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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}
*/
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struct OptionBase {
ok bool
is_none bool
error string
ecode int
// Data is trailing after ecode
// and is not included in here but in the
// derived Option_xxx types
}
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pub fn (o OptionBase) str() string {
if o.ok && !o.is_none {
return 'Option{ valid }'
}
if o.is_none {
return 'Option{ none }'
}
return 'Option{ error: "${o.error}" }'
}
// `fn foo() ?Foo { return foo }` => `fn foo() ?Foo { return opt_ok(foo); }`
fn opt_ok2(data voidptr, mut option &OptionBase, size int) {
unsafe {
*option = OptionBase {
ok: true
}
// use ecode to get the end of OptionBase and then memcpy into it
C.memcpy(byteptr(&option.ecode) + sizeof(int), data, size)
}
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}
// Old option type used for bootstrapping
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struct Option {
ok bool
is_none bool
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error string
ecode int
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data [400]byte
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}
pub fn (o Option) str() string {
if o.ok && !o.is_none {
return 'Option{ data: ' + o.data[0..32].hex() + ' }'
}
if o.is_none {
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return 'Option{ none }'
}
return 'Option{ error: "${o.error}" }'
}
// `fn foo() ?Foo { return foo }` => `fn foo() ?Foo { return opt_ok(foo); }`
fn opt_ok(data voidptr, size int) Option {
if size >= 400 {
panic('option size too big: $size (max is 400), this is a temporary limit')
}
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res := Option{
ok: true
}
C.memcpy(res.data, data, size)
return res
}
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// 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
}
}
pub fn error(s string) Option {
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return Option{
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ok: false
is_none: false
error: s
}
}
pub fn error_with_code(s string, code int) Option {
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return Option{
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ok: false
is_none: false
error: s
ecode: code
}
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}