perf: encode entry in zipmap

internal/hash/zipmap.go

@@ -1,14 +1,15 @@
 package hash
 
 import (
+	"encoding/binary"
 	"unsafe"
 
 	"github.com/xgzlucario/rotom/internal/list"
 )
 
 var _ MapI = (*ZipMap)(nil)
 
-// ZipMap store datas as [key1, val1, key2, val2...] in listpack.
+// ZipMap store datas as [entry1, entry2, entry3...] in listpack.
 type ZipMap struct {
 	m *list.ListPack
 }
@@ -17,57 +18,87 @@ func NewZipMap() *ZipMap {
 	return &ZipMap{list.NewListPack()}
 }
 
+// encodeEntry encode data to [vlen, val, key].
+func encodeEntry(key string, val []byte) []byte {
+	buf := make([]byte, 0, len(key)+len(val)+1)
+	buf = binary.AppendUvarint(buf, uint64(len(val)))
+	buf = append(buf, val...)
+	return append(buf, key...)
+}
+
+func decodeEntry(buf []byte) (key string, val []byte) {
+	vlen, n := binary.Uvarint(buf)
+	val = buf[n : n+int(vlen)]
+	key = b2s(buf[n+int(vlen):])
+	return
+}
+
 func (zm *ZipMap) Set(key string, val []byte) (newField bool) {
 	it := zm.m.Iterator().SeekLast()
+	b := key[len(key)-1]
+	newEntry := b2s(encodeEntry(key, val))
+
 	for !it.IsFirst() {
-		it.Prev()
-		keyBytes := it.Prev()
-		if key == b2s(keyBytes) {
-			// update val
-			it.Next()
-			it.ReplaceNext(b2s(val))
+		entry := it.Prev()
+		// fast equal
+		if entry[len(entry)-1] != b {
+			continue
+		}
+
+		kb, _ := decodeEntry(entry)
+		if key == kb {
+			it.ReplaceNext(newEntry)
 			return false
 		}
 	}
-	zm.m.RPush(key, b2s(val))
+	zm.m.RPush(newEntry)
 	return true
 }
 
 func (zm *ZipMap) Get(key string) ([]byte, bool) {
 	it := zm.m.Iterator().SeekLast()
+	b := key[len(key)-1]
+
 	for !it.IsFirst() {
-		valBytes := it.Prev()
-		keyBytes := it.Prev()
-		if key == b2s(keyBytes) {
-			return valBytes, true
+		entry := it.Prev()
+		// fast equal
+		if entry[len(entry)-1] != b {
+			continue
+		}
+
+		kb, vb := decodeEntry(entry)
+		if key == kb {
+			return vb, true
 		}
 	}
 	return nil, false
 }
 
 func (zm *ZipMap) Remove(key string) bool {
 	it := zm.m.Iterator().SeekLast()
+	b := key[len(key)-1]
+
 	for !it.IsFirst() {
-		it.Prev()
-		keyBytes := it.Prev()
-		if key == b2s(keyBytes) {
-			it.RemoveNexts(2)
+		entry := it.Prev()
+		// fast equal
+		if entry[len(entry)-1] != b {
+			continue
+		}
+
+		kb, _ := decodeEntry(entry)
+		if key == kb {
+			it.RemoveNext()
 			return true
 		}
 	}
 	return false
 }
 
-func (zm *ZipMap) Len() int {
-	return zm.m.Size() / 2
-}
-
 func (zm *ZipMap) Scan(fn func(string, []byte)) {
 	it := zm.m.Iterator().SeekLast()
 	for !it.IsFirst() {
-		valBytes := it.Prev()
-		keyBytes := it.Prev()
-		fn(b2s(keyBytes), valBytes)
+		kb, vb := decodeEntry(it.Prev())
+		fn(kb, vb)
 	}
 }
 
@@ -79,6 +110,8 @@ func (zm *ZipMap) ToMap() *Map {
 	return m
 }
 
+func (zm *ZipMap) Len() int { return zm.m.Size() }
+
 func (zm *ZipMap) Compress() { zm.m.Compress() }
 
 func (zm *ZipMap) Decompress() { zm.m.Decompress() }