From ece3e57c85aa3c5042b6bbb2ad534a9803160374 Mon Sep 17 00:00:00 2001
From: Ken Thompson <ken@golang.org>
Date: Fri, 25 Jul 2008 11:58:26 -0700
Subject: [PATCH] read select

R=r
APPROVED=r
DELTA=120  (108 added, 0 deleted, 12 changed)
OCL=13468
CL=13468
---
 src/cmd/gc/subr.c  |  6 ++++
 src/cmd/gc/walk.c  | 53 ++++++++++++++++++++++++++++++----
 src/runtime/chan.c | 71 ++++++++++++++++++++++++++++++++++++++++++----
 3 files changed, 119 insertions(+), 11 deletions(-)

diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index 8609f39dfc..db76f831ab 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -446,6 +446,7 @@ loop:
 	case OIF:
 	case OSWITCH:
 	case OFOR:
+	case OSELECT:
 		dodump(n->ninit, dep);
 		break;
 	}
@@ -480,6 +481,11 @@ loop:
 		}
 		return;
 
+	case OSELECT:
+		print("%O%J\n", n->op, n);
+		dodump(n->nbody, dep+1);
+		return;
+
 	case OSWITCH:
 	case OFOR:
 		print("%O%J\n", n->op, n);
diff --git a/src/cmd/gc/walk.c b/src/cmd/gc/walk.c
index 422b551367..dcc4fa0770 100644
--- a/src/cmd/gc/walk.c
+++ b/src/cmd/gc/walk.c
@@ -915,13 +915,18 @@ loop:
 }
 
 Node*
-selcase(Node *c, Node *var)
+selcase(Node *n, Node *var)
 {
-	Node *a, *r, *on;
+	Node *a, *r, *on, *c;
 	Type *t;
 
+	c = n->left;
+	if(c->op == ORECV)
+		goto recv;
+
 	walktype(c->left, Erv);		// chan
 	walktype(c->right, Erv);	// elem
+
 	t = fixchan(c->left->type);
 	if(t == T)
 		return;
@@ -937,11 +942,44 @@ selcase(Node *c, Node *var)
 	argtype(on, t->type);
 	argtype(on, t->type);
 
-	a = c->right;		// elem
+	a = c->right;			// elem
 	r = a;
-	a = c->left;		// chan
+	a = c->left;			// chan
 	r = list(a, r);
-	a = var;		// sel-var
+	a = var;			// sel-var
+	r = list(a, r);
+
+	a = nod(OCALL, on, r);
+	r = nod(OIF, N, N);
+	r->ntest = a;
+
+	return r;
+
+recv:
+	walktype(c->left, Elv);		// elem
+	walktype(c->right, Erv);	// chan
+
+	t = fixchan(c->right->type);
+	if(t == T)
+		return;
+
+	convlit(c->left, t->type);
+	if(!ascompat(t->type, c->left->type)) {
+		badtype(c->op, t->type, c->left->type);
+		return;
+	}
+
+	// selectrecv(sel *byte, hchan *chan any, elem *any) (selected bool);
+	on = syslook("selectrecv", 1);
+	argtype(on, t->type);
+	argtype(on, t->type);
+
+	a = c->left;			// elem
+	a = nod(OADDR, a, N);
+	r = a;
+	a = c->right;			// chan
+	r = list(a, r);
+	a = var;			// sel-var
 	r = list(a, r);
 
 	a = nod(OCALL, on, r);
@@ -991,11 +1029,12 @@ walkselect(Node *sel)
 				break;
 
 			case OSEND:
+			case ORECV:
 				if(oc != N) {
 					bod = list(bod, nod(OBREAK, N, N));
 					oc->nbody = rev(bod);
 				}
-				oc = selcase(n->left, var);
+				oc = selcase(n, var);
 				res = list(res, oc);
 				break;
 			}
@@ -1030,6 +1069,8 @@ walkselect(Node *sel)
 	walktype(sel->ninit, Etop);
 	walktype(sel->nbody, Etop);
 
