bdiff.c

   1 #include <inttypes.h>
   2 #include <stddef.h>
   3 #include <string.h>
   4 #include <assert.h>
   5 #include <unistd.h>
   6 #include <sys/stat.h>
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <fcntl.h>
  10 #ifdef USE_LIBULZ
  11 #include <ulz/stdio-repl.h>
  12 #endif
  13
  14 static int fetch(FILE *f, off_t *cnt) {
  15         int c = fgetc(f);
  16         if(c >= 0) *cnt = *cnt + 1;
  17         return c;
  18 }
  19
  20 static int diff(FILE *f1, FILE* f2) {
  21         off_t min;
  22         size_t diffs = 0;
  23         struct stat st1, st2;
  24         if(fstat(fileno(f1), &st1)) return 1;
  25         if(fstat(fileno(f2), &st2)) return 1;
  26         min = st1.st_size;
  27         off_t p1, p2, l, diffbytes = 0;
  28         if (st2.st_size != min) {
  29                 printf("sizes differ! %llu, %llu\n",
  30                        (long long) st1.st_size, (long long) st2.st_size);
  31                 if (st2.st_size < min) min = st2.st_size;
  32         }
  33         p1 = 0;
  34         p2 = 0;
  35         while(p1 < min) {
  36                 l = 0;
  37                 while(p1 < min && fetch(f1, &p1) != fetch(f2, &p2)) l++;
  38                 if(l) {
  39                         printf("difference at offset %llu of size %llu\n",
  40                                (long long) p1-l-1,  (long long) l);
  41                         diffs++;
  42                         diffbytes += l;
  43                 }
  44         }
  45         printf("%zu differences in %llu out of %llu bytes detected.\n",
  46                 diffs, (long long) diffbytes, (long long) min);
  47         return diffs != 0;
  48 }
  49
  50
  51 static void syntax(void) {
  52         printf("syntax: filename1 filename2\nlist differences in binaries\n");
  53         exit(1);
  54 }
  55
  56 static int canread(char* fn) {
  57         return access(fn, R_OK) != -1;
  58 }
  59
  60 int main(int argc, char** argv) {
  61         if(argc < 3) syntax();
  62         if(!canread(argv[1]) || !canread(argv[2])) {
  63                 perror("can not read");
  64                 return 1;
  65         }
  66         return diff(fopen(argv[1], "r"), fopen(argv[2], "r"));
  67 }