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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/include/fx_basic.h"
|
| namespace {
|
| struct JBig2ArithQe {
| unsigned int Qe;
| unsigned int NMPS;
| unsigned int NLPS;
| unsigned int 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_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;
| } 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;
| }
| }
|
| void CJBig2_ArithDecoder::ReadValueA() {
| do {
| if (m_CT == 0)
| BYTEIN();
| m_A <<= 1;
| m_C <<= 1;
| --m_CT;
| } while ((m_A & kDefaultAValue) == 0);
| }
|
|
