83 lines
2.1 KiB
Rust
83 lines
2.1 KiB
Rust
use std::mem::{self, ManuallyDrop};
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/// Allows transmuting between types of different sizes.
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///
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/// Necessary for transmuting in generic functions, since (as of Rust 1.51.0)
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/// transmute doesn't work well with generic types.
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///
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/// # Safety
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///
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/// This function has the same safety requirements as [`std::mem::transmute_copy`].
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///
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/// # Example
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///
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/// ```rust
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/// use core_extensions::utils::transmute_ignore_size;
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///
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/// use std::mem::MaybeUninit;
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///
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/// unsafe fn transmute_into_init<T>(array: [MaybeUninit<T>; 3]) -> [T; 3] {
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/// transmute_ignore_size(array)
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/// }
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///
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/// let array = [MaybeUninit::new(3), MaybeUninit::new(5), MaybeUninit::new(8)];
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///
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/// unsafe{ assert_eq!(transmute_into_init(array), [3, 5, 8]); }
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///
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/// ```
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///
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/// This is the error you get if you tried to use `std::mem::transmute`.
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///
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/// ```text
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/// error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
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/// --> src/lib.rs:4:5
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/// |
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/// 4 | std::mem::transmute(array)
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/// | ^^^^^^^^^^^^^^^^^^^
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/// |
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/// = note: source type: `[MaybeUninit<T>; 3]` (size can vary because of T)
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/// = note: target type: `[T; 3]` (size can vary because of T)
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/// ```
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///
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///
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/// [`std::mem::transmute_copy`]: https://doc.rust-lang.org/std/mem/fn.transmute_copy.html
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#[inline(always)]
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pub unsafe fn transmute_ignore_size<T, U>(v: T) -> U {
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let v = ManuallyDrop::new(v);
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mem::transmute_copy::<T, U>(&v)
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}
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pub trait TypeIdent {
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type Type: ?Sized;
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#[inline(always)]
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fn into_type(self) -> Self::Type
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where
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Self: Sized,
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Self::Type: Sized,
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{
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unsafe { transmute_ignore_size(self) }
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}
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}
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impl<T: ?Sized> TypeIdent for T {
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type Type = T;
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}
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pub trait OptExt<T>: TypeIdent<Type = Option<T>> + Sized {
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fn try_unwrap_or_else<F, E>(self, f: F) -> Result<T, E>
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where
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F: Fn() -> Result<T, E>,
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{
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self.into_type().map(Ok::<T, E>).unwrap_or_else(f)
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}
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fn try_m_unwrap_or_else<F>(self, f: F) -> Result<T, miette::Report>
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where
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F: Fn() -> Result<T, miette::Report>,
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{
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self.try_unwrap_or_else(f)
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}
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}
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impl<T> OptExt<T> for Option<T> {}
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