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

   FSE : Finite State Entropy encoder

   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 :

    - FSE source repository : https://github.com/Cyan4973/FiniteStateEntropy

    - Public forum : https://groups.google.com/forum/#!forum/lz4c

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

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

*  Includes

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

#include <stdlib.h>     /* malloc, free, qsort */

#include <string.h>     /* memcpy, memset */

#include "bitstream.h"

#define FSE_STATIC_LINKING_ONLY

#include "fse.h"

#include "error_private.h"

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

*  Error Management

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

#define FSE_isError ERR_isError

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

*  Templates

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

/*

  designed to be included

  for type-specific functions (template emulation in C)

  Objective is to write these functions only once, for improved maintenance

*/

/* safety checks */

#ifndef FSE_FUNCTION_EXTENSION

#  error "FSE_FUNCTION_EXTENSION must be defined"

#endif

#ifndef FSE_FUNCTION_TYPE

#  error "FSE_FUNCTION_TYPE must be defined"

#endif

/* Function names */

#define FSE_CAT(X,Y) X##Y

#define FSE_FUNCTION_NAME(X,Y) FSE_CAT(X,Y)

#define FSE_TYPE_NAME(X,Y) FSE_CAT(X,Y)

/* Function templates */

/* FSE_buildCTable_wksp() :

 * Same as FSE_buildCTable(), but using an externally allocated scratch buffer (`workSpace`).

 * wkspSize should be sized to handle worst case situation, which is `1<<max_tableLog * sizeof(FSE_FUNCTION_TYPE)`

 * workSpace must also be properly aligned with FSE_FUNCTION_TYPE requirements

 */

{

    U32 const tableSize = 1 << tableLog;

    U32 const tableMask = tableSize - 1;

    void* const ptr = ct;

    U16* const tableU16 = ( (U16*) ptr) + 2;

    void* const FSCT = ((U32*)ptr) + 1 /* header */ + (tableLog ? tableSize>>1 : 1) ;

    FSE_symbolCompressionTransform* const symbolTT = (FSE_symbolCompressionTransform*) (FSCT);

    U32 const step = FSE_TABLESTEP(tableSize);

    U32 cumul[FSE_MAX_SYMBOL_VALUE+2];

    FSE_FUNCTION_TYPE* const tableSymbol = (FSE_FUNCTION_TYPE*)workSpace;

    U32 highThreshold = tableSize-1;

    /* CTable header */

    if (((size_t)1 << tableLog) * sizeof(FSE_FUNCTION_TYPE) > wkspSize) return ERROR(tableLog_tooLarge);

    tableU16[-2] = (U16) tableLog;

    tableU16[-1] = (U16) maxSymbolValue;

    /* For explanations on how to distribute symbol values over the table :

    /* symbol start positions */

    {   U32 u;

        cumul[0] = 0;

        for (u=1; u<=maxSymbolValue+1; u++) {

            if (normalizedCounter[u-1]==-1) {  /* Low proba symbol */

                cumul[u] = cumul[u-1] + 1;

                tableSymbol[highThreshold--] = (FSE_FUNCTION_TYPE)(u-1);

            } else {

                cumul[u] = cumul[u-1] + normalizedCounter[u-1];

        }   }

        cumul[maxSymbolValue+1] = tableSize+1;

    }

    /* Spread symbols */

    {   U32 position = 0;

        U32 symbol;

        for (symbol=0; symbol<=maxSymbolValue; symbol++) {

            int nbOccurences;

                tableSymbol[position] = (FSE_FUNCTION_TYPE)symbol;

                position = (position + step) & tableMask;

        }   }

    }

    /* Build table */

    {   U32 u; for (u=0; u<tableSize; u++) {

        FSE_FUNCTION_TYPE s = tableSymbol[u];   /* note : static analyzer may not understand tableSymbol is properly initialized */

        tableU16[cumul[s]++] = (U16) (tableSize+u);   /* TableU16 : sorted by symbol order; gives next state value */

