初版：http://www.cnblogs.com/wjshan0808/p/6580638.html

說明：在實現了對應的接口後該策略可以適合絕大多數的網絡數據包結構

首先，是三個接口

IProduceProxy.h

#ifndef _I_PRODUCE_PROXY_H_
#define _I_PRODUCE_PROXY_H_

//Code
#define    CODE_PRODUCE_PROXY_OK        0x00    //OK
#define CODE_PRODUCE_PROXY_NI        0x01    //Not Implemented 
#define CODE_PRODUCE_PROXY_NT        0x02    //
 
Nothing
#define CODE_PRODUCE_PROXY_RY        0x0F    //Ready 

//INTERFACE
class CIProduceProxy
{
public:
    virtual int ProduceProxy(char* &szBuffer, int &nBufferLength) = 0;
};

//PFN 
typedef    int(CIProduceProxy::*PFN_PRODUCEPROXY)(char* &szBuffer, int &nBufferLength);

#endif
 
 //_I_PRODUCE_PROXY_H_

IStrategyProtocol.h

#ifndef _I_STRATEGY_PROTOCOL_H_
#define _I_STRATEGY_PROTOCOL_H_

//CODE
#define CODE_STRATEGY_PROTOCOL_OK        0x00        //OK
#define CODE_STRATEGY_PROTOCOL_NI        0x01        //Not Implemented
#define CODE_STRATEGY_PROTOCOL_ML        0x02        //
 
Miss Length
#define CODE_STRATEGY_PROTOCOL_RY        0x0F        //Ready

//INTERFACE
class CIStrategyProtocol
{
public:
    virtual int ExtractLength(const char* szBuffer, int nBufferLength, int &nExtractLength) = 0;
};

//PFN 
typedef    int    (CIStrategyProtocol::*PFN_STRATEGYPROTOCOL)(const char* szBuffer, int nBufferLength, int &nExtractLength);

#endif //_I_STRATEGY_PROTOCOL_H_

IConsumeProxy.h

#ifndef _I_CONSUME_PROXY_H_
#define _I_CONSUME_PROXY_H_

//Code
#define    CODE_CONSUME_PROXY_OK        0x00    //OK
#define CODE_CONSUME_PROXY_NI        0x01    //Not Implemented 
#define CODE_CONSUME_PROXY_RY        0x0F    //Ready

//INTERFACE
class CIConsumeProxy
{
public:
    virtual int ConsumeProxy(const char* szBuffer, int nBufferLength) = 0;
};

//PFN 
typedef    int(CIConsumeProxy::*PFN_CONSUMEPROXY)(const char* szBuffer, int nBufferLength);

#endif //_I_CONSUME_PROXY_H_

然後，例如我們有如下一個協議對象，實現IStrategyProtocol接口

.h

#ifndef _PROTOCOL_H_
#define _PROTOCOL_H_

#include "IStrategyProtocol.h"

class CProtocol : public CIStrategyProtocol
{
public:
    CProtocol();
    ~CProtocol();


public:
    int ExtractLength(const char* szBuffer, int nBufferLength, int &nExtractLength) override;

};


#endif //_PROTOCOL_H_

.cpp

#include "Protocol.h"
 

CProtocol::CProtocol()
{
}
CProtocol::~CProtocol()
{
}
 

int CProtocol::ExtractLength(const char* szBuffer, int nBufferLength, int &nExtractLength)
{
    nExtractLength = 0;

    if (false)
        return CODE_STRATEGY_PROTOCOL_ML;

    //...

    return CODE_STRATEGY_PROTOCOL_OK;
}
 

其次，例如我們有如下的網絡端對象，實現IProduceProxy，IConsumeProxy接口
.h

#ifndef _NET_CLIENT_H_
#define _NET_CLIENT_H_


#include "ExtractTask.h"
#include "Protocol.h"


class CNetClient : public CIProduceProxy, public CIConsumeProxy
{
public:
    CNetClient();
    ~CNetClient();

public:
    int Init();
    int Receive(char* szReceiveBuffer, int nBufferLength);
    int Processing(const char* szData, int nDataLength);

public:
    int ProduceProxy(char* &szBuffer, int &nBufferLength) override;
    int ConsumeProxy(const char* szBuffer, int nBufferLength) override;

private:
    CExtractTask* m_pExtractor;
    CProtocol* m_pProtocol;
};

#endif //_DRIVE_M_40064900_H_

.cpp

#include "NetClient.h"


