Source code
Revision control
Copy as Markdown
Other Tools
// Copyright 2011 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.
// -----------------------------------------------------------------------------
//
// Bit writing and boolean coder
//
// Author: Skal (pascal.massimino@gmail.com)
// Vikas Arora (vikaas.arora@gmail.com)
#include <assert.h>
#include <string.h> // for memcpy()
#include <stdlib.h>
#include "src/utils/bit_writer_utils.h"
#include "src/utils/endian_inl_utils.h"
#include "src/utils/utils.h"
//------------------------------------------------------------------------------
// VP8BitWriter
static int BitWriterResize(VP8BitWriter* const bw, size_t extra_size) {
uint8_t* new_buf;
size_t new_size;
const uint64_t needed_size_64b = (uint64_t)bw->pos_ + extra_size;
const size_t needed_size = (size_t)needed_size_64b;
if (needed_size_64b != needed_size) {
bw->error_ = 1;
return 0;
}
if (needed_size <= bw->max_pos_) return 1;
// If the following line wraps over 32bit, the test just after will catch it.
new_size = 2 * bw->max_pos_;
if (new_size < needed_size) new_size = needed_size;
if (new_size < 1024) new_size = 1024;
new_buf = (uint8_t*)WebPSafeMalloc(1ULL, new_size);
if (new_buf == NULL) {
bw->error_ = 1;
return 0;
}
if (bw->pos_ > 0) {
assert(bw->buf_ != NULL);
memcpy(new_buf, bw->buf_, bw->pos_);
}
WebPSafeFree(bw->buf_);
bw->buf_ = new_buf;
bw->max_pos_ = new_size;
return 1;
}
static void Flush(VP8BitWriter* const bw) {
const int s = 8 + bw->nb_bits_;
const int32_t bits = bw->value_ >> s;
assert(bw->nb_bits_ >= 0);
bw->value_ -= bits << s;
bw->nb_bits_ -= 8;
if ((bits & 0xff) != 0xff) {
size_t pos = bw->pos_;
if (!BitWriterResize(bw, bw->run_ + 1)) {
return;
}
if (bits & 0x100) { // overflow -> propagate carry over pending 0xff's
if (pos > 0) bw->buf_[pos - 1]++;
}
if (bw->run_ > 0) {
const int value = (bits & 0x100) ? 0x00 : 0xff;
for (; bw->run_ > 0; --bw->run_) bw->buf_[pos++] = value;
}
bw->buf_[pos++] = bits & 0xff;
bw->pos_ = pos;
} else {
bw->run_++; // delay writing of bytes 0xff, pending eventual carry.
}
}
//------------------------------------------------------------------------------
// renormalization
static const uint8_t kNorm[128] = { // renorm_sizes[i] = 8 - log2(i)
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
static const uint8_t kNewRange[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
};
int VP8PutBit(VP8BitWriter* const bw, int bit, int prob) {
const int split = (bw->range_ * prob) >> 8;
if (bit) {
bw->value_ += split + 1;
bw->range_ -= split + 1;
} else {
bw->range_ = split;
}
if (bw->range_ < 127) { // emit 'shift' bits out and renormalize
const int shift = kNorm[bw->range_];
bw->range_ = kNewRange[bw->range_];
bw->value_ <<= shift;
bw->nb_bits_ += shift;
if (bw->nb_bits_ > 0) Flush(bw);
}
return bit;
}
int VP8PutBitUniform(VP8BitWriter* const bw, int bit) {
const int split = bw->range_ >> 1;
if (bit) {
bw->value_ += split + 1;
bw->range_ -= split + 1;
} else {
bw->range_ = split;
}
if (bw->range_ < 127) {
bw->range_ = kNewRange[bw->range_];
bw->value_ <<= 1;
bw->nb_bits_ += 1;
if (bw->nb_bits_ > 0) Flush(bw);
}
return bit;
}
void VP8PutBits(VP8BitWriter* const bw, uint32_t value, int nb_bits) {
uint32_t mask;
assert(nb_bits > 0 && nb_bits < 32);
for (mask = 1u << (nb_bits - 1); mask; mask >>= 1) {
VP8PutBitUniform(bw, value & mask);
}
}
void VP8PutSignedBits(VP8BitWriter* const bw, int value, int nb_bits) {
if (!VP8PutBitUniform(bw, value != 0)) return;
if (value < 0) {
