vpx_dsp/bitreader_buffer.c

   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 #include "./vpx_config.h"
  11 #include "./bitreader_buffer.h"
  12
  13 size_t vpx_rb_bytes_read(struct vpx_read_bit_buffer *rb) {
  14   return (rb->bit_offset + 7) >> 3;
  15 }
  16
  17 int vpx_rb_read_bit(struct vpx_read_bit_buffer *rb) {
  18   const size_t off = rb->bit_offset;
  19   const size_t p = off >> 3;
  20   const int q = 7 - (int)(off & 0x7);
  21   if (rb->bit_buffer + p < rb->bit_buffer_end) {
  22     const int bit = (rb->bit_buffer[p] >> q) & 1;
  23     rb->bit_offset = off + 1;
  24     return bit;
  25   } else {
  26     rb->error_handler(rb->error_handler_data);
  27     return 0;
  28   }
  29 }
  30
  31 int vpx_rb_read_literal(struct vpx_read_bit_buffer *rb, int bits) {
  32   int value = 0, bit;
  33   for (bit = bits - 1; bit >= 0; bit--)
  34     value |= vpx_rb_read_bit(rb) << bit;
  35   return value;
  36 }
  37
  38 int vpx_rb_read_signed_literal(struct vpx_read_bit_buffer *rb,
  39                                int bits) {
  40   const int value = vpx_rb_read_literal(rb, bits);
  41   return vpx_rb_read_bit(rb) ? -value : value;
  42 }
  43
  44 int vpx_rb_read_inv_signed_literal(struct vpx_read_bit_buffer *rb,
  45                                    int bits) {
  46 #if CONFIG_MISC_FIXES
  47   const int nbits = sizeof(unsigned) * 8 - bits - 1;
  48   const unsigned value = (unsigned)vpx_rb_read_literal(rb, bits + 1) << nbits;
  49   return ((int) value) >> nbits;
  50 #else
  51   return vpx_rb_read_signed_literal(rb, bits);
  52 #endif
  53 }