1 files changed, 120 insertions, 0 deletions
diff --git a/core/fxcodec/jbig2/JBig2_ArithDecoder.cpp b/core/fxcodec/jbig2/JBig2_ArithDecoder.cpp
new file mode 100644
index 0000000000..1673110c7e
--- /dev/null
+++ b/core/fxcodec/jbig2/JBig2_ArithDecoder.cpp
@@ -0,0 +1,120 @@
+// 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/include/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_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);
+}