dcmjpls/libcharls/ctxtrmod.h

//
// (C) Jan de Vaan 2007-2010, all rights reserved. See the accompanying "License.txt" for licensed use.
//


#ifndef CHARLS_CONTEXTRUNMODE
#define CHARLS_CONTEXTRUNMODE

// Implements statistical modelling for the run mode context.
// Computes model dependent parameters like the golomb code lengths

struct CContextRunMode
{
    CContextRunMode(LONG a, LONG nRItype, LONG nReset) :
        A(a),
        N(1),
        Nn(0),
        _nRItype(nRItype),
        _nReset((BYTE)nReset)
    {
    }

    LONG A;
    BYTE N;
    BYTE Nn;
    LONG _nRItype;
    BYTE _nReset;

    CContextRunMode()
    {}


    inlinehint LONG GetGolomb() const
    {
        LONG Ntest  = N;
        LONG TEMP   = A + (N >> 1) * _nRItype;
        LONG k = 0;
        for(; Ntest < TEMP; k++)
        {
            Ntest <<= 1;
            ASSERT(k <= 32);
        };
        return k;
    }


    void UpdateVariables(LONG Errval, LONG EMErrval)
    {
        if (Errval < 0)
        {
            Nn = Nn + 1;
        }
        A = A + ((EMErrval + 1 - _nRItype) >> 1);
        if (N == _nReset)
        {
            A = A >> 1;
            N = N >> 1;
            Nn = Nn >> 1;
        }
        N = N + 1;
    }

    inlinehint LONG ComputeErrVal(LONG temp, LONG k)
    {
        bool map = temp & 1;

        LONG errvalabs = (temp + map) / 2;

        if ((k != 0 || (2 * Nn >= N)) == map)
        {
            ASSERT(map == ComputeMap(-errvalabs, k));
            return -errvalabs;
        }

        ASSERT(map == ComputeMap(errvalabs, k));
        return errvalabs;
    }


    bool ComputeMap(LONG Errval, LONG k) const
    {
        if ((k == 0) && (Errval > 0) && (2 * Nn < N))
            return 1;

        else if ((Errval < 0) && (2 * Nn >= N))
            return 1;

        else if ((Errval < 0) && (k != 0))
            return 1;

        return 0;
    }


    inlinehint LONG ComputeMapNegativeE(LONG k) const
    {
        return  k != 0 || (2 * Nn >= N );
    }
};

#endif

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