syncutil

Documentation

Overview

Copyright The ORAS Authors. 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.

Index

• type Once
  • func NewOnce() *Once
  • func (o *Once) Do(ctx context.Context, f func() (interface{}, error)) (bool, interface{}, error)

Types

type Once

type Once struct {
	// contains filtered or unexported fields
}

Once is an object that will perform exactly one action. Unlike sync.Once, this Once allowes the action to have return values.

func NewOnce

func NewOnce() *Once

NewOnce creates a new Once instance.

func (*Once) Do

func (o *Once) Do(ctx context.Context, f func() (interface{}, error)) (bool, interface{}, error)

Do calls the function f if and only if Do is being called first time or all previous function calls are cancelled, deadline exceeded, or panicking. When `once.Do(ctx, f)` is called multiple times, the return value of the first call of the function f is stored, and is directly returned for other calls. Besides the return value of the function f, including the error, Do returns true if the function f passed is called first and is not cancelled, deadline exceeded, or panicking. Otherwise, returns false.