    }   }

    /* Build Symbol Transformation Table */

    {   unsigned total = 0;

        unsigned s;

        for (s=0; s<=maxSymbolValue; s++) {

            switch (normalizedCounter[s])

            {

            case -1:

            case  1:

                symbolTT[s].deltaNbBits = (tableLog << 16) - (1<<tableLog);

                symbolTT[s].deltaFindState = total - 1;

                total ++;

                break;

            default :

                {

                    U32 const maxBitsOut = tableLog - BIT_highbit32 (normalizedCounter[s]-1);

                    U32 const minStatePlus = normalizedCounter[s] << maxBitsOut;

                    symbolTT[s].deltaNbBits = (maxBitsOut << 16) - minStatePlus;

                    symbolTT[s].deltaFindState = total - normalizedCounter[s];

                    total +=  normalizedCounter[s];

    }   }   }   }

    return 0;

}

size_t FSE_buildCTable(FSE_CTable* ct, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog)

{

    FSE_FUNCTION_TYPE tableSymbol[FSE_MAX_TABLESIZE];   /* memset() is not necessary, even if static analyzer complain about it */

    return FSE_buildCTable_wksp(ct, normalizedCounter, maxSymbolValue, tableLog, tableSymbol, sizeof(tableSymbol));

}

#ifndef FSE_COMMONDEFS_ONLY

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

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

size_t FSE_NCountWriteBound(unsigned maxSymbolValue, unsigned tableLog)

{

    size_t const maxHeaderSize = (((maxSymbolValue+1) * tableLog) >> 3) + 3;

    return maxSymbolValue ? maxHeaderSize : FSE_NCOUNTBOUND;  /* maxSymbolValue==0 ? use default */

}

{

    BYTE* const ostart = (BYTE*) header;

    BYTE* out = ostart;

    BYTE* const oend = ostart + headerBufferSize;

    int nbBits;

    const int tableSize = 1 << tableLog;

    int remaining;

    int threshold;

    /* Table Size */

    bitStream += (tableLog-FSE_MIN_TABLELOG) << bitCount;

    bitCount  += 4;

    /* Init */

    remaining = tableSize+1;   /* +1 for extra accuracy */

    threshold = tableSize;

    nbBits = tableLog+1;

                start+=24;

                bitStream += 0xFFFFU << bitCount;

                out[0] = (BYTE) bitStream;

                out[1] = (BYTE)(bitStream>>8);

                out+=2;

                bitStream>>=16;

            }

                start+=3;

                bitStream += 3 << bitCount;

                bitCount += 2;

            }

            bitCount += 2;

            if (bitCount>16) {

                out[0] = (BYTE)bitStream;

                out[1] = (BYTE)(bitStream>>8);

                out += 2;

                bitStream >>= 16;

                bitCount -= 16;

        }   }

            remaining -= count < 0 ? -count : count;

            count++;   /* +1 for extra accuracy */

            bitStream += count << bitCount;

            bitCount  += nbBits;

            bitCount  -= (count<max);

            if (remaining<1) return ERROR(GENERIC);

            while (remaining<threshold) { nbBits--; threshold>>=1; }

        }

        if (bitCount>16) {

            out[0] = (BYTE)bitStream;

            out[1] = (BYTE)(bitStream>>8);

            out += 2;

            bitStream >>= 16;

            bitCount -= 16;

    }   }

    /* flush remaining bitStream */

    out[0] = (BYTE)bitStream;

    out[1] = (BYTE)(bitStream>>8);

    out+= (bitCount+7) /8;

    return (out-ostart);

}

{

    if (tableLog > FSE_MAX_TABLELOG) return ERROR(tableLog_tooLarge);   /* Unsupported */

    if (tableLog < FSE_MIN_TABLELOG) return ERROR(GENERIC);   /* Unsupported */

    if (bufferSize < FSE_NCountWriteBound(maxSymbolValue, tableLog))

        return FSE_writeNCount_generic(buffer, bufferSize, normalizedCounter, maxSymbolValue, tableLog, 0);

