+/* return true if the given two files are the same, false otherwise */
+static bool is_same(const char *file1, const char *file2)
+{
+ int fd1, fd2;
+ struct stat st1, st2;
+ void *map1, *map2;
+ bool ret = false;
+
+ fd1 = open(file1, O_RDONLY);
+ if (fd1 < 0)
+ return ret;
+
+ fd2 = open(file2, O_RDONLY);
+ if (fd2 < 0)
+ goto close1;
+
+ ret = fstat(fd1, &st1);
+ if (ret)
+ goto close2;
+ ret = fstat(fd2, &st2);
+ if (ret)
+ goto close2;
+
+ if (st1.st_size != st2.st_size)
+ goto close2;
+
+ map1 = mmap(NULL, st1.st_size, PROT_READ, MAP_PRIVATE, fd1, 0);
+ if (map1 == MAP_FAILED)
+ goto close2;
+
+ map2 = mmap(NULL, st2.st_size, PROT_READ, MAP_PRIVATE, fd2, 0);
+ if (map2 == MAP_FAILED)
+ goto close2;
+
+ if (bcmp(map1, map2, st1.st_size))
+ goto close2;
+
+ ret = true;
+close2:
+ close(fd2);
+close1:
+ close(fd1);
+
+ return ret;
+}
+