text: /*
   * a very simple circular buffer FIFO implementation
   * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
   * Copyright (c) 2006 Roman Shaposhnik
   *
   * 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 "common.h"
  #include "fifo.h"
  
  AVFifoBuffer *av_fifo_alloc(unsigned int size)
  {
      AVFifoBuffer *f= av_mallocz(sizeof(AVFifoBuffer));
      if (!f)
          return NULL;
      f->buffer = av_malloc(size);
      f->end = f->buffer + size;
      av_fifo_reset(f);
      if (!f->buffer)
          av_freep(&f);
      return f;
  }
  
  void av_fifo_free(AVFifoBuffer *f)
  {
      if (f) {
          av_freep(&f->buffer);
          av_free(f);
      }
  }
  
  void av_fifo_reset(AVFifoBuffer *f)
  {
      f->wptr = f->rptr = f->buffer;
      f->wndx = f->rndx = 0;
  }
  
  int av_fifo_size(AVFifoBuffer *f)
  {
      return (uint32_t)(f->wndx - f->rndx);
  }
  
  int av_fifo_space(AVFifoBuffer *f)
  {
      return f->end - f->buffer - av_fifo_size(f);
  }
  
  int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
  {
      unsigned int old_size = f->end - f->buffer;
  
      if (old_size < new_size) {
          int len = av_fifo_size(f);
          AVFifoBuffer *f2 = av_fifo_alloc(new_size);
  
          if (!f2)
              return AVERROR(ENOMEM);
          av_fifo_generic_read(f, f2->buffer, len, NULL);
          f2->wptr += len;
          f2->wndx += len;
          av_free(f->buffer);
          *f = *f2;
          av_free(f2);
      }
      return 0;
  }
  
  // src must NOT be const as it can be a context for func that may need updating (like a pointer or byte counter)
  int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size, int (*func)(void*, void*, int))
  {
      int total = size;
      uint32_t wndx= f->wndx;
      uint8_t *wptr= f->wptr;
  
      do {
          int len = FFMIN(f->end - wptr, size);
          if (func) {
              if (func(src, wptr, len) <= 0)
                  break;
          } else {
              memcpy(wptr, src, len);
              src = (uint8_t*)src + len;
          }
  // Write memory barrier needed for SMP here in theory
          wptr += len;
          if (wptr >= f->end)
              wptr = f->buffer;
          wndx += len;
          size -= len;
      } while (size > 0);
      f->wndx= wndx;
      f->wptr= wptr;
      return total - size;
  }
  
  
  int av_fifo_generic_read(AVFifoBuffer *f, void *dest, int buf_size, void (*func)(void*, void*, int))
  {
  // Read memory barrier needed for SMP here in theory
      do {
          int len = FFMIN(f->end - f->rptr, buf_size);
          if(func) func(dest, f->rptr, len);
          else{
              memcpy(dest, f->rptr, len);
              dest = (uint8_t*)dest + len;
          }
  // memory barrier needed for SMP here in theory
          av_fifo_drain(f, len);
          buf_size -= len;
      } while (buf_size > 0);
      return 0;
  }
  
  /** Discard data from the FIFO. */
  void av_fifo_drain(AVFifoBuffer *f, int size)
  {
      f->rptr += size;
      if (f->rptr >= f->end)
          f->rptr -= f->end - f->buffer;
      f->rndx += size;
  }
  
  #ifdef TEST
  
  #undef printf
  
  int main(void)
  {
      /* create a FIFO buffer */
      AVFifoBuffer *fifo = av_fifo_alloc(13 * sizeof(int));
      int i, j, n;
  
      /* fill data */
      for (i = 0; av_fifo_space(fifo) >= sizeof(int); i++)
          av_fifo_generic_write(fifo, &i, sizeof(int), NULL);
  
      /* peek at FIFO */
      n = av_fifo_size(fifo)/sizeof(int);
      for (i = -n+1; i < n; i++) {
          int *v = (int *)av_fifo_peek2(fifo, i*sizeof(int));
          printf("%d: %d\n", i, *v);
      }
      printf("\n");
  
      /* read data */
      for (i = 0; av_fifo_size(fifo) >= sizeof(int); i++) {
          av_fifo_generic_read(fifo, &j, sizeof(int), NULL);
          printf("%d ", j);
      }
      printf("\n");
  
      av_fifo_free(fifo);
  
      return 0;
  }
  
  #endif
  