github.com/hxx258456/ccgo@v0.0.5-0.20230213014102-48b35f46f66f/net/context/go17.go (about)

     1  // Copyright 2016 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build go1.7
     6  // +build go1.7
     7  
     8  package context
     9  
    10  import (
    11  	"context" // standard library's context, as of Go 1.7
    12  	"time"
    13  )
    14  
    15  var (
    16  	todo       = context.TODO()
    17  	background = context.Background()
    18  )
    19  
    20  // Canceled is the error returned by Context.Err when the context is canceled.
    21  var Canceled = context.Canceled
    22  
    23  // DeadlineExceeded is the error returned by Context.Err when the context's
    24  // deadline passes.
    25  var DeadlineExceeded = context.DeadlineExceeded
    26  
    27  // WithCancel returns a copy of parent with a new Done channel. The returned
    28  // context's Done channel is closed when the returned cancel function is called
    29  // or when the parent context's Done channel is closed, whichever happens first.
    30  //
    31  // Canceling this context releases resources associated with it, so code should
    32  // call cancel as soon as the operations running in this Context complete.
    33  func WithCancel(parent Context) (ctx Context, cancel CancelFunc) {
    34  	ctx, f := context.WithCancel(parent)
    35  	return ctx, CancelFunc(f)
    36  }
    37  
    38  // WithDeadline returns a copy of the parent context with the deadline adjusted
    39  // to be no later than d. If the parent's deadline is already earlier than d,
    40  // WithDeadline(parent, d) is semantically equivalent to parent. The returned
    41  // context's Done channel is closed when the deadline expires, when the returned
    42  // cancel function is called, or when the parent context's Done channel is
    43  // closed, whichever happens first.
    44  //
    45  // Canceling this context releases resources associated with it, so code should
    46  // call cancel as soon as the operations running in this Context complete.
    47  func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc) {
    48  	ctx, f := context.WithDeadline(parent, deadline)
    49  	return ctx, CancelFunc(f)
    50  }
    51  
    52  // WithTimeout returns WithDeadline(parent, time.Now().Add(timeout)).
    53  //
    54  // Canceling this context releases resources associated with it, so code should
    55  // call cancel as soon as the operations running in this Context complete:
    56  //
    57  // 	func slowOperationWithTimeout(ctx context.Context) (Result, error) {
    58  // 		ctx, cancel := context.WithTimeout(ctx, 100*time.Millisecond)
    59  // 		defer cancel()  // releases resources if slowOperation completes before timeout elapses
    60  // 		return slowOperation(ctx)
    61  // 	}
    62  func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc) {
    63  	return WithDeadline(parent, time.Now().Add(timeout))
    64  }
    65  
    66  // WithValue returns a copy of parent in which the value associated with key is
    67  // val.
    68  //
    69  // Use context Values only for request-scoped data that transits processes and
    70  // APIs, not for passing optional parameters to functions.
    71  func WithValue(parent Context, key interface{}, val interface{}) Context {
    72  	return context.WithValue(parent, key, val)
    73  }