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