michael@0: /*
michael@0:  *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
michael@0:  *
michael@0:  *  Use of this source code is governed by a BSD-style license
michael@0:  *  that can be found in the LICENSE file in the root of the source
michael@0:  *  tree. An additional intellectual property rights grant can be found
michael@0:  *  in the file PATENTS.  All contributing project authors may
michael@0:  *  be found in the AUTHORS file in the root of the source tree.
michael@0:  */
michael@0: 
michael@0: #ifndef VP9_DECODER_VP9_READ_BIT_BUFFER_H_
michael@0: #define VP9_DECODER_VP9_READ_BIT_BUFFER_H_
michael@0: 
michael@0: #include <limits.h>
michael@0: 
michael@0: #include "vpx/vpx_integer.h"
michael@0: 
michael@0: typedef void (*vp9_rb_error_handler)(void *data, size_t bit_offset);
michael@0: 
michael@0: struct vp9_read_bit_buffer {
michael@0:   const uint8_t *bit_buffer;
michael@0:   const uint8_t *bit_buffer_end;
michael@0:   size_t bit_offset;
michael@0: 
michael@0:   void *error_handler_data;
michael@0:   vp9_rb_error_handler error_handler;
michael@0: };
michael@0: 
michael@0: static size_t vp9_rb_bytes_read(struct vp9_read_bit_buffer *rb) {
michael@0:   return rb->bit_offset / CHAR_BIT + (rb->bit_offset % CHAR_BIT > 0);
michael@0: }
michael@0: 
michael@0: static int vp9_rb_read_bit(struct vp9_read_bit_buffer *rb) {
michael@0:   const size_t off = rb->bit_offset;
michael@0:   const size_t p = off / CHAR_BIT;
michael@0:   const int q = CHAR_BIT - 1 - (int)off % CHAR_BIT;
michael@0:   if (rb->bit_buffer + p >= rb->bit_buffer_end) {
michael@0:     rb->error_handler(rb->error_handler_data, rb->bit_offset);
michael@0:     return 0;
michael@0:   } else {
michael@0:     const int bit = (rb->bit_buffer[p] & (1 << q)) >> q;
michael@0:     rb->bit_offset = off + 1;
michael@0:     return bit;
michael@0:   }
michael@0: }
michael@0: 
michael@0: static int vp9_rb_read_literal(struct vp9_read_bit_buffer *rb, int bits) {
michael@0:   int value = 0, bit;
michael@0:   for (bit = bits - 1; bit >= 0; bit--)
michael@0:     value |= vp9_rb_read_bit(rb) << bit;
michael@0:   return value;
michael@0: }
michael@0: 
michael@0: static int vp9_rb_read_signed_literal(struct vp9_read_bit_buffer *rb,
michael@0:                                       int bits) {
michael@0:   const int value = vp9_rb_read_literal(rb, bits);
michael@0:   return vp9_rb_read_bit(rb) ? -value : value;
michael@0: }
michael@0: 
michael@0: #endif  // VP9_DECODER_VP9_READ_BIT_BUFFER_H_