Adding the challenge 0501

0501/cell.go

@@ -0,0 +1,115 @@
+package db0501
+
+import (
+	"encoding/binary"
+	"errors"
+	"slices"
+)
+
+type CellType uint8
+
+const (
+	TypeI64 CellType = 1
+	TypeStr CellType = 2
+)
+
+type Cell struct {
+	Type CellType
+	I64  int64
+	Str  []byte
+}
+
+func (cell *Cell) EncodeVal(toAppend []byte) []byte {
+	switch cell.Type {
+	case TypeI64:
+		return binary.LittleEndian.AppendUint64(toAppend, uint64(cell.I64))
+	case TypeStr:
+		toAppend = binary.LittleEndian.AppendUint32(toAppend, uint32(len(cell.Str)))
+		return append(toAppend, cell.Str...)
+	default:
+		panic("unreachable")
+	}
+}
+
+func (cell *Cell) DecodeVal(data []byte) (rest []byte, err error) {
+	switch cell.Type {
+	case TypeI64:
+		if len(data) < 8 {
+			return data, errors.New("expect more data")
+		}
+		cell.I64 = int64(binary.LittleEndian.Uint64(data[0:8]))
+		return data[8:], nil
+	case TypeStr:
+		if len(data) < 4 {
+			return data, errors.New("expect more data")
+		}
+		size := int(binary.LittleEndian.Uint32(data[0:4]))
+		if len(data) < 4+size {
+			return data, errors.New("expect more data")
+		}
+		cell.Str = slices.Clone(data[4 : 4+size])
+		return data[4+size:], nil
+	default:
+		panic("unreachable")
+	}
+}
+
+func encodeStrKey(toAppend []byte, input []byte) []byte {
+	for _, ch := range input {
+		if ch == 0x00 || ch == 0x01 {
+			toAppend = append(toAppend, 0x01, ch+1)
+		} else {
+			toAppend = append(toAppend, ch)
+		}
+	}
+	return append(toAppend, 0x00)
+}
+
+func decodeStrKey(data []byte) (out []byte, rest []byte, err error) {
+	escape := false
+	for i, ch := range data {
+		if escape {
+			if ch != 0x01 && ch != 0x02 {
+				return nil, data, errors.New("bad escape")
+			}
+			out = append(out, ch-1)
+			escape = false
+		} else if ch == 0x00 {
+			return out, data[i+1:], nil
+		} else if ch == 0x01 {
+			escape = true
+		} else {
+			out = append(out, ch)
+		}
+	}
+	return nil, data, errors.New("string is not ended")
+}
+
+func (cell *Cell) EncodeKey(toAppend []byte) []byte {
+	switch cell.Type {
+	case TypeI64:
+		return binary.BigEndian.AppendUint64(toAppend, uint64(cell.I64)^(1<<63))
+	case TypeStr:
+		return encodeStrKey(toAppend, cell.Str)
+	default:
+		panic("unreachable")
+	}
+}
+
+func (cell *Cell) DecodeKey(data []byte) (rest []byte, err error) {
+	switch cell.Type {
+	case TypeI64:
+		if len(data) < 8 {
+			return data, errors.New("expect more data")
+		}
+		cell.I64 = int64(binary.BigEndian.Uint64(data[0:8]) ^ (1 << 63))
+		return data[8:], nil
+	case TypeStr:
+		cell.Str, rest, err = decodeStrKey(data)
+		return rest, err
+	default:
+		panic("unreachable")
+	}
+}
+
+// QzBQWVJJOUhU https://trialofcode.org/