Trait yoke::ZeroCopyFrom [−][src]
pub trait ZeroCopyFrom<C: ?Sized>: for<'a> Yokeable<'a> {
fn zero_copy_from<'b>(cart: &'b C) -> <Self as Yokeable<'b>>::Output;
}Expand description
Trait for types that can be crated from a reference to a cart type C with no allocations.
A type can be the ZeroCopyFrom target of multiple cart types.
The intention is for ZeroCopyFrom to produce a struct from a cart with as little work as
possible. Although it is technically possible to implement ZeroCopyFrom without being
zero-copy (using heap allocations), doing so defeats the purpose of ZeroCopyFrom.
For example, impl ZeroCopyFrom<C> for Cow<str> should return a Cow::Borrowed pointing at
data in the cart C, even if the cart is itself fully owned.
Examples
Implementing ZeroCopyFrom on a custom data struct:
use yoke::Yokeable;
use yoke::ZeroCopyFrom;
use std::borrow::Cow;
struct MyStruct<'data> {
message: Cow<'data, str>,
}
unsafe impl<'a> Yokeable<'a> for MyStruct<'static> {
// (not shown; see `Yokeable` for examples)
}
// Reference from a borrowed version of self
impl<'data> ZeroCopyFrom<MyStruct<'data>> for MyStruct<'static> {
fn zero_copy_from<'b>(cart: &'b MyStruct<'data>) -> MyStruct<'b> {
MyStruct {
message: Cow::Borrowed(&cart.message)
}
}
}
// Reference from a string slice directly
impl ZeroCopyFrom<str> for MyStruct<'static> {
fn zero_copy_from<'b>(cart: &'b str) -> MyStruct<'b> {
MyStruct {
message: Cow::Borrowed(cart)
}
}
}