Adding the challenge 0403

0403/kv.go

@@ -0,0 +1,146 @@
+package db0403
+
+import (
+	"bytes"
+	"slices"
+)
+
+type KV struct {
+	log  Log
+	keys [][]byte
+	vals [][]byte
+}
+
+func (kv *KV) Open() error {
+	if err := kv.log.Open(); err != nil {
+		return err
+	}
+
+	entries := []Entry{}
+	for {
+		ent := Entry{}
+		eof, err := kv.log.Read(&ent)
+		if err != nil {
+			return err
+		} else if eof {
+			break
+		}
+		entries = append(entries, ent)
+	}
+
+	slices.SortStableFunc(entries, func(a, b Entry) int {
+		return bytes.Compare(a.key, b.key)
+	})
+	kv.keys, kv.vals = kv.keys[:0], kv.vals[:0]
+	for _, ent := range entries {
+		n := len(kv.keys)
+		if n > 0 && bytes.Equal(kv.keys[n-1], ent.key) {
+			kv.keys, kv.vals = kv.keys[:n-1], kv.vals[:n-1]
+		}
+		if !ent.deleted {
+			kv.keys = append(kv.keys, ent.key)
+			kv.vals = append(kv.vals, 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) {
+	if idx, ok := slices.BinarySearchFunc(kv.keys, key, bytes.Compare); ok {
+		return kv.vals[idx], true, nil
+	}
+	return nil, false, nil
+}
+
+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) {
+	idx, exist := slices.BinarySearchFunc(kv.keys, key, bytes.Compare)
+	switch mode {
+	case ModeUpsert:
+		updated = !exist || !bytes.Equal(kv.vals[idx], val)
+	case ModeInsert:
+		updated = !exist
+	case ModeUpdate:
+		updated = exist && !bytes.Equal(kv.vals[idx], val)
+	default:
+		panic("unreachable")
+	}
+	if updated {
+		if err = kv.log.Write(&Entry{key: key, val: val}); err != nil {
+			return false, err
+		}
+		if exist {
+			kv.vals[idx] = val
+		} else {
+			kv.keys = slices.Insert(kv.keys, idx, key)
+			kv.vals = slices.Insert(kv.vals, idx, 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) {
+	if idx, ok := slices.BinarySearchFunc(kv.keys, key, bytes.Compare); ok {
+		if err = kv.log.Write(&Entry{key: key, deleted: true}); err != nil {
+			return false, err
+		}
+		kv.keys = slices.Delete(kv.keys, idx, idx+1)
+		kv.vals = slices.Delete(kv.vals, idx, idx+1)
+		return true, nil
+	}
+	return false, nil
+}
+
+type KVIterator struct {
+	keys [][]byte
+	vals [][]byte
+	pos  int
+}
+
+func (kv *KV) Seek(key []byte) (*KVIterator, error) {
+	pos, _ := slices.BinarySearchFunc(kv.keys, key, bytes.Compare)
+	return &KVIterator{keys: kv.keys, vals: kv.vals, pos: pos}, nil
+}
+
+func (iter *KVIterator) Valid() bool {
+	return 0 <= iter.pos && iter.pos < len(iter.keys)
+}
+
+func (iter *KVIterator) Key() []byte {
+	check(iter.Valid())
+	return iter.keys[iter.pos]
+}
+
+func (iter *KVIterator) Val() []byte {
+	check(iter.Valid())
+	return iter.vals[iter.pos]
+}
+
+func (iter *KVIterator) Next() error {
+	if iter.pos < len(iter.keys) {
+		iter.pos++
+	}
+	return nil
+}
+
+func (iter *KVIterator) Prev() error {
+	if iter.pos >= 0 {
+		iter.pos--
+	}
+	return nil
+}
+
+// QzBQWVJJOUhU https://trialofcode.org/