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:

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#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;
}

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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...

You're trying to endian-swap the pointer itself, instead of the integer it points to!

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

Code:

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

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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 *.

OK, so I dereference it. That works. It makes it compile, and so I run it (drag and drop) with a file that has hex values of 043E7A4F. But my output confuses me... I get:

Code:

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Original hex: 3E24E0
;Swapped hex: 43E7A4F

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First of all, how do I make it register the leading 0's in the values and not drop them, and second, is my file not really 043E7A4F if my program reads it as 3E24E0? Or am I having it read it wrong?

EDIT: OK, that's odd... I change two parts of the program that shouldn't have anything to do with the output, and I sort of get it. (P.S. I changed the fwrite portion at the end to have it be "fwrite(buffer, 1, 4..." instead, and I took the "+" off of the "wb" in the newSave fopen). So now I've got:

Code:

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Original hex: 4F7A3E04
;Swapped hex:43E7A4F

---

But that's backwards... The original hex is actually the swapped one, and vice versa...

Oh, and I've been leaving the last fwrite/fclose/fclose/free section uncommented, but it's also still not creating the new file...

EDIT 2: Using fwrite on the original save stream doesn't even work...