+ case NMH_MESSAGE_ID_RANDOM: {
+ char *format = content_id
+ ? "<%d-%ld.%06ld%%d@%.*s.%.*s.%.*s>"
+ : "<%d-%ld.%06ld@%.*s.%.*s.%.*s>";
+ /* Use a sequence of digits divisible by 3 because that will
+ expand to base64 without any waste. Must be shorter than 58,
+ see below. */
+ unsigned char rnd[9];
+ /* The part after the '@' is divided into thirds. The base64
+ encoded string will be 4/3 the size of rnd. */
+ size_t one_third = sizeof rnd * 4/3/3;
+
+ if (m_rand (rnd, sizeof rnd) == 0) {
+ struct timeval now;
+ /* All we really need is 4 * [sizeof rnd/3] + 2, as long as
+ the base64 encoding stays shorter than 76 bytes so embedded
+ newlines aren't necessary. But use double the sizeof rnd
+ just to be safe. */
+ unsigned char rnd_base64[2 * sizeof rnd];
+ unsigned char *cp;
+ int i;
+
+ writeBase64 (rnd, sizeof rnd, rnd_base64);
+
+ for (i = strlen ((const char *) rnd_base64) - 1;
+ i > 0 && iscntrl (rnd_base64[i]);
+ --i) {
+ /* Remove trailing newline. rnd_base64 had better be
+ shorter than 76 characters, so don't bother to look for
+ embedded newlines. */
+ rnd_base64[i] = '\0';
+ }
+
+ /* Try to make the base64 string look a little more like a
+ hostname by replacing + with - and / with _. */
+ for (cp = rnd_base64; *cp; ++cp) {
+ if (*cp == '+') {
+ *cp = '-';
+ } else if (*cp == '/') {
+ *cp = '_';
+ }
+ }
+
+ /* gettimeofday() and getpid() shouldn't fail on POSIX platforms. */
+ gettimeofday (&now, 0);
+
+ /* The format string inserts a couple of dots, for the benefit
+ of spam filters that want to see a message id with a final
+ part that resembles a hostname. */
+ snprintf (message_id_, sizeof message_id_, format,
+ getpid (), (long) now.tv_sec, (long) now.tv_usec,
+ one_third, rnd_base64,
+ one_third, &rnd_base64[one_third],
+ one_third, &rnd_base64[2*one_third]);
+ }
+
+ break;
+ }
+ }