From 1a57267a17c2fc17fb6e104846fabc3e363c326c Mon Sep 17 00:00:00 2001
From: Emile <git@emile.space>
Date: Fri, 16 Aug 2024 19:50:26 +0200
Subject: initial commit

---
 vendor/github.com/hashicorp/golang-lru/v2/2q.go | 267 ++++++++++++++++++++++++
 1 file changed, 267 insertions(+)
 create mode 100644 vendor/github.com/hashicorp/golang-lru/v2/2q.go

(limited to 'vendor/github.com/hashicorp/golang-lru/v2/2q.go')

diff --git a/vendor/github.com/hashicorp/golang-lru/v2/2q.go b/vendor/github.com/hashicorp/golang-lru/v2/2q.go
new file mode 100644
index 0000000..8c95252
--- /dev/null
+++ b/vendor/github.com/hashicorp/golang-lru/v2/2q.go
@@ -0,0 +1,267 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package lru
+
+import (
+	"errors"
+	"sync"
+
+	"github.com/hashicorp/golang-lru/v2/simplelru"
+)
+
+const (
+	// Default2QRecentRatio is the ratio of the 2Q cache dedicated
+	// to recently added entries that have only been accessed once.
+	Default2QRecentRatio = 0.25
+
+	// Default2QGhostEntries is the default ratio of ghost
+	// entries kept to track entries recently evicted
+	Default2QGhostEntries = 0.50
+)
+
+// TwoQueueCache is a thread-safe fixed size 2Q cache.
+// 2Q is an enhancement over the standard LRU cache
+// in that it tracks both frequently and recently used
+// entries separately. This avoids a burst in access to new
+// entries from evicting frequently used entries. It adds some
+// additional tracking overhead to the standard LRU cache, and is
+// computationally about 2x the cost, and adds some metadata over
+// head. The ARCCache is similar, but does not require setting any
+// parameters.
+type TwoQueueCache[K comparable, V any] struct {
+	size        int
+	recentSize  int
+	recentRatio float64
+	ghostRatio  float64
+
+	recent      simplelru.LRUCache[K, V]
+	frequent    simplelru.LRUCache[K, V]
+	recentEvict simplelru.LRUCache[K, struct{}]
+	lock        sync.RWMutex
+}
+
+// New2Q creates a new TwoQueueCache using the default
+// values for the parameters.
+func New2Q[K comparable, V any](size int) (*TwoQueueCache[K, V], error) {
+	return New2QParams[K, V](size, Default2QRecentRatio, Default2QGhostEntries)
+}
+
+// New2QParams creates a new TwoQueueCache using the provided
+// parameter values.
+func New2QParams[K comparable, V any](size int, recentRatio, ghostRatio float64) (*TwoQueueCache[K, V], error) {
+	if size <= 0 {
+		return nil, errors.New("invalid size")
+	}
+	if recentRatio < 0.0 || recentRatio > 1.0 {
+		return nil, errors.New("invalid recent ratio")
+	}
+	if ghostRatio < 0.0 || ghostRatio > 1.0 {
+		return nil, errors.New("invalid ghost ratio")
+	}
+
+	// Determine the sub-sizes
+	recentSize := int(float64(size) * recentRatio)
+	evictSize := int(float64(size) * ghostRatio)
+
+	// Allocate the LRUs
+	recent, err := simplelru.NewLRU[K, V](size, nil)
+	if err != nil {
+		return nil, err
+	}
+	frequent, err := simplelru.NewLRU[K, V](size, nil)
+	if err != nil {
+		return nil, err
+	}
+	recentEvict, err := simplelru.NewLRU[K, struct{}](evictSize, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// Initialize the cache
+	c := &TwoQueueCache[K, V]{
+		size:        size,
+		recentSize:  recentSize,
+		recentRatio: recentRatio,
+		ghostRatio:  ghostRatio,
+		recent:      recent,
+		frequent:    frequent,
+		recentEvict: recentEvict,
+	}
+	return c, nil
+}
+
+// Get looks up a key's value from the cache.
+func (c *TwoQueueCache[K, V]) Get(key K) (value V, ok bool) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	// Check if this is a frequent value
+	if val, ok := c.frequent.Get(key); ok {
+		return val, ok
+	}
+
+	// If the value is contained in recent, then we
+	// promote it to frequent
+	if val, ok := c.recent.Peek(key); ok {
+		c.recent.Remove(key)
+		c.frequent.Add(key, val)
+		return val, ok
+	}
+
+	// No hit
+	return
+}
+
+// Add adds a value to the cache.
