/
broadcast.go
59 lines (54 loc) · 1.55 KB
/
broadcast.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
// Copyright (C) 2017 Google Inc.
//
// 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 event
import (
"context"
"io"
)
// Broadcast implements a list of handlers that itself is a handler.
// Events written to the broadcast are sent to all handlers in the list
type Broadcast []Handler
// Listen adds a new handler to the set.
// It conforms to the Listener signature.
func (b *Broadcast) Listen(ctx context.Context, h Handler) {
*b = append(*b, h)
}
// Send implements Handler to send (sequentially) to all current handlers.
// Handlers that return an error will be dropped from the broadcast list.
func (b *Broadcast) Send(ctx context.Context, event interface{}) error {
if len(*b) == 0 {
return nil
}
out := 0
var result error
for _, h := range *b {
res := h(ctx, event)
switch res {
case nil:
(*b)[out] = h
out++
case io.EOF:
if result == nil {
result = res
}
default:
// TODO: build a compound error if we already have one?
if result == nil || result == io.EOF {
result = res
}
}
}
*b = (*b)[:out]
return result
}