Adding the challenge 0305

0305/kv_entry.go

@@ -0,0 +1,63 @@
+package db0305
+
+import (
+	"encoding/binary"
+	"errors"
+	"hash/crc32"
+	"io"
+)
+
+type Entry struct {
+	key     []byte
+	val     []byte
+	deleted bool
+}
+
+func (ent *Entry) Encode() []byte {
+	data := make([]byte, 4+4+4+1+len(ent.key)+len(ent.val))
+	binary.LittleEndian.PutUint32(data[4:8], uint32(len(ent.key)))
+	copy(data[4+4+4+1:], ent.key)
+	if ent.deleted {
+		data[4+4+4] = 1
+	} else {
+		binary.LittleEndian.PutUint32(data[8:12], uint32(len(ent.val)))
+		copy(data[4+4+4+1+len(ent.key):], ent.val)
+	}
+	binary.LittleEndian.PutUint32(data[0:4], crc32.ChecksumIEEE(data[4:]))
+	return data
+}
+
+var ErrBadSum = errors.New("bad checksum")
+
+func (ent *Entry) Decode(r io.Reader) error {
+	var header [4 + 4 + 4 + 1]byte
+	if _, err := io.ReadFull(r, header[:]); err != nil {
+		return err
+	}
+	klen := int(binary.LittleEndian.Uint32(header[4:8]))
+	vlen := int(binary.LittleEndian.Uint32(header[8:12]))
+	deleted := header[4+4+4]
+
+	data := make([]byte, klen+vlen)
+	if _, err := io.ReadFull(r, data); err != nil {
+		return err
+	}
+
+	h := crc32.NewIEEE()
+	h.Write(header[4:])
+	h.Write(data)
+	if h.Sum32() != binary.LittleEndian.Uint32(header[0:4]) {
+		return ErrBadSum
+	}
+
+	ent.key = data[:klen]
+	if deleted != 0 {
+		ent.deleted = true
+	} else {
+		ent.deleted = false
+		ent.val = data[klen:]
+	}
+	return nil
+}
+
+// QzBQWVJJOUhU https://trialofcode.org/