Macro hex_conservative::display::impl_fmt_traits
source · macro_rules! impl_fmt_traits { (impl fmt_traits for $ty:ident { const LENGTH: usize = $len:expr; }) => { ... }; (#[display_backward($reverse:expr)] impl fmt_traits for $ty:ident { const LENGTH: usize = $len:expr; }) => { ... }; (impl<$($gen:ident: $gent:ident),*> fmt_traits for $ty:ident<$($unused:ident),*> { const LENGTH: usize = $len:expr; }) => { ... }; (#[display_backward($reverse:expr)] impl<$($gen:ident: $gent:ident),*> fmt_traits for $ty:ident<$($unused:ident),*> { const LENGTH: usize = $len:expr; }) => { ... }; }
Expand description
Adds core::fmt
trait implementations to type $ty
.
Implements:
fmt::{LowerHex, UpperHex}
usingfmt_hex_exact
.fmt::{Display, Debug}
by callingLowerHex
.
Requires:
$ty
must implementIntoIterator<Item=Borrow<u8>>
.
§Parameters
$ty
- the type to implement traits on.$len
- known length of$bytes
, must be a const expression.$bytes
- bytes to be encoded, most likely a reference to an array.$reverse
- true if you want the array to be displayed backwards.$gen: $gent
- optional generic type(s) and trait bound(s) to put on$ty
e.g,F: Foo
.
§Examples
struct Wrapper([u8; 4]);
impl Borrow<[u8]> for Wrapper {
fn borrow(&self) -> &[u8] { &self.0[..] }
}
impl_fmt_traits! {
impl fmt_traits for Wrapper {
const LENGTH: usize = 4;
}
}
let w = Wrapper([0x12, 0x34, 0x56, 0x78]);
assert_eq!(format!("{}", w), "12345678");
We support generics on $ty
:
struct Wrapper<T>([u8; 4], PhantomData<T>);
// `Clone` is just some arbitrary trait.
impl<T: Clone> Borrow<[u8]> for Wrapper<T> {
fn borrow(&self) -> &[u8] { &self.0[..] }
}
impl_fmt_traits! {
impl<T: Clone> fmt_traits for Wrapper<T> {
const LENGTH: usize = 4;
}
}
let w = Wrapper([0x12, 0x34, 0x56, 0x78], PhantomData::<u32>);
assert_eq!(format!("{}", w), "12345678");
And also, as is required by rust-bitcoin
, we support displaying
the hex string byte-wise backwards:
struct Wrapper([u8; 4]);
impl Borrow<[u8]> for Wrapper {
fn borrow(&self) -> &[u8] { &self.0[..] }
}
impl_fmt_traits! {
#[display_backward(true)]
impl fmt_traits for Wrapper {
const LENGTH: usize = 4;
}
}
let w = Wrapper([0x12, 0x34, 0x56, 0x78]);
assert_eq!(format!("{}", w), "78563412");