/*
  * 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 "libavutil/attributes.h"

 #include "libavutil/common.h"
 #include "png.h"
 #include "pngdsp.h"
 
 // 0x7f7f7f7f or 0x7f7f7f7f7f7f7f7f or whatever, depending on the cpu's native arithmetic size

 #define pb_7f (~0UL / 255 * 0x7f)
 #define pb_80 (~0UL / 255 * 0x80)

 
 static void add_bytes_l2_c(uint8_t *dst, uint8_t *src1, uint8_t *src2, int w)
 {
     long i;

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

         long a = *(long *)(src1 + i);
         long b = *(long *)(src2 + i);
         *(long *)(dst + i) = ((a & pb_7f) + (b & pb_7f)) ^ ((a ^ b) & pb_80);
     }
     for (; i < w; i++)
         dst[i] = src1[i] + src2[i];
 }
 

 av_cold void ff_pngdsp_init(PNGDSPContext *dsp)

 {
     dsp->add_bytes_l2         = add_bytes_l2_c;
     dsp->add_paeth_prediction = ff_add_png_paeth_prediction;
 

     if (ARCH_X86)
         ff_pngdsp_init_x86(dsp);

 }