_count(unsigned* count, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize);
|
|
|
|
/*!
|
|
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 <= initial 'tableLog') */
|
|
unsigned FSE_optimalTableLog(unsigned tableLog, size_t srcSize, unsigned maxSymbolValue);
|
|
|
|
/*!
|
|
FSE_normalizeCount():
|
|
normalize counters so that sum(count[]) == Power_of_2 (2^tableLog)
|
|
'normalizedCounter' is a table of short, of minimum size (maxSymbolValue+1).
|
|
return : tableLog,
|
|
or an errorCode, which can be tested using FSE_isError() */
|
|
size_t FSE_normalizeCount(short* normalizedCounter, unsigned tableLog, const unsigned* count, size_t srcSize, unsigned maxSymbolValue);
|
|
|
|
/*!
|
|
FSE_NCountWriteBound():
|
|
Provides the maximum possible size of an FSE normalized table, given 'maxSymbolValue' and 'tableLog'
|
|
Typically useful for allocation purpose. */
|
|
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() */
|
|
size_t FSE_writeNCount (void* buffer, size_t bufferSize, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog);
|
|
|
|
|
|
/*!
|
|
Constructor and Destructor of type FSE_CTable
|
|
Note that its 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_CTable* FSE_createCTable (unsigned tableLog, unsigned maxSymbolValue);
|
|
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() */
|
|
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() */
|
|
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 */
|
|
size_t FSE_readNCount (short* normalizedCounter, unsigned* maxSymbolValuePtr, unsigned* tableLogPtr, const void* rBuffer, size_t rBuffSize);
|
|
|
|
/*!
|
|
Constructor and Destructor of type 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_DTable* FSE_createDTable(unsigned tableLog);
|
|
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() */
|
|
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() */
|
|
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 (<=maxDstSize).
|
|
If there is an error, the function will return an error code, which can be tested using FSE_isError(). (ex: dst buffer too small)
|
|
*/
|
|
|
|
|
|
#if defined (__cplusplus)
|
|
}
|
|
#endif
|
|
|
|
#endif /* FSE_H */
|