CNetClient::CNetClient()
{
    m_pProtocol = new CProtocol();
    m_pExtractor = new CExtractTask();
}
CNetClient::~CNetClient()
{
}



int CNetClient::Init()
{
    m_pExtractor->Proxies(this, this->m_pProtocol, this);

    return 0;
}

int CNetClient::ProduceProxy(char* &szBuffer, int &nBufferLength)
{
    nBufferLength = Receive(szBuffer, nBufferLength);
    if (nBufferLength <= 0)
        return CODE_PRODUCE_PROXY_NT;
    return CODE_PRODUCE_PROXY_OK;
}

int CNetClient::ConsumeProxy(const char* szBuffer, int nBufferLength)
{
    Processing(szBuffer, nBufferLength);
    return CODE_CONSUME_PROXY_OK;
}
 

最終是我們的解析策略實現對象
.h

#ifndef _EXTRACT_TASK_H_
#define _EXTRACT_TASK_H_

#include "IStrategyProtocol.h"
#include "IProduceProxy.h"
#include "IConsumeProxy.h"


class CExtractTask
{
public:
    CExtractTask();
    virtual ~CExtractTask();
        
public:
    int Proxies(CIProduceProxy* pProducer, CIStrategyProtocol* pStrategy, CIConsumeProxy* pConsumer);
    //int Proxies(PFN_PRODUCEPROXY pfnProducer, PFN_STRATEGYPROTOCOL pfnStrategy, PFN_CONSUMEPROXY pfnConsumer);

protected:
    virtual int ProduceImply(char* &szBuffer, int &nBufferLength);
    virtual int StrategyImply(const char* szBuffer, int nBufferLength, int &nExtractLength);
    virtual int ConsumeImply(const char* szExtractCopier, int nExtractLength);

private:
    int Extractor();


private:
    CIProduceProxy*        m_pProducer;
    //PFN_PRODUCEPROXY    m_pfnProducer;
    CIStrategyProtocol*        m_pStrategy; 
    //PFN_STRATEGYPROTOCOL    m_pfnStrategy;
    CIConsumeProxy*        m_pConsumer;
    //PFN_CONSUMEPROXY    m_pfnConsumer;
};
 
#endif //_EXTRACT_TASK_H_

.cpp

#include "ExtractTask.h"
#include <cstring>
#ifdef WIN32
#include <Windows.h>
#else
#include <unistd.h>
#endif //WIN32


#define    TIME_BASE_UNIT_VALUE        1000
#define TIME_TASK_SLEEP_16MS        16
#ifdef WIN32
#define    TIME_EXTRACT_8MS        8
#else
#define    TIME_EXTRACT_8MS        (8 * TIME_BASE_UNIT_VALUE)
#endif // WIN32

#define LENGTH_EXTRACT_BUFFER        (1024 * 4)    //接收緩沖區大小 


using namespace std;


CExtractTask::CExtractTask() : 
m_pProducer(NULL), m_pStrategy(NULL), m_pConsumer(NULL)
//, m_pfnProducer(NULL), m_pfnStrategy(NULL), m_pfnConsumer(NULL)
{
}
CExtractTask::~CExtractTask(void)
{
    /*
    m_pfnProducer = NULL;
    m_pfnStrategy = NULL;
    m_pfnConsumer = NULL;
    */
    /*
    if (m_pProducer != NULL)
        delete m_pProducer;
    if (m_pStrategy != NULL)
        delete m_pStrategy;
    if (m_pConsumer != NULL)
        delete m_pConsumer;
        */
}


int CExtractTask::Proxies(CIProduceProxy* pProducer, CIStrategyProtocol* pStrategy, CIConsumeProxy* pConsumer)
{
    m_pProducer = pProducer;
    m_pStrategy = pStrategy;
    m_pConsumer = pConsumer;

    return 0;
}
/*
int CExtractTask::Proxies(PFN_PRODUCEPROXY pfnProducer, PFN_STRATEGYPROTOCOL pfnStrategy, PFN_CONSUMEPROXY pfnConsumer)
{
    m_pfnProducer = pfnProducer;
    m_pfnStrategy = pfnStrategy;
    m_pfnConsumer = pfnConsumer;

    return 0;
}
*/
int CExtractTask::ProduceImply(char* &szBuffer, int &nBufferLength)
{
    if (m_pProducer == NULL)// && m_pfnProducer == NULL)
        return CODE_PRODUCE_PROXY_NI;

    if (m_pProducer != NULL)
        return m_pProducer->ProduceProxy(szBuffer, nBufferLength);
    //else if (m_pfnProducer != NULL)
    //    return m_pfnProducer(szBuffer, nBufferLength);

    return CODE_PRODUCE_PROXY_RY;
}

int CExtractTask::StrategyImply(const char* szBuffer, int nBufferLength, int &nExtractLength)
{
    if (m_pStrategy == NULL)// && m_pfnStrategy == NULL)
        return CODE_STRATEGY_PROTOCOL_NI;

