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1 /* | 1 /* |
2 * Copyright (c) 2013 The WebM project authors. All Rights Reserved. | 2 * Copyright (c) 2013 The WebM project authors. All Rights Reserved. |
3 * | 3 * |
4 * Use of this source code is governed by a BSD-style license | 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 | 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 | 6 * tree. An additional intellectual property rights grant can be found |
7 * in the file PATENTS. All contributing project authors may | 7 * in the file PATENTS. All contributing project authors may |
8 * be found in the AUTHORS file in the root of the source tree. | 8 * be found in the AUTHORS file in the root of the source tree. |
9 */ | 9 */ |
10 | 10 |
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23 | 23 |
24 struct vp9_read_bit_buffer { | 24 struct vp9_read_bit_buffer { |
25 const uint8_t *bit_buffer; | 25 const uint8_t *bit_buffer; |
26 const uint8_t *bit_buffer_end; | 26 const uint8_t *bit_buffer_end; |
27 size_t bit_offset; | 27 size_t bit_offset; |
28 | 28 |
29 void *error_handler_data; | 29 void *error_handler_data; |
30 vp9_rb_error_handler error_handler; | 30 vp9_rb_error_handler error_handler; |
31 }; | 31 }; |
32 | 32 |
33 static size_t vp9_rb_bytes_read(struct vp9_read_bit_buffer *rb) { | 33 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); | |
35 } | |
36 | 34 |
37 static int vp9_rb_read_bit(struct vp9_read_bit_buffer *rb) { | 35 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); | |
43 return 0; | |
44 } else { | |
45 const int bit = (rb->bit_buffer[p] & (1 << q)) >> q; | |
46 rb->bit_offset = off + 1; | |
47 return bit; | |
48 } | |
49 } | |
50 | 36 |
51 static int vp9_rb_read_literal(struct vp9_read_bit_buffer *rb, int bits) { | 37 int vp9_rb_read_literal(struct vp9_read_bit_buffer *rb, int bits); |
52 int value = 0, bit; | |
53 for (bit = bits - 1; bit >= 0; bit--) | |
54 value |= vp9_rb_read_bit(rb) << bit; | |
55 return value; | |
56 } | |
57 | 38 |
58 static int vp9_rb_read_signed_literal(struct vp9_read_bit_buffer *rb, | 39 int vp9_rb_read_signed_literal(struct vp9_read_bit_buffer *rb, int bits); |
59 int bits) { | |
60 const int value = vp9_rb_read_literal(rb, bits); | |
61 return vp9_rb_read_bit(rb) ? -value : value; | |
62 } | |
63 | 40 |
64 #ifdef __cplusplus | 41 #ifdef __cplusplus |
65 } // extern "C" | 42 } // extern "C" |
66 #endif | 43 #endif |
67 | 44 |
68 #endif // VP9_DECODER_VP9_READ_BIT_BUFFER_H_ | 45 #endif // VP9_DECODER_VP9_READ_BIT_BUFFER_H_ |
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