Question

我尝试创建一个比较2个文件的程序，并检查第一个文件中是否存在第二个文件。函数r_scan进入无限循环。有人知道为什么它不起作用？

这是我的代码：

    /**
    The function scan the file and check if there is a virus in the file.

    Input:
    virus_address - The address of the virus file.
    scaned_address - The adress of the file that we scan.
    Output:
    end - If the the file infected. 0 - infected, 1 - not infected.
    **/

   int r_scan(char* virus_address, char* scaned_address)
    {
        //INIT
        char v = ' ', s = ' ';
        int end = 1, i = 0;
        long seek = 0;
        FILE* vp = NULL;
        FILE* sp = NULL;
        //Open th5e files.
        vp = fopen(virus_address, "rb");
        sp = fopen(scaned_address, "rb");
        fseek(vp, 0, SEEK_SET);
        fseek(sp, 0, SEEK_SET);
        //pre scanning
        seek = 0;
        //Check if the file infected.
        while (!(feof(sp)) && end)
        {           
            fread(&s, 1, 1, sp);

            if (v == s)
            {
                v = fgetc(vp);
            }
            else
            {
                seek++;
                fseek(vp, 0, SEEK_SET);
                fseek(sp, seek, SEEK_SET);
                fread(&v, 1, 1, vp);
            }
            if (v == EOF)
            {
                end = 0;
            }
        }
    fclose(vp);
    fclose(sp);
    return end;
}

Answer 1

fseek的手册页说：

成功调用fseek（）函数会清除文件结束指示符

当你的程序循环时，在fseek(sp, seek, SEEK_SET);之前调用feof(sp)，这就是feof总是返回0的原因。并且因为你没有测试fread(&s, 1, 1, sp);的返回值你的程序循环永远。

无尽的循环 - C编程

1 个答案: