git.sr.ht/~pingoo/stdx@v0.0.0-20240218134121-094174641f6e/uuid/null.go (about)

     1  // Copyright 2021 Google Inc.  All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package uuid
     6  
     7  import (
     8  	"bytes"
     9  	"database/sql/driver"
    10  	"encoding/json"
    11  	"fmt"
    12  )
    13  
    14  var jsonNull = []byte("null")
    15  
    16  // NullUUID represents a UUID that may be null.
    17  // NullUUID implements the SQL driver.Scanner interface so
    18  // it can be used as a scan destination:
    19  //
    20  //  var u uuid.NullUUID
    21  //  err := db.QueryRow("SELECT name FROM foo WHERE id=?", id).Scan(&u)
    22  //  ...
    23  //  if u.Valid {
    24  //     // use u.UUID
    25  //  } else {
    26  //     // NULL value
    27  //  }
    28  //
    29  type NullUUID struct {
    30  	UUID  UUID
    31  	Valid bool // Valid is true if UUID is not NULL
    32  }
    33  
    34  // Scan implements the SQL driver.Scanner interface.
    35  func (nu *NullUUID) Scan(value interface{}) error {
    36  	if value == nil {
    37  		nu.UUID, nu.Valid = Nil, false
    38  		return nil
    39  	}
    40  
    41  	err := nu.UUID.Scan(value)
    42  	if err != nil {
    43  		nu.Valid = false
    44  		return err
    45  	}
    46  
    47  	nu.Valid = true
    48  	return nil
    49  }
    50  
    51  // Value implements the driver Valuer interface.
    52  func (nu NullUUID) Value() (driver.Value, error) {
    53  	if !nu.Valid {
    54  		return nil, nil
    55  	}
    56  	// Delegate to UUID Value function
    57  	return nu.UUID.Value()
    58  }
    59  
    60  // MarshalBinary implements encoding.BinaryMarshaler.
    61  func (nu NullUUID) MarshalBinary() ([]byte, error) {
    62  	if nu.Valid {
    63  		return nu.UUID[:], nil
    64  	}
    65  
    66  	return []byte(nil), nil
    67  }
    68  
    69  // UnmarshalBinary implements encoding.BinaryUnmarshaler.
    70  func (nu *NullUUID) UnmarshalBinary(data []byte) error {
    71  	if len(data) != 16 {
    72  		return fmt.Errorf("invalid UUID (got %d bytes)", len(data))
    73  	}
    74  	copy(nu.UUID[:], data)
    75  	nu.Valid = true
    76  	return nil
    77  }
    78  
    79  // MarshalText implements encoding.TextMarshaler.
    80  func (nu NullUUID) MarshalText() ([]byte, error) {
    81  	if nu.Valid {
    82  		return nu.UUID.MarshalText()
    83  	}
    84  
    85  	return jsonNull, nil
    86  }
    87  
    88  // UnmarshalText implements encoding.TextUnmarshaler.
    89  func (nu *NullUUID) UnmarshalText(data []byte) error {
    90  	id, err := ParseBytes(data)
    91  	if err != nil {
    92  		nu.Valid = false
    93  		return err
    94  	}
    95  	nu.UUID = id
    96  	nu.Valid = true
    97  	return nil
    98  }
    99  
   100  // MarshalJSON implements json.Marshaler.
   101  func (nu NullUUID) MarshalJSON() ([]byte, error) {
   102  	if nu.Valid {
   103  		return json.Marshal(nu.UUID)
   104  	}
   105  
   106  	return jsonNull, nil
   107  }
   108  
   109  // UnmarshalJSON implements json.Unmarshaler.
   110  func (nu *NullUUID) UnmarshalJSON(data []byte) error {
   111  	if bytes.Equal(data, jsonNull) {
   112  		*nu = NullUUID{}
   113  		return nil // valid null UUID
   114  	}
   115  	err := json.Unmarshal(data, &nu.UUID)
   116  	nu.Valid = err == nil
   117  	return err
   118  }