examples/go/util/queue.go

/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/

package util

import (
	"qpid.apache.org/amqp"
	"sync"
)

// Use a buffered channel as a very simple queue.
type Queue chan amqp.Message

// Put a message back on the queue, does not block.
func (q Queue) PutBack(m amqp.Message) {
	select {
	case q <- m:
	default:
		// Not an efficient implementation but ensures we don't block the caller.
		go func() { q <- m }()
	}
}

// Concurrent-safe map of queues.
type Queues struct {
	queueSize int
	m         map[string]Queue
	lock      sync.Mutex
}

func MakeQueues(queueSize int) Queues {
	return Queues{queueSize: queueSize, m: make(map[string]Queue)}
}

// Create a queue if not found.
func (qs *Queues) Get(name string) Queue {
	qs.lock.Lock()
	defer qs.lock.Unlock()
	q := qs.m[name]
	if q == nil {
		q = make(Queue, qs.queueSize)
		qs.m[name] = q
	}
	return q
}