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receiver.go
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receiver.go
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// Copyright 2019 - See NOTICE file for copyright holders.
//
// 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 wire
import (
"context"
"github.com/pkg/errors"
"perun.network/go-perun/pkg/sync"
)
const (
// receiverBufferSize controls how many messages can be queued in a
// receiver before blocking.
receiverBufferSize = 16
)
var _ Consumer = (*Receiver)(nil)
// Receiver is a helper object that can subscribe to different message
// categories from multiple peers. Receivers must only be used by a single
// execution context at a time. If multiple contexts need to access a peer's
// messages, then multiple receivers have to be created.
type Receiver struct {
msgs chan *Envelope
sync.Closer
}
// Next returns a channel to the next message.
func (r *Receiver) Next(ctx context.Context) (*Envelope, error) {
select {
case <-ctx.Done():
return nil, errors.Wrap(ctx.Err(), "context closed")
case <-r.Closed():
return nil, errors.New("receiver closed")
default:
}
select {
case <-ctx.Done():
return nil, errors.Wrap(ctx.Err(), "context closed")
case <-r.Closed():
return nil, errors.New("receiver closed")
case e := <-r.msgs:
return e, nil
}
}
// Put puts a new message into the queue.
func (r *Receiver) Put(e *Envelope) {
select {
case r.msgs <- e:
case <-r.Closed():
}
}
// NewReceiver creates a new receiver.
func NewReceiver() *Receiver {
return &Receiver{
msgs: make(chan *Envelope, receiverBufferSize),
}
}