Cache serialization

cache.go

@@ -83,13 +83,29 @@ package cache
 //     2
 
 import (
+	"encoding/gob"
 	"fmt"
+	"io"
+	"os"
 	"reflect"
 	"runtime"
 	"sync"
 	"time"
 )
 
+type Item struct {
+	Object     interface{}
+	Expiration *time.Time
+}
+
+// Returns true if the item has expired.
+func (i *Item) Expired() bool {
+	if i.Expiration == nil {
+		return false
+	}
+	return i.Expiration.Before(time.Now())
+}
+
 type Cache struct {
 	*cache
 	// If this is confusing, see the comment at the bottom of the New() function
@@ -102,16 +118,6 @@ type cache struct {
 	janitor           *janitor
 }
 
-type Item struct {
-	Object     interface{}
-	Expiration *time.Time
-}
-
-type janitor struct {
-	Interval time.Duration
-	stop     chan bool
-}
-
 // Adds an item to the cache, replacing any existing item. If the duration is 0, the
 // cache's default expiration time is used. If it is -1, the item never expires.
 func (c *cache) Set(k string, x interface{}, d time.Duration) {
@@ -272,6 +278,63 @@ func (c *cache) DeleteExpired() {
 	}
 }
 
+// Writes the cache's items using Gob to an io.Writer
+func (c *cache) Save(w io.Writer) error {
+	enc := gob.NewEncoder(w)
+
+	defer func() {
+		if x := recover(); x != nil {
+			fmt.Printf(`The Gob library paniced while registering the cache's item types!
+Information: %v
+
+The cache will not be saved.
+Please report under what conditions this happened, and particularly what special type of objects
+were stored in cache, at https://github.com/pmylund/go-cache/issues/new`, x)
+		}
+	}()
+	for _, v := range c.Items {
+		gob.Register(v.Object)
+	}
+	err := enc.Encode(&c.Items)
+	return err
+}
+
+// Saves the cache's items to the given filename, creating the file if it
+// doesn't exist, and overwriting it if it does
+func (c *cache) SaveFile(fname string) error {
+	fp, err := os.Create(fname)
+	if err != nil {
+		return err
+	}
+	return c.Save(fp)
+}
+
+// Adds gob-serialized cache items from an io.Reader, excluding any items that
+// already exist in the current cache
+func (c *cache) Load(r io.Reader) error {
+	dec := gob.NewDecoder(r)
+	items := map[string]*Item{}
+	err := dec.Decode(&items)
+	if err == nil {
+		for k, v := range items {
+			_, found := c.Items[k]
+			if !found {
+				c.Items[k] = v
+			}
+		}
+	}
+	return err
+}
+
+// Loads and adds cache items from the given filename
+func (c *cache) LoadFile(fname string) error {
+	fp, err := os.Open(fname)
+	if err != nil {
+		return err
+	}
+	return c.Load(fp)
+}
+
 // Deletes all items from the cache.
 func (c *cache) Flush() {
 	c.mu.Lock()
@@ -280,12 +343,9 @@ func (c *cache) Flush() {
 	c.Items = map[string]*Item{}
 }
 
-// Returns true if the item has expired.
-func (i *Item) Expired() bool {
-	if i.Expiration == nil {
-		return false
-	}
-	return i.Expiration.Before(time.Now())
+type janitor struct {
+	Interval time.Duration
+	stop     chan bool
 }
 
 func (j *janitor) Run(c *cache) {

cache_test.go

@@ -1,6 +1,7 @@
 package cache
 
 import (
+	"bytes"
 	"testing"
 	"time"
 )
@@ -452,6 +453,104 @@ func TestDecrementUnderflowUint(t *testing.T) {
 	}
 }
 
+func TestCacheSerialization(t *testing.T) {
+	tc := New(0, 0)
+	testFillAndSerialize(t, tc)
+
+	// Check if gob.Register behaves properly even after multiple gob.Register
+	// on c.Items (many of which will be the same type)
+	testFillAndSerialize(t, tc)
+}
+
+func testFillAndSerialize(t *testing.T, tc *Cache) {
+	tc.Set("a", "a", 0)
+	tc.Set("b", "b", 0)
+	tc.Set("*struct", &TestStruct{Num: 1}, 0)
+	tc.Set("[]struct", []TestStruct{
+		{Num: 2},
+		{Num: 3},
+	}, 0)
+	tc.Set("[]*struct", []*TestStruct{
+		&TestStruct{Num: 4},
+		&TestStruct{Num: 5},
+	}, 0)
+	tc.Set("c", "c", 0) // ordering should be meaningless, but just in case
+
+	fp := &bytes.Buffer{}
+	err := tc.Save(fp)
+	if err != nil {
+		t.Fatal("Couldn't save cache to fp:", err)
+	}
+
+	oc := New(0, 0)
+	err = oc.Load(fp)
+	if err != nil {
+		t.Fatal("Couldn't load cache from fp:", err)
+	}
+
+	a, found := oc.Get("a")
+	if !found {
+		t.Error("a was not found")
+	}
+	if a.(string) != "a" {
+		t.Error("a is not a")
+	}
+
+	b, found := oc.Get("b")
+	if !found {
+		t.Error("b was not found")
+	}
+	if b.(string) != "b" {
+		t.Error("b is not b")
+	}
+
+	c, found := oc.Get("c")
+	if !found {
+		t.Error("c was not found")
+	}
+	if c.(string) != "c" {
+		t.Error("c is not c")
+	}
+
+	s1, found := oc.Get("*struct")
+	if !found {
+		t.Error("*struct was not found")
+	}
+	if s1.(*TestStruct).Num != 1 {
+		t.Error("*struct.Num is not 1")
+	}
+
+	s2, found := oc.Get("[]struct")
+	if !found {
+		t.Error("[]struct was not found")
+	}
+	s2r := s2.([]TestStruct)
+	if len(s2r) != 2 {
+		t.Error("Length of s2r is not 2")
+	}
+	if s2r[0].Num != 2 {
+		t.Error("s2r[0].Num is not 2")
+	}
+	if s2r[1].Num != 3 {
+		t.Error("s2r[1].Num is not 3")
+	}
+
+	s3, found := oc.get("[]*struct")
+	if !found {
+		t.Error("[]*struct was not found")
+	}
+	s3r := s3.([]*TestStruct)
+	if len(s3r) != 2 {
+		t.Error("Length of s3r is not 2")
+	}
+	if s3r[0].Num != 4 {
+		t.Error("s3r[0].Num is not 4")
+	}
+	if s3r[1].Num != 5 {
+		t.Error("s3r[1].Num is not 5")
+	}
+}
+
 func BenchmarkCacheGet(b *testing.B) {
 	tc := New(0, 0)
 	tc.Set("foo", "bar", 0)