1 // Copyright 2014 PDFium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com 6 7 #include "core/fxcodec/jbig2/JBig2_ArithDecoder.h" 8 9 #include "core/fxcodec/jbig2/JBig2_BitStream.h" 10 #include "core/fxcrt/fx_basic.h" 11 12 namespace { 13 14 struct JBig2ArithQe { 15 unsigned int Qe; 16 unsigned int NMPS; 17 unsigned int NLPS; 18 unsigned int nSwitch; 19 }; 20 21 const JBig2ArithQe kQeTable[] = { 22 // Stupid hack to keep clang-format from reformatting this badly. 23 {0x5601, 1, 1, 1}, {0x3401, 2, 6, 0}, {0x1801, 3, 9, 0}, 24 {0x0AC1, 4, 12, 0}, {0x0521, 5, 29, 0}, {0x0221, 38, 33, 0}, 25 {0x5601, 7, 6, 1}, {0x5401, 8, 14, 0}, {0x4801, 9, 14, 0}, 26 {0x3801, 10, 14, 0}, {0x3001, 11, 17, 0}, {0x2401, 12, 18, 0}, 27 {0x1C01, 13, 20, 0}, {0x1601, 29, 21, 0}, {0x5601, 15, 14, 1}, 28 {0x5401, 16, 14, 0}, {0x5101, 17, 15, 0}, {0x4801, 18, 16, 0}, 29 {0x3801, 19, 17, 0}, {0x3401, 20, 18, 0}, {0x3001, 21, 19, 0}, 30 {0x2801, 22, 19, 0}, {0x2401, 23, 20, 0}, {0x2201, 24, 21, 0}, 31 {0x1C01, 25, 22, 0}, {0x1801, 26, 23, 0}, {0x1601, 27, 24, 0}, 32 {0x1401, 28, 25, 0}, {0x1201, 29, 26, 0}, {0x1101, 30, 27, 0}, 33 {0x0AC1, 31, 28, 0}, {0x09C1, 32, 29, 0}, {0x08A1, 33, 30, 0}, 34 {0x0521, 34, 31, 0}, {0x0441, 35, 32, 0}, {0x02A1, 36, 33, 0}, 35 {0x0221, 37, 34, 0}, {0x0141, 38, 35, 0}, {0x0111, 39, 36, 0}, 36 {0x0085, 40, 37, 0}, {0x0049, 41, 38, 0}, {0x0025, 42, 39, 0}, 37 {0x0015, 43, 40, 0}, {0x0009, 44, 41, 0}, {0x0005, 45, 42, 0}, 38 {0x0001, 45, 43, 0}, {0x5601, 46, 46, 0}}; 39 40 const unsigned int kDefaultAValue = 0x8000; 41 42 int DecodeNMPS(JBig2ArithCtx* pCX, const JBig2ArithQe& qe) { 43 pCX->I = qe.NMPS; 44 return pCX->MPS; 45 } 46 47 int DecodeNLPS(JBig2ArithCtx* pCX, const JBig2ArithQe& qe) { 48 // TODO(thestig): |D|, |MPS| and friends probably should be booleans. 49 int D = 1 - pCX->MPS; 50 if (qe.nSwitch == 1) 51 pCX->MPS = 1 - pCX->MPS; 52 pCX->I = qe.NLPS; 53 return D; 54 } 55 56 } // namespace 57 58 CJBig2_ArithDecoder::CJBig2_ArithDecoder(CJBig2_BitStream* pStream) 59 : m_pStream(pStream) { 60 m_B = m_pStream->getCurByte_arith(); 61 m_C = (m_B ^ 0xff) << 16; 62 BYTEIN(); 63 m_C = m_C << 7; 64 m_CT = m_CT - 7; 65 m_A = kDefaultAValue; 66 } 67 68 CJBig2_ArithDecoder::~CJBig2_ArithDecoder() {} 69 70 int CJBig2_ArithDecoder::DECODE(JBig2ArithCtx* pCX) { 71 if (!pCX || pCX->I >= FX_ArraySize(kQeTable)) 72 return 0; 73 74 const JBig2ArithQe& qe = kQeTable[pCX->I]; 75 m_A -= qe.Qe; 76 if ((m_C >> 16) < m_A) { 77 if (m_A & kDefaultAValue) 78 return pCX->MPS; 79 80 const int D = m_A < qe.Qe ? DecodeNLPS(pCX, qe) : DecodeNMPS(pCX, qe); 81 ReadValueA(); 82 return D; 83 } 84 85 m_C -= m_A << 16; 86 const int D = m_A < qe.Qe ? DecodeNMPS(pCX, qe) : DecodeNLPS(pCX, qe); 87 m_A = qe.Qe; 88 ReadValueA(); 89 return D; 90 } 91 92 void CJBig2_ArithDecoder::BYTEIN() { 93 unsigned char B1; 94 if (m_B == 0xff) { 95 B1 = m_pStream->getNextByte_arith(); 96 if (B1 > 0x8f) { 97 m_CT = 8; 98 } else { 99 m_pStream->incByteIdx(); 100 m_B = B1; 101 m_C = m_C + 0xfe00 - (m_B << 9); 102 m_CT = 7; 103 } 104 } else { 105 m_pStream->incByteIdx(); 106 m_B = m_pStream->getCurByte_arith(); 107 m_C = m_C + 0xff00 - (m_B << 8); 108 m_CT = 8; 109 } 110 } 111 112 void CJBig2_ArithDecoder::ReadValueA() { 113 do { 114 if (m_CT == 0) 115 BYTEIN(); 116 m_A <<= 1; 117 m_C <<= 1; 118 --m_CT; 119 } while ((m_A & kDefaultAValue) == 0); 120 } 121
