/* ******************************************************************

   bitstream

   Part of FSE library

   header file (to include)

   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

****************************************************************** */

#ifndef BITSTREAM_H_MODULE

#define BITSTREAM_H_MODULE

#if defined (__cplusplus)

extern "C" {

#endif

/*

*  This API consists of small unitary functions, which must be inlined for best performance.

*  Since link-time-optimization is not available for all compilers,

*  these functions are defined into a .h to be included.

*/

/*-****************************************

*  Dependencies

******************************************/

#include "mem.h"            /* unaligned access routines */

#include "error_private.h"  /* error codes and messages */

/*=========================================

*  Target specific

=========================================*/

#if defined(__BMI__) && defined(__GNUC__)

#  include <immintrin.h>   /* support for bextr (experimental) */

#endif

/*-******************************************

*  bitStream encoding API (write forward)

********************************************/

/* bitStream can mix input from multiple sources.

typedef struct

{

    size_t bitContainer;

    char*  startPtr;

    char*  ptr;

    char*  endPtr;

} BIT_CStream_t;

MEM_STATIC size_t BIT_initCStream(BIT_CStream_t* bitC, void* dstBuffer, size_t dstCapacity);

MEM_STATIC void   BIT_addBits(BIT_CStream_t* bitC, size_t value, unsigned nbBits);

MEM_STATIC void   BIT_flushBits(BIT_CStream_t* bitC);

MEM_STATIC size_t BIT_closeCStream(BIT_CStream_t* bitC);

/* Start with initCStream, providing the size of buffer to write into.

*  bitStream will never write outside of this buffer.

*  `dstCapacity` must be >= sizeof(bitD->bitContainer), otherwise @return will be an error code.

*

*  bits are first added to a local register.

*  Local register is size_t, hence 64-bits on 64-bits systems, or 32-bits on 32-bits systems.

*  Writing data into memory is an explicit operation, performed by the flushBits function.

*  Hence keep track how many bits are potentially stored into local register to avoid register overflow.

*  After a flushBits, a maximum of 7 bits might still be stored into local register.

*

*  Avoid storing elements of more than 24 bits if you want compatibility with 32-bits bitstream readers.

*

*  Last operation is to close the bitStream.

*  The function returns the final size of CStream in bytes.

*  If data couldn't fit into `dstBuffer`, it will return a 0 ( == not storable)

*/

/*-********************************************

*  bitStream decoding API (read backward)

**********************************************/

typedef struct

{

    size_t   bitContainer;

    unsigned bitsConsumed;

    const char* ptr;

    const char* start;

} BIT_DStream_t;

typedef enum { BIT_DStream_unfinished = 0,

               BIT_DStream_endOfBuffer = 1,

               BIT_DStream_completed = 2,

               BIT_DStream_overflow = 3 } BIT_DStream_status;  /* result of BIT_reloadDStream() */

               /* 1,2,4,8 would be better for bitmap combinations, but slows down performance a bit ... :( */

MEM_STATIC size_t   BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, size_t srcSize);

MEM_STATIC size_t   BIT_readBits(BIT_DStream_t* bitD, unsigned nbBits);

MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD);

MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* bitD);

/* Start by invoking BIT_initDStream().

*  A chunk of the bitStream is then stored into a local register.

*  Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t).

*  You can then retrieve bitFields stored into the local register, **in reverse order**.

*  Local register is explicitly reloaded from memory by the BIT_reloadDStream() method.

*  A reload guarantee a minimum of ((8*sizeof(bitD->bitContainer))-7) bits when its result is BIT_DStream_unfinished.

*  Otherwise, it can be less than that, so proceed accordingly.

*  Checking if DStream has reached its end can be performed with BIT_endOfDStream().

*/

/*-****************************************

*  unsafe API

******************************************/

MEM_STATIC void BIT_addBitsFast(BIT_CStream_t* bitC, size_t value, unsigned nbBits);

/* faster, but works only if value is "clean", meaning all high bits above nbBits are 0 */

MEM_STATIC void BIT_flushBitsFast(BIT_CStream_t* bitC);

/* unsafe version; does not check buffer overflow */

MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits);

/* faster, but works only if nbBits >= 1 */

/*-**************************************************************

*  Internal functions

****************************************************************/

{

#   if defined(_MSC_VER)   /* Visual */

#   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* Use GCC Intrinsic */

#   else   /* Software version */

#   endif

}

/*=====    Local Constants   =====*/

/*-**************************************************************

*  bitStream encoding

****************************************************************/

/*! BIT_initCStream() :

 *  @return : 0 if success,

{

    bitC->bitContainer = 0;

    bitC->bitPos = 0;

    bitC->startPtr = (char*)startPtr;

    bitC->ptr = bitC->startPtr;

    return 0;

}

/*! BIT_addBits() :

{

    bitC->bitContainer |= (value & BIT_mask[nbBits]) << bitC->bitPos;

    bitC->bitPos += nbBits;

}

/*! BIT_addBitsFast() :

 *  works only if `value` is _clean_, meaning all high bits above nbBits are 0 */

{

    bitC->bitContainer |= value << bitC->bitPos;

    bitC->bitPos += nbBits;

}

/*! BIT_flushBitsFast() :

 *  unsafe version; does not check buffer overflow */

MEM_STATIC void BIT_flushBitsFast(BIT_CStream_t* bitC)

{

    size_t const nbBytes = bitC->bitPos >> 3;

    MEM_writeLEST(bitC->ptr, bitC->bitContainer);

    bitC->ptr += nbBytes;

    bitC->bitPos &= 7;

}

/*! BIT_flushBits() :

 *  safe version; check for buffer overflow, and prevents it.

