mirror of
https://github.com/Lokathor/bytemuck.git
synced 2024-10-30 05:40:50 +00:00
Merge branch 'main' of https://github.com/Lokathor/bytemuck into main
This commit is contained in:
Lokathor
commit
763d69eb15
4
.github/workflows/rust.yml
vendored
4
.github/workflows/rust.yml
vendored
@ -46,8 +46,8 @@ jobs:
|
||||
runs-on: ubuntu-latest
|
||||
strategy:
|
||||
matrix:
|
||||
# note: the mips targets are here so that we have big-endian coverage (both 32bit and 64bit)
|
||||
target: [i686-unknown-linux-gnu, mips-unknown-linux-gnu, mips64-unknown-linux-gnuabi64]
|
||||
# we once had mips runners for Big-endian coverage but those got demoted to tier 3.
|
||||
target: [i686-unknown-linux-gnu]
|
||||
steps:
|
||||
- uses: hecrj/setup-rust-action@v1
|
||||
with:
|
||||
|
||||
@ -1,7 +1,7 @@
|
||||
[package]
|
||||
name = "bytemuck"
|
||||
description = "A crate for mucking around with piles of bytes."
|
||||
version = "1.13.1"
|
||||
version = "1.13.2"
|
||||
authors = ["Lokathor <zefria@gmail.com>"]
|
||||
repository = "https://github.com/Lokathor/bytemuck"
|
||||
readme = "README.md"
|
||||
@ -20,6 +20,7 @@ zeroable_maybe_uninit = []
|
||||
zeroable_atomics = []
|
||||
min_const_generics = []
|
||||
wasm_simd = [] # Until >= 1.54.0 is MSRV this is an off-by-default feature.
|
||||
must_cast = [] # Until >= 1.57.0 is MSRV this is an off-by-default feature.
|
||||
aarch64_simd = [] # Until >= 1.59.0 is MSRV this is an off-by-default feature.
|
||||
|
||||
# Do not use if you can avoid it, because this is unsound.
|
||||
@ -42,6 +43,7 @@ features = [
|
||||
"zeroable_atomics",
|
||||
"min_const_generics",
|
||||
"wasm_simd",
|
||||
"must_cast",
|
||||
]
|
||||
|
||||
[package.metadata.playground]
|
||||
@ -54,4 +56,5 @@ features = [
|
||||
"zeroable_atomics",
|
||||
"min_const_generics",
|
||||
"wasm_simd",
|
||||
"must_cast",
|
||||
]
|
||||
|
||||
@ -18,7 +18,7 @@ proc-macro = true
|
||||
# syn seems to have broken backwards compatibility in this version https://github.com/dtolnay/syn/issues/1194
|
||||
syn = "2.0.1"
|
||||
quote = "1"
|
||||
proc-macro2 = "1"
|
||||
proc-macro2 = "1.0.60"
|
||||
|
||||
[dev-dependencies]
|
||||
bytemuck = { path = "../", features = ["derive"] }
|
||||
|
||||
@ -77,7 +77,6 @@ pub fn derive_anybitpattern(
|
||||
///
|
||||
/// ```rust
|
||||
/// # use bytemuck_derive::{Zeroable};
|
||||
///
|
||||
/// #[derive(Copy, Clone, Zeroable)]
|
||||
/// #[repr(C)]
|
||||
/// struct Test {
|
||||
@ -85,7 +84,65 @@ pub fn derive_anybitpattern(
|
||||
/// b: u16,
|
||||
/// }
|
||||
/// ```
|
||||
#[proc_macro_derive(Zeroable)]
|
||||
///
|
||||
/// # Custom bounds
|
||||
///
|
||||
/// Custom bounds for the derived `Zeroable` impl can be given using the
|
||||
/// `#[zeroable(bound = "")]` helper attribute.
|
||||
///
|
||||
/// Using this attribute additionally opts-in to "perfect derive" semantics,
|
||||
/// where instead of adding bounds for each generic type parameter, bounds are
|
||||
/// added for each field's type.
