diff options
author | Luke Shumaker <lukeshu@lukeshu.com> | 2023-02-05 12:06:30 -0700 |
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committer | Luke Shumaker <lukeshu@lukeshu.com> | 2023-02-05 13:32:56 -0700 |
commit | 2d939c9c6e62395ed924fe7c5cd4c4b294e391a9 (patch) | |
tree | f292beebe17f48a56550bea1435808b965ce6764 /value.go | |
parent | d69037701f6cdd4f5bb98c20af329c02ba89bb90 (diff) |
Rename to git.lukeshu.com/go/containers, split in to 2 separate packages
Diffstat (limited to 'value.go')
-rw-r--r-- | value.go | 67 |
1 files changed, 0 insertions, 67 deletions
diff --git a/value.go b/value.go deleted file mode 100644 index 99c8876..0000000 --- a/value.go +++ /dev/null @@ -1,67 +0,0 @@ -// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com> -// -// SPDX-License-Identifier: GPL-2.0-or-later - -package typedsync - -import ( - "sync" -) - -// Value is a typed equivalent of sync/atomic.Value. -// -// It is not actually a wrapper around sync/atomic.Value for -// allocation-performance reasons. -type Value[T comparable] struct { - mu sync.Mutex - ok bool - val T -} - -// This uses a dumb mutex-based solution because -// -// 1. Performance is good enough, because in the fast-path mutexes -// use the same compare-and-swap as sync/atomic.Value; and because -// all of these methods are short we're unlikely to hit the -// mutex's slow path. -// -// 2. We could use sync/atomic.Pointer[T], which by itself would have -// the same performance characteristics as sync/atomic.Value but -// without the benefit of runtime_procPin()/runtime_procUnpin(). -// We want to avoid that because it means we're doing an -// allocation for every store/swap; avoiding that is our whole -// reason for not just wraping sync/atomic.Value. So then we'd -// want to use a Pool to reuse allocations; but (1) that adds more -// sync-overhead, and (2) it also gets trickier because we'd have -// to be careful about not adding a pointer back to the pool when -// load has grabbed the pointer but not yet dereferenced it. - -func (v *Value[T]) Load() (val T, ok bool) { - v.mu.Lock() - defer v.mu.Unlock() - return v.val, v.ok -} - -func (v *Value[T]) Store(val T) { - v.mu.Lock() - defer v.mu.Unlock() - v.val, v.ok = val, true -} - -func (v *Value[T]) Swap(newV T) (oldV T, oldOK bool) { - v.mu.Lock() - defer v.mu.Unlock() - oldV, oldOK = v.val, v.ok - v.val, v.ok = newV, true - return -} - -func (v *Value[T]) CompareAndSwap(oldV, newV T) (swapped bool) { - v.mu.Lock() - defer v.mu.Unlock() - if !v.ok || v.val != oldV { - return false - } - v.val = newV - return true -} |