From 9ad0f9bb2bdfe47f144e2a0e8951dcfe6344a4ea Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Sat, 24 Aug 2024 16:58:01 -0400
Subject: Queue

---
 queue.go | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 queue.go

(limited to 'queue.go')

diff --git a/queue.go b/queue.go
new file mode 100644
index 0000000..5e28412
--- /dev/null
+++ b/queue.go
@@ -0,0 +1,49 @@
+package share
+
+// Queue is a FIFO queue with an unlimited capacity.
+//
+// Closing the Enqueue channel closes the Queue. The Queue waits
+// until all elements have been drained from the Dequeue channel
+// before closing it.
+type Queue[T any] struct {
+	// Sending to Enqueue adds an element to the back of the Queue
+	// and never blocks.
+	Enqueue chan<-T
+
+
+	// Receiving from Dequeue removes an element from the front
+	// of the queue or, if the queue is empty, blocks until an element
+	// is enqueued.
+	Dequeue <-chan T
+}
+
+func NewQueue[T any]() Queue[T] {
+	in, out := make(chan T), make(chan T)
+
+	go func() {
+		defer close(out)
+
+		var queue []T
+
+		for v := range in {
+			queue = append(queue, v)
+
+			for len(queue) > 0 {
+				select {
+				case out <- queue[0]:
+					queue = queue[1:]
+				case v, ok := <-in:
+					if !ok {
+						for _, x := range queue {
+							out <- x
+						}
+						return
+					}
+					queue = append(queue, v)
+				}
+			}
+		}
+	}()
+
+	return Queue[T]{Enqueue: in, Dequeue: out}
+}
-- 
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