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68 lines
1.6 KiB
Go
68 lines
1.6 KiB
Go
/*
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Maddy Mail Server - Composable all-in-one email server.
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Copyright © 2019-2020 Max Mazurov <fox.cpp@disroot.org>, Maddy Mail Server contributors
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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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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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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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package limiters
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import "context"
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// Semaphore is a convenience wrapper for a channel that implements
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// semaphore-kind synchronization.
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//
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// If the argument given to the NewSemaphore is negative or zero,
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// all methods are no-op.
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type Semaphore struct {
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c chan struct{}
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}
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func NewSemaphore(max int) Semaphore {
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return Semaphore{c: make(chan struct{}, max)}
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}
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func (s Semaphore) Take() bool {
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if cap(s.c) <= 0 {
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return true
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}
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s.c <- struct{}{}
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return true
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}
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func (s Semaphore) TakeContext(ctx context.Context) error {
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if cap(s.c) <= 0 {
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return nil
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}
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select {
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case s.c <- struct{}{}:
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return nil
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case <-ctx.Done():
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return ctx.Err()
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}
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}
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func (s Semaphore) Release() {
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if cap(s.c) <= 0 {
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return
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}
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select {
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case <-s.c:
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default:
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panic("limiters: mismatched Release call")
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}
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}
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func (s Semaphore) Close() {
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}
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