/* ******************************************************************
 * FSE : Finite State Entropy codec
 * Public Prototypes declaration
 * Copyright (c) 2013-2020, Yann Collet, Facebook, Inc.
 *
 * 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.
****************************************************************** */

#ifndef FSE_H
#define FSE_H


/*-*****************************************
*  Dependencies
******************************************/
#include <stddef.h>    /* size_t, ptrdiff_t */


namespace duckdb_zstd {
/*-*****************************************
*  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).
    @return : tableLog,
              or an errorCode, which can be tested using FSE_isError() */
FSE_PUBLIC_API 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. */
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);

/*! 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 */

