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47 lines
1014 B
Go
47 lines
1014 B
Go
// Copyright (c) HashiCorp, Inc.
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// SPDX-License-Identifier: MPL-2.0
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package tofu
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// Semaphore is a wrapper around a channel to provide
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// utility methods to clarify that we are treating the
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// channel as a semaphore
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type Semaphore chan struct{}
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// NewSemaphore creates a semaphore that allows up
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// to a given limit of simultaneous acquisitions
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func NewSemaphore(n int) Semaphore {
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if n <= 0 {
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panic("semaphore with limit <=0")
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}
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ch := make(chan struct{}, n)
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return Semaphore(ch)
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}
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// Acquire is used to acquire an available slot.
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// Blocks until available.
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func (s Semaphore) Acquire() {
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s <- struct{}{}
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}
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// TryAcquire is used to do a non-blocking acquire.
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// Returns a bool indicating success
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func (s Semaphore) TryAcquire() bool {
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select {
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case s <- struct{}{}:
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return true
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default:
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return false
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}
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}
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// Release is used to return a slot. Acquire must
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// be called as a pre-condition.
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func (s Semaphore) Release() {
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select {
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case <-s:
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default:
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panic("release without an acquire")
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}
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}
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