/* Copyright (c) 2005 Russ Cox, MIT; see COPYRIGHT */#include "taskimpl.h"Channel*chancreate(int elemsize, int bufsize){	Channel *c;	c = malloc(sizeof *c+bufsize*elemsize);	if(c == nil){		fprint(2, "chancreate malloc: %r");		exit(1);	}	memset(c, 0, sizeof *c);	c->elemsize = elemsize;	c->bufsize = bufsize;	c->nbuf = 0;	c->buf = (uchar*)(c+1);	return c;}/* bug - work out races */voidchanfree(Channel *c){	if(c == nil)		return;	free(c->name);	free(c->arecv.a);	free(c->asend.a);	free(c);}static voidaddarray(Altarray *a, Alt *alt){	if(a->n == a->m){		a->m += 16;		a->a = realloc(a->a, a->m*sizeof a->a[0]);	}	a->a[a->n++] = alt;}static voiddelarray(Altarray *a, int i){	--a->n;	a->a[i] = a->a[a->n];}/* * doesn't really work for things other than CHANSND and CHANRCV * but is only used as arg to chanarray, which can handle it */#define otherop(op)	(CHANSND+CHANRCV-(op))static Altarray*chanarray(Channel *c, uint op){	switch(op){	default:		return nil;	case CHANSND:		return &c->asend;	case CHANRCV:		return &c->arecv;	}}static intaltcanexec(Alt *a){	Altarray *ar;	Channel *c;	if(a->op == CHANNOP)		return 0;	c = a->c;	if(c->bufsize == 0){		ar = chanarray(c, otherop(a->op));		return ar && ar->n;	}else{		switch(a->op){		default:			return 0;		case CHANSND:			return c->nbuf < c->bufsize;		case CHANRCV:			return c->nbuf > 0;		}	}}static voidaltqueue(Alt *a){	Altarray *ar;	ar = chanarray(a->c, a->op);	addarray(ar, a);}static voidaltdequeue(Alt *a){	int i;	Altarray *ar;	ar = chanarray(a->c, a->op);	if(ar == nil){		fprint(2, "bad use of altdequeue op=%d\n", a->op);		abort();	}	for(i=0; i<ar->n; i++)		if(ar->a[i] == a){			delarray(ar, i);			return;		}	fprint(2, "cannot find self in altdq\n");	abort();}static voidaltalldequeue(Alt *a){	int i;	for(i=0; a[i].op!=CHANEND && a[i].op!=CHANNOBLK; i++)		if(a[i].op != CHANNOP)			altdequeue(&a[i]);}static voidamove(void *dst, void *src, uint n){	if(dst){		if(src == nil)			memset(dst, 0, n);		else			memmove(dst, src, n);	}}/* * Actually move the data around.  There are up to three * players: the sender, the receiver, and the channel itself. * If the channel is unbuffered or the buffer is empty, * data goes from sender to receiver.  If the channel is full, * the receiver removes some from the channel and the sender * gets to put some in. */static voidaltcopy(Alt *s, Alt *r){	Alt *t;	Channel *c;	uchar *cp;	/*	 * Work out who is sender and who is receiver	 */	if(s == nil && r == nil)		return;	assert(s != nil);	c = s->c;	if(s->op == CHANRCV){		t = s;		s = r;		r = t;	}	assert(s==nil || s->op == CHANSND);	assert(r==nil || r->op == CHANRCV);	/*	 * Channel is empty (or unbuffered) - copy directly.	 */	if(s && r && c->nbuf == 0){		amove(r->v, s->v, c->elemsize);		return;	}	/*	 * Otherwise it's always okay to receive and then send.	 */	if(r){		cp = c->buf + c->off*c->elemsize;		amove(r->v, cp, c->elemsize);		--c->nbuf;		if(++c->off == c->bufsize)			c->off = 0;	}	if(s){		cp = c->buf + (c->off+c->nbuf)%c->bufsize*c->elemsize;		amove(cp, s->v, c->elemsize);		++c->nbuf;	}}static voidaltexec(Alt *a){	int i;	Altarray *ar;	Alt *other;	Channel *c;	c = a->c;	ar = chanarray(c, otherop(a->op));	if(ar && ar->n){		i = rand()%ar->n;		other = ar->a[i];		altcopy(a, other);		altalldequeue(other->xalt);		other->xalt[0].xalt = other;		taskready(other->task);	}else		altcopy(a, nil);}#define dbgalt 0intchanalt(Alt *a){	int i, j, ncan, n, canblock;	Channel *c;	Task *t;	needstack(512);	for(i=0; a[i].op != CHANEND && a[i].op != CHANNOBLK; i++)		;	n = i;	canblock = a[i].op == CHANEND;	t = taskrunning;	for(i=0; i<n; i++){		a[i].task = t;		a[i].xalt = a;	}if(dbgalt) print("alt ");	ncan = 0;	for(i=0; i<n; i++){		c = a[i].c;if(dbgalt) print(" %c:", "esrnb"[a[i].op]);if(dbgalt) { if(c->name) print("%s", c->name); else print("%p", c); }		if(altcanexec(&a[i])){if(dbgalt) print("*");			ncan++;		}	}	if(ncan){		j = rand()%ncan;		for(i=0; i<n; i++){			if(altcanexec(&a[i])){				if(j-- == 0){if(dbgalt){c = a[i].c;print(" => %c:", "esrnb"[a[i].op]);if(c->name) print("%s", c->name); else print("%p", c);print("\n");}					altexec(&a[i]);					return i;				}			}		}	}if(dbgalt)print("\n");	if(!canblock)		return -1;	for(i=0; i<n; i++){		if(a[i].op != CHANNOP)			altqueue(&a[i]);	}	taskswitch();	/*	 * the guy who ran the op took care of dequeueing us	 * and then set a[0].alt to the one that was executed.	 */	return a[0].xalt - a;}static int_chanop(Channel *c, int op, void *p, int canblock){	Alt a[2];	a[0].c = c;	a[0].op = op;	a[0].v = p;	a[1].op = canblock ? CHANEND : CHANNOBLK;	if(chanalt(a) < 0)		return -1;	return 1;}intchansend(Channel *c, void *v){	return _chanop(c, CHANSND, v, 1);}intchannbsend(Channel *c, void *v){	return _chanop(c, CHANSND, v, 0);}intchanrecv(Channel *c, void *v){	return _chanop(c, CHANRCV, v, 1);}intchannbrecv(Channel *c, void *v){	return _chanop(c, CHANRCV, v, 0);}intchansendp(Channel *c, void *v){	return _chanop(c, CHANSND, (void*)&v, 1);}void*chanrecvp(Channel *c){	void *v;	_chanop(c, CHANRCV, (void*)&v, 1);	return v;}intchannbsendp(Channel *c, void *v){	return _chanop(c, CHANSND, (void*)&v, 0);}void*channbrecvp(Channel *c){	void *v;	_chanop(c, CHANRCV, (void*)&v, 0);	return v;}intchansendul(Channel *c, ulong val){	return _chanop(c, CHANSND, &val, 1);}ulongchanrecvul(Channel *c){	ulong val;	_chanop(c, CHANRCV, &val, 1);	return val;}intchannbsendul(Channel *c, ulong val){	return _chanop(c, CHANSND, &val, 0);}ulongchannbrecvul(Channel *c){	ulong val;	_chanop(c, CHANRCV, &val, 0);	return val;}