381 lines
10 KiB
C++
381 lines
10 KiB
C++
// Copyright 2019 The PDFium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "core/fxcodec/basic/basicmodule.h"
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#include <stdint.h>
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#include <algorithm>
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#include <utility>
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#include "core/fxcodec/scanlinedecoder.h"
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#include "core/fxcrt/data_vector.h"
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#include "core/fxcrt/fx_memory_wrappers.h"
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#include "core/fxcrt/fx_safe_types.h"
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#include "core/fxcrt/fx_system.h"
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#include "core/fxcrt/span_util.h"
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#include "third_party/base/check.h"
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#include "third_party/base/numerics/safe_conversions.h"
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namespace fxcodec {
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namespace {
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class RLScanlineDecoder final : public ScanlineDecoder {
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public:
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RLScanlineDecoder();
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~RLScanlineDecoder() override;
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bool Create(pdfium::span<const uint8_t> src_buf,
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int width,
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int height,
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int nComps,
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int bpc);
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// ScanlineDecoder:
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bool Rewind() override;
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pdfium::span<uint8_t> GetNextLine() override;
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uint32_t GetSrcOffset() override;
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private:
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bool CheckDestSize();
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void GetNextOperator();
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void UpdateOperator(uint8_t used_bytes);
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DataVector<uint8_t> m_Scanline;
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pdfium::span<const uint8_t> m_SrcBuf;
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size_t m_dwLineBytes = 0;
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size_t m_SrcOffset = 0;
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bool m_bEOD = false;
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uint8_t m_Operator = 0;
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};
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RLScanlineDecoder::RLScanlineDecoder() = default;
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RLScanlineDecoder::~RLScanlineDecoder() {
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// Span in superclass can't outlive our buffer.
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m_pLastScanline = pdfium::span<uint8_t>();
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}
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bool RLScanlineDecoder::CheckDestSize() {
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size_t i = 0;
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uint32_t old_size = 0;
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uint32_t dest_size = 0;
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while (i < m_SrcBuf.size()) {
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if (m_SrcBuf[i] < 128) {
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old_size = dest_size;
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dest_size += m_SrcBuf[i] + 1;
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if (dest_size < old_size) {
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return false;
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}
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i += m_SrcBuf[i] + 2;
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} else if (m_SrcBuf[i] > 128) {
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old_size = dest_size;
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dest_size += 257 - m_SrcBuf[i];
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if (dest_size < old_size) {
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return false;
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}
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i += 2;
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} else {
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break;
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}
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}
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if (((uint32_t)m_OrigWidth * m_nComps * m_bpc * m_OrigHeight + 7) / 8 >
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dest_size) {
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return false;
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}
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return true;
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}
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bool RLScanlineDecoder::Create(pdfium::span<const uint8_t> src_buf,
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int width,
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int height,
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int nComps,
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int bpc) {
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m_SrcBuf = src_buf;
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m_OutputWidth = m_OrigWidth = width;
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m_OutputHeight = m_OrigHeight = height;
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m_nComps = nComps;
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m_bpc = bpc;
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// Aligning the pitch to 4 bytes requires an integer overflow check.
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FX_SAFE_UINT32 pitch = width;
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pitch *= nComps;
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pitch *= bpc;
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pitch += 31;
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pitch /= 32;
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pitch *= 4;
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if (!pitch.IsValid()) {
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return false;
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}
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m_Pitch = pitch.ValueOrDie();
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// Overflow should already have been checked before this is called.