MEM_STATIC void BIT_flushBits(BIT_CStream_t* bitC)

{

    size_t const nbBytes = bitC->bitPos >> 3;

    MEM_writeLEST(bitC->ptr, bitC->bitContainer);

    bitC->ptr += nbBytes;

    if (bitC->ptr > bitC->endPtr) bitC->ptr = bitC->endPtr;

    bitC->bitPos &= 7;

}

/*! BIT_closeCStream() :

 *  @return : size of CStream, in bytes,

MEM_STATIC size_t BIT_closeCStream(BIT_CStream_t* bitC)

{

    BIT_addBitsFast(bitC, 1, 1);   /* endMark */

    BIT_flushBits(bitC);

    return (bitC->ptr - bitC->startPtr) + (bitC->bitPos > 0);

}

/*-********************************************************

**********************************************************/

/*! BIT_initDStream() :

MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, size_t srcSize)

{

    if (srcSize < 1) { memset(bitD, 0, sizeof(*bitD)); return ERROR(srcSize_wrong); }

    if (srcSize >=  sizeof(bitD->bitContainer)) {  /* normal case */

        bitD->ptr   = (const char*)srcBuffer + srcSize - sizeof(bitD->bitContainer);

        bitD->bitContainer = MEM_readLEST(bitD->ptr);

        { BYTE const lastByte = ((const BYTE*)srcBuffer)[srcSize-1];

          bitD->bitsConsumed = lastByte ? 8 - BIT_highbit32(lastByte) : 0;  /* ensures bitsConsumed is always set */

          if (lastByte == 0) return ERROR(GENERIC); /* endMark not present */ }

    } else {

        bitD->ptr   = bitD->start;

        bitD->bitContainer = *(const BYTE*)(bitD->start);

        switch(srcSize)

        {

        }

        bitD->bitsConsumed += (U32)(sizeof(bitD->bitContainer) - srcSize)*8;

    }

    return srcSize;

}

MEM_STATIC size_t BIT_getUpperBits(size_t bitContainer, U32 const start)

{

    return bitContainer >> start;

}

MEM_STATIC size_t BIT_getMiddleBits(size_t bitContainer, U32 const start, U32 const nbBits)

{

#if defined(__BMI__) && defined(__GNUC__) && __GNUC__*1000+__GNUC_MINOR__ >= 4008  /* experimental */

#  if defined(__x86_64__)

    if (sizeof(bitContainer)==8)

        return _bextr_u64(bitContainer, start, nbBits);

    else

#  endif

        return _bextr_u32(bitContainer, start, nbBits);

#else

    return (bitContainer >> start) & BIT_mask[nbBits];

#endif

}

MEM_STATIC size_t BIT_getLowerBits(size_t bitContainer, U32 const nbBits)

{

    return bitContainer & BIT_mask[nbBits];

}

/*! BIT_lookBits() :

 *  Provides next n bits from local register.

 *  local register is not modified.

 *  On 32-bits, maxNbBits==24.

 *  On 64-bits, maxNbBits==56.

{

#if defined(__BMI__) && defined(__GNUC__)   /* experimental; fails if bitD->bitsConsumed + nbBits > sizeof(bitD->bitContainer)*8 */

    return BIT_getMiddleBits(bitD->bitContainer, (sizeof(bitD->bitContainer)*8) - bitD->bitsConsumed - nbBits, nbBits);

#else

#endif

}

/*! BIT_lookBitsFast() :

MEM_STATIC size_t BIT_lookBitsFast(const BIT_DStream_t* bitD, U32 nbBits)

{

}

MEM_STATIC void BIT_skipBits(BIT_DStream_t* bitD, U32 nbBits)

{

    bitD->bitsConsumed += nbBits;

}

/*! BIT_readBits() :

 *  Read (consume) next n bits from local register and update.

 *  Pay attention to not read more than nbBits contained into local register.

MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, U32 nbBits)

{

    size_t const value = BIT_lookBits(bitD, nbBits);

    BIT_skipBits(bitD, nbBits);

    return value;

}

/*! BIT_readBitsFast() :

MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, U32 nbBits)

{

    size_t const value = BIT_lookBitsFast(bitD, nbBits);

    BIT_skipBits(bitD, nbBits);

    return value;

}

/*! BIT_reloadDStream() :

MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD)

{

        bitD->ptr -= bitD->bitsConsumed >> 3;

        bitD->bitsConsumed &= 7;

        bitD->bitContainer = MEM_readLEST(bitD->ptr);

        return BIT_DStream_unfinished;

    }

    if (bitD->ptr == bitD->start) {

        if (bitD->bitsConsumed < sizeof(bitD->bitContainer)*8) return BIT_DStream_endOfBuffer;

        return BIT_DStream_completed;

    }

    {   U32 nbBytes = bitD->bitsConsumed >> 3;

        BIT_DStream_status result = BIT_DStream_unfinished;

        if (bitD->ptr - nbBytes < bitD->start) {

            nbBytes = (U32)(bitD->ptr - bitD->start);  /* ptr > start */

            result = BIT_DStream_endOfBuffer;

        }

        bitD->ptr -= nbBytes;

        bitD->bitsConsumed -= nbBytes*8;

        return result;

    }

}

/*! BIT_endOfDStream() :

MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* DStream)

{

    return ((DStream->ptr == DStream->start) && (DStream->bitsConsumed == sizeof(DStream->bitContainer)*8));

}

#if defined (__cplusplus)

}

#endif

#endif /* BITSTREAM_H_MODULE */