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
20 extern "C" {
21 #endif
22
23 //------------------------------------------------------------------------------
24 // Bit-writing
25
26 typedef struct VP8BitWriter VP8BitWriter;
27 struct 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.
39 int VP8BitWriterInit(VP8BitWriter* const bw, size_t expected_size);
40 // Finalize the bitstream coding. Returns a pointer to the internal buffer.
41 uint8_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!
44 void VP8BitWriterWipeOut(VP8BitWriter* const bw);
45
46 int VP8PutBit(VP8BitWriter* const bw, int bit, int prob);
47 int VP8PutBitUniform(VP8BitWriter* const bw, int bit);
48 void VP8PutBits(VP8BitWriter* const bw, uint32_t value, int nb_bits);
49 void VP8PutSignedBits(VP8BitWriter* const bw, int value, int nb_bits);
50
51 // Appends some bytes to the internal buffer. Data is copied.
52 int VP8BitWriterAppend(VP8BitWriter* const bw,
53 const uint8_t* data, size_t size);
54
55 // return approximate write position (in bits)
VP8BitWriterPos(const VP8BitWriter * const bw)56 static 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.
VP8BitWriterBuf(const VP8BitWriter * const bw)62 static WEBP_INLINE uint8_t* VP8BitWriterBuf(const VP8BitWriter* const bw) {
63 return bw->buf_;
64 }
65 // Returns the size of the internal buffer.
VP8BitWriterSize(const VP8BitWriter * const bw)66 static 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
74 typedef uint64_t vp8l_atype_t; // accumulator type
75 typedef 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
81 typedef uint32_t vp8l_atype_t;
82 typedef 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
89 typedef 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
VP8LBitWriterNumBytes(VP8LBitWriter * const bw)103 static 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.
108 int VP8LBitWriterInit(VP8LBitWriter* const bw, size_t expected_size);
109 // Finalize the bitstream coding. Returns a pointer to the internal buffer.
110 uint8_t* VP8LBitWriterFinish(VP8LBitWriter* const bw);
111 // Release any pending memory and zeroes the object.
112 void VP8LBitWriterWipeOut(VP8LBitWriter* const bw);
113
114 // Internal function for VP8LPutBits flushing 32 bits from the written state.
115 void VP8LPutBitsFlushBits(VP8LBitWriter* const bw);
116
117 // PutBits internal function used in the 16 bit vp8l_wtype_t case.
118 void 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.
VP8LPutBits(VP8LBitWriter * const bw,uint32_t bits,int n_bits)125 static 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