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go-cache
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Converting to generics proof of concept

This commit is contained in:
Luke Massa 2020-08-22 18:38:29 -04:00
parent 46f4078530
commit 4bdacd9be3
4 changed files with 91 additions and 99 deletions
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184
cache.go → cache.go2
View File

@ -1,22 +1,24 @@
package cache
package main
import (
"encoding/gob"
"fmt"
"io"
"os"
"runtime"
//"runtime"
"sync"
"time"
)
type Item struct {
Object interface{}
type Item(type T ) struct {
Object T
Expiration int64
}
type ItemMap(type T ) map[string]Item(T)
// Returns true if the item has expired.
func (item Item) Expired() bool {
func (item Item(T)) Expired() bool {
if item.Expiration == 0 {
return false
}
@ -32,23 +34,23 @@ const (
DefaultExpiration time.Duration = 0
)
type Cache struct {
*cache
type Cache(type T ) struct {
*cache(T)
// If this is confusing, see the comment at the bottom of New()
}
type cache struct {
type cache(type T ) struct {
defaultExpiration time.Duration
items map[string]Item
items map[string]Item(T)
mu sync.RWMutex
onEvicted func(string, interface{})
janitor *janitor
onEvicted func(string, T)
janitor *janitor(T)
}
// Add an item to the cache, replacing any existing item. If the duration is 0
// (DefaultExpiration), the cache's default expiration time is used. If it is -1
// (NoExpiration), the item never expires.
func (c *cache) Set(k string, x interface{}, d time.Duration) {
func (c *cache(T)) Set(k string, x T, d time.Duration) {
// "Inlining" of set
var e int64
if d == DefaultExpiration {
@ -58,7 +60,7 @@ func (c *cache) Set(k string, x interface{}, d time.Duration) {
e = time.Now().Add(d).UnixNano()
}
c.mu.Lock()
c.items[k] = Item{
c.items[k] = Item(T){
Object: x,
Expiration: e,
}
@ -67,7 +69,7 @@ func (c *cache) Set(k string, x interface{}, d time.Duration) {
c.mu.Unlock()
}
func (c *cache) set(k string, x interface{}, d time.Duration) {
func (c *cache(T)) set(k string, x T, d time.Duration) {
var e int64
if d == DefaultExpiration {
d = c.defaultExpiration
@ -75,7 +77,7 @@ func (c *cache) set(k string, x interface{}, d time.Duration) {
if d > 0 {
e = time.Now().Add(d).UnixNano()
}
c.items[k] = Item{
c.items[k] = Item(T){
Object: x,
Expiration: e,
}
@ -83,13 +85,13 @@ func (c *cache) set(k string, x interface{}, d time.Duration) {
// Add an item to the cache, replacing any existing item, using the default
// expiration.
func (c *cache) SetDefault(k string, x interface{}) {
func (c *cache(T)) SetDefault(k string, x T) {
c.Set(k, x, DefaultExpiration)
}
// Add an item to the cache only if an item doesn't already exist for the given
// key, or if the existing item has expired. Returns an error otherwise.
func (c *cache) Add(k string, x interface{}, d time.Duration) error {
func (c *cache(T)) Add(k string, x T, d time.Duration) error {
c.mu.Lock()
_, found := c.get(k)
if found {
@ -103,7 +105,7 @@ func (c *cache) Add(k string, x interface{}, d time.Duration) error {
// Set a new value for the cache key only if it already exists, and the existing
// item hasn't expired. Returns an error otherwise.
func (c *cache) Replace(k string, x interface{}, d time.Duration) error {
func (c *cache(T)) Replace(k string, x T, d time.Duration) error {
c.mu.Lock()
_, found := c.get(k)
if !found {
@ -117,18 +119,20 @@ func (c *cache) Replace(k string, x interface{}, d time.Duration) error {
// Get an item from the cache. Returns the item or nil, and a bool indicating
// whether the key was found.
