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v/vlib/builtin/option.v

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// Copyright (c) 2019-2022 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 {
// >> Hack to allow old style custom error implementations
// TODO: remove once deprecation period for `IError` methods has ended
msg string
code int // <<
msg() string
code() int
}
pub fn (err IError) str() string {
return match err {
None__ {
'none'
}
Error {
err.msg()
}
MessageError {
err.msg()
}
else {
// >> Hack to allow old style custom error implementations
// TODO: remove once deprecation period for `IError` methods has ended
old_error_style := unsafe { voidptr(&err.msg) != voidptr(&err.code) } // if fields are not defined (new style) they don't have an offset between
if old_error_style {
'$err.type_name(): $err.msg'
} else {
// <<
'$err.type_name(): $err.msg()'
}
}
}
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}
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// Error is the empty default implementation of `IError`.
pub struct Error {}
pub fn (err Error) msg() string {
return ''
}
pub fn (err Error) code() int {
return 0
}
// MessageError is the default implementation of the `IError` interface that is returned by the `error()` function
struct MessageError {
pub:
msg string
code int
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}
pub fn (err MessageError) msg() string {
return err.msg
}
pub fn (err MessageError) code() int {
return err.code
}
[unsafe]
pub fn (err &MessageError) free() {
unsafe { err.msg.free() }
}
const none__ = IError(&None__{})
struct None__ {
Error
}
fn (_ None__) str() string {
return 'none'
}
[if trace_error ?]
fn trace_error(x string) {
eprintln('> ${@FN} | $x')
}
// error returns a default error instance containing the error given in `message`.
// Example: if ouch { return error('an error occurred') }
[inline]
pub fn error(message string) IError {
trace_error(message)
return &MessageError{
msg: message
}
}
// error_with_code returns a default error instance containing the given `message` and error `code`.
// Example: if ouch { return error_with_code('an error occurred', 1) }
[inline]
pub fn error_with_code(message string, code int) IError {
trace_error('$message | code: $code')
return &MessageError{
msg: message
code: code
}
}
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// Option is the base of V's internal optional return system.
struct Option {
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state byte
err IError = none__
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// Data is trailing after err
// and is not included in here but in the
// derived Option_xxx types
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}
fn opt_ok(data voidptr, mut option Option, size int) {
unsafe {
*option = Option{}
// use err to get the end of OptionBase and then memcpy into it
vmemcpy(&byte(&option.err) + sizeof(IError), data, size)
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}
}
pub fn (_ none) str() string {
return 'none'
}