【c++文本文件操作之替换】mac系统xcode编译环境

#include <iostream>
#include<fstream>
using namespace std;

void myreplace(const string& filename,const string& tofind,const string& toreplace);

int main()
{
    myreplace("/Users/xuconglong/Desktop/text/1.txt", "5", "m");
    return 0;
}

void myreplace(const string& filename,const string& tofind,const string& toreplace)
{
    ifstream fin(filename.c_str(),ios_base::binary);
    string str(1024*1024*2,0);
    fin.read(&str[0],2*1024*1024);
    fin.close();
    ofstream fout(filename.c_str(),ios_base::binary);
    
    string::size_type beg=0;
    string::size_type pos;
    string::size_type find_size=tofind.size();
    string::size_type replace_size=toreplace.size();

    if(0 == find_size)
    {
        cout << "no such file or no content" << endl;
        return;
    }
    
    unsigned count = 0;
    while((pos=str.find(tofind,beg))!=string::npos)
    {
        fout.write(&str[beg],pos-beg);
        fout.write(&toreplace[0],replace_size);
        beg=pos+find_size;
        count++;
    }
    fout.write(&str[beg],strlen(str.c_str())-beg);
    fout.close();
    cout << "has replaced number:" << count << endl;
}