feat(uuid): Added support for NullUUID

null.go

@@ -0,0 +1,89 @@
+// Copyright 2021 Google Inc.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package uuid
+
+import (
+	"database/sql/driver"
+	"fmt"
+)
+
+// NullUUID represents a UUID that may be null.
+// NullUUID implements the Scanner interface so
+// it can be used as a scan destination:
+//
+//  var u uuid.NullUUID
+//  err := db.QueryRow("SELECT name FROM foo WHERE id=?", id).Scan(&u)
+//  ...
+//  if u.Valid {
+//     // use u.UUID
+//  } else {
+//     // NULL value
+//  }
+//
+type NullUUID struct {
+	UUID  UUID
+	Valid bool // Valid is true if UUID is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (nu *NullUUID) Scan(value interface{}) error {
+	if value == nil {
+		nu.UUID, nu.Valid = Nil, false
+		return nil
+	}
+
+	// Delegate to UUID Scan function
+	nu.Valid = true
+	return nu.UUID.Scan(value)
+}
+
+// Value implements the driver Valuer interface.
+func (nu NullUUID) Value() (driver.Value, error) {
+	if !nu.Valid {
+		return nil, nil
+	}
+	// Delegate to UUID Value function
+	return nu.UUID.Value()
+}
+
+// MarshalText implements encoding.TextMarshaler.
+func (nu NullUUID) MarshalText() ([]byte, error) {
+	if nu.Valid {
+		return nu.UUID.MarshalText()
+	}
+
+	return []byte("null"), nil
+}
+
+// UnmarshalText implements encoding.TextUnmarshaler.
+func (nu *NullUUID) UnmarshalText(data []byte) error {
+	id, err := ParseBytes(data)
+	if err != nil {
+		nu.Valid = false
+		return err
+	}
+	nu.UUID = id
+	nu.Valid = true
+	return nil
+}
+
+// MarshalBinary implements encoding.BinaryMarshaler.
+func (nu NullUUID) MarshalBinary() ([]byte, error) {
+	if nu.Valid {
+		return nu.UUID[:], nil
+	}
+
+	return []byte("null"), nil
+}
+
+// UnmarshalBinary implements encoding.BinaryUnmarshaler.
+func (nu *NullUUID) UnmarshalBinary(data []byte) error {
+	if len(data) != 16 {
+		return fmt.Errorf("invalid UUID (got %d bytes)", len(data))
+	}
+	copy(nu.UUID[:], data)
+	nu.Valid = true
+	return nil
+}