1 files changed, 92 insertions, 0 deletions
diff --git a/core/fxcodec/jbig2/JBig2_ArithIntDecoder.cpp b/core/fxcodec/jbig2/JBig2_ArithIntDecoder.cpp
new file mode 100644
index 0000000000..63594672c7
--- /dev/null
+++ b/core/fxcodec/jbig2/JBig2_ArithIntDecoder.cpp
@@ -0,0 +1,92 @@
+// 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_ArithIntDecoder.h"
+
+#include <vector>
+
+#include "core/include/fxcrt/fx_basic.h"
+
+namespace {
+
+int ShiftOr(int val, int bitwise_or_val) {
+  return (val << 1) | bitwise_or_val;
+}
+
+const struct ArithIntDecodeData {
+  int nNeedBits;
+  int nValue;
+} g_ArithIntDecodeData[] = {
+    {2, 0}, {4, 4}, {6, 20}, {8, 84}, {12, 340}, {32, 4436},
+};
+
+size_t RecursiveDecode(CJBig2_ArithDecoder* decoder,
+                       std::vector<JBig2ArithCtx>* context,
+                       int* prev,
+                       size_t depth) {
+  static const size_t kDepthEnd = FX_ArraySize(g_ArithIntDecodeData) - 1;
+  if (depth == kDepthEnd)
+    return kDepthEnd;
+
+  JBig2ArithCtx* pCX = &(*context)[*prev];
+  int D = decoder->DECODE(pCX);
+  *prev = ShiftOr(*prev, D);
+  if (!D)
+    return depth;
+  return RecursiveDecode(decoder, context, prev, depth + 1);
+}
+
+}  // namespace
+
+CJBig2_ArithIntDecoder::CJBig2_ArithIntDecoder() {
+  m_IAx.resize(512);
+}
+
+CJBig2_ArithIntDecoder::~CJBig2_ArithIntDecoder() {}
+
+bool CJBig2_ArithIntDecoder::decode(CJBig2_ArithDecoder* pArithDecoder,
+                                    int* nResult) {
+  int PREV = 1;
+  const int S = pArithDecoder->DECODE(&m_IAx[PREV]);
+  PREV = ShiftOr(PREV, S);
+
+  const size_t nDecodeDataIndex =
+      RecursiveDecode(pArithDecoder, &m_IAx, &PREV, 0);
+
+  int nTemp = 0;
+  for (int i = 0; i < g_ArithIntDecodeData[nDecodeDataIndex].nNeedBits; ++i) {
+    int D = pArithDecoder->DECODE(&m_IAx[PREV]);
+    PREV = ShiftOr(PREV, D);
+    if (PREV >= 256)
+      PREV = (PREV & 511) | 256;
+    nTemp = ShiftOr(nTemp, D);
+  }
+  int nValue = g_ArithIntDecodeData[nDecodeDataIndex].nValue;
+  nValue += nTemp;
+  if (S == 1 && nValue > 0)
+    nValue = -nValue;
+
+  *nResult = nValue;
+  return S != 1 || nValue != 0;
+}
+
+CJBig2_ArithIaidDecoder::CJBig2_ArithIaidDecoder(unsigned char SBSYMCODELENA)
+    : SBSYMCODELEN(SBSYMCODELENA) {
+  m_IAID.resize(1 << SBSYMCODELEN);
+}
+
+CJBig2_ArithIaidDecoder::~CJBig2_ArithIaidDecoder() {}
+
+void CJBig2_ArithIaidDecoder::decode(CJBig2_ArithDecoder* pArithDecoder,
+                                     FX_DWORD* nResult) {
+  int PREV = 1;
+  for (unsigned char i = 0; i < SBSYMCODELEN; ++i) {
+    JBig2ArithCtx* pCX = &m_IAID[PREV];
+    int D = pArithDecoder->DECODE(pCX);
+    PREV = ShiftOr(PREV, D);
+  }
+  *nResult = PREV - (1 << SBSYMCODELEN);
+}