283 lines
8.7 KiB
C
283 lines
8.7 KiB
C
// Copyright 2011 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Bit writing and boolean coder
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//
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// Author: Skal (pascal.massimino@gmail.com)
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// Vikas Arora (vikaas.arora@gmail.com)
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#include <assert.h>
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#include <string.h> // for memcpy()
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#include <stdlib.h>
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#include "./bit_writer.h"
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//------------------------------------------------------------------------------
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// VP8BitWriter
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static int BitWriterResize(VP8BitWriter* const bw, size_t extra_size) {
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uint8_t* new_buf;
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size_t new_size;
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const uint64_t needed_size_64b = (uint64_t)bw->pos_ + extra_size;
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const size_t needed_size = (size_t)needed_size_64b;
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if (needed_size_64b != needed_size) {
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bw->error_ = 1;
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return 0;
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}
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if (needed_size <= bw->max_pos_) return 1;
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// If the following line wraps over 32bit, the test just after will catch it.
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new_size = 2 * bw->max_pos_;
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if (new_size < needed_size) new_size = needed_size;
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if (new_size < 1024) new_size = 1024;
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new_buf = (uint8_t*)malloc(new_size);
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if (new_buf == NULL) {
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bw->error_ = 1;
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return 0;
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}
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if (bw->pos_ > 0) {
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assert(bw->buf_ != NULL);
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memcpy(new_buf, bw->buf_, bw->pos_);
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}
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free(bw->buf_);
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bw->buf_ = new_buf;
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bw->max_pos_ = new_size;
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return 1;
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}
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static void kFlush(VP8BitWriter* const bw) {
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const int s = 8 + bw->nb_bits_;
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const int32_t bits = bw->value_ >> s;
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assert(bw->nb_bits_ >= 0);
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bw->value_ -= bits << s;
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bw->nb_bits_ -= 8;
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if ((bits & 0xff) != 0xff) {
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size_t pos = bw->pos_;
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if (!BitWriterResize(bw, bw->run_ + 1)) {
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return;
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}
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if (bits & 0x100) { // overflow -> propagate carry over pending 0xff's
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if (pos > 0) bw->buf_[pos - 1]++;
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}
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if (bw->run_ > 0) {
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const int value = (bits & 0x100) ? 0x00 : 0xff;
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for (; bw->run_ > 0; --bw->run_) bw->buf_[pos++] = value;
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}
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bw->buf_[pos++] = bits;
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bw->pos_ = pos;
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} else {
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bw->run_++; // delay writing of bytes 0xff, pending eventual carry.
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}
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}
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//------------------------------------------------------------------------------
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// renormalization
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static const uint8_t kNorm[128] = { // renorm_sizes[i] = 8 - log2(i)
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7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
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3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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0
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};
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// range = ((range + 1) << kVP8Log2Range[range]) - 1
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static const uint8_t kNewRange[128] = {
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127, 127, 191, 127, 159, 191, 223, 127, 143, 159, 175, 191, 207, 223, 239,
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127, 135, 143, 151, 159, 167, 175, 183, 191, 199, 207, 215, 223, 231, 239,
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247, 127, 131, 135, 139, 143, 147, 151, 155, 159, 163, 167, 171, 175, 179,
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183, 187, 191, 195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239,
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243, 247, 251, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149,
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151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179,
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181, 183, 185, 187, 189, 191, 193, 195, 197, 199, 201, 203, 205, 207, 209,
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211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 235, 237, 239,
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241, 243, 245, 247, 249, 251, 253, 127
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};
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int VP8PutBit(VP8BitWriter* const bw, int bit, int prob) {
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const int split = (bw->range_ * prob) >> 8;
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if (bit) {
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bw->value_ += split + 1;
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bw->range_ -= split + 1;
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} else {
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bw->range_ = split;
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}
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if (bw->range_ < 127) { // emit 'shift' bits out and renormalize
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const int shift = kNorm[bw->range_];
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bw->range_ = kNewRange[bw->range_];
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bw->value_ <<= shift;
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bw->nb_bits_ += shift;
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if (bw->nb_bits_ > 0) kFlush(bw);
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}
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return bit;
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}
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int VP8PutBitUniform(VP8BitWriter* const bw, int bit) {
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const int split = bw->range_ >> 1;
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if (bit) {
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bw->value_ += split + 1;
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bw->range_ -= split + 1;
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} else {
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bw->range_ = split;
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}
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if (bw->range_ < 127) {
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bw->range_ = kNewRange[bw->range_];
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bw->value_ <<= 1;
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bw->nb_bits_ += 1;
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if (bw->nb_bits_ > 0) kFlush(bw);
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}
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return bit;
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}
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void VP8PutValue(VP8BitWriter* const bw, int value, int nb_bits) {
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int mask;
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for (mask = 1 << (nb_bits - 1); mask; mask >>= 1)
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VP8PutBitUniform(bw, value & mask);
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}
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void VP8PutSignedValue(VP8BitWriter* const bw, int value, int nb_bits) {
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if (!VP8PutBitUniform(bw, value != 0))
