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errorcontext.go
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errorcontext.go
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// Copyright © 2019 The Things Network Foundation, The Things Industries B.V.
//
// 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 errorcontext implements a Context that can be canceled with a specific error instead of the usual context.Canceled.
package errorcontext
import (
"context"
"sync"
)
// CancelFunc extends the regular context.CancelFunc with an error argument
type CancelFunc func(error)
// ErrorContext can be used to attach errors to a context cancelation.
type ErrorContext struct {
context.Context
cancel context.CancelFunc
mu sync.Mutex
err error
}
// Cancel the ErrorContext with an error. The context can not be re-used or re-canceled after this function is called.
func (c *ErrorContext) Cancel(err error) {
c.mu.Lock()
defer c.mu.Unlock()
if c.err != nil {
return
}
c.err = err
c.cancel()
}
// Err returns the err of the ErrorContext if non-nil, or the error of the underlying Context.
func (c *ErrorContext) Err() error {
c.mu.Lock()
defer c.mu.Unlock()
if c.err != nil {
return c.err
}
return c.Context.Err()
}
// New returns a new ErrorContext that extends the parent context
func New(parent context.Context) (context.Context, CancelFunc) {
parent, cancel := context.WithCancel(parent)
ctx := &ErrorContext{Context: parent, cancel: cancel}
return ctx, ctx.Cancel
}