v/vlib/builtin/option.v

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// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
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module builtin
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/*
struct Option2<T> {
ok bool
is_none bool
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error string
ecode int
data T
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}
*/
// OptionBase is the the base of V's internal optional return system.
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struct OptionBase {
ok bool
is_none bool
error string
ecode int
// Data is trailing after ecode
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// and is not included in here but in the
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// derived Option_xxx types
}
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// `fn foo() ?Foo { return foo }` => `fn foo() ?Foo { return opt_ok(foo); }`
fn opt_ok2(data voidptr, mut option OptionBase, size int) {
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unsafe {
*option = OptionBase{
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ok: true
}
// use ecode to get the end of OptionBase and then memcpy into it
C.memcpy(byteptr(&option.ecode) + sizeof(int), data, size)
}
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}
// Option is the old option type used for bootstrapping
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struct Option {
ok bool
is_none bool
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error string
ecode int
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}
// str returns the string representation of the Option.
pub fn (o Option) str() string {
if o.ok && !o.is_none {
return 'Option{ ok }'
}
if o.is_none {
return 'Option{ none }'
}
return 'Option{ error: "$o.error" }'
}
// opt_none is used internally when returning `none`.
fn opt_none() Option {
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return Option{
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ok: false
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is_none: true
}
}
// error returns an optional containing the error given in `message`.
// `if ouch { return error('an error occurred') }`
pub fn error(message string) Option {
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return Option{
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ok: false
is_none: false
error: message
}
}
// error_with_code returns an optional containing both error `message` and error `code`.
// `if ouch { return error_with_code('an error occurred',1) }`
pub fn error_with_code(message string, code int) Option {
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return Option{
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ok: false
is_none: false
error: message
ecode: code
}
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}