1/* 2 * Copyright 2019 gRPC authors. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 * 16 */ 17 18// Package buffer provides an implementation of an unbounded buffer. 19package buffer 20 21import "sync" 22 23// Unbounded is an implementation of an unbounded buffer which does not use 24// extra goroutines. This is typically used for passing updates from one entity 25// to another within gRPC. 26// 27// All methods on this type are thread-safe and don't block on anything except 28// the underlying mutex used for synchronization. 29type Unbounded struct { 30 c chan interface{} 31 mu sync.Mutex 32 backlog []interface{} 33} 34 35// NewUnbounded returns a new instance of Unbounded. 36func NewUnbounded() *Unbounded { 37 return &Unbounded{c: make(chan interface{}, 1)} 38} 39 40// Put adds t to the unbounded buffer. 41func (b *Unbounded) Put(t interface{}) { 42 b.mu.Lock() 43 if len(b.backlog) == 0 { 44 select { 45 case b.c <- t: 46 b.mu.Unlock() 47 return 48 default: 49 } 50 } 51 b.backlog = append(b.backlog, t) 52 b.mu.Unlock() 53} 54 55// Load sends the earliest buffered data, if any, onto the read channel 56// returned by Get(). Users are expected to call this every time they read a 57// value from the read channel. 58func (b *Unbounded) Load() { 59 b.mu.Lock() 60 if len(b.backlog) > 0 { 61 select { 62 case b.c <- b.backlog[0]: 63 b.backlog[0] = nil 64 b.backlog = b.backlog[1:] 65 default: 66 } 67 } 68 b.mu.Unlock() 69} 70 71// Get returns a read channel on which values added to the buffer, via Put(), 72// are sent on. 73// 74// Upon reading a value from this channel, users are expected to call Load() to 75// send the next buffered value onto the channel if there is any. 76func (b *Unbounded) Get() <-chan interface{} { 77 return b.c 78} 79