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// 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 prioritization 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 []any
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([]any, 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 any) {
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() (any, 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() (any, bool) {
if q.len == 0 {
return nil, false
}
return q.elems[q.head], true
}
func (q *queue) clear() {
*q = queue{}
}
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