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m_dwLineBytes = (static_cast<uint32_t>(width) * nComps * bpc + 7) / 8;
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m_Scanline.resize(m_Pitch);
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return CheckDestSize();
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}
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bool RLScanlineDecoder::Rewind() {
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fxcrt::spanclr(pdfium::make_span(m_Scanline));
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m_SrcOffset = 0;
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m_bEOD = false;
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m_Operator = 0;
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return true;
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}
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pdfium::span<uint8_t> RLScanlineDecoder::GetNextLine() {
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if (m_SrcOffset == 0) {
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GetNextOperator();
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} else if (m_bEOD) {
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return pdfium::span<uint8_t>();
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}
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uint32_t col_pos = 0;
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bool eol = false;
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auto scan_span = pdfium::make_span(m_Scanline);
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fxcrt::spanclr(scan_span);
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while (m_SrcOffset < m_SrcBuf.size() && !eol) {
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if (m_Operator < 128) {
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uint32_t copy_len = m_Operator + 1;
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if (col_pos + copy_len >= m_dwLineBytes) {
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copy_len =
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pdfium::base::checked_cast<uint32_t>(m_dwLineBytes - col_pos);
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eol = true;
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}
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if (copy_len >= m_SrcBuf.size() - m_SrcOffset) {
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copy_len =
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pdfium::base::checked_cast<uint32_t>(m_SrcBuf.size() - m_SrcOffset);
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m_bEOD = true;
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}
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auto copy_span = m_SrcBuf.subspan(m_SrcOffset, copy_len);
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fxcrt::spancpy(scan_span.subspan(col_pos), copy_span);
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col_pos += copy_len;
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UpdateOperator((uint8_t)copy_len);
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} else if (m_Operator > 128) {
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int fill = 0;
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if (m_SrcOffset - 1 < m_SrcBuf.size() - 1) {
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fill = m_SrcBuf[m_SrcOffset];
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}
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uint32_t duplicate_len = 257 - m_Operator;
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if (col_pos + duplicate_len >= m_dwLineBytes) {
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duplicate_len =
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pdfium::base::checked_cast<uint32_t>(m_dwLineBytes - col_pos);
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eol = true;
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}
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fxcrt::spanset(scan_span.subspan(col_pos, duplicate_len), fill);
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col_pos += duplicate_len;
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UpdateOperator((uint8_t)duplicate_len);
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} else {
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m_bEOD = true;
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break;
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}
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}
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return m_Scanline;
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}
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uint32_t RLScanlineDecoder::GetSrcOffset() {
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return pdfium::base::checked_cast<uint32_t>(m_SrcOffset);
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}
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void RLScanlineDecoder::GetNextOperator() {
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if (m_SrcOffset >= m_SrcBuf.size()) {
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m_Operator = 128;
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return;
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}
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m_Operator = m_SrcBuf[m_SrcOffset];
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m_SrcOffset++;
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}
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void RLScanlineDecoder::UpdateOperator(uint8_t used_bytes) {
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if (used_bytes == 0) {
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return;
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}
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if (m_Operator < 128) {
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DCHECK((uint32_t)m_Operator + 1 >= used_bytes);
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if (used_bytes == m_Operator + 1) {
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m_SrcOffset += used_bytes;
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GetNextOperator();
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return;
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}
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m_Operator -= used_bytes;
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m_SrcOffset += used_bytes;
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if (m_SrcOffset >= m_SrcBuf.size()) {
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m_Operator = 128;
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}
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return;
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}
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uint8_t count = 257 - m_Operator;
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DCHECK((uint32_t)count >= used_bytes);
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if (used_bytes == count) {
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m_SrcOffset++;
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GetNextOperator();
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return;
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}
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count -= used_bytes;
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m_Operator = 257 - count;
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}
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} // namespace
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// static
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std::unique_ptr<ScanlineDecoder> BasicModule::CreateRunLengthDecoder(
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pdfium::span<const uint8_t> src_buf,
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int width,
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int height,
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int nComps,
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int bpc) {
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auto pDecoder = std::make_unique<RLScanlineDecoder>();
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if (!pDecoder->Create(src_buf, width, height, nComps, bpc))
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return nullptr;
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return std::move(pDecoder);
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}
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// static
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DataVector<uint8_t> BasicModule::RunLengthEncode(
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pdfium::span<const uint8_t> src_span) {
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if (src_span.empty())
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return {};
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// Handle edge case.
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if (src_span.size() == 1)
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return {0, src_span[0], 128};
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// Worst case: 1 nonmatch, 2 match, 1 nonmatch, 2 match, etc. This becomes
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// 4 output chars for every 3 input, plus up to 4 more for the 1-2 chars
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// rounded off plus the terminating character.
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FX_SAFE_SIZE_T estimated_size = src_span.size();
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estimated_size += 2;
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estimated_size /= 3;
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estimated_size *= 4;
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estimated_size += 1;
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DataVector<uint8_t> result(estimated_size.ValueOrDie());
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// Set up span and counts.
