refactor channel registration

irc/utils/bitset.go

@@ -9,17 +9,6 @@ import "sync/atomic"
 // For examples of use, see caps.Set and modes.ModeSet; the array has to be converted to a
 // slice to use these functions.
 
-// BitsetInitialize initializes a bitset.
-func BitsetInitialize(set []uint64) {
-	// XXX re-zero the bitset using atomic stores. it's unclear whether this is required,
-	// however, golang issue #5045 suggests that you shouldn't mix atomic operations
-	// with non-atomic operations (such as the runtime's automatic zero-initialization) on
-	// the same word
-	for i := 0; i < len(set); i++ {
-		atomic.StoreUint64(&set[i], 0)
-	}
-}
-
 // BitsetGet returns whether a given bit of the bitset is set.
 func BitsetGet(set []uint64, position uint) bool {
 	idx := position / 64

irc/utils/bitset_test.go

@@ -10,7 +10,6 @@ type testBitset [2]uint64
 func TestSets(t *testing.T) {
 	var t1 testBitset
 	t1s := t1[:]
-	BitsetInitialize(t1s)
 
 	if BitsetGet(t1s, 0) || BitsetGet(t1s, 63) || BitsetGet(t1s, 64) || BitsetGet(t1s, 127) {
 		t.Error("no bits should be set in a newly initialized bitset")
@@ -47,7 +46,6 @@ func TestSets(t *testing.T) {
 
 	var t2 testBitset
 	t2s := t2[:]
-	BitsetInitialize(t2s)
 
 	for i = 0; i < 128; i++ {
 		if i%2 == 1 {

irc/utils/sync.go

@@ -0,0 +1,35 @@
+// 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.
+
+package utils
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+// Once is a fork of sync.Once to expose a Done() method.
+type Once struct {
+	done uint32
+	m    sync.Mutex
+}
+
+func (o *Once) Do(f func()) {
+	if atomic.LoadUint32(&o.done) == 0 {
+		o.doSlow(f)
+	}
+}
+
+func (o *Once) doSlow(f func()) {
+	o.m.Lock()
+	defer o.m.Unlock()
+	if o.done == 0 {
+		defer atomic.StoreUint32(&o.done, 1)
+		f()
+	}
+}
+
+func (o *Once) Done() bool {
+	return atomic.LoadUint32(&o.done) == 1
+}