Add Rename function

Rename function is added. Usage added to pkg/main.go and README

Signed-off-by: Gökhan Özeloğlu <gozeloglu@gmail.com>

README.md

@@ -99,6 +99,12 @@ func main() {
 	exist = db.Exists("jack")
 	fmt.Println(exist)
 
+	ok, err := db.Rename("john", "john john")
+	if err != nil {
+		log.Fatalf(err.Error())
+	}
+	fmt.Printf("key name changed: %v1\n", ok)
+
 	err = db.Close() // Call while closing the database.
 	if err != nil {
 		log.Fatalf(err.Error())

example/pkg/main.go

@@ -45,6 +45,12 @@ func main() {
 	exist = db.Exists("jack")
 	fmt.Println(exist)
 
+	ok, err := db.Rename("john", "john john")
+	if err != nil {
+		log.Fatalf(err.Error())
+	}
+	fmt.Printf("key name changed: %v1\n", ok)
+
 	err = db.Close()
 	if err != nil {
 		log.Fatalf(err.Error())

rename.go

@@ -0,0 +1,18 @@
+package kvs
+
+import "errors"
+
+// Rename changes the name of the key. It deletes the old key-value pair. If the
+// new key already exists, renaming cannot be done.
+func (k *Kvs) Rename(key string, newKey string) (bool, error) {
+	k.mu.Lock()
+	defer k.mu.Unlock()
+
+	if k.Exists(newKey) {
+		return false, errors.New("new key is already exists")
+	}
+
+	k.kv[newKey] = k.kv[key]
+	k.Del(key)
+	return true, nil
+}

rename_test.go

@@ -0,0 +1,89 @@
+package kvs
+
+import (
+	"os"
+	"testing"
+	"time"
+)
+
+func TestKvs_Rename(t *testing.T) {
+	db, err := open(t.Name(), "", 2*time.Minute)
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	t.Logf("db created.")
+
+	k, v := "foo", "bar"
+	db.Set(k, v)
+	t.Logf("Key-value pair is set.")
+	t.Logf("%s: %s", k, v)
+
+	ok, err := db.Rename(k, k+k)
+	if err != nil {
+		t.Errorf(err.Error())
+	}
+	if !ok {
+		t.Errorf("key didn't change")
+	} else {
+		t.Logf("key renamed.")
+	}
+
+	val := db.Get(k)
+	if val != "" {
+		t.Errorf("%s-%s pair is still exits.", k, val)
+	}
+	t.Logf("%s-%s", k, val)
+
+	val = db.Get(k + k)
+	if val != v {
+		t.Errorf("expected %s-%s pair, but got %s-%s", k+k, v, k+k, val)
+	}
+	t.Logf("%s-%s", k+k, val)
+
+	err = db.Close()
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	t.Logf("db closed.")
+
+	err = os.RemoveAll(db.dir)
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	t.Logf("temp db removed.")
+}
+
+func TestKvs_RenameExistsNewKey(t *testing.T) {
+	db, err := open(t.Name(), "", 2*time.Minute)
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	t.Logf("db created.")
+
+	k, v := "foo", "bar"
+	db.Set(k, v)
+	t.Logf("Key-value pair is set.")
+	t.Logf("%s: %s", k, v)
+
+	ok, err := db.Rename(k, k)
+	if !ok {
+		t.Logf("key didn't change")
+	}
+
+	val := db.Get(k)
+	if val != v {
+		t.Errorf("%s-%s pair is wrong.", k, val)
+	}
+
+	err = db.Close()
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	t.Logf("db closed.")
+
+	err = os.RemoveAll(db.dir)
+	if err != nil {
+		t.Fatalf(err.Error())
+	}
+	t.Logf("temp db removed.")
+}