source: code/trunk/vendor/github.com/google/uuid/null.go@ 822

// 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 (
        "bytes"
        "database/sql/driver"
        "encoding/json"
        "fmt"
)

var jsonNull = []byte("null")

// NullUUID represents a UUID that may be null.
// NullUUID implements the SQL driver.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 SQL driver.Scanner interface.
func (nu *NullUUID) Scan(value interface{}) error {
        if value == nil {
                nu.UUID, nu.Valid = Nil, false
                return nil
        }

        err := nu.UUID.Scan(value)
        if err != nil {
                nu.Valid = false
                return err
        }

        nu.Valid = true
        return nil
}

// 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()
}

// MarshalBinary implements encoding.BinaryMarshaler.
func (nu NullUUID) MarshalBinary() ([]byte, error) {
        if nu.Valid {
                return nu.UUID[:], nil
        }

        return []byte(nil), 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
}

// MarshalText implements encoding.TextMarshaler.
func (nu NullUUID) MarshalText() ([]byte, error) {
        if nu.Valid {
                return nu.UUID.MarshalText()
        }

        return jsonNull, 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
}

// MarshalJSON implements json.Marshaler.
func (nu NullUUID) MarshalJSON() ([]byte, error) {
        if nu.Valid {
                return json.Marshal(nu.UUID)
        }

        return jsonNull, nil
}

// UnmarshalJSON implements json.Unmarshaler.
func (nu *NullUUID) UnmarshalJSON(data []byte) error {
        if bytes.Equal(data, jsonNull) {
                *nu = NullUUID{}
                return nil // valid null UUID
        }
        err := json.Unmarshal(data, &nu.UUID)
        nu.Valid = err == nil
        return err
}