summaryrefslogtreecommitdiffstats
path: root/media/libwebp/src/utils/bit_reader_utils.c
blob: 857cd6098882ef096ea9d2c59f9e720c1b755e17 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
// Copyright 2010 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING 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.
// -----------------------------------------------------------------------------
//
// Boolean decoder non-inlined methods
//
// Author: Skal (pascal.massimino@gmail.com)

#ifdef HAVE_CONFIG_H
#include "src/webp/config.h"
#endif

#include "src/utils/bit_reader_inl_utils.h"
#include "src/utils/utils.h"

//------------------------------------------------------------------------------
// VP8BitReader

void VP8BitReaderSetBuffer(VP8BitReader* const br,
                           const uint8_t* const start,
                           size_t size) {
  br->buf_     = start;
  br->buf_end_ = start + size;
  br->buf_max_ =
      (size >= sizeof(lbit_t)) ? start + size - sizeof(lbit_t) + 1
                               : start;
}

void VP8InitBitReader(VP8BitReader* const br,
                      const uint8_t* const start, size_t size) {
  assert(br != NULL);
  assert(start != NULL);
  assert(size < (1u << 31));   // limit ensured by format and upstream checks
  br->range_   = 255 - 1;
  br->value_   = 0;
  br->bits_    = -8;   // to load the very first 8bits
  br->eof_     = 0;
  VP8BitReaderSetBuffer(br, start, size);
  VP8LoadNewBytes(br);
}

void VP8RemapBitReader(VP8BitReader* const br, ptrdiff_t offset) {
  if (br->buf_ != NULL) {
    br->buf_ += offset;
    br->buf_end_ += offset;
    br->buf_max_ += offset;
  }
}

const uint8_t kVP8Log2Range[128] = {
     7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  0
};

// range = ((range - 1) << kVP8Log2Range[range]) + 1
const uint8_t kVP8NewRange[128] = {
  127, 127, 191, 127, 159, 191, 223, 127,
  143, 159, 175, 191, 207, 223, 239, 127,
  135, 143, 151, 159, 167, 175, 183, 191,
  199, 207, 215, 223, 231, 239, 247, 127,
  131, 135, 139, 143, 147, 151, 155, 159,
  163, 167, 171, 175, 179, 183, 187, 191,
  195, 199, 203, 207, 211, 215, 219, 223,
  227, 231, 235, 239, 243, 247, 251, 127,
  129, 131, 133, 135, 137, 139, 141, 143,
  145, 147, 149, 151, 153, 155, 157, 159,
  161, 163, 165, 167, 169, 171, 173, 175,
  177, 179, 181, 183, 185, 187, 189, 191,
  193, 195, 197, 199, 201, 203, 205, 207,
  209, 211, 213, 215, 217, 219, 221, 223,
  225, 227, 229, 231, 233, 235, 237, 239,
  241, 243, 245, 247, 249, 251, 253, 127
};

void VP8LoadFinalBytes(VP8BitReader* const br) {
  assert(br != NULL && br->buf_ != NULL);
  // Only read 8bits at a time
  if (br->buf_ < br->buf_end_) {
    br->bits_ += 8;
    br->value_ = (bit_t)(*br->buf_++) | (br->value_ << 8);
  } else if (!br->eof_) {
    br->value_ <<= 8;
    br->bits_ += 8;
    br->eof_ = 1;
  } else {
    br->bits_ = 0;  // This is to avoid undefined behaviour with shifts.
  }
}

//------------------------------------------------------------------------------
// Higher-level calls

uint32_t VP8GetValue(VP8BitReader* const br, int bits, const char label[]) {
  uint32_t v = 0;
  while (bits-- > 0) {
    v |= VP8GetBit(br, 0x80, label) << bits;
  }
  return v;
}

int32_t VP8GetSignedValue(VP8BitReader* const br, int bits,
                          const char label[]) {
  const int value = VP8GetValue(br, bits, label);
  return VP8Get(br, label) ? -value : value;
}

//------------------------------------------------------------------------------
// VP8LBitReader

#define VP8L_LOG8_WBITS 4  // Number of bytes needed to store VP8L_WBITS bits.

#if defined(__arm__) || defined(_M_ARM) || defined(__aarch64__) || \
    defined(__i386__) || defined(_M_IX86) || \
    defined(__x86_64__) || defined(_M_X64)
#define VP8L_USE_FAST_LOAD
#endif

static const uint32_t kBitMask[VP8L_MAX_NUM_BIT_READ + 1] = {
  0,
  0x000001, 0x000003, 0x000007, 0x00000f,
  0x00001f, 0x00003f, 0x00007f, 0x0000ff,
  0x0001ff, 0x0003ff, 0x0007ff, 0x000fff,
  0x001fff, 0x003fff, 0x007fff, 0x00ffff,
  0x01ffff, 0x03ffff, 0x07ffff, 0x0fffff,
  0x1fffff, 0x3fffff, 0x7fffff, 0xffffff
};

void VP8LInitBitReader(VP8LBitReader* const br, const uint8_t* const start,
                       size_t length) {
  size_t i;
  vp8l_val_t value = 0;
  assert(br != NULL);
  assert(start != NULL);
  assert(length < 0xfffffff8u);   // can't happen with a RIFF chunk.