func (c *cache) Get(k string) (interface{}, bool) {
func (c *cache(T)) Get(k string) (T, bool) {
c.mu.RLock()
// "Inlining" of get and Expired
item, found := c.items[k]
if !found {
c.mu.RUnlock()
return nil, false
var zero T
return zero, false
}
if item.Expiration > 0 {
if time.Now().UnixNano() > item.Expiration {
c.mu.RUnlock()
return nil, false
var zero T
return zero, false
}
}
c.mu.RUnlock()
@ -136,22 +140,24 @@ func (c *cache) Get(k string) (interface{}, bool) {
}
// GetWithExpiration returns an item and its expiration time from the cache.
// It returns the item or nil, the expiration time if one is set (if the item
// It returns the item or the zero value, the expiration time if one is set (if the item
// never expires a zero value for time.Time is returned), and a bool indicating
// whether the key was found.
func (c *cache) GetWithExpiration(k string) (interface{}, time.Time, bool) {
func (c *cache(T)) GetWithExpiration(k string) (T, time.Time, bool) {
c.mu.RLock()
// "Inlining" of get and Expired
item, found := c.items[k]
if !found {
c.mu.RUnlock()
return nil, time.Time{}, false
var zero T
return zero, time.Time{}, false
}
if item.Expiration > 0 {
if time.Now().UnixNano() > item.Expiration {
c.mu.RUnlock()
return nil, time.Time{}, false
var zero T
return zero, time.Time{}, false
}
// Return the item and the expiration time
@ -165,63 +171,36 @@ func (c *cache) GetWithExpiration(k string) (interface{}, time.Time, bool) {
return item.Object, time.Time{}, true
}
func (c *cache) get(k string) (interface{}, bool) {
func (c *cache(T)) get(k string) (T, bool) {
item, found := c.items[k]
var zero T
if !found {
return nil, false
return zero, false
}
// "Inlining" of Expired
if item.Expiration > 0 {
if time.Now().UnixNano() > item.Expiration {
return nil, false
return zero, false
}
}
return item.Object, true
}
/*
// Increment an item of type int, int8, int16, int32, int64, uintptr, uint,
// uint8, uint32, or uint64, float32 or float64 by n. Returns an error if the
// item's value is not an integer, if it was not found, or if it is not
// possible to increment it by n. To retrieve the incremented value, use one
// of the specialized methods, e.g. IncrementInt64.
func (c *cache) Increment(k string, n int64) error {
func (c *cache(T)) Increment(k string, n T) error {
c.mu.Lock()
v, found := c.items[k]
if !found || v.Expired() {
c.mu.Unlock()
return fmt.Errorf("Item %s not found", k)
}
switch v.Object.(type) {
case int:
v.Object = v.Object.(int) + int(n)
case int8:
v.Object = v.Object.(int8) + int8(n)
case int16:
v.Object = v.Object.(int16) + int16(n)
case int32:
v.Object = v.Object.(int32) + int32(n)
case int64:
v.Object = v.Object.(int64) + n
case uint:
v.Object = v.Object.(uint) + uint(n)
case uintptr:
v.Object = v.Object.(uintptr) + uintptr(n)
case uint8:
v.Object = v.Object.(uint8) + uint8(n)
case uint16:
v.Object = v.Object.(uint16) + uint16(n)
case uint32:
v.Object = v.Object.(uint32) + uint32(n)
case uint64:
v.Object = v.Object.(uint64) + uint64(n)
case float32:
v.Object = v.Object.(float32) + float32(n)
case float64:
v.Object = v.Object.(float64) + float64(n)
default:
c.mu.Unlock()
return fmt.Errorf("The value for %s is not an integer", k)
}
// TODO: How to make this work
v.Object += n
c.items[k] = v
c.mu.Unlock()
return nil
@ -900,9 +879,10 @@ func (c *cache) DecrementFloat64(k string, n float64) (float64, error) {
c.mu.Unlock()
return nv, nil
}
*/
// Delete an item from the cache. Does nothing if the key is not in the cache.
func (c *cache) Delete(k string) {
func (c *cache(T)) Delete(k string) {
c.mu.Lock()
