#define LARGEFILE_SOURCE
#define LARGEFILE64_SOURCE 
#define FILE_OFFSET_BITS 64

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


#define BUFFER_SIZE 0x100000

int main(int argc, char *argv[])
{
	if(argc < 3)
	{
		fprintf(stderr, "Need 2 files to compare.\n");
		exit(1);
	}

	FILE *file1 = fopen64(argv[1], "r");
	if(!file1)
	{
		perror("Opening file 1");
		exit(1);
	}

	FILE *file2 = fopen64(argv[2], "r");
	if(!file2)
	{
		perror("Opening file 2");
		exit(1);
	}

	unsigned char *buffer1 = calloc(1, BUFFER_SIZE);
	unsigned char *buffer2 = calloc(1, BUFFER_SIZE);
	int i;
	int64_t current_position = 0;
	while(!feof(file1) && !feof(file2))
	{
		printf("Testing byte 0x%x\r", current_position);
		fflush(stdout);
		int file1_bytes = fread(buffer1, 1, BUFFER_SIZE, file1);
		int file2_bytes = fread(buffer2, 1, BUFFER_SIZE, file2);
		for(i = 0; i < file1_bytes && i < file2_bytes; i++)
		{
			if(buffer1[i] != buffer2[i])
			{
				printf("Got a difference at byte 0x%x\n", current_position + i);
//				exit(0);
			}
		}
		if(file1_bytes != file2_bytes)
		{
			printf("Files are different lengths.\n");
			exit(0);
		}
		current_position += file1_bytes;
	}
}