1/*
2 *  Copyright (c) 2010 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_ENCODER_VP9_WRITER_H_
12#define VP9_ENCODER_VP9_WRITER_H_
13
14#include "vpx_ports/mem.h"
15
16#include "vp9/common/vp9_prob.h"
17
18#ifdef __cplusplus
19extern "C" {
20#endif
21
22typedef struct {
23  unsigned int lowvalue;
24  unsigned int range;
25  int count;
26  unsigned int pos;
27  uint8_t *buffer;
28} vp9_writer;
29
30void vp9_start_encode(vp9_writer *bc, uint8_t *buffer);
31void vp9_stop_encode(vp9_writer *bc);
32
33static INLINE void vp9_write(vp9_writer *br, int bit, int probability) {
34  unsigned int split;
35  int count = br->count;
36  unsigned int range = br->range;
37  unsigned int lowvalue = br->lowvalue;
38  register unsigned int shift;
39
40  split = 1 + (((range - 1) * probability) >> 8);
41
42  range = split;
43
44  if (bit) {
45    lowvalue += split;
46    range = br->range - split;
47  }
48
49  shift = vp9_norm[range];
50
51  range <<= shift;
52  count += shift;
53
54  if (count >= 0) {
55    int offset = shift - count;
56
57    if ((lowvalue << (offset - 1)) & 0x80000000) {
58      int x = br->pos - 1;
59
60      while (x >= 0 && br->buffer[x] == 0xff) {
61        br->buffer[x] = 0;
62        x--;
63      }
64
65      br->buffer[x] += 1;
66    }
67
68    br->buffer[br->pos++] = (lowvalue >> (24 - offset));
69    lowvalue <<= offset;
70    shift = count;
71    lowvalue &= 0xffffff;
72    count -= 8;
73  }
74
75  lowvalue <<= shift;
76  br->count = count;
77  br->lowvalue = lowvalue;
78  br->range = range;
79}
80
81static INLINE void vp9_write_bit(vp9_writer *w, int bit) {
82  vp9_write(w, bit, 128);  // vp9_prob_half
83}
84
85static INLINE void vp9_write_literal(vp9_writer *w, int data, int bits) {
86  int bit;
87
88  for (bit = bits - 1; bit >= 0; bit--)
89    vp9_write_bit(w, 1 & (data >> bit));
90}
91
92#define vp9_write_prob(w, v) vp9_write_literal((w), (v), 8)
93
94#ifdef __cplusplus
95}  // extern "C"
96#endif
97
98#endif  // VP9_ENCODER_VP9_WRITER_H_
99