+dump("sel", sel);
+
 	lineno = lno;
 }
 
diff --git a/src/runtime/chan.c b/src/runtime/chan.c
index 9f48c5d7ca..ffaf55448f 100644
--- a/src/runtime/chan.c
+++ b/src/runtime/chan.c
@@ -54,7 +54,10 @@ struct	Scase
 	byte*	pc;			// return pc
 	uint16	send;			// 0-recv 1-send
 	uint16	so;			// vararg of selected bool
-	byte	elem[8];		// element
+	union {
+		byte	elem[8];	// element (send)
+		byte*	elemp;		// pointer to element (recv)
+	} u;
 };
 
 struct	Select
@@ -390,7 +393,7 @@ sys·selectsend(Select *sel, Hchan *c, ...)
 	cas->send = 1;
 
 	ae = (byte*)&sel + eo;
-	c->elemalg->copy(c->elemsize, cas->elem, ae);
+	c->elemalg->copy(c->elemsize, cas->u.elem, ae);
 
 	as = (byte*)&sel + cas->so;
 	*as = false;
@@ -414,7 +417,45 @@ sys·selectsend(Select *sel, Hchan *c, ...)
 void
 sys·selectrecv(Select *sel, Hchan *c, ...)
 {
-	throw("selectrecv");
+	int32 i, epo;
+	Scase *cas;
+	byte *as;
+
+	// return val, selected, is preset to false
+	if(c == nil)
+		return;
+
+	i = sel->ncase;
+	if(i >= sel->tcase)
+		throw("selectsend: too many cases");
+	sel->ncase = i+1;
+	cas = &sel->scase[i];
+
+	cas->pc = sys·getcallerpc(&sel);
+	cas->chan = c;
+
+	epo = rnd(sizeof(sel), sizeof(c));
+	epo = rnd(epo+sizeof(c), sizeof(byte*));
+	cas->so = rnd(epo+sizeof(byte*), 1);
+	cas->send = 0;
+	cas->u.elemp = *(byte**)((byte*)&sel + epo);
+
+	as = (byte*)&sel + cas->so;
+	*as = false;
+
+	if(debug) {
+		prints("newselect s=");
+		sys·printpointer(sel);
+		prints(" pc=");
+		sys·printpointer(cas->pc);
+		prints(" chan=");
+		sys·printpointer(cas->chan);
+		prints(" so=");
+		sys·printint(cas->so);
+		prints(" send=");
+		sys·printint(cas->send);
+		prints("\n");
+	}
 }
 
 // selectgo(sel *byte);
@@ -429,6 +470,9 @@ sys·selectgo(Select *sel)
 	SudoG *sgr;
 	G *gr;
 
+	SudoG *sgs;
+	G *gs;
+
 	if(sel->ncase < 1) {
 		throw("selectgo: no cases");
 	}
@@ -453,16 +497,33 @@ sys·selectgo(Select *sel)
 		c = cas->chan;
 		if(cas->send) {
 			if(c->dataqsiz > 0) {
-				throw("selectgo: asynch");
+				throw("selectgo: send asynch");
 			}
 			sgr = dequeue(&c->recvq, c);
 			if(sgr == nil)
 				continue;
 
-			c->elemalg->copy(c->elemsize, sgr->elem, cas->elem);
+			c->elemalg->copy(c->elemsize, sgr->elem, cas->u.elem);
 			gr = sgr->g;
 			gr->status = Grunnable;
 
+			goto retc;
+		} else {
+			if(c->dataqsiz > 0) {
+				throw("selectgo: recv asynch");
+			}
+			sgs = dequeue(&c->sendq, c);
+			if(sgs == nil)
+				continue;
+
+			if(cas->u.elemp != nil)
+				c->elemalg->copy(c->elemsize, cas->u.elemp, sgs->elem);
+
+			gs = sgs->g;
+			gs->status = Grunnable;
+
+			freesg(c, sgs);
+
 			goto retc;
 		}
 
-- 
2.48.1