Enclose repeated buffer draining code in a new msgbuf_drain()

function, which is additionally exported for use by others.
It will be needed by smtpd's SSL module when the SMTP client code
is changed to replace libevent's evbuffers with our msgbuf_* API.
ok gilles@ henning@ guenther@ eric@

src/usr.sbin/ntpd/buffer.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: buffer.c,v 1.11 2009/07/23 18:58:42 eric Exp $	*/
+/*	$OpenBSD: buffer.c,v 1.12 2009/09/15 10:54:59 jacekm Exp $	*/
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -144,7 +144,7 @@ int
 buf_write(struct msgbuf *msgbuf)
 {
 	struct iovec	 iov[IOV_MAX];
-	struct buf	*buf, *next;
+	struct buf	*buf;
 	unsigned int	 i = 0;
 	ssize_t	n;
 
@@ -170,17 +170,7 @@ buf_write(struct msgbuf *msgbuf)
 		return (-2);
 	}
 
-	for (buf = TAILQ_FIRST(&msgbuf->bufs); buf != NULL && n > 0;
-	    buf = next) {
-		next = TAILQ_NEXT(buf, entry);
-		if (buf->rpos + n >= buf->wpos) {
-			n -= buf->wpos - buf->rpos;
-			buf_dequeue(msgbuf, buf);
-		} else {
-			buf->rpos += n;
-			n = 0;
-		}
-	}
+	msgbuf_drain(msgbuf, n);
 
 	return (0);
 }
@@ -200,6 +190,24 @@ msgbuf_init(struct msgbuf *msgbuf)
 	TAILQ_INIT(&msgbuf->bufs);
 }
 
+void
+msgbuf_drain(struct msgbuf *msgbuf, size_t n)
+{
+	struct buf	*buf, *next;
+
+	for (buf = TAILQ_FIRST(&msgbuf->bufs); buf != NULL && n > 0;
+	    buf = next) {
+		next = TAILQ_NEXT(buf, entry);
+		if (buf->rpos + n >= buf->wpos) {
+			n -= buf->wpos - buf->rpos;
+			buf_dequeue(msgbuf, buf);
+		} else {
+			buf->rpos += n;
+			n = 0;
+		}
+	}
+}
+
 void
 msgbuf_clear(struct msgbuf *msgbuf)
 {
@@ -213,7 +221,7 @@ int
 msgbuf_write(struct msgbuf *msgbuf)
 {
 	struct iovec	 iov[IOV_MAX];
-	struct buf	*buf, *next;
+	struct buf	*buf;
 	unsigned int	 i = 0;
 	ssize_t		 n;
 	struct msghdr	 msg;
@@ -270,17 +278,7 @@ msgbuf_write(struct msgbuf *msgbuf)
 		buf->fd = -1;
 	}
 
-	for (buf = TAILQ_FIRST(&msgbuf->bufs); buf != NULL && n > 0;
-	    buf = next) {
-		next = TAILQ_NEXT(buf, entry);
-		if (buf->rpos + n >= buf->wpos) {
-			n -= buf->wpos - buf->rpos;
-			buf_dequeue(msgbuf, buf);
-		} else {
-			buf->rpos += n;
-			n = 0;
-		}
-	}
+	msgbuf_drain(msgbuf, n);
 
 	return (0);
 }

src/usr.sbin/ntpd/imsg.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: imsg.h,v 1.3 2009/06/07 05:56:25 eric Exp $	*/
+/*	$OpenBSD: imsg.h,v 1.4 2009/09/15 10:54:59 jacekm Exp $	*/
 
 /*
  * Copyright (c) 2006, 2007 Pierre-Yves Ritschard <pyr@openbsd.org>
@@ -90,6 +90,7 @@ void		 buf_free(struct buf *);
 void		 msgbuf_init(struct msgbuf *);
 void		 msgbuf_clear(struct msgbuf *);
 int		 msgbuf_write(struct msgbuf *);
+void		 msgbuf_drain(struct msgbuf *, size_t);
 
 /* imsg.c */
 void	 imsg_init(struct imsgbuf *, int);