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// Copyright 2017 PDFium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
#include "core/fxcodec/lgif/cfx_lzwdecoder.h"
#include <algorithm>
#include <memory>
#include <utility>
#include "core/fxcodec/lbmp/fx_bmp.h"
#include "third_party/base/numerics/safe_math.h"
#include "third_party/base/ptr_util.h"
#include "third_party/base/stl_util.h"
std::unique_ptr<CFX_LZWDecoder> CFX_LZWDecoder::Create(uint8_t color_exp,
uint8_t code_exp) {
if (code_exp > GIF_MAX_LZW_EXP || code_exp + 1 < color_exp)
return nullptr;
return std::unique_ptr<CFX_LZWDecoder>(
new CFX_LZWDecoder(color_exp, code_exp));
}
CFX_LZWDecoder::CFX_LZWDecoder(uint8_t color_exp, uint8_t code_exp)
: code_size_(code_exp),
code_size_cur_(0),
code_color_end_(static_cast<uint16_t>(2 << color_exp)),
code_clear_(static_cast<uint16_t>(1 << code_exp)),
code_end_(static_cast<uint16_t>((1 << code_exp) + 1)),
code_next_(0),
code_first_(0),
stack_size_(0),
code_old_(0),
next_in_(nullptr),
avail_in_(0),
bits_left_(0),
code_store_(0) {}
CFX_LZWDecoder::~CFX_LZWDecoder() {}
GifDecodeStatus CFX_LZWDecoder::Decode(uint8_t* src_buf,
uint32_t src_size,
uint8_t* des_buf,
uint32_t* des_size) {
if (!src_buf || src_size == 0 || !des_buf || !des_size)
return GifDecodeStatus::Error;
if (*des_size == 0)
return GifDecodeStatus::InsufficientDestSize;
next_in_ = src_buf;
avail_in_ = src_size;
ClearTable();
uint32_t i = 0;
if (stack_size_ != 0) {
if (*des_size < stack_size_) {
memcpy(des_buf, &stack_[GIF_MAX_LZW_CODE - stack_size_], *des_size);
stack_size_ -= static_cast<uint16_t>(*des_size);
return GifDecodeStatus::InsufficientDestSize;
}
memcpy(des_buf, &stack_[GIF_MAX_LZW_CODE - stack_size_], stack_size_);
des_buf += stack_size_;
i += stack_size_;
stack_size_ = 0;
}
while (i <= *des_size && (avail_in_ > 0 || bits_left_ >= code_size_cur_)) {
if (code_size_cur_ > GIF_MAX_LZW_EXP)
return GifDecodeStatus::Error;
if (avail_in_ > 0) {
if (bits_left_ > 31)
return GifDecodeStatus::Error;
pdfium::base::CheckedNumeric<uint32_t> safe_code = *next_in_++;
safe_code <<= bits_left_;
safe_code |= code_store_;
if (!safe_code.IsValid())
return GifDecodeStatus::Error;
code_store_ = safe_code.ValueOrDie();
--avail_in_;
bits_left_ += 8;
}
while (bits_left_ >= code_size_cur_) {
uint16_t code =
static_cast<uint16_t>(code_store_) & ((1 << code_size_cur_) - 1);
code_store_ >>= code_size_cur_;
bits_left_ -= code_size_cur_;
if (code == code_clear_) {
ClearTable();
continue;
}
if (code == code_end_) {
*des_size = i;
return GifDecodeStatus::Success;
}
if (code_old_ != static_cast<uint16_t>(-1)) {
if (code_next_ < GIF_MAX_LZW_CODE) {
if (code == code_next_) {
AddCode(code_old_, code_first_);
if (!DecodeString(code))
return GifDecodeStatus::Error;
} else if (code > code_next_) {
return GifDecodeStatus::Error;
} else {
if (!DecodeString(code))
return GifDecodeStatus::Error;
uint8_t append_char = stack_[GIF_MAX_LZW_CODE - stack_size_];
AddCode(code_old_, append_char);
}
}
} else {
if (!DecodeString(code))
return GifDecodeStatus::Error;
}
code_old_ = code;
if (i + stack_size_ > *des_size) {
memcpy(des_buf, &stack_[GIF_MAX_LZW_CODE - stack_size_], *des_size - i);
stack_size_ -= static_cast<uint16_t>(*des_size - i);
return GifDecodeStatus::InsufficientDestSize;
}
memcpy(des_buf, &stack_[GIF_MAX_LZW_CODE - stack_size_], stack_size_);
des_buf += stack_size_;
i += stack_size_;
stack_size_ = 0;
}
}
if (avail_in_ != 0)
return GifDecodeStatus::Error;
*des_size = i;
return GifDecodeStatus::Unfinished;
}
void CFX_LZWDecoder::ClearTable() {
code_size_cur_ = code_size_ + 1;
code_next_ = code_end_ + 1;
code_old_ = static_cast<uint16_t>(-1);
memset(code_table_, 0, sizeof(code_table_));
memset(stack_, 0, sizeof(stack_));
for (uint16_t i = 0; i < code_clear_; i++)
code_table_[i].suffix = static_cast<uint8_t>(i);
}
void CFX_LZWDecoder::AddCode(uint16_t prefix_code, uint8_t append_char) {
if (code_next_ == GIF_MAX_LZW_CODE)
return;
code_table_[code_next_].prefix = prefix_code;
code_table_[code_next_].suffix = append_char;
if (++code_next_ < GIF_MAX_LZW_CODE) {
if (code_next_ >> code_size_cur_)
code_size_cur_++;
}
}
bool CFX_LZWDecoder::DecodeString(uint16_t code) {
stack_size_ = 0;
while (code >= code_clear_ && code <= code_next_) {
if (code == code_table_[code].prefix || stack_size_ == GIF_MAX_LZW_CODE - 1)
return false;
stack_[GIF_MAX_LZW_CODE - 1 - stack_size_++] = code_table_[code].suffix;
code = code_table_[code].prefix;
}
if (code >= code_color_end_)
return false;
stack_[GIF_MAX_LZW_CODE - 1 - stack_size_++] = static_cast<uint8_t>(code);
code_first_ = static_cast<uint8_t>(code);
return true;
}
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