add simple support for kv scan

ledis/const.go

@@ -15,6 +15,10 @@ const (
 	zScoreType
 )
 
+const (
+	defaultScanCount int = 20
+)
+
 const (
 	//we don't support too many databases
 	MaxDBNumber uint8 = 16

ledis/t_kv.go

@@ -35,6 +35,17 @@ func (db *DB) decodeKVKey(ek []byte) ([]byte, error) {
 	return ek[2:], nil
 }
 
+func (db *DB) encodeKVMinKey() []byte {
+	ek := db.encodeKVKey(nil)
+	return ek
+}
+
+func (db *DB) encodeKVMaxKey() []byte {
+	ek := db.encodeKVKey(nil)
+	ek[len(ek)-1] = kvType + 1
+	return ek
+}
+
 func (db *DB) incr(key []byte, delta int64) (int64, error) {
 	if err := checkKeySize(key); err != nil {
 		return 0, err
@@ -265,13 +276,8 @@ func (db *DB) KvFlush() (drop int64, err error) {
 	t.Lock()
 	defer t.Unlock()
 
-	minKey := make([]byte, 2)
-	minKey[0] = db.index
-	minKey[1] = kvType
-
-	maxKey := make([]byte, 2)
-	maxKey[0] = db.index
-	maxKey[1] = kvType + 1
+	minKey := db.encodeKVMinKey()
+	maxKey := db.encodeKVMaxKey()
 
 	it := db.db.Iterator(minKey, maxKey, leveldb.RangeROpen, 0, -1)
 	for ; it.Valid(); it.Next() {
@@ -282,3 +288,37 @@ func (db *DB) KvFlush() (drop int64, err error) {
 	err = t.Commit()
 	return
 }
+
+func (db *DB) Scan(cursor int, count int) ([]interface{}, error) {
+	minKey := db.encodeKVMinKey()
+	maxKey := db.encodeKVMaxKey()
+
+	if count <= 0 {
+		count = defaultScanCount
+	}
+
+	v := make([]interface{}, 2)
+	r := make([]interface{}, 0, count)
+
+	var num int = 0
+	it := db.db.Iterator(minKey, maxKey, leveldb.RangeROpen, cursor, count)
+	for ; it.Valid(); it.Next() {
+		num++
+
+		if key, err := db.decodeKVKey(it.Key()); err != nil {
+			continue
+		} else {
+			r = append(r, key)
+		}
+	}
+
+	if num < count {
+		v[0] = int64(0)
+	} else {
+		v[0] = int64(cursor + count)
+	}
+
+	v[1] = r
+
+	return v, nil
+}

server/cmd_kv.go

@@ -2,6 +2,7 @@ package server
 
 import (
 	"github.com/siddontang/ledisdb/ledis"
+	"strings"
 )
 
 func getCommand(c *client) error {
@@ -203,6 +204,40 @@ func mgetCommand(c *client) error {
 	return nil
 }
 
+func scanCommand(c *client) error {
+	args := c.args
+
+	if len(args) != 1 && len(args) != 3 {
+		return ErrCmdParams
+	}
+	var offset int64
+	var count int64
+	var err error
+
+	if offset, err = ledis.StrInt64(args[0], nil); err != nil {
+		return err
+	}
+
+	//now we only support count
+	if len(args) == 3 {
+		if strings.ToLower(ledis.String(args[1])) != "count" {
+			return ErrCmdParams
+		}
+
+		if count, err = ledis.StrInt64(args[2], nil); err != nil {
+			return err
+		}
+	}
+
+	if v, err := c.db.Scan(int(offset), int(count)); err != nil {
+		return err
+	} else {
+		c.writeArray(v)
+	}
+
+	return nil
+}
+
 func init() {
 	register("decr", decrCommand)
 	register("decrby", decrbyCommand)
@@ -216,4 +251,5 @@ func init() {
 	register("mset", msetCommand)
 	register("set", setCommand)
 	register("setnx", setnxCommand)
+	register("scan", scanCommand)
 }