qtail.c
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/* @(#) qtail.c 1.2 1/27/86 17:48:08 */
/*ident "@(#)cfront:lib/task/qtail.c 1.2"*/
#include "task.h"
qtail.qtail(int mode, int max) : (QTAIL)
/*
construct qtail <--> oqueue
*/
{
DB(("x%x->qtail( %d, %d )\n", this, mode, max));
if (0 < max) {
qt_queue = new class oqueue(max);
qt_queue->q_tail = this;
};
qt_mode = mode;
}
qtail.~qtail()
/*
destroy q if not also pointed to by a qhead
*/
{
DB(("x%x->~qtail()\n", this));
oqueue* q = qt_queue;
if (q->q_head)
q->q_tail = 0;
else
delete q;
}
int
qtail.put(object* p)
/*
insert object at rear of q (becoming new value of oqueue->q_ptr)
*/
{
DB(("x%x->qtail::put( x%x )\n", this, p));
register oqueue* q = qt_queue;
ll:
if (p->o_next) task_error(E_PUTOBJ,this);
if (q->q_count < q->q_max) {
if (q->q_count++) {
register object* oo = q->q_ptr;
p->o_next = oo->o_next;
q->q_ptr = oo->o_next = p;
}
else {
qhead* h = q->q_head;
q->q_ptr = p->o_next = p;
if (h) h->alert();
}
return 1;
}
switch (qt_mode) {
case WMODE:
remember(thistask);
thistask->sleep();
forget(thistask);
goto ll;
case EMODE:
task_error(E_PUTFULL,this);
goto ll;
case ZMODE:
return 0;
}
}
qhead*
qtail.head()
/*
create head for this q
*/
{
DB(("x%x->qtail::head()\n", this));
oqueue* q = qt_queue;
register qhead* h = q->q_head;
if (h == 0) {
h = new qhead(qt_mode,0);
q->q_head = h;
h->qh_queue = q;
};
return h;
}
qtail*
qtail.cut()
/*
result: ?qhead<-->? oldq<-->(new)qtail newq<-->(this)qtail
*/
{
DB(("x%x->qtail::cut()\n", this));
oqueue* oldq = qt_queue;
qtail* t = new qtail(qt_mode,oldq->q_max);
oqueue* newq = t->qt_queue;
t->qt_queue = oldq;
oldq->q_tail = t;
newq->q_tail = this;
qt_queue = newq;
return t;
}
void
qtail.splice(qhead* h)
/*
this qtail is supposed to be downstream from the qhead h
*/
{
DB(("x%x->qtail::splice( x%x )\n", this,h));
h->splice(this);
}
void
qtail.print(int n)
{
DB(("x%x->qtail::print( %d )\n", this,n));
int m = qt_queue->q_max;
int c = qt_queue->q_count;
class qhead * h = qt_queue->q_head;
printf("qtail (%d): mode=%d, max=%d, space=%d, head=%d\n",
this,qt_mode,m,m-c,h);
if (n&VERBOSE) {
int m = n & ~(CHAIN|VERBOSE);
if (h) {
printf("head of queue:\n");
h->print(m);
}
qt_queue->print(m);
}
}