rename bdiff.c to isequal.c, make it handle different line-endings as equal

test/isequal.c

@@ -0,0 +1,54 @@
+
+// minimal tool to compare two text files
+
+#include <stdlib.h>
+#include <stdio.h>
+
+/* get the next character from FILE and convert commonly used line-endings all
+   into the same value (0x0a, as used on *nix systems)
+
+   recognized values/pairs:
+
+   0x0a (LF)                Linux, macOS
+   0x0d, 0x0a (CR, LF)      Windows, MSDOS, OS/2
+   0x0d (CR)                classic MacOS
+*/
+
+int getnext(FILE *f)
+{
+    int c = fgetc(f);
+    if (c == 0x0d) {
+        if (!feof(f)) {
+            int n = fgetc(f);
+            if (n != 0x0a) {
+                ungetc(n, f);
+            }
+            clearerr(f); /* clears EOF when we did not push back */
+        }
+        return 0x0a;
+    }
+    return c;
+}
+
+int main(int argc, char *argv[])
+{
+    FILE *f1, *f2;
+    if (argc < 3) {
+        return EXIT_FAILURE;
+    }
+    f1 = fopen(argv[1], "rb");
+    f2 = fopen(argv[2], "rb");
+    if ((f1 == NULL) || (f2 == NULL)) {
+        return EXIT_FAILURE;
+    }
+    for(;;) {
+        if (feof(f1) && feof(f2)) {
+            return EXIT_SUCCESS;
+        } else if (feof(f1) || feof(f2)) {
+            return EXIT_FAILURE;
+        }
+        if (getnext(f1) != getnext(f2)) {
+            return EXIT_FAILURE;
+        }
+    }
+}