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auto result_span = pdfium::make_span(result);
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uint32_t run_start = 0;
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uint32_t run_end = 1;
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uint8_t x = src_span[run_start];
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uint8_t y = src_span[run_end];
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while (run_end < src_span.size()) {
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size_t max_len = std::min<size_t>(128, src_span.size() - run_start);
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while (x == y && (run_end - run_start < max_len - 1))
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y = src_span[++run_end];
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// Reached end with matched run. Update variables to expected values.
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if (x == y) {
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run_end++;
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if (run_end < src_span.size())
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y = src_span[run_end];
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}
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if (run_end - run_start > 1) { // Matched run but not at end of input.
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result_span[0] = 257 - (run_end - run_start);
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result_span[1] = x;
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x = y;
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run_start = run_end;
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run_end++;
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if (run_end < src_span.size())
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y = src_span[run_end];
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result_span = result_span.subspan(2);
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continue;
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}
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// Mismatched run
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while (x != y && run_end <= run_start + max_len) {
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result_span[run_end - run_start] = x;
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x = y;
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run_end++;
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if (run_end == src_span.size()) {
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if (run_end <= run_start + max_len) {
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result_span[run_end - run_start] = x;
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run_end++;
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}
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break;
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}
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y = src_span[run_end];
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}
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result_span[0] = run_end - run_start - 2;
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result_span = result_span.subspan(run_end - run_start);
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run_start = run_end - 1;
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}
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if (run_start < src_span.size()) { // 1 leftover character
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result_span[0] = 0;
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result_span[1] = x;
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result_span = result_span.subspan(2);
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}
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result_span[0] = 128;
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size_t new_size = 1 + result.size() - result_span.size();
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CHECK_LE(new_size, result.size());
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result.resize(new_size);
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return result;
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}
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// static
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DataVector<uint8_t> BasicModule::A85Encode(
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pdfium::span<const uint8_t> src_span) {
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DataVector<uint8_t> result;
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if (src_span.empty())
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return result;
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// Worst case: 5 output for each 4 input (plus up to 4 from leftover), plus
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// 2 character new lines each 75 output chars plus 2 termination chars. May
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// have fewer if there are special "z" chars.
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FX_SAFE_SIZE_T estimated_size = src_span.size();
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estimated_size /= 4;
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estimated_size *= 5;
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estimated_size += 4;
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estimated_size += src_span.size() / 30;
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estimated_size += 2;
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result.resize(estimated_size.ValueOrDie());
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// Set up span and counts.
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auto result_span = pdfium::make_span(result);
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uint32_t pos = 0;
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uint32_t line_length = 0;
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while (src_span.size() >= 4 && pos < src_span.size() - 3) {
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auto val_span = src_span.subspan(pos, 4);
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uint32_t val = FXSYS_UINT32_GET_MSBFIRST(val_span);
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pos += 4;
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if (val == 0) { // All zero special case
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result_span[0] = 'z';
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result_span = result_span.subspan(1);
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line_length++;
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} else { // Compute base 85 characters and add 33.
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for (int i = 4; i >= 0; i--) {
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result_span[i] = (val % 85) + 33;
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val /= 85;
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}
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result_span = result_span.subspan(5);
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line_length += 5;
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}
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if (line_length >= 75) { // Add a return.
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result_span[0] = '\r';
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result_span[1] = '\n';
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result_span = result_span.subspan(2);
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line_length = 0;
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}
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}
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if (pos < src_span.size()) { // Leftover bytes
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uint32_t val = 0;
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int count = 0;
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while (pos < src_span.size()) {
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val += (uint32_t)(src_span[pos]) << (8 * (3 - count));
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count++;
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pos++;
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}
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for (int i = 4; i >= 0; i--) {
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if (i <= count)
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result_span[i] = (val % 85) + 33;
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val /= 85;
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}
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result_span = result_span.subspan(count + 1);
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}
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// Terminating characters.
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result_span[0] = '~';
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result_span[1] = '>';
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size_t new_size = 2 + result.size() - result_span.size();
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CHECK_LE(new_size, result.size());
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result.resize(new_size);
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return result;
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}
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} // namespace fxcodec
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