blob: 2cb3109d807998f967abe776c7264774154a6d6c [file] [log] [blame]
/*
* Copyright 2019 gRPC authors.
*
* Licensed 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 buffer provides an implementation of an unbounded buffer.
package buffer
import "sync"
// Unbounded is an implementation of an unbounded buffer which does not use
// extra goroutines. This is typically used for passing updates from one entity
// to another within gRPC.
//
// All methods on this type are thread-safe and don't block on anything except
// the underlying mutex used for synchronization.
type Unbounded struct {
c chan interface{}
mu sync.Mutex
backlog []interface{}
}
// NewUnbounded returns a new instance of Unbounded.
func NewUnbounded() *Unbounded {
return &Unbounded{c: make(chan interface{}, 1)}
}
// Put adds t to the unbounded buffer.
func (b *Unbounded) Put(t interface{}) {
b.mu.Lock()
if len(b.backlog) == 0 {
select {
case b.c <- t:
b.mu.Unlock()
return
default:
}
}
b.backlog = append(b.backlog, t)
b.mu.Unlock()
}
// Load sends the earliest buffered data, if any, onto the read channel
// returned by Get(). Users are expected to call this every time they read a
// value from the read channel.
func (b *Unbounded) Load() {
b.mu.Lock()
if len(b.backlog) > 0 {
select {
case b.c <- b.backlog[0]:
b.backlog[0] = nil
b.backlog = b.backlog[1:]
default:
}
}
b.mu.Unlock()
}
// Get returns a read channel on which values added to the buffer, via Put(),
// are sent on.
//
// Upon reading a value from this channel, users are expected to call Load() to
// send the next buffered value onto the channel if there is any.
func (b *Unbounded) Get() <-chan interface{} {
return b.c
}