如何在 C++ 中从文件中读取小端整数?

How to read little endian integers from file in C++?(如何在 C++ 中从文件中读取小端整数?)

问题描述

假设我有一个二进制文件；它包含正二进制数，但以 little endian 为 32 位整数

Say I have a binary file; it contains positive binary numbers, but written in little endian as 32-bit integers

如何阅读此文件?我现在有这个.

How do I read this file? I have this right now.

int main() {
    FILE * fp;
    char buffer[4];
    int num = 0;
    fp=fopen("file.txt","rb");
    while ( fread(&buffer, 1, 4,fp) != 0) {

        // I think buffer should be 32 bit integer I read,
        // how can I let num equal to 32 bit little endian integer?
    }
    // Say I just want to get the sum of all these binary little endian integers,
    // is there an another way to make read and get sum faster since it's all 
    // binary, shouldnt it be faster if i just add in binary? not sure..
    return 0;
}

推荐答案

这是一种适用于大端或小端架构的方法:

This is one way to do it that works on either big-endian or little-endian architectures:

int main() {
    unsigned char bytes[4];
    int sum = 0;
    FILE *fp=fopen("file.txt","rb");
    while ( fread(bytes, 4, 1,fp) != 0) {
        sum += bytes[0] | (bytes[1]<<8) | (bytes[2]<<16) | (bytes[3]<<24);
    }
    return 0;
}

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