1 // Copyright 2020 Google LLC 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 14 package pubsub 15 16 import "context" 17 18 // A PublishResult holds the result from a call to Publish. 19 type PublishResult struct { 20 ready chan struct{} 21 serverID string 22 err error 23 } 24 25 // Ready returns a channel that is closed when the result is ready. 26 // When the Ready channel is closed, Get is guaranteed not to block. 27 func (r *PublishResult) Ready() <-chan struct{} { return r.ready } 28 29 // Get returns the server-generated message ID and/or error result of a Publish call. 30 // Get blocks until the Publish call completes or the context is done. 31 func (r *PublishResult) Get(ctx context.Context) (serverID string, err error) { 32 // If the result is already ready, return it even if the context is done. 33 select { 34 case <-r.Ready(): 35 return r.serverID, r.err 36 default: 37 } 38 select { 39 case <-ctx.Done(): 40 return "", ctx.Err() 41 case <-r.Ready(): 42 return r.serverID, r.err 43 } 44 } 45 46 // NewPublishResult creates a PublishResult. 47 func NewPublishResult() *PublishResult { 48 return &PublishResult{ready: make(chan struct{})} 49 } 50 51 // SetPublishResult sets the server ID and error for a publish result and closes 52 // the Ready channel. 53 func SetPublishResult(r *PublishResult, sid string, err error) { 54 r.serverID = sid 55 r.err = err 56 close(r.ready) 57 } 58