|
||||
///
|
||||
/// ## Examples
|
||||
///
|
||||
/// ```rust
|
||||
/// # use bytemuck::Zeroable;
|
||||
/// # use std::marker::PhantomData;
|
||||
/// #[derive(Clone, Zeroable)]
|
||||
/// #[zeroable(bound = "")]
|
||||
/// struct AlwaysZeroable<T> {
|
||||
/// a: PhantomData<T>,
|
||||
/// }
|
||||
///
|
||||
/// AlwaysZeroable::<std::num::NonZeroU8>::zeroed();
|
||||
/// ```
|
||||
///
|
||||
/// ```rust,compile_fail
|
||||
/// # use bytemuck::Zeroable;
|
||||
/// # use std::marker::PhantomData;
|
||||
/// #[derive(Clone, Zeroable)]
|
||||
/// #[zeroable(bound = "T: Copy")]
|
||||
/// struct ZeroableWhenTIsCopy<T> {
|
||||
/// a: PhantomData<T>,
|
||||
/// }
|
||||
///
|
||||
/// ZeroableWhenTIsCopy::<String>::zeroed();
|
||||
/// ```
|
||||
///
|
||||
/// The restriction that all fields must be Zeroable is still applied, and this
|
||||
/// is enforced using the mentioned "perfect derive" semantics.
|
||||
///
|
||||
/// ```rust
|
||||
/// # use bytemuck::Zeroable;
|
||||
/// #[derive(Clone, Zeroable)]
|
||||
/// #[zeroable(bound = "")]
|
||||
/// struct ZeroableWhenTIsZeroable<T> {
|
||||
/// a: T,
|
||||
/// }
|
||||
/// ZeroableWhenTIsZeroable::<u32>::zeroed();
|
||||
/// ```
|
||||
///
|
||||
/// ```rust,compile_fail
|
||||
/// # use bytemuck::Zeroable;
|
||||
/// # #[derive(Clone, Zeroable)]
|
||||
/// # #[zeroable(bound = "")]
|
||||
/// # struct ZeroableWhenTIsZeroable<T> {
|
||||
/// # a: T,
|
||||
/// # }
|
||||
/// ZeroableWhenTIsZeroable::<String>::zeroed();
|
||||
/// ```
|
||||
#[proc_macro_derive(Zeroable, attributes(zeroable))]
|
||||
pub fn derive_zeroable(
|
||||
input: proc_macro::TokenStream,
|
||||
) -> proc_macro::TokenStream {
|
||||
@ -317,12 +374,127 @@ fn derive_marker_trait<Trait: Derivable>(input: DeriveInput) -> TokenStream {
|
||||
.unwrap_or_else(|err| err.into_compile_error())
|
||||
}
|
||||
|
||||
/// Find `#[name(key = "value")]` helper attributes on the struct, and return
|
||||
/// their `"value"`s parsed with `parser`.
|
||||
///
|
||||
/// Returns an error if any attributes with the given `name` do not match the
|
||||
/// expected format. Returns `Ok([])` if no attributes with `name` are found.
|
||||
fn find_and_parse_helper_attributes<P: syn::parse::Parser + Copy>(
|
||||
attributes: &[syn::Attribute], name: &str, key: &str, parser: P,
|
||||
example_value: &str, invalid_value_msg: &str,
|
||||
) -> Result<Vec<P::Output>> {
|
||||
let invalid_format_msg =
|
||||
format!("{name} attribute must be `{name}({key} = \"{example_value}\")`",);
|
||||
let values_to_check = attributes.iter().filter_map(|attr| match &attr.meta {
|
||||
// If a `Path` matches our `name`, return an error, else ignore it.
|
||||
// e.g. `#[zeroable]`
|
||||
syn::Meta::Path(path) => path
|
||||
.is_ident(name)
|
||||
.then(|| Err(syn::Error::new_spanned(path, &invalid_format_msg))),
|
||||
// If a `NameValue` matches our `name`, return an error, else ignore it.