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return;
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if (value < 0) {
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VP8PutValue(bw, ((-value) << 1) | 1, nb_bits + 1);
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} else {
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VP8PutValue(bw, value << 1, nb_bits + 1);
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}
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}
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//------------------------------------------------------------------------------
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int VP8BitWriterInit(VP8BitWriter* const bw, size_t expected_size) {
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bw->range_ = 255 - 1;
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bw->value_ = 0;
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bw->run_ = 0;
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bw->nb_bits_ = -8;
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bw->pos_ = 0;
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bw->max_pos_ = 0;
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bw->error_ = 0;
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bw->buf_ = NULL;
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return (expected_size > 0) ? BitWriterResize(bw, expected_size) : 1;
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}
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uint8_t* VP8BitWriterFinish(VP8BitWriter* const bw) {
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VP8PutValue(bw, 0, 9 - bw->nb_bits_);
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bw->nb_bits_ = 0; // pad with zeroes
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kFlush(bw);
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return bw->buf_;
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}
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int VP8BitWriterAppend(VP8BitWriter* const bw,
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const uint8_t* data, size_t size) {
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assert(data);
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if (bw->nb_bits_ != -8) return 0; // kFlush() must have been called
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if (!BitWriterResize(bw, size)) return 0;
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memcpy(bw->buf_ + bw->pos_, data, size);
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bw->pos_ += size;
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return 1;
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}
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void VP8BitWriterWipeOut(VP8BitWriter* const bw) {
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if (bw) {
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free(bw->buf_);
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memset(bw, 0, sizeof(*bw));
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}
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}
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//------------------------------------------------------------------------------
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// VP8LBitWriter
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// Returns 1 on success.
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static int VP8LBitWriterResize(VP8LBitWriter* const bw, size_t extra_size) {
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uint8_t* allocated_buf;
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size_t allocated_size;
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const size_t current_size = VP8LBitWriterNumBytes(bw);
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const uint64_t size_required_64b = (uint64_t)current_size + extra_size;
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const size_t size_required = (size_t)size_required_64b;
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if (size_required != size_required_64b) {
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bw->error_ = 1;
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return 0;
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}
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if (bw->max_bytes_ > 0 && size_required <= bw->max_bytes_) return 1;
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allocated_size = (3 * bw->max_bytes_) >> 1;
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if (allocated_size < size_required) allocated_size = size_required;
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// make allocated size multiple of 1k
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allocated_size = (((allocated_size >> 10) + 1) << 10);
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allocated_buf = (uint8_t*)malloc(allocated_size);
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if (allocated_buf == NULL) {
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bw->error_ = 1;
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return 0;
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}
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memcpy(allocated_buf, bw->buf_, current_size);
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free(bw->buf_);
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bw->buf_ = allocated_buf;
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bw->max_bytes_ = allocated_size;
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memset(allocated_buf + current_size, 0, allocated_size - current_size);
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return 1;
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}
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int VP8LBitWriterInit(VP8LBitWriter* const bw, size_t expected_size) {
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memset(bw, 0, sizeof(*bw));
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return VP8LBitWriterResize(bw, expected_size);
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}
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void VP8LBitWriterDestroy(VP8LBitWriter* const bw) {
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if (bw != NULL) {
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free(bw->buf_);
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memset(bw, 0, sizeof(*bw));
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}
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}
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void VP8LWriteBits(VP8LBitWriter* const bw, int n_bits, uint32_t bits) {
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if (n_bits < 1) return;
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#if !defined(__BIG_ENDIAN__)
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// Technically, this branch of the code can write up to 25 bits at a time,
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// but in prefix encoding, the maximum number of bits written is 18 at a time.
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{
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uint8_t* const p = &bw->buf_[bw->bit_pos_ >> 3];
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uint32_t v = *(const uint32_t*)p;
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v |= bits << (bw->bit_pos_ & 7);
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*(uint32_t*)p = v;
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bw->bit_pos_ += n_bits;
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}
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#else // BIG_ENDIAN
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{
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uint8_t* p = &bw->buf_[bw->bit_pos_ >> 3];
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const int bits_reserved_in_first_byte = bw->bit_pos_ & 7;
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const int bits_left_to_write = n_bits - 8 + bits_reserved_in_first_byte;
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// implicit & 0xff is assumed for uint8_t arithmetic
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*p++ |= bits << bits_reserved_in_first_byte;
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bits >>= 8 - bits_reserved_in_first_byte;
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if (bits_left_to_write >= 1) {
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*p++ = bits;
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bits >>= 8;
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if (bits_left_to_write >= 9) {
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*p++ = bits;
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bits >>= 8;
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}
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}
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assert(n_bits <= 25);
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*p = bits;
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bw->bit_pos_ += n_bits;
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}
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#endif
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if ((bw->bit_pos_ >> 3) > (bw->max_bytes_ - 8)) {
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const uint64_t extra_size = 32768ULL + bw->max_bytes_;
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if (extra_size != (size_t)extra_size ||
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!VP8LBitWriterResize(bw, (size_t)extra_size)) {
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bw->bit_pos_ = 0;
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bw->error_ = 1;
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}
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}
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}
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//------------------------------------------------------------------------------
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