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 <assert.h>
12 #include <limits.h>
13 #include <stdlib.h>
14
15 #include "./vpx_config.h"
16 #include "./bitwriter_buffer.h"
17
vpx_wb_init(struct vpx_write_bit_buffer * wb,uint8_t * bit_buffer,size_t size)18 void vpx_wb_init(struct vpx_write_bit_buffer *wb, uint8_t *bit_buffer,
19 size_t size) {
20 wb->error = 0;
21 wb->bit_offset = 0;
22 wb->size = size;
23 wb->bit_buffer = bit_buffer;
24 }
25
vpx_wb_has_error(const struct vpx_write_bit_buffer * wb)26 int vpx_wb_has_error(const struct vpx_write_bit_buffer *wb) {
27 return wb->error;
28 }
29
vpx_wb_bytes_written(const struct vpx_write_bit_buffer * wb)30 size_t vpx_wb_bytes_written(const struct vpx_write_bit_buffer *wb) {
31 assert(!wb->error);
32 return wb->bit_offset / CHAR_BIT + (wb->bit_offset % CHAR_BIT > 0);
33 }
34
vpx_wb_write_bit(struct vpx_write_bit_buffer * wb,int bit)35 void vpx_wb_write_bit(struct vpx_write_bit_buffer *wb, int bit) {
36 if (wb->error) return;
37 const int off = (int)wb->bit_offset;
38 const int p = off / CHAR_BIT;
39 const int q = CHAR_BIT - 1 - off % CHAR_BIT;
40 if ((size_t)p >= wb->size) {
41 wb->error = 1;
42 return;
43 }
44 if (q == CHAR_BIT - 1) {
45 wb->bit_buffer[p] = bit << q;
46 } else {
47 assert((wb->bit_buffer[p] & (1 << q)) == 0);
48 wb->bit_buffer[p] |= bit << q;
49 }
50 wb->bit_offset = off + 1;
51 }
52
vpx_wb_write_literal(struct vpx_write_bit_buffer * wb,int data,int bits)53 void vpx_wb_write_literal(struct vpx_write_bit_buffer *wb, int data, int bits) {
54 int bit;
55 for (bit = bits - 1; bit >= 0; bit--) vpx_wb_write_bit(wb, (data >> bit) & 1);
56 }
57
vpx_wb_write_inv_signed_literal(struct vpx_write_bit_buffer * wb,int data,int bits)58 void vpx_wb_write_inv_signed_literal(struct vpx_write_bit_buffer *wb, int data,
59 int bits) {
60 vpx_wb_write_literal(wb, abs(data), bits);
61 vpx_wb_write_bit(wb, data < 0);
62 }
63