duplicate tile thing

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define TILE_SIZE 16

unsigned char *chr;
FILE *output_file;

int tiles_equal(int tile1, int tile2) {
  return !memcmp(&chr[tile1*TILE_SIZE], &chr[tile2*TILE_SIZE], TILE_SIZE);
}

void write_tile(int tile) {
  int i;
  for(i=0; i<TILE_SIZE; i++)
    fputc(chr[tile*TILE_SIZE+i], output_file);
}

int main(int argc, char *argv[]) {
  int i, j;
  int cur_tile;
  const char *input_name = NULL;
  const char *output_name = NULL;
  int bank_size = 64;
  int written_tiles = 0;

  // parse parameters
  for(i=1; i<(argc-1); i++) {
    if(!strcmp(argv[i], "-i"))
      input_name = argv[i+1];
    if(!strcmp(argv[i], "-o"))
      output_name = argv[i+1];
    if(!strcmp(argv[i], "-banksize"))
      bank_size = atoi(argv[i+1]);
  }

  if(!input_name || !output_name) {
    puts("Must specify input and output files");
    return -1;
  }

  // open the input CHR
  FILE *input_file = fopen(input_name,"rb");
  if(!input_file) {
    fputs("Failed to open input file", stderr);
    return -1;
  }
  fseek(input_file, 0, SEEK_END);
  long file_size = ftell(input_file);
  rewind(input_file);

  chr = (char*)malloc(sizeof(char)*file_size);
  if(chr == NULL) {
    fputs("Failed to allocate space for the input file", stderr);
    return -1;
  }
  if(file_size != fread(chr, 1, file_size, input_file)) {
    fputs("Failed to read the input file", stderr);
    return -1;
  }
  fclose(input_file);

  // open output file
  output_file = fopen(output_name, "wb");
  for(cur_tile = 0; cur_tile < file_size/TILE_SIZE; cur_tile++) {
    int already_written = 0;
    for(i=cur_tile-1; i>=0; i--) {
      if(tiles_equal(i, cur_tile)) {
        already_written = 1;
        break;
      }
    }
    if(!already_written)
      write_tile(cur_tile);
  }
  fclose(output_file);

  free(chr);
  return 0;
}