Thread: Endian swapping (byte-order reversal) on a file

OK, so I found the C programming posts by a few people about byte-order swapping, and I've got that working just fine, but I'm a little confused as to how to grab those informations from a file, convert it, and then save that to a different file.

Code:

#include <cstdio>
#include <cstdlib>
#include <climits>
#include <iostream>
#include <stdint.h>

using namespace std;

main(int argc, char *argv[])
{
    FILE* originalSave;
    FILE* newSave;
    long fSize;
    uint32_t *buffer;
    int x;
    
    uint32_t input = 0, j, result = 0, temp, final = 0, k;
    
    originalSave = fopen(argv[1], "rb");
    if (originalSave == NULL) {fputs("File error",stderr); exit(1);}
    
    newSave = fopen("newSave.fla", "wb+");
    
    fseek(originalSave, 0, SEEK_END);
    fSize = ftell(originalSave);
    rewind(originalSave);
    
    buffer = (char*) malloc(sizeof(char)*fSize);
    if (buffer == NULL)
    {
        fputs("Memory error",stderr); exit(2);
    }
        
    fread(buffer, 1, 4, originalSave);
    
    result = ((buffer << 24) & 0xFF000000) | 
        ((buffer << 8) & 0x00FF0000) |
        ((buffer >> 8) & 0x0000FF00) |
        ((buffer >> 24) & 0X000000FF);
    
    printf("Original hex: %X\n;Swapped hex: %X\n", buffer, result);
    
    //fwrite(buffer, fSize/4, 4, newSave);
    //fclose(newSave);
    //fclose(originalSave);
    //free(buffer);
    
    
    
    cout << "Press ENTER to continue...";
    cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );

  	
  return 0;
}

I don't even know if my code is functional (I get an error about invalid char or int to binary "operator>>" or whatever about the swap lines), but the structure should work, right? I'm completely confused by this.

Oh, and eventually, I want to be able to do this with a file of up to 128KB size, so...

OK, so I put in the pointer reference (&), and I still get those errors... Here's what they are exactly:

Code:

main.cpp invalid operands of types `uint32_t**' and `int' to binary `operator>>'

That's for all four lines with the bit shifts in them.

So & is soooo not "the pointer reference". If you want what the pointer points to, you need to dereference the pointer, using *.