77 lines
2.9 KiB
Go
77 lines
2.9 KiB
Go
// Mgmt
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// Copyright (C) 2013-2024+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//
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// Additional permission under GNU GPL version 3 section 7
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//
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// If you modify this program, or any covered work, by linking or combining it
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// with embedded mcl code and modules (and that the embedded mcl code and
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// modules which link with this program, contain a copy of their source code in
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// the authoritative form) containing parts covered by the terms of any other
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// license, the licensors of this program grant you additional permission to
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// convey the resulting work. Furthermore, the licensors of this program grant
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// the original author, James Shubin, additional permission to update this
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// additional permission if he deems it necessary to achieve the goals of this
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// additional permission.
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package util
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import (
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"context"
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"sync"
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)
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// ContextWithCloser wraps a context and returns a new one exactly like the
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// other context.With* functions, except that it takes a channel as an alternate
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// cancel signal.
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// TODO: switch to interface{} instead of <-chan struct to allow any chan type.
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func ContextWithCloser(ctx context.Context, ch <-chan struct{}) (context.Context, context.CancelFunc) {
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newCtx, cancel := context.WithCancel(ctx)
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go func() {
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defer cancel()
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select {
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case <-ch: // what we're waiting for
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case <-newCtx.Done(): // parent ctx was canceled
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}
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}()
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return newCtx, cancel
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}
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// ctxKeyWg is the context value key used by CtxWithWg and WgFromCtx.
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type ctxKeyWg struct{}
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// CtxWithWg takes a context and a wait group, and returns a new context that is
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// embedded with the wait group. You must use WgFromCtx to extract it.
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func CtxWithWg(ctx context.Context, wg *sync.WaitGroup) context.Context {
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//if wg == nil {
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// return ctx // return the parent?
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//}
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key := ctxKeyWg(struct{}{})
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return context.WithValue(ctx, key, wg)
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}
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// WgFromCtx takes a context and returns the stored wait group. You must use
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// CtxWithWg to store it.
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func WgFromCtx(ctx context.Context) *sync.WaitGroup {
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key := ctxKeyWg(struct{}{})
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if val := ctx.Value(key); val != nil {
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return val.(*sync.WaitGroup) // panic's if assertion fails
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}
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//return &sync.WaitGroup{} // return a dud?
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return nil
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}
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