VP8PutBits(bw, ((-value) << 1) | 1, nb_bits + 1);
} else {
VP8PutBits(bw, value << 1, nb_bits + 1);
}
}
//------------------------------------------------------------------------------
int VP8BitWriterInit(VP8BitWriter* const bw, size_t expected_size) {
bw->range_ = 255 - 1;
bw->value_ = 0;
bw->run_ = 0;
bw->nb_bits_ = -8;
bw->pos_ = 0;
bw->max_pos_ = 0;
bw->error_ = 0;
bw->buf_ = NULL;
return (expected_size > 0) ? BitWriterResize(bw, expected_size) : 1;
}
uint8_t* VP8BitWriterFinish(VP8BitWriter* const bw) {
VP8PutBits(bw, 0, 9 - bw->nb_bits_);
bw->nb_bits_ = 0; // pad with zeroes
Flush(bw);
return bw->buf_;
}
int VP8BitWriterAppend(VP8BitWriter* const bw,
const uint8_t* data, size_t size) {
assert(data != NULL);
if (bw->nb_bits_ != -8) return 0; // Flush() must have been called
if (!BitWriterResize(bw, size)) return 0;
memcpy(bw->buf_ + bw->pos_, data, size);
bw->pos_ += size;
return 1;
}
void VP8BitWriterWipeOut(VP8BitWriter* const bw) {
if (bw != NULL) {
WebPSafeFree(bw->buf_);
memset(bw, 0, sizeof(*bw));
}
}
//------------------------------------------------------------------------------
// VP8LBitWriter
// This is the minimum amount of size the memory buffer is guaranteed to grow
// when extra space is needed.
#define MIN_EXTRA_SIZE (32768ULL)
// Returns 1 on success.
static int VP8LBitWriterResize(VP8LBitWriter* const bw, size_t extra_size) {
uint8_t* allocated_buf;
size_t allocated_size;
const size_t max_bytes = bw->end_ - bw->buf_;
const size_t current_size = bw->cur_ - bw->buf_;
const uint64_t size_required_64b = (uint64_t)current_size + extra_size;
const size_t size_required = (size_t)size_required_64b;
if (size_required != size_required_64b) {
bw->error_ = 1;
return 0;
}
if (max_bytes > 0 && size_required <= max_bytes) return 1;
allocated_size = (3 * max_bytes) >> 1;
if (allocated_size < size_required) allocated_size = size_required;
// make allocated size multiple of 1k
allocated_size = (((allocated_size >> 10) + 1) << 10);
allocated_buf = (uint8_t*)WebPSafeMalloc(1ULL, allocated_size);
if (allocated_buf == NULL) {
bw->error_ = 1;
return 0;
}
if (current_size > 0) {
memcpy(allocated_buf, bw->buf_, current_size);
}
WebPSafeFree(bw->buf_);
bw->buf_ = allocated_buf;
bw->cur_ = bw->buf_ + current_size;
bw->end_ = bw->buf_ + allocated_size;
return 1;
}
int VP8LBitWriterInit(VP8LBitWriter* const bw, size_t expected_size) {
memset(bw, 0, sizeof(*bw));
return VP8LBitWriterResize(bw, expected_size);
}
int VP8LBitWriterClone(const VP8LBitWriter* const src,
VP8LBitWriter* const dst) {
const size_t current_size = src->cur_ - src->buf_;
assert(src->cur_ >= src->buf_ && src->cur_ <= src->end_);
if (!VP8LBitWriterResize(dst, current_size)) return 0;
memcpy(dst->buf_, src->buf_, current_size);
dst->bits_ = src->bits_;
dst->used_ = src->used_;
dst->error_ = src->error_;
dst->cur_ = dst->buf_ + current_size;
return 1;
}
void VP8LBitWriterWipeOut(VP8LBitWriter* const bw) {
if (bw != NULL) {
WebPSafeFree(bw->buf_);
memset(bw, 0, sizeof(*bw));
}
}
void VP8LBitWriterReset(const VP8LBitWriter* const bw_init,
VP8LBitWriter* const bw) {
bw->bits_ = bw_init->bits_;
bw->used_ = bw_init->used_;
bw->cur_ = bw->buf_ + (bw_init->cur_ - bw_init->buf_);
assert(bw->cur_ <= bw->end_);
bw->error_ = bw_init->error_;
}
void VP8LBitWriterSwap(VP8LBitWriter* const src, VP8LBitWriter* const dst) {
const VP8LBitWriter tmp = *src;
*src = *dst;
*dst = tmp;
}
void VP8LPutBitsFlushBits(VP8LBitWriter* const bw) {
// If needed, make some room by flushing some bits out.
