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 /*

  *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.

  *

  *  Use of this source code is governed by a BSD-style license

  *  that can be found in the LICENSE file in the root of the source

  *  tree. An additional intellectual property rights grant can be found

  *  in the file PATENTS.  All contributing project authors may

  *  be found in the AUTHORS file in the root of the source tree.

  */

 #ifndef VP9_DECODER_VP9_READ_BIT_BUFFER_H_

 #define VP9_DECODER_VP9_READ_BIT_BUFFER_H_

 #include <limits.h>

 #include "vpx/vpx_integer.h"

 typedef void (*vp9_rb_error_handler)(void *data, size_t bit_offset);

 struct vp9_read_bit_buffer {

   const uint8_t *bit_buffer;

   const uint8_t *bit_buffer_end;

   size_t bit_offset;

   void *error_handler_data;

   vp9_rb_error_handler error_handler;

 };

 static size_t vp9_rb_bytes_read(struct vp9_read_bit_buffer *rb) {

   return rb->bit_offset / CHAR_BIT + (rb->bit_offset % CHAR_BIT > 0);

 }

 static int vp9_rb_read_bit(struct vp9_read_bit_buffer *rb) {

   const size_t off = rb->bit_offset;

   const size_t p = off / CHAR_BIT;

   const int q = CHAR_BIT - 1 - (int)off % CHAR_BIT;

   if (rb->bit_buffer + p >= rb->bit_buffer_end) {

     rb->error_handler(rb->error_handler_data, rb->bit_offset);

     return 0;

   } else {

     const int bit = (rb->bit_buffer[p] & (1 << q)) >> q;

     rb->bit_offset = off + 1;

     return bit;

   }

 }

 static int vp9_rb_read_literal(struct vp9_read_bit_buffer *rb, int bits) {

   int value = 0, bit;

   for (bit = bits - 1; bit >= 0; bit--)

     value |= vp9_rb_read_bit(rb) << bit;

   return value;

 }

 static int vp9_rb_read_signed_literal(struct vp9_read_bit_buffer *rb,

                                       int bits) {

   const int value = vp9_rb_read_literal(rb, bits);

   return vp9_rb_read_bit(rb) ? -value : value;

 }

 #endif  // VP9_DECODER_VP9_READ_BIT_BUFFER_H_