/*

  * 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 "config.h"
 #include "libavutil/attributes.h"
 #include "huffyuvencdsp.h"
 #include "mathops.h"
 

 // 0x00010001 or 0x0001000100010001 or whatever, depending on the cpu's native arithmetic size
 #define pw_1 (ULONG_MAX / UINT16_MAX)
 

 static void diff_int16_c(uint16_t *dst, const uint16_t *src1, const uint16_t *src2, unsigned mask, int w){
     long i;
 #if !HAVE_FAST_UNALIGNED
     if((long)src2 & (sizeof(long)-1)){
         for(i=0; i+3<w; i+=4){
             dst[i+0] = (src1[i+0]-src2[i+0]) & mask;
             dst[i+1] = (src1[i+1]-src2[i+1]) & mask;
             dst[i+2] = (src1[i+2]-src2[i+2]) & mask;
             dst[i+3] = (src1[i+3]-src2[i+3]) & mask;
         }
     }else
 #endif
     {

         unsigned long pw_lsb = (mask >> 1) * pw_1;
         unsigned long pw_msb = pw_lsb +  pw_1;

 
         for (i = 0; i <= w - (int)sizeof(long)/2; i += sizeof(long)/2) {
             long a = *(long*)(src1+i);
             long b = *(long*)(src2+i);
             *(long*)(dst+i) = ((a|pw_msb) - (b&pw_lsb)) ^ ((a^b^pw_msb)&pw_msb);
         }
     }
     for (; i<w; i++)
         dst[i] = (src1[i] - src2[i]) & mask;
 }
 
 static void sub_hfyu_median_pred_int16_c(uint16_t *dst, const uint16_t *src1, const uint16_t *src2, unsigned mask, int w, int *left, int *left_top){
     int i;
     uint16_t l, lt;
 
     l  = *left;
     lt = *left_top;
 
     for(i=0; i<w; i++){
         const int pred = mid_pred(l, src1[i], (l + src1[i] - lt) & mask);
         lt = src1[i];
         l  = src2[i];
         dst[i] = (l - pred) & mask;
     }
 
     *left     = l;
     *left_top = lt;
 }
 
 av_cold void ff_huffyuvencdsp_init(HuffYUVEncDSPContext *c, AVCodecContext *avctx)

 {

     c->diff_int16           = diff_int16_c;
     c->sub_hfyu_median_pred_int16 = sub_hfyu_median_pred_int16_c;

 
     if (ARCH_X86)

         ff_huffyuvencdsp_init_x86(c, avctx);

 }