/*
  * Direct Stream Digital (DSD) decoder
  * based on BSD licensed dsd2pcm by Sebastian Gesemann
  * Copyright (c) 2009, 2011 Sebastian Gesemann. All rights reserved.
  * Copyright (c) 2014 Peter Ross
  *
  * 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 "libavcodec/internal.h"
 #include "libavcodec/mathops.h"
 #include "avcodec.h"
 #include "dsd_tablegen.h"
 #include "dsd.h"
 
 static av_cold void dsd_ctables_tableinit(void)
 {
     int t, e, m, sign;
     double acc[CTABLES];
     for (e = 0; e < 256; ++e) {
         memset(acc, 0, sizeof(acc));
         for (m = 0; m < 8; ++m) {
             sign = (((e >> (7 - m)) & 1) * 2 - 1);
             for (t = 0; t < CTABLES; ++t)
                 acc[t] += sign * htaps[t * 8 + m];
         }
         for (t = 0; t < CTABLES; ++t)
             ctables[CTABLES - 1 - t][e] = acc[t];
     }
 }
 
 av_cold void ff_init_dsd_data(void)
 {
     static int done = 0;
     if (done)
         return;
     dsd_ctables_tableinit();
     done = 1;
 }
 
 void ff_dsd2pcm_translate(DSDContext* s, size_t samples, int lsbf,
                           const unsigned char *src, ptrdiff_t src_stride,
                           float *dst, ptrdiff_t dst_stride)
 {
     unsigned pos, i;
     unsigned char* p;
     double sum;
 
     pos = s->pos;
 
     while (samples-- > 0) {
         s->buf[pos] = lsbf ? ff_reverse[*src] : *src;
         src += src_stride;
 
         p = s->buf + ((pos - CTABLES) & FIFOMASK);
         *p = ff_reverse[*p];
 
         sum = 0.0;
         for (i = 0; i < CTABLES; i++) {
             unsigned char a = s->buf[(pos                   - i) & FIFOMASK];
             unsigned char b = s->buf[(pos - (CTABLES*2 - 1) + i) & FIFOMASK];
             sum += ctables[i][a] + ctables[i][b];
         }
 
         *dst = (float)sum;
         dst += dst_stride;
 
         pos = (pos + 1) & FIFOMASK;
     }
 
     s->pos = pos;
 }