55 lines
1.4 KiB
Rust
55 lines
1.4 KiB
Rust
//! A helper module containing unsafe utility functions.
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#[cfg(feature = "no_std")]
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use std::prelude::v1::*;
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use std::{
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any::{Any, TypeId},
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mem, ptr,
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};
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/// Cast a type into another type.
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///
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/// # Undefined Behavior
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///
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/// It is UB if the types are not compatible.
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#[inline(always)]
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#[must_use]
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pub fn unsafe_cast<A: Any, B: Any>(a: A) -> B {
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unsafe {
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let ret: B = ptr::read(&a as *const _ as *const B);
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// We explicitly forget the value immediately after moving out,
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// removing any chance of a destructor running or value otherwise
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// being used again.
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mem::forget(a);
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ret
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}
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}
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/// Cast a type into another type.
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#[inline(always)]
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#[must_use]
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pub fn unsafe_try_cast<A: Any, B: Any>(a: A) -> Option<B> {
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if TypeId::of::<B>() == a.type_id() {
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// SAFETY: Just checked we have the right type.
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Some(unsafe_cast(a))
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} else {
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None
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}
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}
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/// Cast a Boxed type into another type.
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#[inline(always)]
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#[must_use]
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pub fn unsafe_cast_box<X: Any, T: Any>(item: Box<X>) -> Option<T> {
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// Only allow casting to the exact same type
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if TypeId::of::<X>() == TypeId::of::<T>() {
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// SAFETY: just checked whether we are pointing to the correct type
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unsafe {
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let raw: *mut dyn Any = Box::into_raw(item as Box<dyn Any>);
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Some(*Box::from_raw(raw as *mut T))
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}
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} else {
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None
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}
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}
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