}

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

*  FSE Compression Code

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

FSE_CTable* FSE_createCTable (unsigned maxSymbolValue, unsigned tableLog)

{

    size_t size;

    if (tableLog > FSE_TABLELOG_ABSOLUTE_MAX) tableLog = FSE_TABLELOG_ABSOLUTE_MAX;

    size = FSE_CTABLE_SIZE_U32 (tableLog, maxSymbolValue) * sizeof(U32);

    return (FSE_CTable*)malloc(size);

}

void FSE_freeCTable (FSE_CTable* ct) { free(ct); }

/* provides the minimum logSize to safely represent a distribution */

static unsigned FSE_minTableLog(size_t srcSize, unsigned maxSymbolValue)

{

    U32 minBitsSymbols = BIT_highbit32(maxSymbolValue) + 2;

    U32 minBits = minBitsSrc < minBitsSymbols ? minBitsSrc : minBitsSymbols;

    assert(srcSize > 1); /* Not supported, RLE should be used instead */

    return minBits;

}

unsigned FSE_optimalTableLog_internal(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue, unsigned minus)

{

    U32 maxBitsSrc = BIT_highbit32((U32)(srcSize - 1)) - minus;

    U32 tableLog = maxTableLog;

    U32 minBits = FSE_minTableLog(srcSize, maxSymbolValue);

    assert(srcSize > 1); /* Not supported, RLE should be used instead */

    if (tableLog==0) tableLog = FSE_DEFAULT_TABLELOG;

    if (maxBitsSrc < tableLog) tableLog = maxBitsSrc;   /* Accuracy can be reduced */

    if (minBits > tableLog) tableLog = minBits;   /* Need a minimum to safely represent all symbol values */

    if (tableLog < FSE_MIN_TABLELOG) tableLog = FSE_MIN_TABLELOG;

    if (tableLog > FSE_MAX_TABLELOG) tableLog = FSE_MAX_TABLELOG;

    return tableLog;

}

unsigned FSE_optimalTableLog(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue)

{

    return FSE_optimalTableLog_internal(maxTableLog, srcSize, maxSymbolValue, 2);

}

/* Secondary normalization method.

   To be used when primary method fails. */

static size_t FSE_normalizeM2(short* norm, U32 tableLog, const unsigned* count, size_t total, U32 maxSymbolValue)

{

    short const NOT_YET_ASSIGNED = -2;

    U32 s;

    U32 distributed = 0;

    U32 ToDistribute;

    /* Init */

    U32 const lowThreshold = (U32)(total >> tableLog);

    U32 lowOne = (U32)((total * 3) >> (tableLog + 1));

    for (s=0; s<=maxSymbolValue; s++) {

        if (count[s] == 0) {

            norm[s]=0;

            continue;

        }

        if (count[s] <= lowThreshold) {

            norm[s] = -1;

            distributed++;

            total -= count[s];

            continue;

        }

        if (count[s] <= lowOne) {

            norm[s] = 1;

            distributed++;

            total -= count[s];

            continue;

        }

        norm[s]=NOT_YET_ASSIGNED;

    }

    ToDistribute = (1 << tableLog) - distributed;

    if ((total / ToDistribute) > lowOne) {

        /* risk of rounding to zero */

        lowOne = (U32)((total * 3) / (ToDistribute * 2));

        for (s=0; s<=maxSymbolValue; s++) {

            if ((norm[s] == NOT_YET_ASSIGNED) && (count[s] <= lowOne)) {

                norm[s] = 1;

                distributed++;

                total -= count[s];

                continue;

        }   }

        ToDistribute = (1 << tableLog) - distributed;

    }

    if (distributed == maxSymbolValue+1) {

        /* all values are pretty poor;

           probably incompressible data (should have already been detected);

           find max, then give all remaining points to max */

        U32 maxV = 0, maxC = 0;

        for (s=0; s<=maxSymbolValue; s++)

            if (count[s] > maxC) { maxV=s; maxC=count[s]; }

        norm[maxV] += (short)ToDistribute;

        return 0;

