1 files changed, 71 insertions, 0 deletions
diff --git a/src/internal/fuzz/queue.go b/src/internal/fuzz/queue.go
new file mode 100644
index 0000000000..cf67a28ba7
--- /dev/null
+++ b/src/internal/fuzz/queue.go
@@ -0,0 +1,71 @@
+// Copyright 2021 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 fuzz
+
+// queue holds a growable sequence of inputs for fuzzing and minimization.
+//
+// For now, this is a simple ring buffer
+// (https://en.wikipedia.org/wiki/Circular_buffer).
+//
+// TODO(golang.org/issue/46224): use a priotization algorithm based on input
+// size, previous duration, coverage, and any other metrics that seem useful.
+type queue struct {
+	// elems holds a ring buffer.
+	// The queue is empty when begin = end.
+	// The queue is full (until grow is called) when end = begin + N - 1 (mod N)
+	// where N = cap(elems).
+	elems     []interface{}
+	head, len int
+}
+
+func (q *queue) cap() int {
+	return len(q.elems)
+}
+
+func (q *queue) grow() {
+	oldCap := q.cap()
+	newCap := oldCap * 2
+	if newCap == 0 {
+		newCap = 8
+	}
+	newElems := make([]interface{}, newCap)
+	oldLen := q.len
+	for i := 0; i < oldLen; i++ {
+		newElems[i] = q.elems[(q.head+i)%oldCap]
+	}
+	q.elems = newElems
+	q.head = 0
+}
+
+func (q *queue) enqueue(e interface{}) {
+	if q.len+1 > q.cap() {
+		q.grow()
+	}
+	i := (q.head + q.len) % q.cap()
+	q.elems[i] = e
+	q.len++
+}
+
+func (q *queue) dequeue() (interface{}, bool) {
+	if q.len == 0 {
+		return nil, false
+	}
+	e := q.elems[q.head]
+	q.elems[q.head] = nil
+	q.head = (q.head + 1) % q.cap()
+	q.len--
+	return e, true
+}
+
+func (q *queue) peek() (interface{}, bool) {
+	if q.len == 0 {
+		return nil, false
+	}
+	return q.elems[q.head], true
+}
+
+func (q *queue) clear() {
+	*q = queue{}
+}