2 * Copyright (c) 2013 The WebM project authors. All Rights Reserved.
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.
11 #ifndef VP9_DECODER_VP9_READ_BIT_BUFFER_H_
12 #define VP9_DECODER_VP9_READ_BIT_BUFFER_H_
16 #include "vpx/vpx_integer.h"
22 typedef void (*vp9_rb_error_handler)(void *data, size_t bit_offset);
24 struct vp9_read_bit_buffer {
25 const uint8_t *bit_buffer;
26 const uint8_t *bit_buffer_end;
29 void *error_handler_data;
30 vp9_rb_error_handler error_handler;
33 static size_t vp9_rb_bytes_read(struct vp9_read_bit_buffer *rb) {
34 return rb->bit_offset / CHAR_BIT + (rb->bit_offset % CHAR_BIT > 0);
37 static int vp9_rb_read_bit(struct vp9_read_bit_buffer *rb) {
38 const size_t off = rb->bit_offset;
39 const size_t p = off / CHAR_BIT;
40 const int q = CHAR_BIT - 1 - (int)off % CHAR_BIT;
41 if (rb->bit_buffer + p >= rb->bit_buffer_end) {
42 rb->error_handler(rb->error_handler_data, rb->bit_offset);
45 const int bit = (rb->bit_buffer[p] & (1 << q)) >> q;
46 rb->bit_offset = off + 1;
51 static int vp9_rb_read_literal(struct vp9_read_bit_buffer *rb, int bits) {
53 for (bit = bits - 1; bit >= 0; bit--)
54 value |= vp9_rb_read_bit(rb) << bit;
58 static int vp9_rb_read_signed_literal(struct vp9_read_bit_buffer *rb,
60 const int value = vp9_rb_read_literal(rb, bits);
61 return vp9_rb_read_bit(rb) ? -value : value;
68 #endif // VP9_DECODER_VP9_READ_BIT_BUFFER_H_