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 #ifndef VP9_DECODER_VP9_READ_BIT_BUFFER_H_ 12 #define VP9_DECODER_VP9_READ_BIT_BUFFER_H_ 13 14 #include <limits.h> 15 16 #include "vpx/vpx_integer.h" 17 18 typedef void (*vp9_rb_error_handler)(void *data, size_t bit_offset); 19 20 struct vp9_read_bit_buffer { 21 const uint8_t *bit_buffer; 22 const uint8_t *bit_buffer_end; 23 size_t bit_offset; 24 25 void *error_handler_data; 26 vp9_rb_error_handler error_handler; 27 }; 28 29 static size_t vp9_rb_bytes_read(struct vp9_read_bit_buffer *rb) { 30 return rb->bit_offset / CHAR_BIT + (rb->bit_offset % CHAR_BIT > 0); 31 } 32 33 static int vp9_rb_read_bit(struct vp9_read_bit_buffer *rb) { 34 const size_t off = rb->bit_offset; 35 const size_t p = off / CHAR_BIT; 36 const int q = CHAR_BIT - 1 - (int)off % CHAR_BIT; 37 if (rb->bit_buffer + p >= rb->bit_buffer_end) { 38 rb->error_handler(rb->error_handler_data, rb->bit_offset); 39 return 0; 40 } else { 41 const int bit = (rb->bit_buffer[p] & (1 << q)) >> q; 42 rb->bit_offset = off + 1; 43 return bit; 44 } 45 } 46 47 static int vp9_rb_read_literal(struct vp9_read_bit_buffer *rb, int bits) { 48 int value = 0, bit; 49 for (bit = bits - 1; bit >= 0; bit--) 50 value |= vp9_rb_read_bit(rb) << bit; 51 return value; 52 } 53 54 static int vp9_rb_read_signed_literal(struct vp9_read_bit_buffer *rb, 55 int bits) { 56 const int value = vp9_rb_read_literal(rb, bits); 57 return vp9_rb_read_bit(rb) ? -value : value; 58 } 59 60 #endif // VP9_DECODER_VP9_READ_BIT_BUFFER_H_ 61
