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