  br->len_ = length;
  br->val_ = 0;
  br->bit_pos_ = 0;
  br->eos_ = 0;

  if (length > sizeof(br->val_)) {
    length = sizeof(br->val_);
  }
  for (i = 0; i < length; ++i) {
    value |= (vp8l_val_t)start[i] << (8 * i);
  }
  br->val_ = value;
  br->pos_ = length;
  br->buf_ = start;
}

void VP8LBitReaderSetBuffer(VP8LBitReader* const br,
                            const uint8_t* const buf, size_t len) {
  assert(br != NULL);
  assert(buf != NULL);
  assert(len < 0xfffffff8u);   // can't happen with a RIFF chunk.
  br->buf_ = buf;
  br->len_ = len;
  // pos_ > len_ should be considered a param error.
  br->eos_ = (br->pos_ > br->len_) || VP8LIsEndOfStream(br);
}

static void VP8LSetEndOfStream(VP8LBitReader* const br) {
  br->eos_ = 1;
  br->bit_pos_ = 0;  // To avoid undefined behaviour with shifts.
}

// If not at EOS, reload up to VP8L_LBITS byte-by-byte
static void ShiftBytes(VP8LBitReader* const br) {
  while (br->bit_pos_ >= 8 && br->pos_ < br->len_) {
    br->val_ >>= 8;
    br->val_ |= ((vp8l_val_t)br->buf_[br->pos_]) << (VP8L_LBITS - 8);
    ++br->pos_;
    br->bit_pos_ -= 8;
  }
  if (VP8LIsEndOfStream(br)) {
    VP8LSetEndOfStream(br);
  }
}

void VP8LDoFillBitWindow(VP8LBitReader* const br) {
  assert(br->bit_pos_ >= VP8L_WBITS);
#if defined(VP8L_USE_FAST_LOAD)
  if (br->pos_ + sizeof(br->val_) < br->len_) {
    br->val_ >>= VP8L_WBITS;
    br->bit_pos_ -= VP8L_WBITS;
    br->val_ |= (vp8l_val_t)HToLE32(WebPMemToUint32(br->buf_ + br->pos_)) <<
                (VP8L_LBITS - VP8L_WBITS);
    br->pos_ += VP8L_LOG8_WBITS;
    return;
  }
#endif
  ShiftBytes(br);       // Slow path.
}

uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits) {
  assert(n_bits >= 0);
  // Flag an error if end_of_stream or n_bits is more than allowed limit.
  if (!br->eos_ && n_bits <= VP8L_MAX_NUM_BIT_READ) {
    const uint32_t val = VP8LPrefetchBits(br) & kBitMask[n_bits];
    const int new_bits = br->bit_pos_ + n_bits;
    br->bit_pos_ = new_bits;
    ShiftBytes(br);
    return val;
  } else {
    VP8LSetEndOfStream(br);
    return 0;
  }
}

//------------------------------------------------------------------------------
// Bit-tracing tool

#if (BITTRACE > 0)

#include <stdlib.h>   // for atexit()
#include <stdio.h>
#include <string.h>

#define MAX_NUM_LABELS 32
static struct {
  const char* label;
  int size;
  int count;
} kLabels[MAX_NUM_LABELS];

static int last_label = 0;
static int last_pos = 0;
static const uint8_t* buf_start = NULL;
static int init_done = 0;

static void PrintBitTraces(void) {
  int i;
  int scale = 1;
  int total = 0;
  const char* units = "bits";
#if (BITTRACE == 2)
  scale = 8;
  units = "bytes";
#endif
  for (i = 0; i < last_label; ++i) total += kLabels[i].size;
  if (total < 1) total = 1;   // avoid rounding errors
  printf("=== Bit traces ===\n");
  for (i = 0; i < last_label; ++i) {
    const int skip = 16 - (int)strlen(kLabels[i].label);
    const int value = (kLabels[i].size + scale - 1) / scale;
    assert(skip > 0);
    printf("%s \%*s: %6d %s   \t[%5.2f%%] [count: %7d]\n",
           kLabels[i].label, skip, "", value, units,
           100.f * kLabels[i].size / total,
           kLabels[i].count);
  }
  total = (total + scale - 1) / scale;
  printf("Total: %d %s\n", total, units);
}

void BitTrace(const struct VP8BitReader* const br, const char label[]) {
  int i, pos;
  if (!init_done) {
    memset(kLabels, 0, sizeof(kLabels));
    atexit(PrintBitTraces);
    buf_start = br->buf_;
    init_done = 1;
  }
  pos = (int)(br->buf_ - buf_start) * 8 - br->bits_;
  // if there's a too large jump, we've changed partition -> reset counter
  if (abs(pos - last_pos) > 32) {
    buf_start = br->buf_;
    pos = 0;
    last_pos = 0;
  }
  if (br->range_ >= 0x7f) pos += kVP8Log2Range[br->range_ - 0x7f];
  for (i = 0; i < last_label; ++i) {
    if (!strcmp(label, kLabels[i].label)) break;
  }
  if (i == MAX_NUM_LABELS) abort();   // overflow!
  kLabels[i].label = label;
  kLabels[i].size += pos - last_pos;
  kLabels[i].count += 1;
  if (i == last_label) ++last_label;
  last_pos = pos;
}

#endif  // BITTRACE > 0

//------------------------------------------------------------------------------