From 879626d0e94fd4310be02aa0a9e962beee4a065f Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Tue, 27 Sep 1994 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1994-09-27

---
 port/devns16552.c |  4 ++++
 port/portfns.h    |  1 +
 port/qio.c        | 28 +++++++++++++++++++++++++++-
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/port/devns16552.c b/port/devns16552.c
index 3425bad367a058c08a0412e104c3a0183b8bb22c..a6f5975d09f555acef299541a44ccb12de62d27a 100644
--- a/port/devns16552.c
+++ b/port/devns16552.c
@@ -830,6 +830,10 @@ ns16552ctl(Uart *p, char *cmd)
 	case 'd':
 		ns16552dtr(p, n);
 		break;
+	case 'f':
+	case 'F':
+		qflush(p->oq);
+		break;
 	case 'H':
 	case 'h':
 		qhangup(p->iq);
diff --git a/port/portfns.h b/port/portfns.h
index 040f21e348ba9a660e1dbe1c6846855026d642f7..dfbea994803a6226878501caa2d958a262437b9c 100644
--- a/port/portfns.h
+++ b/port/portfns.h
@@ -192,6 +192,7 @@ ulong		pwait(Waitmsg*);
 int		qcanread(Queue*);
 void		qclose(Queue*);
 int		qconsume(Queue*, void*, int);
+void		qflush(Queue*);
 void		qhangup(Queue*);
 void		qinit(void);
 int		qlen(Queue*);
diff --git a/port/qio.c b/port/qio.c
index 264307c837a0fb951b636e47f4a21fb2df3d698d..09e8737777c93ec2cb77230bb8465dfd599f55f4 100644
--- a/port/qio.c
+++ b/port/qio.c
@@ -609,6 +609,7 @@ qclose(Queue *q)
 	bfirst = q->bfirst;
 	q->bfirst = 0;
 	q->len = 0;
+	q->noblock = 0;
 	iunlock(q);
 
 	/* free queued blocks */
@@ -649,7 +650,6 @@ qreopen(Queue *q)
 	q->state &= ~Qclosed;
 	q->state |= Qstarve;
 	q->eof = 0;
-	q->noblock = 0;
 	q->limit = q->inilim;
 }
 
@@ -702,3 +702,29 @@ qnoblock(Queue *q, int onoff)
 {
 	q->noblock = onoff;
 }
+
+/*
+ *  flush the output queue
+ */
+void
+qflush(Queue *q)
+{
+	Block *b, *bfirst;
+
+	/* mark it */
+	ilock(q);
+	bfirst = q->bfirst;
+	q->bfirst = 0;
+	q->len = 0;
+	iunlock(q);
+
+	/* free queued blocks */
+	while(bfirst){
+		b = bfirst->next;
+		freeb(bfirst);
+		bfirst = b;
+	}
+
+	/* wake up readers/writers */
+	wakeup(&q->wr);
+}