string自建常用函式(3)

enum eGET_SUBSTR_TYPE
{
    eGET_SUBSTR_BEGIN,    // 遇到token後，取得token之前的字串
    eGET_SUBSTR_END,    // 遇到token後，取得token之後的字串

    eGET_SUBSTR_MAX,
};

enum eGET_SUBSTR_DIRECTION
{
    eGET_SUBSTR_DIR_FORWARD,    // 從字串前面開始找
    eGET_SUBSTR_DIR_BACKWARD,    // 從字串後面開始找

    eGET_SUBSTR_DIR_MAX,
};


bool GetSubStrFromString(string& strSource, string strToken, string::size_type stPos, eGET_SUBSTR_TYPE eType, eGET_SUBSTR_DIRECTION eDirection);    // 從字串中往eDirection方向取得stPos個strToken之前(或之後，依照eType而定)的剩餘字串



bool GetSubStrFromString(string& strSource, string strToken, string::size_type stPos, eGET_SUBSTR_TYPE eType, eGET_SUBSTR_DIRECTION eDirection)
{
    if(stPos <= 0)
        return false;

    string::size_type stPos_ = string::npos,  stPostmp_= 0;
    if(eDirection == eGET_SUBSTR_DIR_FORWARD)
        stPostmp_ = 0;
    else if(eDirection == eGET_SUBSTR_DIR_BACKWARD)
        stPostmp_ = string::npos;

    string::iterator str_Iter_Begin, str_Iter_End, str_Iter_Pos;
    str_Iter_Begin = strSource.begin();
    str_Iter_End = strSource.end();

    switch(eType)
    {
    case eGET_SUBSTR_BEGIN:
        {
            for(string::size_type stCounter = 0; stCounter < stPos; ++stCounter)
            {
                if(eDirection == eGET_SUBSTR_DIR_FORWARD)
                    stPostmp_ = strSource.find(strToken, stPostmp_);
                else if(eDirection == eGET_SUBSTR_DIR_BACKWARD)
                    stPostmp_ = strSource.rfind(strToken, stPostmp_);

                if(stPostmp_ == string::npos)
                    return false;
                else
                {
                    stPos_ = stPostmp_ + 1;
                    if(eDirection == eGET_SUBSTR_DIR_FORWARD)
                        ++stPostmp_;
                    else if(eDirection == eGET_SUBSTR_DIR_BACKWARD)
                        --stPostmp_;                
                }
            }

            if(stPos_ != string::npos)
            {
                str_Iter_Begin += stPos_ - 1;

                strSource.erase(str_Iter_Begin, str_Iter_End);
            }
        }
        break;

    case eGET_SUBSTR_END:
        {
            for(string::size_type stCounter = 0; stCounter < stPos; ++stCounter)
            {
                if(eDirection == eGET_SUBSTR_DIR_FORWARD)
                    stPostmp_ = strSource.find(strToken, stPostmp_);
                else if(eDirection == eGET_SUBSTR_DIR_BACKWARD)
                    stPostmp_ = strSource.rfind(strToken, stPostmp_);

                if(stPostmp_ == string::npos)
                    return false;
                else
                {
                    stPos_ = stPostmp_ + 1;
                    if(eDirection == eGET_SUBSTR_DIR_FORWARD)
                        ++stPostmp_;
                    else if(eDirection == eGET_SUBSTR_DIR_BACKWARD)
                        --stPostmp_;
                }
            }

            if(stPos_ != string::npos)
            {
                str_Iter_End -= strSource.size() - stPos_;

                strSource.erase(str_Iter_Begin, str_Iter_End);
            }
        }
        break;

    }

    return true;
}

 

使用方式舉例如下：

 

string strPath("C:\\WINDOWS\\system32\\hahaha.exe");

GetSubStrFromString(strPath, ".", 1, eGET_SUBSTR_BEGIN, eGET_SUBSTR_DIR_FORWARD);
// strPath == "C:\\WINDOWS\\system32\\hahaha"

GetSubStrFromString(strPath, "\\", 1, eGET_SUBSTR_END, eGET_SUBSTR_DIR_BACKWARD);
// strPath == "hahaha"


strPath = "C:\\WINDOWS\\system32\\hahaha.exe";

GetSubStrFromString(strPath, "\\", 3, eGET_SUBSTR_BEGIN, eGET_SUBSTR_DIR_BACKWARD);
// strPath == "c:"