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

int main(int argc, char ** argv) {
    FILE * in1, * in2, * out;
    size_t s1, s2, p, b, c;
    int b1, b2;
    
    if (argc != 4) { printf("Usage: %s fin1 fin2 fout\n", argv[0]); exit(-1); }
    
    if ((in1 = fopen(argv[1], "rb")) == 0) { printf("Error opening %s\n", argv[1]); perror("fopen"); exit(-1); }
    if ((in2 = fopen(argv[2], "rb")) == 0) { printf("Error opening %s\n", argv[2]); perror("fopen"); exit(-1); }
    if ((out = fopen(argv[3], "wb")) == 0) { printf("Error opening %s\n", argv[3]); perror("fopen"); exit(-1); }
    
    fseek(in1, 0, SEEK_END); s1 = ftell(in1); fseek(in1, 0, SEEK_SET);
    fseek(in2, 0, SEEK_END); s2 = ftell(in2); fseek(in2, 0, SEEK_SET);
    
    if (s1 != s2) { printf("Error: files are of different sizes.\n"); exit(-1); }
    
    b = s1 - 1;
    
    fprintf(out, "patch = {\n");
    
    for (p = 0; p < s1; p++) {
        b1 = fgetc(in1);
        b2 = fgetc(in2);
        
        if (b1 != b2) {
            b++;
            if ((b != p) && (b != s1)) fprintf(out, " },\n");
            if (b != p) { fprintf(out, "    [0x%06x] = { ", p); c = 0; } else { fprintf(out, ", "); c++; }
            if (c == 16) { fprintf(out, "\n                   "); c = 0; }
            fprintf(out, "0x%02x", b2);
            b = p;
        }
    }
    
    fprintf(out, " },\n}\n");
    
    fclose(in1); fclose(in2); fclose(out);
}