Question

I am trying to write some simple program to uploading files to my server. I’ d like to convert binary files to hex. I have written something, but it does not work properly.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

static int bufferSize = 1024;
FILE *source;
FILE *dest;

int n;
int counter;

int main() {
    unsigned char buffer[bufferSize];
    source = fopen("server.pdf", "rb");
    if (source) {
        dest = fopen("file_test", "wb");

        while (!feof(source)) {
            n = fread(buffer, 1, bufferSize, source);
            counter += n;
            strtol(buffer, NULL, 2);
            fwrite(buffer, 1, n, dest);
        }
    }
    else {
        printf("Error");
    }
    fclose(source);
    fclose(dest);
}

I use strtol to convert binary do hex. After invoking this code I have still strange characters in my file_test file.

I’ d like to upload a file on server, for example a PDF file. But firstly I have to write a program, that will convert this file to a hex file. I’d like that the length of a line in hex file would be equal 1024. After that, I will upload this file line by line with PL/SQL.

Answer 1

Your code is fantastically confused.

It’s reading in the data, then doing a strtol() call on it, with a base of 2, and then ignoring the return value. What’s the point in that?

To convert the first loaded byte of data to hexadecimal string, you should probably use something like:

char hex[8];

sprintf(hex, "%02x", (unsigned int) buffer[0] & 0xff);

Then write hex to the output file. You need to do this for all bytes loaded, of course, not just buffer[0].

Also, as a minor point, you can’t call feof() before you’ve tried reading the file. It’s better to not use feof() and instead check the return value of fread() to detect when it fails.