move StringSet to utils package

irc/utils/semaphores.go

@@ -10,27 +10,25 @@ import (
 	"time"
 )
 
-type e struct{}
-
 // Semaphore is a counting semaphore.
 // A semaphore of capacity 1 can be used as a trylock.
-type Semaphore (chan e)
+type Semaphore (chan empty)
 
 // Initialize initializes a semaphore to a given capacity.
 func (semaphore *Semaphore) Initialize(capacity int) {
-	*semaphore = make(chan e, capacity)
+	*semaphore = make(chan empty, capacity)
 }
 
 // Acquire acquires a semaphore, blocking if necessary.
 func (semaphore *Semaphore) Acquire() {
-	(*semaphore) <- e{}
+	(*semaphore) <- empty{}
 }
 
 // TryAcquire tries to acquire a semaphore, returning whether the acquire was
 // successful. It never blocks.
 func (semaphore *Semaphore) TryAcquire() (acquired bool) {
 	select {
-	case (*semaphore) <- e{}:
+	case (*semaphore) <- empty{}:
 		return true
 	default:
 		return false
@@ -47,7 +45,7 @@ func (semaphore *Semaphore) AcquireWithTimeout(timeout time.Duration) (acquired
 
 	timer := time.NewTimer(timeout)
 	select {
-	case (*semaphore) <- e{}:
+	case (*semaphore) <- empty{}:
 		acquired = true
 	case <-timer.C:
 		acquired = false
@@ -61,7 +59,7 @@ func (semaphore *Semaphore) AcquireWithTimeout(timeout time.Duration) (acquired
 // Note that if the context is already expired, the acquire may succeed anyway.
 func (semaphore *Semaphore) AcquireWithContext(ctx context.Context) (acquired bool) {
 	select {
-	case (*semaphore) <- e{}:
+	case (*semaphore) <- empty{}:
 		acquired = true
 	case <-ctx.Done():
 		acquired = false

irc/utils/types.go

@@ -0,0 +1,17 @@
+// Copyright (c) 2020 Shivaram Lingamneni
+// released under the MIT license
+
+package utils
+
+type empty struct{}
+
+type StringSet map[string]empty
+
+func (s StringSet) Has(str string) bool {
+	_, ok := s[str]
+	return ok
+}
+
+func (s StringSet) Add(str string) {
+	s[str] = empty{}
+}