3.13

7zip/Compress/Implode/ImplodeHuffmanDecoder.cpp

@@ -0,0 +1,88 @@
+// ImplodeHuffmanDecoder.cpp
+
+#include "StdAfx.h"
+
+#include "ImplodeHuffmanDecoder.h"
+
+namespace NCompress {
+namespace NImplode {
+namespace NHuffman {
+
+CDecoder::CDecoder(UINT32 numSymbols):
+  m_NumSymbols(numSymbols)
+{
+  m_Symbols = new UINT32[m_NumSymbols];
+}
+
+CDecoder::~CDecoder()
+{
+  delete []m_Symbols;
+}
+
+void CDecoder::SetCodeLengths(const BYTE *codeLengths)
+{
+  // int lenCounts[kNumBitsInLongestCode + 1], tmpPositions[kNumBitsInLongestCode + 1];
+  int lenCounts[kNumBitsInLongestCode + 2], tmpPositions[kNumBitsInLongestCode + 1];
+  int i;
+  for(i = 0; i <= kNumBitsInLongestCode; i++)
+    lenCounts[i] = 0;
+  UINT32 symbolIndex;
+  for (symbolIndex = 0; symbolIndex < m_NumSymbols; symbolIndex++)
+    lenCounts[codeLengths[symbolIndex]]++;
+  // lenCounts[0] = 0;
+  
+  // tmpPositions[0] = m_Positions[0] = m_Limitits[0] = 0;
+  m_Limitits[kNumBitsInLongestCode + 1] = 0;
+  m_Positions[kNumBitsInLongestCode + 1] = 0;
+  lenCounts[kNumBitsInLongestCode + 1] =  0;
+
+
+  UINT32 startPos = 0;
+  static const UINT32 kMaxValue = (1 << kNumBitsInLongestCode);
+
+  for (i = kNumBitsInLongestCode; i > 0; i--)
+  {
+    startPos += lenCounts[i] << (kNumBitsInLongestCode - i);
+    if (startPos > kMaxValue)
+      throw CDecoderException();
+    m_Limitits[i] = startPos;
+    m_Positions[i] = m_Positions[i + 1] + lenCounts[i + 1];
+    tmpPositions[i] = m_Positions[i] + lenCounts[i];
+
+  }
+
+  // if _ZIP_MODE do not throw exception for trees containing only one node 
+  // #ifndef _ZIP_MODE 
+  if (startPos != kMaxValue)
+    throw CDecoderException();
+  // #endif
+
+  for (symbolIndex = 0; symbolIndex < m_NumSymbols; symbolIndex++)
+    if (codeLengths[symbolIndex] != 0)
+      m_Symbols[--tmpPositions[codeLengths[symbolIndex]]] = symbolIndex;
+}
+
+UINT32 CDecoder::DecodeSymbol(CInBit *inStream)
+{
+  UINT32 numBits;
+  UINT32 value = inStream->GetValue(kNumBitsInLongestCode);
+  int i;
+  for(i = kNumBitsInLongestCode; i > 0; i--)
+  {
+    if (value < m_Limitits[i])
+    {
+      numBits = i;
+      break;
+    }
+  }
+  if (i == 0)
+    throw CDecoderException();
+  inStream->MovePos(numBits);
+  UINT32 index = m_Positions[numBits] + 
+      ((value - m_Limitits[numBits + 1]) >> (kNumBitsInLongestCode - numBits));
+  if (index >= m_NumSymbols)
+    throw CDecoderException(); // test it
+  return m_Symbols[index];
+}
+
+}}}