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