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// Copyright 2014 The PDFium Authors
// 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/jbig2/JBig2_ArithDecoder.h"
#include <iterator>
#include "core/fxcodec/jbig2/JBig2_BitStream.h"
#include "third_party/base/check_op.h"
namespace {
const JBig2ArithCtx::JBig2ArithQe kQeTable[] = {
// Stupid hack to keep clang-format from reformatting this badly.
{0x5601, 1, 1, true}, {0x3401, 2, 6, false}, {0x1801, 3, 9, false},
{0x0AC1, 4, 12, false}, {0x0521, 5, 29, false}, {0x0221, 38, 33, false},
{0x5601, 7, 6, true}, {0x5401, 8, 14, false}, {0x4801, 9, 14, false},
{0x3801, 10, 14, false}, {0x3001, 11, 17, false}, {0x2401, 12, 18, false},
{0x1C01, 13, 20, false}, {0x1601, 29, 21, false}, {0x5601, 15, 14, true},
{0x5401, 16, 14, false}, {0x5101, 17, 15, false}, {0x4801, 18, 16, false},
{0x3801, 19, 17, false}, {0x3401, 20, 18, false}, {0x3001, 21, 19, false},
{0x2801, 22, 19, false}, {0x2401, 23, 20, false}, {0x2201, 24, 21, false},
{0x1C01, 25, 22, false}, {0x1801, 26, 23, false}, {0x1601, 27, 24, false},
{0x1401, 28, 25, false}, {0x1201, 29, 26, false}, {0x1101, 30, 27, false},
{0x0AC1, 31, 28, false}, {0x09C1, 32, 29, false}, {0x08A1, 33, 30, false},
{0x0521, 34, 31, false}, {0x0441, 35, 32, false}, {0x02A1, 36, 33, false},
{0x0221, 37, 34, false}, {0x0141, 38, 35, false}, {0x0111, 39, 36, false},
{0x0085, 40, 37, false}, {0x0049, 41, 38, false}, {0x0025, 42, 39, false},
{0x0015, 43, 40, false}, {0x0009, 44, 41, false}, {0x0005, 45, 42, false},
{0x0001, 45, 43, false}, {0x5601, 46, 46, false}};
const unsigned int kDefaultAValue = 0x8000;
} // namespace
JBig2ArithCtx::JBig2ArithCtx() = default;
int JBig2ArithCtx::DecodeNLPS(const JBig2ArithQe& qe) {
bool D = !m_MPS;
if (qe.bSwitch)
m_MPS = !m_MPS;
m_I = qe.NLPS;
DCHECK_LT(m_I, std::size(kQeTable));
return D;
}
int JBig2ArithCtx::DecodeNMPS(const JBig2ArithQe& qe) {
m_I = qe.NMPS;
DCHECK_LT(m_I, std::size(kQeTable));
return MPS();
}
CJBig2_ArithDecoder::CJBig2_ArithDecoder(CJBig2_BitStream* pStream)
: m_pStream(pStream) {
m_B = m_pStream->getCurByte_arith();
m_C = (m_B ^ 0xff) << 16;
BYTEIN();
m_C = m_C << 7;
m_CT = m_CT - 7;
m_A = kDefaultAValue;
}
CJBig2_ArithDecoder::~CJBig2_ArithDecoder() = default;
int CJBig2_ArithDecoder::Decode(JBig2ArithCtx* pCX) {
DCHECK(pCX);
DCHECK_LT(pCX->I(), std::size(kQeTable));
const JBig2ArithCtx::JBig2ArithQe& qe = kQeTable[pCX->I()];
m_A -= qe.Qe;
if ((m_C >> 16) < m_A) {
if (m_A & kDefaultAValue)
return pCX->MPS();
const int D = m_A < qe.Qe ? pCX->DecodeNLPS(qe) : pCX->DecodeNMPS(qe);
ReadValueA();
return D;
}
m_C -= m_A << 16;
const int D = m_A < qe.Qe ? pCX->DecodeNMPS(qe) : pCX->DecodeNLPS(qe);
m_A = qe.Qe;
ReadValueA();
return D;
}
void CJBig2_ArithDecoder::BYTEIN() {
if (m_B == 0xff) {
unsigned char B1 = m_pStream->getNextByte_arith();
if (B1 > 0x8f) {
m_CT = 8;
switch (m_State) {
case StreamState::kDataAvailable:
// Finished decoding data (see JBIG2 spec, Section E.3.4).
m_State = StreamState::kDecodingFinished;
break;
case StreamState::kDecodingFinished:
// Allow one more call in the finished state. https://crbug.com/947622
m_State = StreamState::kLooping;
break;
case StreamState::kLooping:
// Looping state detected. Mark decoding as complete to bail out.
// https://crbug.com/767156
m_Complete = true;
break;
}
} else {
m_pStream->incByteIdx();
m_B = B1;
m_C = m_C + 0xfe00 - (m_B << 9);
m_CT = 7;
}
} else {
m_pStream->incByteIdx();
m_B = m_pStream->getCurByte_arith();
m_C = m_C + 0xff00 - (m_B << 8);
m_CT = 8;
}
if (!m_pStream->IsInBounds())
m_Complete = true;
}
void CJBig2_ArithDecoder::ReadValueA() {
do {
if (m_CT == 0)
BYTEIN();
m_A <<= 1;
m_C <<= 1;
--m_CT;
} while ((m_A & kDefaultAValue) == 0);
}
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