+func (c *TwoQueueCache[K, V]) Add(key K, value V) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	// Check if the value is frequently used already,
+	// and just update the value
+	if c.frequent.Contains(key) {
+		c.frequent.Add(key, value)
+		return
+	}
+
+	// Check if the value is recently used, and promote
+	// the value into the frequent list
+	if c.recent.Contains(key) {
+		c.recent.Remove(key)
+		c.frequent.Add(key, value)
+		return
+	}
+
+	// If the value was recently evicted, add it to the
+	// frequently used list
+	if c.recentEvict.Contains(key) {
+		c.ensureSpace(true)
+		c.recentEvict.Remove(key)
+		c.frequent.Add(key, value)
+		return
+	}
+
+	// Add to the recently seen list
+	c.ensureSpace(false)
+	c.recent.Add(key, value)
+}
+
+// ensureSpace is used to ensure we have space in the cache
+func (c *TwoQueueCache[K, V]) ensureSpace(recentEvict bool) {
+	// If we have space, nothing to do
+	recentLen := c.recent.Len()
+	freqLen := c.frequent.Len()
+	if recentLen+freqLen < c.size {
+		return
+	}
+
+	// If the recent buffer is larger than
+	// the target, evict from there
+	if recentLen > 0 && (recentLen > c.recentSize || (recentLen == c.recentSize && !recentEvict)) {
+		k, _, _ := c.recent.RemoveOldest()
+		c.recentEvict.Add(k, struct{}{})
+		return
+	}
+
+	// Remove from the frequent list otherwise
+	c.frequent.RemoveOldest()
+}
+
+// Len returns the number of items in the cache.
+func (c *TwoQueueCache[K, V]) Len() int {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	return c.recent.Len() + c.frequent.Len()
+}
+
+// Resize changes the cache size.
+func (c *TwoQueueCache[K, V]) Resize(size int) (evicted int) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	// Recalculate the sub-sizes
+	recentSize := int(float64(size) * c.recentRatio)
+	evictSize := int(float64(size) * c.ghostRatio)
+	c.size = size
+	c.recentSize = recentSize
+
+	// ensureSpace
+	diff := c.recent.Len() + c.frequent.Len() - size
+	if diff < 0 {
+		diff = 0
+	}
+	for i := 0; i < diff; i++ {
+		c.ensureSpace(true)
+	}
+
+	// Reallocate the LRUs
+	c.recent.Resize(size)
+	c.frequent.Resize(size)
+	c.recentEvict.Resize(evictSize)
+
+	return diff
+}
+
+// Keys returns a slice of the keys in the cache.
+// The frequently used keys are first in the returned slice.
+func (c *TwoQueueCache[K, V]) Keys() []K {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	k1 := c.frequent.Keys()
+	k2 := c.recent.Keys()
+	return append(k1, k2...)
+}
+
+// Values returns a slice of the values in the cache.
+// The frequently used values are first in the returned slice.
+func (c *TwoQueueCache[K, V]) Values() []V {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	v1 := c.frequent.Values()
+	v2 := c.recent.Values()
+	return append(v1, v2...)
+}
+
+// Remove removes the provided key from the cache.
+func (c *TwoQueueCache[K, V]) Remove(key K) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	if c.frequent.Remove(key) {
+		return
+	}
+	if c.recent.Remove(key) {
+		return
+	}
+	if c.recentEvict.Remove(key) {
+		return
+	}
+}
+
+// Purge is used to completely clear the cache.
+func (c *TwoQueueCache[K, V]) Purge() {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	c.recent.Purge()
+	c.frequent.Purge()
+	c.recentEvict.Purge()
+}
+
+// Contains is used to check if the cache contains a key
+// without updating recency or frequency.
+func (c *TwoQueueCache[K, V]) Contains(key K) bool {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	return c.frequent.Contains(key) || c.recent.Contains(key)
+}
+
+// Peek is used to inspect the cache value of a key
+// without updating recency or frequency.
+func (c *TwoQueueCache[K, V]) Peek(key K) (value V, ok bool) {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+	if val, ok := c.frequent.Peek(key); ok {
+		return val, ok
+	}
+	return c.recent.Peek(key)
+}
-- 
cgit 1.4.1