if (bw->cur_ + VP8L_WRITER_BYTES > bw->end_) {
const uint64_t extra_size = (bw->end_ - bw->buf_) + MIN_EXTRA_SIZE;
if (!CheckSizeOverflow(extra_size) ||
!VP8LBitWriterResize(bw, (size_t)extra_size)) {
bw->cur_ = bw->buf_;
bw->error_ = 1;
return;
}
}
*(vp8l_wtype_t*)bw->cur_ = (vp8l_wtype_t)WSWAP((vp8l_wtype_t)bw->bits_);
bw->cur_ += VP8L_WRITER_BYTES;
bw->bits_ >>= VP8L_WRITER_BITS;
bw->used_ -= VP8L_WRITER_BITS;
}
void VP8LPutBitsInternal(VP8LBitWriter* const bw, uint32_t bits, int n_bits) {
assert(n_bits <= 32);
// That's the max we can handle:
assert(sizeof(vp8l_wtype_t) == 2);
if (n_bits > 0) {
vp8l_atype_t lbits = bw->bits_;
int used = bw->used_;
// Special case of overflow handling for 32bit accumulator (2-steps flush).
#if VP8L_WRITER_BITS == 16
if (used + n_bits >= VP8L_WRITER_MAX_BITS) {
// Fill up all the VP8L_WRITER_MAX_BITS so it can be flushed out below.
const int shift = VP8L_WRITER_MAX_BITS - used;
lbits |= (vp8l_atype_t)bits << used;
used = VP8L_WRITER_MAX_BITS;
n_bits -= shift;
bits >>= shift;
assert(n_bits <= VP8L_WRITER_MAX_BITS);
}
#endif
// If needed, make some room by flushing some bits out.
while (used >= VP8L_WRITER_BITS) {
if (bw->cur_ + VP8L_WRITER_BYTES > bw->end_) {
const uint64_t extra_size = (bw->end_ - bw->buf_) + MIN_EXTRA_SIZE;
if (!CheckSizeOverflow(extra_size) ||
!VP8LBitWriterResize(bw, (size_t)extra_size)) {
bw->cur_ = bw->buf_;
bw->error_ = 1;
return;
}
}
*(vp8l_wtype_t*)bw->cur_ = (vp8l_wtype_t)WSWAP((vp8l_wtype_t)lbits);
bw->cur_ += VP8L_WRITER_BYTES;
lbits >>= VP8L_WRITER_BITS;
used -= VP8L_WRITER_BITS;
}
bw->bits_ = lbits | ((vp8l_atype_t)bits << used);
bw->used_ = used + n_bits;
}
}
uint8_t* VP8LBitWriterFinish(VP8LBitWriter* const bw) {
// flush leftover bits
if (VP8LBitWriterResize(bw, (bw->used_ + 7) >> 3)) {
while (bw->used_ > 0) {
*bw->cur_++ = (uint8_t)bw->bits_;
bw->bits_ >>= 8;
bw->used_ -= 8;
}
bw->used_ = 0;
}
return bw->buf_;
}
//------------------------------------------------------------------------------