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mumbledj/queue.go
Matthieu Grieger 991046c90f Add queue.go
2014-12-14 20:41:28 -08:00

117 lines
2.7 KiB
Go

//
// queue.go
//
// Created by Hicham Bouabdallah
// Copyright (c) 2012 SimpleRocket LLC
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
//
package main
import "sync"
type queuenode struct {
data interface{}
next *queuenode
}
// A go-routine safe FIFO (first in first out) data stucture.
type Queue struct {
head *queuenode
tail *queuenode
count int
lock *sync.Mutex
}
// Creates a new pointer to a new queue.
func NewQueue() *Queue {
q := &Queue{}
q.lock = &sync.Mutex{}
return q
}
// Returns the number of elements in the queue (i.e. size/length)
// go-routine safe.
func (q *Queue) Len() int {
q.lock.Lock()
defer q.lock.Unlock()
return q.count
}
// Pushes/inserts a value at the end/tail of the queue.
// Note: this function does mutate the queue.
// go-routine safe.
func (q *Queue) Push(item interface{}) {
q.lock.Lock()
defer q.lock.Unlock()
n := &queuenode{data: item}
if q.tail == nil {
q.tail = n
q.head = n
} else {
q.tail.next = n
q.tail = n
}
q.count++
}
// Returns the value at the front of the queue.
// i.e. the oldest value in the queue.
// Note: this function does mutate the queue.
// go-routine safe.
func (q *Queue) Poll() interface{} {
q.lock.Lock()
defer q.lock.Unlock()
if q.head == nil {
return nil
}
n := q.head
q.head = n.next
if q.head == nil {
q.tail = nil
}
q.count--
return n.data
}
// Returns a read value at the front of the queue.
// i.e. the oldest value in the queue.
// Note: this function does NOT mutate the queue.
// go-routine safe.
func (q *Queue) Peek() interface{} {
q.lock.Lock()
defer q.lock.Unlock()
n := q.head
if n == nil || n.data == nil {
return nil
}
return n.data
}