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68 lines
1.6 KiB
Go
68 lines
1.6 KiB
Go
// Copyright (c) Liam Stanley <me@liamstanley.io>. All rights reserved. Use
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// of this source code is governed by the MIT license that can be found in
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// the LICENSE file.
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package ctxgroup
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import (
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"context"
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"sync"
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)
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// A Group is a collection of goroutines working on subtasks that are part of
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// the same overall task.
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type Group struct {
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ctx context.Context
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cancel func()
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wg sync.WaitGroup
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errOnce sync.Once
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err error
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}
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// New returns a new Group and an associated context derived from ctx.
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// Obtain the derived context from calling Group.Context().
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//
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// The derived context is canceled the first time a function passed to Go
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// returns a non-nil error or the first time Wait returns, whichever occurs
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// first.
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func New(ctx context.Context) *Group {
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nctx, cancel := context.WithCancel(ctx)
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return &Group{ctx: nctx, cancel: cancel}
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}
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// Context returns the context for this group. It may be canceled by the first
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// function to return a non-nil error.
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func (g *Group) Context() context.Context {
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return g.ctx
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}
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// Wait blocks until all function calls from the Go method have returned, then
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// returns the first non-nil error (if any) from them.
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func (g *Group) Wait() error {
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g.wg.Wait()
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if g.cancel != nil {
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g.cancel()
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}
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return g.err
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}
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// Go calls the given function in a new goroutine. The first call to return a
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// non-nil error cancels the group; its error will be returned by Wait.
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func (g *Group) Go(f func(ctx context.Context) error) {
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g.wg.Add(1)
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go func() {
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defer g.wg.Done()
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if err := f(g.ctx); err != nil {
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g.errOnce.Do(func() {
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g.err = err
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if g.cancel != nil {
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g.cancel()
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}
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})
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}
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}()
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}
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