    if (m_pStrategy != NULL)
        return m_pStrategy->ExtractLength(szBuffer, nBufferLength, nExtractLength);
    //else if (m_pfnStrategy != NULL)
    //    return m_pfnStrategy(szBuffer, nBufferLength, nExtractLength);

    return CODE_STRATEGY_PROTOCOL_RY;
}

int CExtractTask::ConsumeImply(const char* szExtractCopier, int nExtractLength)
{
    if (m_pConsumer == NULL)// && m_pfnConsumer == NULL)
        return CODE_CONSUME_PROXY_NI;

    if (m_pConsumer != NULL)
        return m_pConsumer->ConsumeProxy(szExtractCopier, nExtractLength);
    //else if (m_pfnConsumer != NULL)
    //    return m_pfnConsumer(szExtractCopier, nExtractLength);

    return CODE_CONSUME_PROXY_RY;
}

int CExtractTask::Extractor()
{
    int nSurplusLength = 0;
    char* szExtractCopier = NULL;
    char* szExtractCopyIterator = NULL;
    //Extract Buffer from Product Proxy.
    do
    {
        //Extract Buffer
        char* szExtractBuffer = new char[LENGTH_EXTRACT_BUFFER]();
        //Extract Length
        int nExtractBufferLength = LENGTH_EXTRACT_BUFFER;
        //Productor Proxy
        int nRet = ProduceImply(szExtractBuffer, nExtractBufferLength);
        if (nRet != CODE_PRODUCE_PROXY_OK)
        {
            //LogMessage(LOGLEVEL_DEBUG, "ProduceProxy Return(%d).", nRet);
            delete[] szExtractBuffer;
            break;
        }
        //LogMessage(LOGLEVEL_INFO, "ProduceProxy Extract Buffer-Length(%d).", nExtractBufferLength);

        //Clone Extractor to extract
        char* szExtractor = szExtractBuffer;
        //Begin to Extract by The Rules
        do
        {
            //Surplus Length less than or equal to zero that Means new could be create
            if (nSurplusLength <= 0)
            {
                //Got Extract-Length from RuleProxy(Extract Whole Length)
                int nExtractLength = 0;
                nRet = StrategyImply(szExtractor, nExtractBufferLength, nExtractLength);
                if (nRet != CODE_STRATEGY_PROTOCOL_OK)
                {
                    break;
                }
                //To new that Means variate value is equal between nSurplusLength and nExtractLength.
                nSurplusLength = nExtractLength;

                //Allocate enough space for new
                szExtractCopier = new char[nExtractLength + 1]();
                //Mark Movable Pointer for Copier
                szExtractCopyIterator = szExtractCopier;
            }
            //when ExtractBufferLength is less than SurplusLength that Means Data copy is continue
            if (nExtractBufferLength < nSurplusLength)
            {
                //Doing copy
                memcpy(szExtractCopyIterator, szExtractor, nExtractBufferLength);
                //Move ExtractCopyIterator position
                szExtractCopyIterator += nExtractBufferLength;
                //Cut down SurplusLength
                nSurplusLength -= nExtractBufferLength;
                //Move Extractor position
                szExtractor += nExtractBufferLength;
                //Cut down ExtractBufferLength
                nExtractBufferLength -= nExtractBufferLength;
            }
            else//(nExtractBufferLength >= nSurplusLength)
            {
                //Doing copy
                memcpy(szExtractCopyIterator, szExtractor, nSurplusLength);
                //Move Extractor position
                szExtractor += nSurplusLength;
                //Cut down ExtractBufferLength
                nExtractBufferLength -= nSurplusLength;
                //Move ExtractCopyIterator position
                szExtractCopyIterator += nSurplusLength;
                //Cut down SurplusLength
                nSurplusLength -= nSurplusLength;
                //Package Whole Length
                ConsumeImply(szExtractCopier, (szExtractCopyIterator - szExtractCopier));
                //Clean szExtractCopier 
                delete[] szExtractCopier;
                szExtractCopier = NULL;
            }
        } while (nExtractBufferLength > 0);
        //Clean szExtractBuffer
        delete[] szExtractBuffer;

#ifdef WIN32
        Sleep(TIME_EXTRACT_8MS);
#else
        usleep(TIME_EXTRACT_8MS);
#endif // WIN32
    } while (!m_bStopStream);
    //Clean szExtractCopier
    if (szExtractCopier != NULL)
        delete[] szExtractCopier;
    return 0;
}

C++版的網絡數據包解析策略(升級版)