TLV消息传输格式

原文地址: http://blog.csdn.net/chexlong/article/details/6974201

这里有个传输格式的讨论风暴挺精彩的:https://bbs.csdn.net/topics/380167545

废话不多说,,拿代码到VS去单步调试,什么都能懂

#include   
#include   
#include   

#pragma comment(lib, "WS2_32")  

enum emTLVNodeType
{
    emTlvNNone = 0,
    emTlvNRoot,         //根节点  
    emTlvName,          //名字  
    emTlvAge,           //年龄  
    emTlvColor          //颜色 1 白色 2 黑色  
};


typedef struct _CAT_INFO
{
    char szName[12];
    int iAge;
    int iColor;
}CAT_INFO, *LPCAT_INFO;

class CTlvPacket
{
public:
    CTlvPacket(char *pBuf, unsigned int len) :m_pData(pBuf), m_uiLength(len), m_pEndData(m_pData + len), m_pWritePtr(m_pData), m_pReadPtr(m_pData) { }
    ~CTlvPacket() { }

    bool WriteInt(int data, bool bMovePtr = true)
    {
        int tmp = htonl(data);
        return Write(&tmp, sizeof(int));
    }

    bool Write(const void *pDst, unsigned int uiCount)
    {
        ::memcpy(m_pWritePtr, pDst, uiCount);
        m_pWritePtr += uiCount;
        return m_pWritePtr < m_pEndData ? true : false;
    }

    bool ReadInt(int *data, bool bMovePtr = true)
    {
        Read(data, sizeof(int));
        *data = ntohl(*data);
        return true;
    }

    bool Read(void *pDst, unsigned int uiCount)
    {
        ::memcpy(pDst, m_pReadPtr, uiCount);
        m_pReadPtr += uiCount;
        return m_pReadPtr < m_pEndData ? true : false;
    }

private:
    char *m_pData;
    unsigned int m_uiLength;
    char *m_pEndData;
    char *m_pWritePtr;
    char *m_pReadPtr;
};

/*

**格式:**
root L1 V
T L V T L V T L V

L1 的长度即为“T L V T L V T L V”的长度

*/

int TLV_EncodeCat(LPCAT_INFO pCatInfo, char *pBuf, int &iLen)
{
    if (!pCatInfo || !pBuf)
    {
        return -1;
    }

    CTlvPacket enc(pBuf, iLen);
    enc.WriteInt(emTlvNRoot);
    enc.WriteInt(20 + 12 + 12); //length   不懂这个怎么来,看上边  **格式**(一个值一个TLV)

    enc.WriteInt(emTlvName);
    enc.WriteInt(12);
    enc.Write(pCatInfo->szName, 12);

    enc.WriteInt(emTlvAge);
    enc.WriteInt(4);
    enc.WriteInt(pCatInfo->iAge);

    enc.WriteInt(emTlvColor);
    enc.WriteInt(4);
    enc.WriteInt(pCatInfo->iColor);

    iLen = 8 + 20 + 12 + 12;

    return 0;
}

int TLV_DecodeCat(char *pBuf, int iLen, LPCAT_INFO pCatInfo)
{
    if (!pCatInfo || !pBuf)
    {
        return -1;
    }

    CTlvPacket encDec(pBuf, iLen);
    int iType;
    int iSum, iLength;

    encDec.ReadInt(&iType);
    if (emTlvNRoot != iType)
    {
        return -2;
    }
    encDec.ReadInt(&iSum);

    while (iSum > 0)
    {
        encDec.ReadInt(&iType);
        encDec.ReadInt(&iLength);
        switch (iType)
        {
        case emTlvName:
            encDec.Read(pCatInfo->szName, 12);
            iSum -= 20;
            break;
        case emTlvAge:
            encDec.ReadInt(&pCatInfo->iAge);
            iSum -= 12;
            break;
        case emTlvColor:
            encDec.ReadInt(&pCatInfo->iColor);
            iSum -= 12;
            break;
        default:
            printf("TLV_DecodeCat unkonwn error. \n");
            break;
        }
    }

    return 0;
}

int main(int argc, char* argv[])
{

    int iRet, iLen;
    char buf[256] = { 0 };

    CAT_INFO cat;
    memset(&cat, 0, sizeof(cat));
    strcpy(cat.szName, "Tom");
    cat.iAge = 5;
    cat.iColor = 2;

    iRet = TLV_EncodeCat(&cat, buf, iLen);
    if (0 == iRet)
    {
        printf("TLV_EncodeCat ok, iLen = %d. \n", iLen);
    }
    else
    {
        printf("TLV_EncodeCat error \n");
    }

    memset(&cat, 0, sizeof(cat));
    iRet = TLV_DecodeCat(buf, iLen, &cat);
    if (0 == iRet)
    {
        printf("TLV_DecodeCat ok, cat name = %s, age = %d, color = %d. \n", cat.szName, cat.iAge, cat.iColor);
    }
    else
    {
        printf("TLV_DecodeCat error, code = %d. \n", iRet);
    }

    int iWait = getchar();
    return 0;
}