Trait boxext::Zero
[−]
[src]
pub unsafe trait Zero: Sized { }
Trait indicating whether a value full of zeroes is valid.
This trait is used to enable the Box::new_zeroed method for types where
it's safe to use.
Safety
Do not implement this trait for types where a raw byte array of 0 doesn't represent a valid value for the type. Please double check it is valid and corresponds to what you want.
Examples
extern crate boxext; use boxext::{BoxExt, Zero}; #[derive(Debug, PartialEq)] struct Foo(usize); unsafe impl Zero for Foo {} fn main() { // equivalent to `Box::new(Foo(0))` let buf: Box<Foo> = Box::new_zeroed(); assert_eq!(*buf, Foo(0)); }
For convenience, a boxext_derive crate is provided that provides a
custom derive for Zero.
extern crate boxext; #[macro_use] extern crate boxext_derive; use boxext::BoxExt; #[derive(Zero, Debug, PartialEq)] struct Foo(usize); fn main() { // equivalent to `Box::new(Foo(0))` let buf: Box<Foo> = Box::new_zeroed(); assert_eq!(*buf, Foo(0)); }
ⓘThis example deliberately fails to compile
extern crate boxext; #[macro_use] extern crate boxext_derive; use boxext::BoxExt; #[derive(Zero)] // ^ the trait `boxext::Zero` is not implemented for `Bar` struct Foo(Bar); struct Bar; fn main() { // equivalent to `Box::new(Foo(0))` let buf: Box<Foo> = Box::new_zeroed(); }