50 lines
1.2 KiB
Rust
50 lines
1.2 KiB
Rust
use implementations::NarrowerThan;
|
|
|
|
/// Replacement for `as` casts going from wide integer to narrower integer.
|
|
///
|
|
/// # Example
|
|
///
|
|
/// ```ignore
|
|
/// let x = 99_u64;
|
|
/// let lo = x.truncate::<u16>();
|
|
/// // lo is of type u16, equivalent to `x as u16`.
|
|
/// ```
|
|
pub(crate) trait Truncate: Sized {
|
|
fn truncate<To>(self) -> To
|
|
where
|
|
To: NarrowerThan<Self>,
|
|
{
|
|
NarrowerThan::truncate_from(self)
|
|
}
|
|
}
|
|
|
|
impl Truncate for u16 {}
|
|
impl Truncate for u32 {}
|
|
impl Truncate for u64 {}
|
|
impl Truncate for u128 {}
|
|
|
|
mod implementations {
|
|
pub(crate) trait NarrowerThan<T> {
|
|
fn truncate_from(wide: T) -> Self;
|
|
}
|
|
|
|
macro_rules! impl_narrower_than {
|
|
($(NarrowerThan<{$($ty:ty),*}> for $self:ty)*) => {
|
|
$($(
|
|
impl NarrowerThan<$ty> for $self {
|
|
fn truncate_from(wide: $ty) -> Self {
|
|
wide as Self
|
|
}
|
|
}
|
|
)*)*
|
|
};
|
|
}
|
|
|
|
impl_narrower_than! {
|
|
NarrowerThan<{u128, u64, u32, u16}> for u8
|
|
NarrowerThan<{u128, u64, u32}> for u16
|
|
NarrowerThan<{u128, u64}> for u32
|
|
NarrowerThan<{u128}> for u64
|
|
}
|
|
}
|