Question

我正在尝试以二进制模式编写和附加到文件但是文件如何被破坏。我无法理解它出错的地方，m_strReceivedMessage的类型是std :: string

 const char * c = m_strReceivedMessage.c_str();
 std::ofstream out(file, std::ios::binary | std::ios_base::app | std::ios_base::out);
 int i = m_strReceivedMessage.size();
 if (out.is_open()) {
   out.write(c, i);
 }
 out.close();

Answer 1

不确定是什么问题，也许你会重复内容。

改变：

std::ofstream out(file, std::ios::binary | std::ios_base::app | std::ios_base::out);

到那个：

std::ofstream out(file, std::ios::binary);

如果你的字符串很好，你应该没问题。

检查这个小例子：

#include <iostream>
#include <fstream>
#include <string>
#include <iterator>
#include <vector>

using namespace std;

int main() {
        string m_strReceivedMessage = "foo";
        const char * c = m_strReceivedMessage.c_str();
        ofstream out("test.bin", ios::binary);
        int i = m_strReceivedMessage.size();
        if (out.is_open()) {
                out.write(c, i);
        }
        out.close();

        ifstream input("test.bin", ios::binary );
        // copies all data into buffer
        vector<char> buffer((
            istreambuf_iterator<char>(input)), 
            (istreambuf_iterator<char>()));

        for(unsigned int i = 0; i < buffer.size(); ++i)
                cout << buffer[i] << endl;
        return 0;
}

输出：

gsamaras@gsamaras-A15:~$ g++ -Wall px.cpp 
gsamaras@gsamaras-A15:~$ ./a.out 
f
o
o

有关详情，请阅读Reading and writing binary file。

以二进制模式写入文件不起作用

1 个答案: