1 #include <u.h>
2 #include <libc.h>
3 #include <thread.h>
4 #include <venti.h>
5 #include <diskfs.h>
6 #include "queue.h"
7 
8 Queue*
9 qalloc(void)
10 {
11 	Queue *q;
12 
13 	q = vtmallocz(sizeof(Queue));
14 	q->r.l = &q->lk;
15 	return q;
16 }
17 
18 Block*
19 qread(Queue *q, u32int *pbno)
20 {
21 	Block *db;
22 	u32int bno;
23 
24 	qlock(&q->lk);
25 	while(q->nel == 0 && !q->closed)
26 		rsleep(&q->r);
27 	if(q->nel == 0 && q->closed){
28 		qunlock(&q->lk);
29 		return nil;
30 	}
31 	db = q->el[q->ri].db;
32 	bno = q->el[q->ri].bno;
33 	if(++q->ri == MAXQ)
34 		q->ri = 0;
35 	if(q->nel-- == MAXQ/2)
36 		rwakeup(&q->r);
37 	qunlock(&q->lk);
38 	*pbno = bno;
39 	return db;
40 }
41 
42 void
43 qwrite(Queue *q, Block *db, u32int bno)
44 {
45 	qlock(&q->lk);
46 	while(q->nel == MAXQ)
47 		rsleep(&q->r);
48 	q->el[q->wi].db = db;
49 	q->el[q->wi].bno = bno;
50 	if(++q->wi == MAXQ)
51 		q->wi = 0;
52 	if(q->nel++ == MAXQ/2)
53 		rwakeup(&q->r);
54 	qunlock(&q->lk);
55 }
56 
57 void
58 qclose(Queue *q)
59 {
60 	qlock(&q->lk);
61 	q->closed = 1;
62 	rwakeup(&q->r);
63 	qunlock(&q->lk);
64 }
65 
66 void
67 qfree(Queue *q)
68 {
69 	vtfree(q);
70 }