shithub: libvpx

ref: 3bda634576e14c67f692d0c3a9654b765ba40868
dir: /vpx_dsp/bitreader_buffer.c/

/*
 *  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.
 */
#include "./vpx_config.h"
#include "./bitreader_buffer.h"

size_t vpx_rb_bytes_read(struct vpx_read_bit_buffer *rb) {
  return (rb->bit_offset + 7) >> 3;
}

int vpx_rb_read_bit(struct vpx_read_bit_buffer *rb) {
  const size_t off = rb->bit_offset;
  const size_t p = off >> 3;
  const int q = 7 - (int)(off & 0x7);
  if (rb->bit_buffer + p < rb->bit_buffer_end) {
    const int bit = (rb->bit_buffer[p] >> q) & 1;
    rb->bit_offset = off + 1;
    return bit;
  } else {
    rb->error_handler(rb->error_handler_data);
    return 0;
  }
}

int vpx_rb_read_literal(struct vpx_read_bit_buffer *rb, int bits) {
  int value = 0, bit;
  for (bit = bits - 1; bit >= 0; bit--) value |= vpx_rb_read_bit(rb) << bit;
  return value;
}

int vpx_rb_read_signed_literal(struct vpx_read_bit_buffer *rb, int bits) {
  const int value = vpx_rb_read_literal(rb, bits);
  return vpx_rb_read_bit(rb) ? -value : value;
}

int vpx_rb_read_inv_signed_literal(struct vpx_read_bit_buffer *rb, int bits) {
#if CONFIG_MISC_FIXES
  const int nbits = sizeof(unsigned) * 8 - bits - 1;
  const unsigned value = (unsigned)vpx_rb_read_literal(rb, bits + 1) << nbits;
  return ((int)value) >> nbits;
#else
  return vpx_rb_read_signed_literal(rb, bits);
#endif
}