Single-threaded plumber that can run "start" rules.

Thanks to Caerwyn Jones.

src/libplumb/event.c

@@ -0,0 +1,108 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <event.h>
+#include "plumb.h"
+
+typedef struct EQueue EQueue;
+
+struct EQueue
+{
+	int		id;
+	char		*buf;
+	int		nbuf;
+	EQueue	*next;
+};
+
+static	EQueue	*equeue;
+static	Lock		eqlock;
+
+static
+int
+partial(int id, Event *e, uchar *b, int n)
+{
+	EQueue *eq, *p;
+	int nmore;
+
+	lock(&eqlock);
+	for(eq = equeue; eq != nil; eq = eq->next)
+		if(eq->id == id)
+			break;
+	unlock(&eqlock);
+	if(eq == nil)
+		return 0;
+	/* partial message exists for this id */
+	eq->buf = realloc(eq->buf, eq->nbuf+n);
+	if(eq->buf == nil)
+		drawerror(display, "eplumb: cannot allocate buffer");
+	memmove(eq->buf+eq->nbuf, b, n);
+	eq->nbuf += n;
+	e->v = plumbunpackpartial((char*)eq->buf, eq->nbuf, &nmore);
+	if(nmore == 0){	/* no more to read in this message */
+		lock(&eqlock);
+		if(eq == equeue)
+			equeue = eq->next;
+		else{
+			for(p = equeue; p!=nil && p->next!=eq; p = p->next)
+				;
+			if(p == nil)
+				drawerror(display, "eplumb: bad event queue");
+			p->next = eq->next;
+		}
+		unlock(&eqlock);
+		free(eq->buf);
+		free(eq);
+	}
+	return 1;
+}
+
+static
+void
+addpartial(int id, char *b, int n)
+{
+	EQueue *eq;
+
+	eq = malloc(sizeof(EQueue));
+	if(eq == nil)
+		return;
+	eq->id = id;
+	eq->nbuf = n;
+	eq->buf = malloc(n);
+	if(eq->buf == nil){
+		free(eq);
+		return;
+	}
+	memmove(eq->buf, b, n);
+	lock(&eqlock);
+	eq->next = equeue;
+	equeue = eq;
+	unlock(&eqlock);
+}
+
+static
+int
+plumbevent(int id, Event *e, uchar *b, int n)
+{
+	int nmore;
+
+	if(partial(id, e, b, n) == 0){
+		/* no partial message already waiting for this id */
+		e->v = plumbunpackpartial((char*)b, n, &nmore);
+		if(nmore > 0)	/* incomplete message */
+			addpartial(id, (char*)b, n);
+	}
+	if(e->v == nil)
+		return 0;
+	return id;
+}
+
+int
+eplumb(int key, char *port)
+{
+	int fd;
+
+	fd = plumbopen(port, OREAD|OCEXEC);
+	if(fd < 0)
+		return -1;
+	return estartfn(key, fd, 8192, plumbevent);
+}