是要向文件里面写东西么.
我给出几个简单的函数例子

 void XFileUtil::writeBufferToNewBinFile(const vector<char> *buffer, const string &fileFullName)
{
    fstream fs(fileFullName,ios::out|ios::binary|ios::trunc);
    if(fs.is_open())
    {
        string tmp = string(buffer->begin(), buffer->end());
        fs.write(tmp.c_str(), tmp.size());
    }
    fs.close();
}

void XFileUtil::writeBufferToExistBinFile(const vector<char> *buffer, const string &fileFullName)
{
    fstream fs(fileFullName,ios::out|ios::binary|ios::app);
    if(fs.is_open())
    {
        string tmp = string(buffer->begin(), buffer->end());
        fs.write(tmp.c_str(), tmp.size());
    }
    fs.close();
}


void XFileUtil::writeTxtLineToFile(const string &line, const string &fileFullName)
{
    ofstream outFile(fileFullName,ios::out|ios::app);
    if(outFile.is_open())
    {
        outFile<<line<<endl;
        outFile.close();
    }
    else
        writeTxtLineToNewFile(line, fileFullName);
}

void XFileUtil::writeTxtLineToNewFile(const string &line, const string &fileFullName)
{
    ofstream outFile(fileFullName,ios::out|ios::trunc);
    if(outFile.is_open())
    {
        outFile<<line<<endl;
        outFile.close();
    }
}

void XFileUtil::writeTxtLineToExistFile(const string &line, const string &fileFullName)
{
    ofstream outFile(fileFullName,ios::out|ios::app);
    if(outFile.is_open())
    {
        outFile<<line<<endl;
        outFile.close();
    }
}

源码地址