diff options
Diffstat (limited to 'core/fxcodec/lgif/cfx_lzwdecoder.cpp')
| -rw-r--r-- | core/fxcodec/lgif/cfx_lzwdecoder.cpp | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/core/fxcodec/lgif/cfx_lzwdecoder.cpp b/core/fxcodec/lgif/cfx_lzwdecoder.cpp new file mode 100644 index 0000000000..9479eeafaa --- /dev/null +++ b/core/fxcodec/lgif/cfx_lzwdecoder.cpp @@ -0,0 +1,184 @@ +// 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; +} |