go/src/runtime/chan.c

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#include "runtime.h"

static	int32	debug	= 0;

typedef	struct	Hchan	Hchan;
typedef	struct	Link	Link;

struct	Hchan
{
	uint32	elemsize;
	uint32	dataqsiz;		// size of the circular q
	uint32	qcount;			// total data in the q
	uint32	eo;			// vararg of element
	uint32	po;			// vararg of present bool
	Alg*	elemalg;		// interface for element type
	Link*	senddataq;		// pointer for sender
	Link*	recvdataq;		// pointer for receiver
	WaitQ	recvq;			// list of recv waiters
	WaitQ	sendq;			// list of send waiters
};

struct	Link
{
	Link*	link;
	byte	elem[8];
};

// newchan(elemsize uint32, elemalg uint32, hint uint32) (hchan *chan any);
void
sys·newchan(uint32 elemsize, uint32 elemalg, uint32 hint,
	Hchan* ret)
{
	Hchan *c;
	int32 i;

	if(elemalg >= nelem(algarray)) {
		prints("0<=");
		sys·printint(elemalg);
		prints("<");
		sys·printint(nelem(algarray));
		prints("\n");

		throw("sys·newchan: elem algorithm out of range");
	}

	c = mal(sizeof(*c));

	c->elemsize = elemsize;
	c->elemalg = &algarray[elemalg];

	if(hint > 0) {
		Link *d, *b, *e;

		// make a circular q
		b = nil;
		e = nil;
		for(i=0; i<hint; i++) {
			d = mal(sizeof(*d));
			if(e == nil)
				e = d;
			d->link = b;
			b = d;
		}
		e->link = b;
		c->recvdataq = b;
		c->senddataq = b;
		c->qcount = 0;
		c->dataqsiz = hint;
	}

	// these calculations are compiler dependent
	c->eo = rnd(sizeof(c), elemsize);
	c->po = rnd(c->eo+elemsize, 1);

	ret = c;
	FLUSH(&ret);

	if(debug) {
		prints("newchan: chan=");
		sys·printpointer(c);
		prints("; elemsize=");
		sys·printint(elemsize);
		prints("; elemalg=");
		sys·printint(elemalg);
		prints("; dataqsiz=");
		sys·printint(c->dataqsiz);
		prints("\n");
	}

}

// chansend(hchan *chan any, elem any);
void
sys·chansend(Hchan* c, ...)
{
	byte *ae;
	G *gr;

	ae = (byte*)&c + c->eo;
	if(debug) {
		prints("chansend: chan=");
		sys·printpointer(c);
		prints("; elem=");
		c->elemalg->print(c->elemsize, ae);
		prints("\n");
	}
	if(c->dataqsiz > 0)
		goto asynch;

	gr = dequeue(&c->recvq);
	if(gr != nil) {
		c->elemalg->copy(c->elemsize, gr->elem, ae);
		gr->status = Grunnable;
		return;
	}
	c->elemalg->copy(c->elemsize, g->elem, ae);
	g->status = Gwaiting;
	enqueue(&c->sendq, g);
	sys·gosched();
	return;

asynch:
	while(c->qcount >= c->dataqsiz) {
		g->status = Gwaiting;
		enqueue(&c->sendq, g);
		sys·gosched();
	}
	c->elemalg->copy(c->elemsize, c->senddataq->elem, ae);
	c->senddataq = c->senddataq->link;
	c->qcount++;
	gr = dequeue(&c->recvq);
	if(gr != nil)
		gr->status = Grunnable;
}

// chanrecv1(hchan *chan any) (elem any);
void
sys·chanrecv1(Hchan* c, ...)
{
	byte *ae;
	G *gs;

	ae = (byte*)&c + c->eo;
	if(debug) {
		prints("chanrecv1: chan=");
		sys·printpointer(c);
		prints("\n");
	}
	if(c->dataqsiz > 0)
		goto asynch;

	gs = dequeue(&c->sendq);
	if(gs != nil) {
		c->elemalg->copy(c->elemsize, ae, gs->elem);
		gs->status = Grunnable;
		return;
	}
	g->status = Gwaiting;
	enqueue(&c->recvq, g);
	sys·gosched();
	c->elemalg->copy(c->elemsize, ae, g->elem);
	return;

asynch:
	while(c->qcount <= 0) {
		g->status = Gwaiting;
		enqueue(&c->recvq, g);
		sys·gosched();
	}
	c->elemalg->copy(c->elemsize, ae, c->recvdataq->elem);
	c->recvdataq = c->recvdataq->link;
	c->qcount--;
	gs = dequeue(&c->sendq);
	if(gs != nil)
		gs->status = Grunnable;
}

// chanrecv2(hchan *chan any) (elem any, pres bool);
void
sys·chanrecv2(Hchan* c, ...)
{
	byte *ae, *ap;
	G *gs;

	ae = (byte*)&c + c->eo;
	ap = (byte*)&c + c->po;
	if(debug) {
		prints("chanrecv2: chan=");
		sys·printpointer(c);
		prints("\n");
	}
	if(c->dataqsiz > 0)
		goto asynch;

	gs = dequeue(&c->sendq);
	if(gs != nil) {
		c->elemalg->copy(c->elemsize, ae, gs->elem);
		gs->status = Grunnable;
		*ap = true;
		return;
	}
	*ap = false;
	return;

asynch:
	if(c->qcount <= 0) {
		*ap = false;
		return;
	}
	c->elemalg->copy(c->elemsize, ae, c->recvdataq->elem);
	c->recvdataq = c->recvdataq->link;
	c->qcount--;
	gs = dequeue(&c->sendq);
	if(gs != nil)
		gs->status = Grunnable;
	*ap = true;
}