v, evicted := c.delete(k)
c.mu.Unlock()
@ -911,7 +891,7 @@ func (c *cache) Delete(k string) {
}
}
func (c *cache) delete(k string) (interface{}, bool) {
func (c *cache(T)) delete(k string) (T, bool) {
if c.onEvicted != nil {
if v, found := c.items[k]; found {
delete(c.items, k)
@ -919,17 +899,18 @@ func (c *cache) delete(k string) (interface{}, bool) {
}
}
delete(c.items, k)
return nil, false
var zero T
return zero, false
}
type keyAndValue struct {
type keyAndValue(type T) struct {
key string
value interface{}
value T
}
// Delete all expired items from the cache.
func (c *cache) DeleteExpired() {
var evictedItems []keyAndValue
func (c *cache(T)) DeleteExpired() {
var evictedItems []keyAndValue(T)
now := time.Now().UnixNano()
c.mu.Lock()
for k, v := range c.items {
@ -937,7 +918,7 @@ func (c *cache) DeleteExpired() {
if v.Expiration > 0 && now > v.Expiration {
ov, evicted := c.delete(k)
if evicted {
evictedItems = append(evictedItems, keyAndValue{k, ov})
evictedItems = append(evictedItems, keyAndValue(T){k, ov})
}
}
}
@ -950,7 +931,7 @@ func (c *cache) DeleteExpired() {
// Sets an (optional) function that is called with the key and value when an
// item is evicted from the cache. (Including when it is deleted manually, but
// not when it is overwritten.) Set to nil to disable.
func (c *cache) OnEvicted(f func(string, interface{})) {
func (c *cache(T)) OnEvicted(f func(string, T)) {
c.mu.Lock()
c.onEvicted = f
c.mu.Unlock()
@ -960,7 +941,7 @@ func (c *cache) OnEvicted(f func(string, interface{})) {
//
// NOTE: This method is deprecated in favor of c.Items() and NewFrom() (see the
// documentation for NewFrom().)
func (c *cache) Save(w io.Writer) (err error) {
func (c *cache(T)) Save(w io.Writer) (err error) {
enc := gob.NewEncoder(w)
defer func() {
if x := recover(); x != nil {
@ -981,7 +962,7 @@ func (c *cache) Save(w io.Writer) (err error) {
//
// NOTE: This method is deprecated in favor of c.Items() and NewFrom() (see the
// documentation for NewFrom().)
func (c *cache) SaveFile(fname string) error {
func (c *cache(T)) SaveFile(fname string) error {
fp, err := os.Create(fname)
if err != nil {
return err
@ -999,9 +980,10 @@ func (c *cache) SaveFile(fname string) error {
//
// NOTE: This method is deprecated in favor of c.Items() and NewFrom() (see the
// documentation for NewFrom().)
func (c *cache) Load(r io.Reader) error {
func (c *cache(T)) Load(r io.Reader) error {
dec := gob.NewDecoder(r)
items := map[string]Item{}
var items map[string]Item(T)
err := dec.Decode(&items)
if err == nil {
c.mu.Lock()
@ -1021,7 +1003,7 @@ func (c *cache) Load(r io.Reader) error {
//
// NOTE: This method is deprecated in favor of c.Items() and NewFrom() (see the
// documentation for NewFrom().)
func (c *cache) LoadFile(fname string) error {
func (c *cache(T)) LoadFile(fname string) error {
fp, err := os.Open(fname)
if err != nil {
return err
@ -1035,10 +1017,10 @@ func (c *cache) LoadFile(fname string) error {
}
// Copies all unexpired items in the cache into a new map and returns it.
func (c *cache) Items() map[string]Item {
func (c *cache(T)) Items() map[string]Item(T) {
c.mu.RLock()
defer c.mu.RUnlock()
m := make(map[string]Item, len(c.items))
m := make(ItemMap(T), len(c.items))
now := time.Now().UnixNano()
for k, v := range c.items {
// "Inlining" of Expired
@ -1054,7 +1036,7 @@ func (c *cache) Items() map[string]Item {
// Returns the number of items in the cache. This may include items that have
// expired, but have not yet been cleaned up.
func (c *cache) ItemCount() int {
func (c *cache(T)) ItemCount() int {
