+/* If the EXPECTED_CHARS are the next ones available from PORT, then
+ consume them and return 1. Otherwise leave the port position where
+ it was and return 0. EXPECTED_CHARS should be all lowercase, and
+ will be matched case-insensitively against the characters read from
+ PORT. */
+static int
+try_read_ci_chars (SCM port, const char *expected_chars)
+{
+ int num_chars_wanted = strlen (expected_chars);
+ int num_chars_read = 0;
+ char *chars_read = alloca (num_chars_wanted);
+ int c;
+
+ while (num_chars_read < num_chars_wanted)
+ {
+ c = scm_getc_unlocked (port);
+ if (c == EOF)
+ break;
+ else if (c_tolower (c) != expected_chars[num_chars_read])
+ {
+ scm_ungetc_unlocked (c, port);
+ break;
+ }
+ else
+ chars_read[num_chars_read++] = c;
+ }
+
+ if (num_chars_read == num_chars_wanted)
+ return 1;
+ else
+ {
+ while (num_chars_read > 0)
+ scm_ungetc_unlocked (chars_read[--num_chars_read], port);
+ return 0;
+ }
+}
+