Question

//#include <QtCore/QCoreApplication>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <string>
#include "shift.h"

using namespace::std;

int main(int argc, char *argv[])
{
    unsigned char tmpBuf;
    FILE* fp;
    FILE* fp2;
    char fname[50];
    static unsigned int lSize, count, num;

    cout << "Input the filename:" << endl;
    cin >> fname;

    fp = fopen(fname,"r");
    if(fp == NULL) {
        cout << "The file does not exist!" << endl;
        exit(1);
    }

    // obtain file size:
    fseek(fp , 0 , SEEK_END);
    lSize = ftell(fp);
    rewind(fp);
    cout << "The intput file's size is: " << lSize << endl;

    fp2 = fopen("myfile", "w");

    while(1){
        num = fread(&tmpBuf, 1, 1, fp);
        count += num;
//        putchar(tmpBuf);
//        tmpBuf = cror(tmpBuf, 4);
//        tmpBuf = crol(tmpBuf, 4);
        fwrite(&tmpBuf, 1, num, fp2);

        cout << tmpBuf << " " << num << " " << count << endl;
        if (count == lSize){
            printf("over\n");
            break;
        }
    }

    fclose(fp);
    fclose(fp2);

    while(1){}

    return 0;

    //return a.exec();
}

I made a Qt console program and disable QtCore, like above code. When read some file, e.g. 1.txt (which contains only 1234567890) it succeeds. But when reading some other file, e.g. 1.rar, it failed like below: Why?

Answer 1

Check the value of num coming back from

num = fread(&tmpBuf, 1, 1, fp);

If it comes back as 0, that would explain why

if (count == lSize){

never comes back as true to break you out of the loop.

As to why that could happen, you’re opening fname in “r” mode but a rar file would be binary. For that, I’d suggest opening in “rb” mode. If fread expects txt format but hits the EOF indicator, it’ll stop advancing so num = 0 and count won’t increase.

I don’t have windows available to test this, but other questions have come up on stackoverflow for this reason:

fread/ftell apparently broken under Windows, works fine under Linux