Adding the challenge 0303

0303/kv.go

@@ -0,0 +1,87 @@
+package db0303
+
+import (
+	"bytes"
+)
+
+type KV struct {
+	log Log
+	mem map[string][]byte
+}
+
+func (kv *KV) Open() error {
+	if err := kv.log.Open(); err != nil {
+		return err
+	}
+
+	kv.mem = map[string][]byte{}
+	for {
+		ent := Entry{}
+		eof, err := kv.log.Read(&ent)
+		if err != nil {
+			return err
+		} else if eof {
+			break
+		}
+
+		if ent.deleted {
+			delete(kv.mem, string(ent.key))
+		} else {
+			kv.mem[string(ent.key)] = ent.val
+		}
+	}
+	return nil
+}
+
+func (kv *KV) Close() error { return kv.log.Close() }
+
+func (kv *KV) Get(key []byte) (val []byte, ok bool, err error) {
+	val, ok = kv.mem[string(key)]
+	return
+}
+
+type UpdateMode int
+
+const (
+	ModeUpsert UpdateMode = 0 // insert or update
+	ModeInsert UpdateMode = 1 // insert new
+	ModeUpdate UpdateMode = 2 // update existing
+)
+
+func (kv *KV) SetEx(key []byte, val []byte, mode UpdateMode) (updated bool, err error) {
+	prev, exist := kv.mem[string(key)]
+	switch mode {
+	case ModeUpsert:
+		updated = !exist || !bytes.Equal(prev, val)
+	case ModeInsert:
+		updated = !exist
+	case ModeUpdate:
+		updated = exist && !bytes.Equal(prev, val)
+	default:
+		panic("unreachable")
+	}
+	if updated {
+		if err = kv.log.Write(&Entry{key: key, val: val}); err != nil {
+			return false, err
+		}
+		kv.mem[string(key)] = val
+	}
+	return
+}
+
+func (kv *KV) Set(key []byte, val []byte) (updated bool, err error) {
+	return kv.SetEx(key, val, ModeUpsert)
+}
+
+func (kv *KV) Del(key []byte) (deleted bool, err error) {
+	_, deleted = kv.mem[string(key)]
+	if deleted {
+		if err = kv.log.Write(&Entry{key: key, deleted: true}); err != nil {
+			return false, err
+		}
+		delete(kv.mem, string(key))
+	}
+	return
+}
+
+// QzBQWVJJOUhU https://trialofcode.org/