装饰模式

当存在部分子类共有的成员，但直接提到基类又不必要的情况下。使用装饰模式将那部分共有成员独立出来成为装饰类，包含这些部分共有的成员，需要这些成员的继承自该装饰类，不需要的直接继承基类。
base.h

#pragma  once

class IStream
{
public:
	virtual void Read(int num) = 0;
	virtual void Seek(int pos) = 0;
	virtual void Write(char data) = 0;
	virtual ~IStream(){}
};

imp.h

#pragma once

#include "base.h"

////////////////////////////////
class CFileStream:public IStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CFileStream(){}
};

class CNetStream:public IStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CNetStream(){}
};

class CMemStream:public IStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CMemStream(){}
};
#if 0
//////////////////////////////////////////
class CryptoFileStream:public CFileStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CryptoFileStream(){}
};

class CryptoNetStream:public CNetStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CryptoNetStream(){}
};

class CryptoMemStream:public CMemStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CryptoMemStream(){}
};

//////////////////////////////////////////
class CFileBufferStream:public CFileStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CFileBufferStream(){}
};

class CNetBufferStream:public CNetStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CNetBufferStream(){}
};

class CMemBufferStream:public CMemStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CMemBufferStream(){}
};

//////////////////////////////////////////
class CryptoFileBufferStream:public CFileStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CryptoFileBufferStream(){}
};

class CryptoNetBufferStream:public CFileStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CryptoNetBufferStream(){}
};

class CryptoMemBufferStream:public CFileStream
{
public:
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CryptoMemBufferStream(){}
};
#else

/*
1.通过将使用组合而非继承将stream实际类型在运行时确定，
达到在编译时CryptoStream，CBufferStream，CryptoBufferStream都是稳定的。
2.IStream使用组合后，理论上CryptoStream，CBufferStream，CryptoBufferStream
可以不再继承IStream，但是为接口规范，IStream定义子类接口标准，子类必须签名一致。
3.IStream本身是既被CFileStream等继承
又被CryptoStream，CBufferStream，CryptoBufferStream等继承
但是又不能直接提到IStream基类中，故使用装饰模式，创造一个中间类。
*/
class CDecoratorStream:public IStream
{
protected:
	IStream* m_stream;
	CDecoratorStream(IStream* stm):m_stream(stm){}
};


class CryptoStream:public CDecoratorStream
{
public:
	CryptoStream(IStream* stm):CDecoratorStream(stm){}
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CryptoStream(){}
};

class CBufferStream:public CDecoratorStream
{
public:
	CBufferStream(IStream* stm):CDecoratorStream(stm){}
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CBufferStream(){}
};


class CryptoBufferStream:public CDecoratorStream
{
public:
	CryptoBufferStream(IStream* stm):CDecoratorStream(stm){}
	virtual void Read(int num);
	virtual void Seek(int pos);
	virtual void Write(char data);
	virtual ~CryptoBufferStream(){}
};
#endif

imp.cpp

#include <iostream>
#include "imp.h"

using namespace std;

void CFileStream::Read(int num)
{
	cout << "CFileStream Read" << endl;
}
void CFileStream::Seek(int pos)
{
	cout << "CFileStream Seek" << endl;
}
void CFileStream::Write(char data)
{
	cout << "CFileStream Write" << endl;
}

void CNetStream::Read(int num)
{
	cout << "CNetStream Read" << endl;
}
void CNetStream::Seek(int pos)
{
	cout << "CNetStream Seek" << endl;
}
void CNetStream::Write(char data)
{
	cout << "CNetStream Write" << endl;
}

void CMemStream::Read(int num)
{
	cout << "CMemStream Read" << endl;
}
void CMemStream::Seek(int pos)
{
	cout << "CMemStream Seek" << endl;
}
void CMemStream::Write(char data)
{
	cout << "CMemStream Write" << endl;
}
///////////////////////////////////////////
void CryptoStream::Read(int num)
{
	m_stream->Read(num);
	cout << "CryptoStream Read" << endl;
}
void CryptoStream::Seek(int pos)
{
	m_stream->Seek(pos);
	cout << "CryptoStream Seek" << endl;
}
void CryptoStream::Write(char data)
{
	m_stream->Write(data);
	cout << "CryptoStream Write" << endl;
}
////////////////////////////////////////////
void CBufferStream::Read(int num)
{
	m_stream->Read(num);
	cout << "CBufferStream Read" << endl;
}
void CBufferStream::Seek(int pos)
{
	m_stream->Seek(pos);
	cout << "CBufferStream Seek" << endl;
}
void CBufferStream::Write(char data)
{
	m_stream->Write(data);
	cout << "CBufferStream Write" << endl;
}
/////////////////////////////////////////////
void CryptoBufferStream::Read(int num)
{
	m_stream->Read(num);
	cout << "CryptoBufferStream Read" << endl;
}
void CryptoBufferStream::Seek(int pos)
{
	m_stream->Seek(pos);
	cout << "CryptoBufferStream Seek" << endl;
}
void CryptoBufferStream::Write(char data)
{
	m_stream->Write(data);
	cout << "CryptoBufferStream Write" << endl;
}

main.cpp

#include "base.h"
#include "imp.h"

int main()
{
	CFileStream fileStream;
	CBufferStream bufStream(&fileStream);
	bufStream.Read(5);
	
	CNetStream netStream;
	CryptoStream cryptoStream(&netStream);
	cryptoStream.Seek(10);
	
	CMemStream menStream;
	CryptoBufferStream cryptoBufStream(&menStream);
	cryptoBufStream.Write('x');
	
	return 0;
}