| // 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_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_Complete(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; |
| } 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); |
| } |