pub trait ZeroFrom<'zf, C: ?Sized>: 'zf {
// Required method
fn zero_from(other: &'zf C) -> Self;
}Expand description
Trait for types that can be created from a reference to a different type C with no allocations,
i.e. a zero-copy (zero-alloc) version of “From”
A type can be the ZeroFrom target of multiple other types.
The intention is for ZeroFrom to produce a struct from a other with as little work as
possible. Although it is technically possible to implement ZeroFrom without being
zero-copy (using heap allocations), doing so defeats the purpose of ZeroFrom.
For example, impl ZeroFrom<C> for Cow<str> should return a Cow::Borrowed pointing at
data in the other type C, even if the other type is itself fully owned.
One can use the #[derive(ZeroFrom)] custom derive to automatically
implement this trait.
Examples
Implementing ZeroFrom on a custom data struct:
use std::borrow::Cow;
use zerofrom::ZeroFrom;
struct MyStruct<'data> {
message: Cow<'data, str>,
}
// Reference from a borrowed version of self
impl<'zf> ZeroFrom<'zf, MyStruct<'_>> for MyStruct<'zf> {
fn zero_from(other: &'zf MyStruct<'_>) -> Self {
MyStruct {
message: Cow::Borrowed(&other.message),
}
}
}
// Reference from a string slice directly
impl<'zf> ZeroFrom<'zf, str> for MyStruct<'zf> {
fn zero_from(other: &'zf str) -> Self {
MyStruct {
message: Cow::Borrowed(other),
}
}
}