Dependencies

Godeps/Godeps.json

@@ -30,6 +30,10 @@
 			"Comment": "null-15",
 			"Rev": "12e4b4183793ac4b061921e7980845e750679fd0"
 		},
+		{
+			"ImportPath": "github.com/AudriusButkevicius/lfu-go",
+			"Rev": "164bcecceb92fd6037f4d18a8d97b495ec6ef669"
+		},
 		{
 			"ImportPath": "github.com/bkaradzic/go-lz4",
 			"Rev": "93a831dcee242be64a9cc9803dda84af25932de7"

Godeps/_workspace/src/github.com/AudriusButkevicius/lfu-go/LICENSE

@@ -0,0 +1,19 @@
+Copyright (C) 2012 Dave Grijalva
+
+Permission is hereby granted, free of charge, to any person obtaining a 
+copy of this software and associated documentation files (the "Software"), 
+to deal in the Software without restriction, including without limitation 
+the rights to use, copy, modify, merge, publish, distribute, sublicense, 
+and/or sell copies of the Software, and to permit persons to whom the 
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included 
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+THE SOFTWARE.

Godeps/_workspace/src/github.com/AudriusButkevicius/lfu-go/README.md

@@ -0,0 +1,19 @@
+A simple LFU cache for golang.  Based on the paper [An O(1) algorithm for implementing the LFU cache eviction scheme](http://dhruvbird.com/lfu.pdf).
+
+Usage:
+
+```go
+import "github.com/dgrijalva/lfu-go"
+
+// Make a new thing
+c := lfu.New()
+
+// Set some values
+c.Set("myKey", myValue)
+
+// Retrieve some values
+myValue = c.Get("myKey")
+
+// Evict some values
+c.Evict(1)
+```

Godeps/_workspace/src/github.com/AudriusButkevicius/lfu-go/lfu.go

@@ -0,0 +1,156 @@
+package lfu
+
+import (
+	"container/list"
+	"sync"
+)
+
+type Eviction struct {
+	Key   string
+	Value interface{}
+}
+
+type Cache struct {
+	// If len > UpperBound, cache will automatically evict
+	// down to LowerBound.  If either value is 0, this behavior
+	// is disabled.
+	UpperBound      int
+	LowerBound      int
+	values          map[string]*cacheEntry
+	freqs           *list.List
+	len             int
+	lock            *sync.Mutex
+	EvictionChannel chan<- Eviction
+}
+
+type cacheEntry struct {
+	key      string
+	value    interface{}
+	freqNode *list.Element
+}
+
+type listEntry struct {
+	entries map[*cacheEntry]byte
+	freq    int
+}
+
+func New() *Cache {
+	c := new(Cache)
+	c.values = make(map[string]*cacheEntry)
+	c.freqs = list.New()
+	c.lock = new(sync.Mutex)
+	return c
+}
+
+func (c *Cache) Get(key string) interface{} {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	if e, ok := c.values[key]; ok {
+		c.increment(e)
+		return e.value
+	}
+	return nil
+}
+
+func (c *Cache) Set(key string, value interface{}) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	if e, ok := c.values[key]; ok {
+		// value already exists for key.  overwrite
+		e.value = value
+		c.increment(e)
+	} else {
+		// value doesn't exist.  insert
+		e := new(cacheEntry)
+		e.key = key
+		e.value = value
+		c.values[key] = e
+		c.increment(e)
+		c.len++
+		// bounds mgmt
+		if c.UpperBound > 0 && c.LowerBound > 0 {
+			if c.len > c.UpperBound {
+				c.evict(c.len - c.LowerBound)
+			}
+		}
+	}
+}
+
+func (c *Cache) Len() int {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	return c.len
+}
+
+func (c *Cache) Evict(count int) int {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+	return c.evict(count)
+}
+
+func (c *Cache) evict(count int) int {
+	// No lock here so it can be called
+	// from within the lock (during Set)
+	var evicted int
+	for i := 0; i < count; {
+		if place := c.freqs.Front(); place != nil {
+			for entry, _ := range place.Value.(*listEntry).entries {
+				if i < count {
+					if c.EvictionChannel != nil {
+						c.EvictionChannel <- Eviction{
+							Key:   entry.key,
+							Value: entry.value,
+						}
+					}
+					delete(c.values, entry.key)
+					c.remEntry(place, entry)
+					evicted++
+					c.len--
+					i++
+				}
+			}
+		}
+	}
+	return evicted
+}
+
+func (c *Cache) increment(e *cacheEntry) {
+	currentPlace := e.freqNode
+	var nextFreq int
+	var nextPlace *list.Element
+	if currentPlace == nil {
+		// new entry
+		nextFreq = 1
+		nextPlace = c.freqs.Front()
+	} else {
+		// move up
+		nextFreq = currentPlace.Value.(*listEntry).freq + 1
+		nextPlace = currentPlace.Next()
+	}
+
+	if nextPlace == nil || nextPlace.Value.(*listEntry).freq != nextFreq {
+		// create a new list entry
+		li := new(listEntry)
+		li.freq = nextFreq
+		li.entries = make(map[*cacheEntry]byte)
+		if currentPlace != nil {
+			nextPlace = c.freqs.InsertAfter(li, currentPlace)
+		} else {
+			nextPlace = c.freqs.PushFront(li)
+		}
+	}
+	e.freqNode = nextPlace
+	nextPlace.Value.(*listEntry).entries[e] = 1
+	if currentPlace != nil {
+		// remove from current position
+		c.remEntry(currentPlace, e)
+	}
+}
+
+func (c *Cache) remEntry(place *list.Element, entry *cacheEntry) {
+	entries := place.Value.(*listEntry).entries
+	delete(entries, entry)
+	if len(entries) == 0 {
+		c.freqs.Remove(place)
+	}
+}

