add leveldb implementation in the top-level and dos

README.md

@@ -46,13 +46,20 @@ It requires the key to be a non-empty string and the value to be able to be mars
 
 Creating a Table:
 ```go
+	// In-memory implementation 
+	table := kv.NewMemTable(kv.JsonCodec)
+
+    // Leveldb implementation
+    ldb, err = leveldb.OpenFile("./.leveldb", nil)
+    handle(err)
+    table := kv.NewLevelTable("name", ldb, kv.JsonCodec)
+
 	// BadgerDB implementation 
 	bdb, err:= badger.Open(badger.DefaultOptions("."))
 	handle(err)
 	table := kv.NewBadgerTable("name", bdb, kv.JsonCodec)
 
-	// In-memory implementation 
-	table := kv.NewMemTable(kv.JsonCodec)
+
 
 ```
 
@@ -105,13 +112,20 @@ a specific table of the DB directly. Or your can get the table by it's name and
 
 Creating a DB:
 ```go
+	// In-memory implementation 
+	db := kv.NewMemDB()
+
+    // LevelDB implementation 
+    ldb, err = leveldb.OpenFile("./.leveldb", nil)
+    handle(err)
+    db := kv.NewLevelDB(ldb)
+
 	// BadgerDB implementation 
 	bdb, err:= badger.Open(badger.DefaultOptions("."))
 	handle(err)
 	db := kv.NewBadgerDB(bdb)
 
-	// In-memory implementation 
-	db := kv.NewMemDB()
+
 ```
 
 Creating new tables or accessing existing ones 

kv.go

@@ -9,6 +9,7 @@ import (
 	"github.com/renproject/kv/badgerdb"
 	"github.com/renproject/kv/codec"
 	"github.com/renproject/kv/db"
+	"github.com/renproject/kv/leveldb"
 	"github.com/renproject/kv/memdb"
 )
 
@@ -58,7 +59,7 @@ var (
 	NewMemDB = memdb.New
 )
 
-// BadgerDB implementation of the DB and table
+// BadgerDB implementation of the DB and table.
 var (
 	// TODO: Comment!
 	NewBadgerTable = badgerdb.NewTable
@@ -68,6 +69,16 @@ var (
 	NewBadgerDB = badgerdb.New
 )
 
+// LevelDB implementation of the DB and table.
+var (
+	// TODO: Comment!
+	NewLevelTable = leveldb.NewTable
+
+	// NewLevelDB returns a key-value database that is implemented using
+	// levelDB. For more information, see https://github.com/syndtr/goleveldb.
+	NewLevelDB = leveldb.New
+)
+
 var (
 	// JsonCodec is a json codec that marshals and unmarshals values using the
 	// standard Golang JSON marshalers. For more information, see

testutil/struct.go

@@ -9,6 +9,7 @@ import (
 
 var Ran = rand.New(rand.NewSource(time.Now().Unix()))
 
+// TestStruct is a struct which includes some commonly used types.
 type TestStruct struct {
 	A string
 	B int
@@ -17,6 +18,7 @@ type TestStruct struct {
 	E map[string]float64
 }
 
+// RandomTestStruct returns a random `TestStruct`
 func RandomTestStruct() TestStruct {
 	t := reflect.TypeOf(TestStruct{})
 	value, ok := quick.Value(t, Ran)
@@ -26,6 +28,7 @@ func RandomTestStruct() TestStruct {
 	return value.Interface().(TestStruct)
 }
 
+// RandomTestStructGroups creates a group of random TestStructs.
 func RandomTestStructGroups(group, entriesPerGroup int) [][]TestStruct {
 	testEntries := make([][]TestStruct, group)
 	for i := range testEntries {
@@ -38,12 +41,13 @@ func RandomTestStructGroups(group, entriesPerGroup int) [][]TestStruct {
 	return testEntries
 }
 
+// RandomNonDupStrings returns a list of non-duplicate strings.
 func RandomNonDupStrings(i int) []string {
 	cap := rand.Intn(i)
 	dup := map[string]struct{}{}
 	res := make([]string, 0, cap)
 
-	for len(dup) < cap {
+	for len(res) < cap {
 		t := reflect.TypeOf("")
 		value, ok := quick.Value(t, Ran)
 		if !ok {