2 * Copyright (c) 2010 The WebM project authors. All Rights Reserved.
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.
11 #ifndef VPX_DSP_BITWRITER_H_
12 #define VPX_DSP_BITWRITER_H_
14 #include "vpx_ports/mem.h"
16 #include "vpx_dsp/prob.h"
22 typedef struct vpx_writer {
23 unsigned int lowvalue;
30 void vpx_start_encode(vpx_writer *bc, uint8_t *buffer);
31 void vpx_stop_encode(vpx_writer *bc);
33 static INLINE void vpx_write(vpx_writer *br, int bit, int probability) {
35 int count = br->count;
36 unsigned int range = br->range;
37 unsigned int lowvalue = br->lowvalue;
40 split = 1 + (((range - 1) * probability) >> 8);
46 range = br->range - split;
49 shift = vpx_norm[range];
55 int offset = shift - count;
57 if ((lowvalue << (offset - 1)) & 0x80000000) {
60 while (x >= 0 && br->buffer[x] == 0xff) {
68 br->buffer[br->pos++] = (lowvalue >> (24 - offset));
77 br->lowvalue = lowvalue;
81 static INLINE void vpx_write_bit(vpx_writer *w, int bit) {
82 vpx_write(w, bit, 128); // vpx_prob_half
85 static INLINE void vpx_write_literal(vpx_writer *w, int data, int bits) {
88 for (bit = bits - 1; bit >= 0; bit--) vpx_write_bit(w, 1 & (data >> bit));
91 #define vpx_write_prob(w, v) vpx_write_literal((w), (v), 8)
97 #endif // VPX_DSP_BITWRITER_H_