Godeps/_workspace/src/github.com/AudriusButkevicius/lfu-go/lfu_test.go

@@ -0,0 +1,68 @@
+package lfu
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestLFU(t *testing.T) {
+	c := New()
+	c.Set("a", "a")
+	if v := c.Get("a"); v != "a" {
+		t.Errorf("Value was not saved: %v != 'a'", v)
+	}
+	if l := c.Len(); l != 1 {
+		t.Errorf("Length was not updated: %v != 1", l)
+	}
+
+	c.Set("b", "b")
+	if v := c.Get("b"); v != "b" {
+		t.Errorf("Value was not saved: %v != 'b'", v)
+	}
+	if l := c.Len(); l != 2 {
+		t.Errorf("Length was not updated: %v != 2", l)
+	}
+
+	c.Get("a")
+	evicted := c.Evict(1)
+	if v := c.Get("a"); v != "a" {
+		t.Errorf("Value was improperly evicted: %v != 'a'", v)
+	}
+	if v := c.Get("b"); v != nil {
+		t.Errorf("Value was not evicted: %v", v)
+	}
+	if l := c.Len(); l != 1 {
+		t.Errorf("Length was not updated: %v != 1", l)
+	}
+	if evicted != 1 {
+		t.Errorf("Number of evicted items is wrong: %v != 1", evicted)
+	}
+}
+
+func TestBoundsMgmt(t *testing.T) {
+	c := New()
+	c.UpperBound = 10
+	c.LowerBound = 5
+
+	for i := 0; i < 100; i++ {
+		c.Set(fmt.Sprintf("%v", i), i)
+	}
+	if c.Len() > 10 {
+		t.Errorf("Bounds management failed to evict properly: %v", c.Len())
+	}
+}
+
+func TestEviction(t *testing.T) {
+	ch := make(chan Eviction, 1)
+
+	c := New()
+	c.EvictionChannel = ch
+	c.Set("a", "b")
+	c.Evict(1)
+
+	ev := <-ch
+
+	if ev.Key != "a" || ev.Value.(string) != "b" {
+		t.Error("Incorrect item")
+	}
+}