1// Copyright 2011 Google Inc. All Rights Reserved.
2//
3// Use of this source code is governed by a BSD-style license
4// that can be found in the COPYING file in the root of the source
5// tree. An additional intellectual property rights grant can be found
6// in the file PATENTS. All contributing project authors may
7// be found in the AUTHORS file in the root of the source tree.
8// -----------------------------------------------------------------------------
9//
10// Bit writing and boolean coder
11//
12// Author: Skal (pascal.massimino@gmail.com)
13
14#ifndef WEBP_UTILS_BIT_WRITER_H_
15#define WEBP_UTILS_BIT_WRITER_H_
16
17#include "../webp/types.h"
18
19#ifdef __cplusplus
20extern "C" {
21#endif
22
23//------------------------------------------------------------------------------
24// Bit-writing
25
26typedef struct VP8BitWriter VP8BitWriter;
27struct VP8BitWriter {
28 int32_t range_; // range-1
29 int32_t value_;
30 int run_; // number of outstanding bits
31 int nb_bits_; // number of pending bits
32 uint8_t* buf_; // internal buffer. Re-allocated regularly. Not owned.
33 size_t pos_;
34 size_t max_pos_;
35 int error_; // true in case of error
36};
37
38// Initialize the object. Allocates some initial memory based on expected_size.
39int VP8BitWriterInit(VP8BitWriter* const bw, size_t expected_size);
40// Finalize the bitstream coding. Returns a pointer to the internal buffer.
41uint8_t* VP8BitWriterFinish(VP8BitWriter* const bw);
42// Release any pending memory and zeroes the object. Not a mandatory call.
43// Only useful in case of error, when the internal buffer hasn't been grabbed!
44void VP8BitWriterWipeOut(VP8BitWriter* const bw);
45
46int VP8PutBit(VP8BitWriter* const bw, int bit, int prob);
47int VP8PutBitUniform(VP8BitWriter* const bw, int bit);
48void VP8PutBits(VP8BitWriter* const bw, uint32_t value, int nb_bits);
49void VP8PutSignedBits(VP8BitWriter* const bw, int value, int nb_bits);
50
51// Appends some bytes to the internal buffer. Data is copied.
52int VP8BitWriterAppend(VP8BitWriter* const bw,
53 const uint8_t* data, size_t size);
54
55// return approximate write position (in bits)
56static WEBP_INLINE uint64_t VP8BitWriterPos(const VP8BitWriter* const bw) {
57 const uint64_t nb_bits = 8 + bw->nb_bits_; // bw->nb_bits_ is <= 0, note
58 return (bw->pos_ + bw->run_) * 8 + nb_bits;
59}
60
61// Returns a pointer to the internal buffer.
62static WEBP_INLINE uint8_t* VP8BitWriterBuf(const VP8BitWriter* const bw) {
63 return bw->buf_;
64}
65// Returns the size of the internal buffer.
66static WEBP_INLINE size_t VP8BitWriterSize(const VP8BitWriter* const bw) {
67 return bw->pos_;
68}
69
70//------------------------------------------------------------------------------
71// VP8LBitWriter
72
73#if defined(__x86_64__) || defined(_M_X64) // 64bit
74typedef uint64_t vp8l_atype_t; // accumulator type
75typedef uint32_t vp8l_wtype_t; // writing type
76#define WSWAP HToLE32
77#define VP8L_WRITER_BYTES 4 // sizeof(vp8l_wtype_t)
78#define VP8L_WRITER_BITS 32 // 8 * sizeof(vp8l_wtype_t)
79#define VP8L_WRITER_MAX_BITS 64 // 8 * sizeof(vp8l_atype_t)
80#else
81typedef uint32_t vp8l_atype_t;
82typedef uint16_t vp8l_wtype_t;
83#define WSWAP HToLE16
84#define VP8L_WRITER_BYTES 2
85#define VP8L_WRITER_BITS 16
86#define VP8L_WRITER_MAX_BITS 32
87#endif
88
89typedef struct {
90 vp8l_atype_t bits_; // bit accumulator
91 int used_; // number of bits used in accumulator
92 uint8_t* buf_; // start of buffer
93 uint8_t* cur_; // current write position
94 uint8_t* end_; // end of buffer
95
96 // After all bits are written (VP8LBitWriterFinish()), the caller must observe
97 // the state of error_. A value of 1 indicates that a memory allocation
98 // failure has happened during bit writing. A value of 0 indicates successful
99 // writing of bits.
100 int error_;
101} VP8LBitWriter;
102
103static WEBP_INLINE size_t VP8LBitWriterNumBytes(VP8LBitWriter* const bw) {
104 return (bw->cur_ - bw->buf_) + ((bw->used_ + 7) >> 3);
105}
106
107// Returns false in case of memory allocation error.
108int VP8LBitWriterInit(VP8LBitWriter* const bw, size_t expected_size);
109// Finalize the bitstream coding. Returns a pointer to the internal buffer.
110uint8_t* VP8LBitWriterFinish(VP8LBitWriter* const bw);
111// Release any pending memory and zeroes the object.
112void VP8LBitWriterWipeOut(VP8LBitWriter* const bw);
113
114// Internal function for VP8LPutBits flushing 32 bits from the written state.
115void VP8LPutBitsFlushBits(VP8LBitWriter* const bw);
116
117// PutBits internal function used in the 16 bit vp8l_wtype_t case.
118void VP8LPutBitsInternal(VP8LBitWriter* const bw, uint32_t bits, int n_bits);
119
120// This function writes bits into bytes in increasing addresses (little endian),
121// and within a byte least-significant-bit first.
122// This function can write up to 32 bits in one go, but VP8LBitReader can only
123// read 24 bits max (VP8L_MAX_NUM_BIT_READ).
124// VP8LBitWriter's error_ flag is set in case of memory allocation error.
125static WEBP_INLINE void VP8LPutBits(VP8LBitWriter* const bw,
126 uint32_t bits, int n_bits) {
127 if (sizeof(vp8l_wtype_t) == 4) {
128 if (n_bits > 0) {
129 if (bw->used_ >= 32) {
130 VP8LPutBitsFlushBits(bw);
131 }
132 bw->bits_ |= (vp8l_atype_t)bits << bw->used_;
133 bw->used_ += n_bits;
134 }
135 } else {
136 VP8LPutBitsInternal(bw, bits, n_bits);
137 }
138}
139
140//------------------------------------------------------------------------------
141
142#ifdef __cplusplus
143} // extern "C"
144#endif
145
146#endif /* WEBP_UTILS_BIT_WRITER_H_ */
147