/*

 * PNG image format

 * Copyright (c) 2008 Loren Merrit <lorenm@u.washington.edu>

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include <stdlib.h>

#include "config.h"

#include "libavutil/attributes.h"

#include "libavutil/intreadwrite.h"

#include "libavutil/macros.h"

#include "pngdsp.h"

#if HAVE_FAST_64BIT

#define BITS 64

typedef uint64_t uint_native;

#else

#define BITS 32

typedef uint32_t uint_native;

#endif

#define RN  AV_JOIN(AV_RN, BITS)

#define RNA AV_JOIN(AV_JOIN(AV_RN, BITS),  A)

#define WN  AV_JOIN(AV_WN, BITS)

// 0x7f7f7f7f or 0x7f7f7f7f7f7f7f7f or whatever, depending on the cpu's native arithmetic size

#define pb_7f (~(uint_native)0 / 255 * 0x7f)

#define pb_80 (~(uint_native)0 / 255 * 0x80)

static void add_bytes_l2_c(uint8_t *dst, const uint8_t *src1,

                           const uint8_t *src2, int w)

{

    long i;

    for (i = 0; i <= w - (int) sizeof(uint_native); i += sizeof(uint_native)) {

        uint_native a = RNA(src1 + i);

        uint_native b = RN (src2 + i);

        WN(dst + i, ((a & pb_7f) + (b & pb_7f)) ^ ((a ^ b) & pb_80));

    }

    for (; i < w; i++)

        dst[i] = src1[i] + src2[i];

}

void ff_png_add_paeth_prediction(uint8_t *dst, const uint8_t *src,

                                 const uint8_t *top, int w, int bpp)

{

    for (int i = 0; i < w; ++i) {

        int a, b, c, p, pa, pb, pc;

        a = dst[i - bpp];

        b = top[i];

        c = top[i - bpp];

        p  = b - c;

        pc = a - c;

        pa = abs(p);

        pb = abs(pc);

        pc = abs(p + pc);

        if (pa <= pb && pa <= pc)

            p = a;

        else if (pb <= pc)

            p = b;

        else

            p = c;

        dst[i] = p + src[i];

    }

}

av_cold void ff_pngdsp_init(PNGDSPContext *dsp)

{

    dsp->add_bytes_l2         = add_bytes_l2_c;

    dsp->add_paeth_prediction = ff_png_add_paeth_prediction;

#if ARCH_X86 && HAVE_X86ASM

    ff_pngdsp_init_x86(dsp);

#endif

}