inbuffer.cpp

一个7ZIP的解压源码。比较详细。里面含有四种语言的实现代码。

// InBuffer.cpp

#include "StdAfx.h"

#include "InBuffer.h"

extern "C"
{
  #include "../../../C/Alloc.h"
}

CInBuffer::CInBuffer(): 
  _buffer(0), 
  _bufferLimit(0), 
  _bufferBase(0), 
  _stream(0),
  _bufferSize(0)
{}

bool CInBuffer::Create(UInt32 bufferSize)
{
  const UInt32 kMinBlockSize = 1;
  if (bufferSize < kMinBlockSize)
    bufferSize = kMinBlockSize;
  if (_bufferBase != 0 && _bufferSize == bufferSize)
    return true;
  Free();
  _bufferSize = bufferSize;
  _bufferBase = (Byte *)::MidAlloc(bufferSize);
  return (_bufferBase != 0);
}

void CInBuffer::Free()
{
  ::MidFree(_bufferBase);
  _bufferBase = 0;
}

void CInBuffer::SetStream(ISequentialInStream *stream)
{
  _stream = stream;
}

void CInBuffer::Init()
{
  _processedSize = 0;
  _buffer = _bufferBase;
  _bufferLimit = _buffer;
  _wasFinished = false;
  #ifdef _NO_EXCEPTIONS
  ErrorCode = S_OK;
  #endif
}

bool CInBuffer::ReadBlock()
{
  #ifdef _NO_EXCEPTIONS
  if (ErrorCode != S_OK)
    return false;
  #endif
  if (_wasFinished)
    return false;
  _processedSize += (_buffer - _bufferBase);
  UInt32 numProcessedBytes;
  HRESULT result = _stream->Read(_bufferBase, _bufferSize, &numProcessedBytes);
  #ifdef _NO_EXCEPTIONS
  ErrorCode = result;
  #else
  if (result != S_OK)
    throw CInBufferException(result);
  #endif
  _buffer = _bufferBase;
  _bufferLimit = _buffer + numProcessedBytes;
  _wasFinished = (numProcessedBytes == 0);
  return (!_wasFinished);
}

Byte CInBuffer::ReadBlock2()
{
  if(!ReadBlock())
    return 0xFF;
  return *_buffer++;
}