From b392ad64a8fd04d20b35ad21d2d4ea3ff2778e3f Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Tue, 5 Jul 2022 12:26:45 -0600
Subject: wip file io

---
 cmd/btrfs-mount/lru.go | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 cmd/btrfs-mount/lru.go

(limited to 'cmd/btrfs-mount/lru.go')

diff --git a/cmd/btrfs-mount/lru.go b/cmd/btrfs-mount/lru.go
new file mode 100644
index 0000000..bf91c5e
--- /dev/null
+++ b/cmd/btrfs-mount/lru.go
@@ -0,0 +1,73 @@
+package main
+
+import (
+	"sync"
+
+	lru "github.com/hashicorp/golang-lru"
+)
+
+type LRUCache[K comparable, V any] struct {
+	initOnce sync.Once
+	inner    *lru.ARCCache
+}
+
+func (c *LRUCache[K, V]) init() {
+	c.initOnce.Do(func() {
+		c.inner, _ = lru.NewARC(128)
+	})
+}
+
+func (c *LRUCache[K, V]) Add(key K, value V) {
+	c.init()
+	c.inner.Add(key, value)
+}
+func (c *LRUCache[K, V]) Contains(key K) bool {
+	c.init()
+	return c.inner.Contains(key)
+}
+func (c *LRUCache[K, V]) Get(key K) (value V, ok bool) {
+	c.init()
+	_value, ok := c.inner.Get(key)
+	if ok {
+		value = _value.(V)
+	}
+	return value, ok
+}
+func (c *LRUCache[K, V]) Keys() []K {
+	c.init()
+	untyped := c.inner.Keys()
+	typed := make([]K, len(untyped))
+	for i := range untyped {
+		typed[i] = untyped[i].(K)
+	}
+	return typed
+}
+func (c *LRUCache[K, V]) Len() int {
+	c.init()
+	return c.inner.Len()
+}
+func (c *LRUCache[K, V]) Peek(key K) (value V, ok bool) {
+	c.init()
+	_value, ok := c.inner.Peek(key)
+	if ok {
+		value = _value.(V)
+	}
+	return value, ok
+}
+func (c *LRUCache[K, V]) Purge() {
+	c.init()
+	c.inner.Purge()
+}
+func (c *LRUCache[K, V]) Remove(key K) {
+	c.init()
+	c.inner.Remove(key)
+}
+
+func (c *LRUCache[K, V]) GetOrElse(key K, fn func() V) V {
+	var value V
+	var ok bool
+	for value, ok = c.Get(key); !ok; value, ok = c.Get(key) {
+		c.Add(key, fn())
+	}
+	return value
+}
-- 
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