Adding the challenge 0501

0501/row.go

@@ -0,0 +1,109 @@
+package db0501
+
+import (
+	"errors"
+	"slices"
+)
+
+type Schema struct {
+	Table string
+	Cols  []Column
+	PKey  []int // indexes of primary key columns
+}
+
+type Column struct {
+	Name string
+	Type CellType
+}
+
+type Row []Cell
+
+func (schema *Schema) NewRow() Row {
+	return make(Row, len(schema.Cols))
+}
+
+func (row Row) EncodeKey(schema *Schema) []byte {
+	check(len(row) == len(schema.Cols))
+	key := append([]byte(schema.Table), 0x00)
+	for _, idx := range schema.PKey {
+		cell := row[idx]
+		check(cell.Type == schema.Cols[idx].Type)
+		key = append(key, byte(cell.Type))
+		key = cell.EncodeKey(key)
+	}
+	return append(key, 0x00)
+}
+
+func EncodeKeyPrefix(schema *Schema, prefix []Cell, positive bool) []byte {
+	key := append([]byte(schema.Table), 0x00)
+	for i, cell := range prefix {
+		check(cell.Type == schema.Cols[schema.PKey[i]].Type)
+		key = append(key, byte(cell.Type))
+		key = cell.EncodeKey(key)
+	}
+	if positive {
+		key = append(key, 0xff)
+	}
+	return key
+}
+
+func (row Row) EncodeVal(schema *Schema) (val []byte) {
+	check(len(row) == len(schema.Cols))
+	for idx, value := range row {
+		if !slices.Contains(schema.PKey, idx) {
+			check(value.Type == schema.Cols[idx].Type)
+			val = row[idx].EncodeVal(val)
+		}
+	}
+	return val
+}
+
+var ErrOutOfRange = errors.New("out of range")
+
+func (row Row) DecodeKey(schema *Schema, key []byte) (err error) {
+	check(len(row) == len(schema.Cols))
+
+	if len(key) < len(schema.Table)+1 {
+		return ErrOutOfRange
+	}
+	if string(key[:len(schema.Table)+1]) != schema.Table+"\x00" {
+		return ErrOutOfRange
+	}
+	key = key[len(schema.Table)+1:]
+
+	for _, idx := range schema.PKey {
+		row[idx] = Cell{Type: schema.Cols[idx].Type}
+		if !(len(key) > 0 && key[0] == byte(row[idx].Type)) {
+			return errors.New("bad key")
+		}
+		key = key[1:]
+		if key, err = row[idx].DecodeKey(key); err != nil {
+			return err
+		}
+	}
+	if !(len(key) == 1 && key[0] == 0x00) {
+		return errors.New("bad key")
+	}
+	return nil
+}
+
+func (row Row) DecodeVal(schema *Schema, val []byte) (err error) {
+	check(len(row) == len(schema.Cols))
+
+	for idx, col := range schema.Cols {
+		if slices.Contains(schema.PKey, idx) {
+			continue
+		}
+		row[idx] = Cell{Type: col.Type}
+		if val, err = row[idx].DecodeVal(val); err != nil {
+			return err
+		}
+	}
+
+	if len(val) != 0 {
+		return errors.New("trailing garbage")
+	}
+	return nil
+}
+
+// QzBQWVJJOUhU https://trialofcode.org/