bitwriter_buffer.c revision 7ce0a1d1337c01056ba24006efab21f00e179e04 
1/*
2 *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11#include <limits.h>
12
13#include "./bitwriter_buffer.h"
14
15size_t vpx_wb_bytes_written(const struct vpx_write_bit_buffer *wb) {
16  return wb->bit_offset / CHAR_BIT + (wb->bit_offset % CHAR_BIT > 0);
17}
18
19void vpx_wb_write_bit(struct vpx_write_bit_buffer *wb, int bit) {
20  const int off = (int)wb->bit_offset;
21  const int p = off / CHAR_BIT;
22  const int q = CHAR_BIT - 1 - off % CHAR_BIT;
23  if (q == CHAR_BIT -1) {
24    wb->bit_buffer[p] = bit << q;
25  } else {
26    wb->bit_buffer[p] &= ~(1 << q);
27    wb->bit_buffer[p] |= bit << q;
28  }
29  wb->bit_offset = off + 1;
30}
31
32void vpx_wb_write_literal(struct vpx_write_bit_buffer *wb, int data, int bits) {
33  int bit;
34  for (bit = bits - 1; bit >= 0; bit--)
35    vpx_wb_write_bit(wb, (data >> bit) & 1);
36}
37