Index: app.c
===================================================================
--- app.c	(revision 7684)
+++ app.c	(working copy)
@@ -279,47 +279,52 @@
 	return 0;
 }
 
-int ast_dtmf_stream(struct ast_channel *chan,struct ast_channel *peer,char *digits,int between) 
+int ast_dtmf_stream(struct ast_channel *chan, struct ast_channel *peer, const char *digits, int between) 
 {
-	char *ptr;
+	const char *ptr;
 	int res = 0;
-	struct ast_frame f;
+	struct ast_frame f = {
+		.frametype = AST_FRAME_DTMF,
+		.src = "ast_dtmf_stream"
+	};
+
 	if (!between)
 		between = 100;
 
 	if (peer)
 		res = ast_autoservice_start(peer);
 
-	if (!res) {
-		res = ast_waitfor(chan,100);
-		if (res > -1) {
-			for (ptr=digits; *ptr; ptr++) {
-				if (*ptr == 'w') {
-					res = ast_safe_sleep(chan, 500);
-					if (res) 
-						break;
-					continue;
-				}
-				memset(&f, 0, sizeof(f));
-				f.frametype = AST_FRAME_DTMF;
-				f.subclass = *ptr;
-				f.src = "ast_dtmf_stream";
-				if (strchr("0123456789*#abcdABCD",*ptr)==NULL) {
-					ast_log(LOG_WARNING, "Illegal DTMF character '%c' in string. (0-9*#aAbBcCdD allowed)\n",*ptr);
-				} else {
-					res = ast_write(chan, &f);
-					if (res) 
-						break;
-					/* pause between digits */
-					res = ast_safe_sleep(chan,between);
-					if (res) 
-						break;
-				}
-			}
-		}
-		if (peer)
-			res = ast_autoservice_stop(peer);
+	if (!res)
+		res = ast_waitfor(chan, 100);
+
+	/* ast_waitfor will return the number of remaining ms on success */
+	if (res < 0)
+		return res;
+
+	for (ptr = digits; *ptr; ptr++) {
+		if (*ptr == 'w') {
+			/* 'w' -- wait half a second */
+			if ((res = ast_safe_sleep(chan, 500)))
+				break;
+		} else if (strchr("0123456789*#abcdABCD", *ptr)) {
+			/* Character represents valid DTMF */
+			f.subclass = *ptr;
+			if ((res = ast_write(chan, &f)))
+				break;
+			/* pause between digits */
+			if ((res = ast_safe_sleep(chan, between)))
+				break;
+		} else
+			ast_log(LOG_WARNING, "Illegal DTMF character '%c' in string. (0-9*#aAbBcCdD allowed)\n",*ptr);
 	}
+
+	if (peer) {
+		/* Stop autoservice on the peer channel, but don't overwrite any error condition 
+		   that has occurred previously while acting on the primary channel */
+		if (ast_autoservice_stop(peer) && !res)
+			res = -1;
+	}
+
 	return res;
 }
 
Index: include/asterisk/app.h
===================================================================
--- include/asterisk/app.h	(revision 7684)
+++ include/asterisk/app.h	(working copy)
@@ -118,9 +118,19 @@
 */
 extern int ast_safe_system(const char *s);
 
-/*! Send DTMF to chan (optionally entertain peer)   */
-int ast_dtmf_stream(struct ast_channel *chan, struct ast_channel *peer, char *digits, int between);
+/*!
+  \brief Send DTMF to a channel
 
+  \param chan    The channel that will receive the DTMF frames
+  \param peer    (optional) Peer channel that will be autoserviced while the primary
+                 channel is receiving DTMF
+  \param digits  This is a string of characters representing the DTMF digits to be sent
+                 to the channel.  Valid characters are "0123456789*#abcdABCD".
+  \param between This is the number of milliseconds to wait in between each DTMF digit.
+                 If zero milliseconds is specified, then the default value of 100 will be used.
+*/
+int ast_dtmf_stream(struct ast_channel *chan, struct ast_channel *peer, const char *digits, int between);
+
 /*! Stream a filename (or file descriptor) as a generator. */
 int ast_linear_stream(struct ast_channel *chan, const char *filename, int fd, int allowoverride);