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// Copyright 2014 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/jbig2/JBig2_ArithDecoder.h"
#include "core/fxcodec/jbig2/JBig2_BitStream.h"
#include "core/fxcrt/fx_memory.h"
namespace {
struct JBig2ArithQe {
uint16_t Qe;
uint8_t NMPS;
uint8_t NLPS;
uint8_t nSwitch;
};
const JBig2ArithQe kQeTable[] = {
// Stupid hack to keep clang-format from reformatting this badly.
{0x5601, 1, 1, 1}, {0x3401, 2, 6, 0}, {0x1801, 3, 9, 0},
{0x0AC1, 4, 12, 0}, {0x0521, 5, 29, 0}, {0x0221, 38, 33, 0},
{0x5601, 7, 6, 1}, {0x5401, 8, 14, 0}, {0x4801, 9, 14, 0},
{0x3801, 10, 14, 0}, {0x3001, 11, 17, 0}, {0x2401, 12, 18, 0},
{0x1C01, 13, 20, 0}, {0x1601, 29, 21, 0}, {0x5601, 15, 14, 1},
{0x5401, 16, 14, 0}, {0x5101, 17, 15, 0}, {0x4801, 18, 16, 0},
{0x3801, 19, 17, 0}, {0x3401, 20, 18, 0}, {0x3001, 21, 19, 0},
{0x2801, 22, 19, 0}, {0x2401, 23, 20, 0}, {0x2201, 24, 21, 0},
{0x1C01, 25, 22, 0}, {0x1801, 26, 23, 0}, {0x1601, 27, 24, 0},
{0x1401, 28, 25, 0}, {0x1201, 29, 26, 0}, {0x1101, 30, 27, 0},
{0x0AC1, 31, 28, 0}, {0x09C1, 32, 29, 0}, {0x08A1, 33, 30, 0},
{0x0521, 34, 31, 0}, {0x0441, 35, 32, 0}, {0x02A1, 36, 33, 0},
{0x0221, 37, 34, 0}, {0x0141, 38, 35, 0}, {0x0111, 39, 36, 0},
{0x0085, 40, 37, 0}, {0x0049, 41, 38, 0}, {0x0025, 42, 39, 0},
{0x0015, 43, 40, 0}, {0x0009, 44, 41, 0}, {0x0005, 45, 42, 0},
{0x0001, 45, 43, 0}, {0x5601, 46, 46, 0}};
const unsigned int kDefaultAValue = 0x8000;
int DecodeNMPS(JBig2ArithCtx* pCX, const JBig2ArithQe& qe) {
pCX->I = qe.NMPS;
return pCX->MPS;
}
int DecodeNLPS(JBig2ArithCtx* pCX, const JBig2ArithQe& qe) {
// TODO(thestig): |D|, |MPS| and friends probably should be booleans.
int D = 1 - pCX->MPS;
if (qe.nSwitch == 1)
pCX->MPS = 1 - pCX->MPS;
pCX->I = qe.NLPS;
return D;
}
} // namespace
CJBig2_ArithDecoder::CJBig2_ArithDecoder(CJBig2_BitStream* pStream)
: m_Complete(false), m_FinishedStream(false), 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() {}
int CJBig2_ArithDecoder::DECODE(JBig2ArithCtx* pCX) {
if (!pCX || pCX->I >= FX_ArraySize(kQeTable))
return 0;
const 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 ? DecodeNLPS(pCX, qe) : DecodeNMPS(pCX, qe);
ReadValueA();
return D;
}
m_C -= m_A << 16;
const int D = m_A < qe.Qe ? DecodeNMPS(pCX, qe) : DecodeNLPS(pCX, qe);
m_A = qe.Qe;
ReadValueA();
return D;
}
void CJBig2_ArithDecoder::BYTEIN() {
unsigned char B1;
if (m_B == 0xff) {
B1 = m_pStream->getNextByte_arith();
if (B1 > 0x8f) {
m_CT = 8;
// If we are here, it means that we have finished decoding data (see JBIG2
// spec, Section E.3.4). If we arrive here a second time, we're looping,
// so complete decoding.
if (m_FinishedStream)
m_Complete = true;
m_FinishedStream = true;
} 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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