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This package allows caching arbitrary key/value pairs in-memory, along with an interface implemented by the cache types. Extracted from #7493 Signed-off-by: Andrew Dunham <andrew@du.nham.ca> Change-Id: Ic8ca820927c456721cf324a0c8f3882a57752cc9
41 lines
1.6 KiB
Go
41 lines
1.6 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package cache contains an interface for a cache around a typed value, and
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// various cache implementations that implement that interface.
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package cache
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import "time"
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// Cache is the interface for the cache types in this package.
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//
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// Functions in this interface take a key parameter, but it is valid for a
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// cache type to hold a single value associated with a key, and simply drop the
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// cached value if provided with a different key.
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//
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// It is valid for Cache implementations to be concurrency-safe or not, and
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// each implementation should document this. If you need a concurrency-safe
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// cache, an existing cache can be wrapped with a lock using NewLocking(inner).
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//
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// K and V should be types that can be successfully passed to json.Marshal.
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type Cache[K comparable, V any] interface {
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// Get should return a previously-cached value or call the provided
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// FillFunc to obtain a new one. The provided key can be used either to
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// allow multiple cached values, or to drop the cache if the key
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// changes; either is valid.
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Get(K, FillFunc[V]) (V, error)
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// Forget should remove the given key from the cache, if it is present.
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// If it is not present, nothing should be done.
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Forget(K)
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// Empty should empty the cache such that the next call to Get should
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// call the provided FillFunc for all possible keys.
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Empty()
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}
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// FillFunc is the signature of a function for filling a cache. It should
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// return the value to be cached, the time that the cached value is valid
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// until, or an error.
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type FillFunc[T any] func() (T, time.Time, error)
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