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v/vlib/builtin/option.v

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// Copyright (c) 2019-2021 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
// IError holds information about an error instance
pub interface IError {
msg string
code int
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}
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// Error is the default implementation of IError, that is returned by e.g. `error()`
pub struct Error {
pub:
msg string
code int
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}
pub struct Option3 {
state byte
err IError
}
[inline]
fn (e IError) str() string {
return e.msg
}
fn opt_ok3(data voidptr, mut option Option3, size int) {
unsafe {
*option = Option3{}
// use err to get the end of Option3 and then memcpy into it
C.memcpy(byteptr(&option.err) + sizeof(IError), data, size)
}
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}
pub fn (o Option3) str() string {
if o.state == 0 {
return 'Option{ ok }'
}
if o.state == 1 {
return 'Option{ none }'
}
return 'Option{ err: "$o.err" }'
}
[inline]
pub fn error3(message string) IError {
return &Error{
msg: message
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}
}
pub fn error_with_code3(message string, code int) IError {
return &Error {
msg: message
code: code
}
}
////////////////////////////////////////
// these are just here temporarily to avoid breaking the compiler; they will be removed soon
pub fn error(a string) Option2 { return {} }
pub fn error_with_code(a string, b int) Option2 { return {} }
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// Option2 is the base of V's new internal optional return system.
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struct Option2 {
state byte
err Error
// Data is trailing after err
// and is not included in here but in the
// derived Option2_xxx types
}
[inline]
fn (e Error) str() string {
// TODO: this should probably have a better str method,
// but this minimizes the amount of broken code after #8924
return e.msg
}
// `fn foo() ?Foo { return foo }` => `fn foo() ?Foo { return opt_ok(foo); }`
fn opt_ok(data voidptr, mut option Option2, size int) {
unsafe {
*option = Option2{}
// use err to get the end of OptionBase and then memcpy into it
C.memcpy(byteptr(&option.err) + sizeof(Error), data, size)
}
}
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pub fn (o Option2) str() string {
if o.state == 0 {
return 'Option{ ok }'
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}
if o.state == 1 {
return 'Option{ none }'
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}
return 'Option{ error: "$o.err" }'
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}
// error returns an optional containing the error given in `message`.
// `if ouch { return error('an error occurred') }`
pub fn error2(message string) Option2 {
return Option2{
state: 2
err: {
msg: 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_code2(message string, code int) Option2 {
return Option2{
state: 2
err: {
msg: message
code: code
}
}
}