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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package containers
import (
"io"
"git.lukeshu.com/go/lowmemjson"
)
type Optional[T any] struct {
OK bool
Val T
}
func OptionalValue[T any](val T) Optional[T] {
return Optional[T]{
OK: true,
Val: val,
}
}
func OptionalNil[T any]() Optional[T] {
return Optional[T]{
OK: false,
}
}
var (
_ lowmemjson.Encodable = Optional[bool]{}
_ lowmemjson.Decodable = (*Optional[bool])(nil)
)
func (o Optional[T]) EncodeJSON(w io.Writer) error {
if !o.OK {
_, err := io.WriteString(w, "null")
return err
}
return lowmemjson.NewEncoder(w).Encode(o.Val)
}
func (o *Optional[T]) DecodeJSON(r io.RuneScanner) error {
c, _, _ := r.ReadRune()
if c == 'n' {
_, _, _ = r.ReadRune() // u
_, _, _ = r.ReadRune() // l
_, _, _ = r.ReadRune() // l
*o = Optional[T]{}
return nil
}
_ = r.UnreadRune()
o.OK = true
return lowmemjson.NewDecoder(r).Decode(&o.Val)
}
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