c.mu.RLock()
n := len(c.items)
c.mu.RUnlock()
@ -1062,18 +1044,18 @@ func (c *cache) ItemCount() int {
}
// Delete all items from the cache.
func (c *cache) Flush() {
func (c *cache(T)) Flush() {
c.mu.Lock()
c.items = map[string]Item{}
c.items = make(ItemMap(T))
c.mu.Unlock()
}
type janitor struct {
type janitor(type T ) struct {
Interval time.Duration
stop chan bool
}
func (j *janitor) Run(c *cache) {
func (j *janitor(T)) Run(c *cache(T)) {
ticker := time.NewTicker(j.Interval)
for {
select {
@ -1086,12 +1068,8 @@ func (j *janitor) Run(c *cache) {
}
}
func stopJanitor(c *Cache) {
c.janitor.stop <- true
}
func runJanitor(c *cache, ci time.Duration) {
j := &janitor{
func runJanitor(type T )(c *cache(T), ci time.Duration) {
j := &janitor(T){
Interval: ci,
stop: make(chan bool),
}
@ -1099,28 +1077,28 @@ func runJanitor(c *cache, ci time.Duration) {
go j.Run(c)
}
func newCache(de time.Duration, m map[string]Item) *cache {
func newCache(type T )(de time.Duration, m map[string]Item(T)) *cache(T) {
if de == 0 {
de = -1
}
c := &cache{
c := &cache(T){
defaultExpiration: de,
items: m,
}
return c
}
func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]Item) *Cache {
c := newCache(de, m)
func newCacheWithJanitor(type T )(de time.Duration, ci time.Duration, m map[string]Item(T)) *Cache(T) {
c := newCache(T)(de, m)
// This trick ensures that the janitor goroutine (which--granted it
// was enabled--is running DeleteExpired on c forever) does not keep
// the returned C object from being garbage collected. When it is
// garbage collected, the finalizer stops the janitor goroutine, after
// which c can be collected.
C := &Cache{c}
C := &Cache(T){c}
if ci > 0 {
runJanitor(c, ci)
runtime.SetFinalizer(C, stopJanitor)
//runtime.SetFinalizer(C, stopJanitor(T))
}
return C
}
@ -1130,8 +1108,8 @@ func newCacheWithJanitor(de time.Duration, ci time.Duration, m map[string]Item)
// the items in the cache never expire (by default), and must be deleted
// manually. If the cleanup interval is less than one, expired items are not
// deleted from the cache before calling c.DeleteExpired().
func New(defaultExpiration, cleanupInterval time.Duration) *Cache {
items := make(map[string]Item)
func New(type T)(defaultExpiration, cleanupInterval time.Duration) *Cache(T) {
items := make(ItemMap(T))
return newCacheWithJanitor(defaultExpiration, cleanupInterval, items)
}
@ -1156,6 +1134,20 @@ func New(defaultExpiration, cleanupInterval time.Duration) *Cache {
// gob.Register() the individual types stored in the cache before encoding a
// map retrieved with c.Items(), and to register those same types before
// decoding a blob containing an items map.
func NewFrom(defaultExpiration, cleanupInterval time.Duration, items map[string]Item) *Cache {
func NewFrom(type T )(defaultExpiration, cleanupInterval time.Duration, items map[string]Item(T)) *Cache(T) {
return newCacheWithJanitor(defaultExpiration, cleanupInterval, items)
}
func main() {
c := New(string)(5*time.Minute, 10*time.Minute)
// Set the value of the key "foo" to "bar", with the default expiration time
c.cache.Set("foo", "world", DefaultExpiration)
// Get the string associated with the key "foo" from the cache
foo, found := c.cache.Get("foo")
if found {
fmt.Println("Hello " + foo)
}
}

2
cache_test.go → cache_test.go2
View File

@ -1,4 +1,4 @@
package cache
package main
import (
"bytes"

2
sharded.go → sharded.go2
View File

@ -1,4 +1,4 @@
package cache
package main
import (
"crypto/rand"

2
sharded_test.go → sharded_test.go2
View File

@ -1,4 +1,4 @@
package cache
package main
import (
"strconv"