60 lines
2.0 KiB
Go
60 lines
2.0 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package syncevent
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// Source represents an event source.
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type Source interface {
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// SubscribeEvents causes the Source to notify the given Receiver of the
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// given subset of events.
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//
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// Preconditions: r != nil. The ReceiverCallback for r must not take locks
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// that are ordered prior to the Source; for example, it cannot call any
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// Source methods.
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SubscribeEvents(r *Receiver, filter Set) SubscriptionID
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// UnsubscribeEvents causes the Source to stop notifying the Receiver
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// subscribed by a previous call to SubscribeEvents that returned the given
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// SubscriptionID.
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//
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// Preconditions: UnsubscribeEvents may be called at most once for any
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// given SubscriptionID.
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UnsubscribeEvents(id SubscriptionID)
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}
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// SubscriptionID identifies a call to Source.SubscribeEvents.
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type SubscriptionID uint64
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// UnsubscribeAndAck is a convenience function that unsubscribes r from the
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// given events from src and also clears them from r.
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func UnsubscribeAndAck(src Source, r *Receiver, filter Set, id SubscriptionID) {
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src.UnsubscribeEvents(id)
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r.Ack(filter)
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}
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// NoopSource implements Source by never sending events to subscribed
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// Receivers.
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type NoopSource struct{}
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// SubscribeEvents implements Source.SubscribeEvents.
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func (NoopSource) SubscribeEvents(*Receiver, Set) SubscriptionID {
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return 0
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}
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// UnsubscribeEvents implements Source.UnsubscribeEvents.
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func (NoopSource) UnsubscribeEvents(SubscriptionID) {
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}
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// See Broadcaster for a non-noop implementations of Source.
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