7. C++ 经验技巧

7.1. C++ 读写二进制文件

读取一个二进制文件，并写入另外一个二进制文件：

#include <fstream>
#include <iterator>
#include <algorithm>

int main()
{
    std::ifstream input( "C:\\Final.gif", std::ios::binary );
    std::ofstream output( "C:\\myfile.gif", std::ios::binary );

    std::copy(
        std::istreambuf_iterator<char>(input),
        std::istreambuf_iterator<char>( ),
        std::ostreambuf_iterator<char>(output));
}

将二进制文件读入内存，用于后续处理：

#include <fstream>
#include <iterator>
#include <vector>

int main()
{
    std::ifstream input( "C:\\Final.gif", std::ios::binary );
    // copies all data into buffer
    std::vector<char> buffer((
            std::istreambuf_iterator<char>(input)),
            (std::istreambuf_iterator<char>()));
}

7.2. typedef 定长数组

想定义一个 3 字节的数组为一个新的类型，方法如下：

typedef char[3] type24;

但编译不通过。

正确的做法如下：

typedef char type24[3];

However, this is probably a very bad idea, because the resulting type is an array type, but users of it won’t see that it’s an array type. If used as a function argument, it will be passed by reference, not by value, and the sizeof for it will then be wrong.

A better solution would be

typedef struct type24 { char x[3]; } type24;

You probably also want to be using unsigned char instead of char, since the latter has implementation-defined signedness.

7.2.1. 参考：