    }

    if (total == 0) {

        /* all of the symbols were low enough for the lowOne or lowThreshold */

        for (s=0; ToDistribute > 0; s = (s+1)%(maxSymbolValue+1))

            if (norm[s] > 0) { ToDistribute--; norm[s]++; }

        return 0;

    }

    {   U64 const vStepLog = 62 - tableLog;

        U64 const mid = (1ULL << (vStepLog-1)) - 1;

        U64 const rStep = ((((U64)1<<vStepLog) * ToDistribute) + mid) / total;   /* scale on remaining */

        U64 tmpTotal = mid;

        for (s=0; s<=maxSymbolValue; s++) {

            if (norm[s]==NOT_YET_ASSIGNED) {

                U64 const end = tmpTotal + (count[s] * rStep);

                U32 const sStart = (U32)(tmpTotal >> vStepLog);

                U32 const sEnd = (U32)(end >> vStepLog);

                U32 const weight = sEnd - sStart;

                if (weight < 1)

                    return ERROR(GENERIC);

                norm[s] = (short)weight;

                tmpTotal = end;

    }   }   }

    return 0;

}

size_t FSE_normalizeCount (short* normalizedCounter, unsigned tableLog,

                           const unsigned* count, size_t total,

                           unsigned maxSymbolValue)

{

    /* Sanity checks */

    if (tableLog==0) tableLog = FSE_DEFAULT_TABLELOG;

    if (tableLog < FSE_MIN_TABLELOG) return ERROR(GENERIC);   /* Unsupported size */

    if (tableLog > FSE_MAX_TABLELOG) return ERROR(tableLog_tooLarge);   /* Unsupported size */

    if (tableLog < FSE_minTableLog(total, maxSymbolValue)) return ERROR(GENERIC);   /* Too small tableLog, compression potentially impossible */

    {   static U32 const rtbTable[] = {     0, 473195, 504333, 520860, 550000, 700000, 750000, 830000 };

        U64 const scale = 62 - tableLog;

        U64 const step = ((U64)1<<62) / total;   /* <== here, one division ! */

        U64 const vStep = 1ULL<<(scale-20);

        int stillToDistribute = 1<<tableLog;

        unsigned s;

        unsigned largest=0;

        short largestP=0;

        U32 lowThreshold = (U32)(total >> tableLog);

        for (s=0; s<=maxSymbolValue; s++) {

            if (count[s] == total) return 0;   /* rle special case */

            if (count[s] == 0) { normalizedCounter[s]=0; continue; }

            if (count[s] <= lowThreshold) {

                normalizedCounter[s] = -1;

                stillToDistribute--;

            } else {

                short proba = (short)((count[s]*step) >> scale);

                if (proba<8) {

                    U64 restToBeat = vStep * rtbTable[proba];

                    proba += (count[s]*step) - ((U64)proba<<scale) > restToBeat;

                }

                if (proba > largestP) { largestP=proba; largest=s; }

                normalizedCounter[s] = proba;

                stillToDistribute -= proba;

        }   }

        if (-stillToDistribute >= (normalizedCounter[largest] >> 1)) {

            /* corner case, need another normalization method */

            size_t const errorCode = FSE_normalizeM2(normalizedCounter, tableLog, count, total, maxSymbolValue);

            if (FSE_isError(errorCode)) return errorCode;

        }

        else normalizedCounter[largest] += (short)stillToDistribute;

    }

#if 0

    {   /* Print Table (debug) */

        U32 s;

        U32 nTotal = 0;

        for (s=0; s<=maxSymbolValue; s++)

        for (s=0; s<=maxSymbolValue; s++)

            nTotal += abs(normalizedCounter[s]);

        if (nTotal != (1U<<tableLog))

        getchar();

    }

#endif