|
||||
// e.g. `#[zeroable = "hello"]`
|
||||
syn::Meta::NameValue(namevalue) => {
|
||||
namevalue.path.is_ident(name).then(|| {
|
||||
Err(syn::Error::new_spanned(&namevalue.path, &invalid_format_msg))
|
||||
})
|
||||
}
|
||||
// If a `List` matches our `name`, match its contents to our format, else
|
||||
// ignore it. If its contents match our format, return the value, else
|
||||
// return an error.
|
||||
syn::Meta::List(list) => list.path.is_ident(name).then(|| {
|
||||
let namevalue: syn::MetaNameValue = syn::parse2(list.tokens.clone())
|
||||
.map_err(|_| {
|
||||
syn::Error::new_spanned(&list.tokens, &invalid_format_msg)
|
||||
})?;
|
||||
if namevalue.path.is_ident(key) {
|
||||
match namevalue.value {
|
||||
syn::Expr::Lit(syn::ExprLit {
|
||||
lit: syn::Lit::Str(strlit), ..
|
||||
}) => Ok(strlit),
|
||||
_ => {
|
||||
Err(syn::Error::new_spanned(&namevalue.path, &invalid_format_msg))
|
||||
}
|
||||
}
|
||||
} else {
|
||||
Err(syn::Error::new_spanned(&namevalue.path, &invalid_format_msg))
|
||||
}
|
||||
}),
|
||||
});
|
||||
// Parse each value found with the given parser, and return them if no errors
|
||||
// occur.
|
||||
values_to_check
|
||||
.map(|lit| {
|
||||
let lit = lit?;
|
||||
lit.parse_with(parser).map_err(|err| {
|
||||
syn::Error::new_spanned(&lit, format!("{invalid_value_msg}: {err}"))
|
||||
})
|
||||
})
|
||||
.collect()
|
||||
}
|
||||
|
||||
fn derive_marker_trait_inner<Trait: Derivable>(
|
||||
mut input: DeriveInput,
|
||||
) -> Result<TokenStream> {
|
||||
// Enforce Pod on all generic fields.
|
||||
let trait_ = Trait::ident(&input)?;
|
||||
add_trait_marker(&mut input.generics, &trait_);
|
||||
// If this trait allows explicit bounds, and any explicit bounds were given,
|
||||
// then use those explicit bounds. Else, apply the default bounds (bound
|
||||
// each generic type on this trait).
|
||||
if let Some(name) = Trait::explicit_bounds_attribute_name() {
|
||||
// See if any explicit bounds were given in attributes.
|
||||
let explicit_bounds = find_and_parse_helper_attributes(
|
||||
&input.attrs,
|
||||
name,
|
||||
"bound",
|
||||
<syn::punctuated::Punctuated<syn::WherePredicate, syn::Token![,]>>::parse_terminated,
|
||||
"Type: Trait",
|
||||
"invalid where predicate",
|
||||
)?;
|
||||
|
||||
if !explicit_bounds.is_empty() {
|
||||
// Explicit bounds were given.
|
||||
// Enforce explicitly given bounds, and emit "perfect derive" (i.e. add
|
||||
// bounds for each field's type).
|
||||
let explicit_bounds = explicit_bounds
|
||||
.into_iter()
|
||||
.flatten()
|
||||
.collect::<Vec<syn::WherePredicate>>();
|
||||
|
||||
let predicates = &mut input.generics.make_where_clause().predicates;
|
||||
|
||||
predicates.extend(explicit_bounds);
|
||||
|
||||
let fields = match &input.data {
|
||||
syn::Data::Struct(syn::DataStruct { fields, .. }) => fields.clone(),
|
||||
syn::Data::Union(_) => {
|
||||
return Err(syn::Error::new_spanned(
|
||||
trait_,
|
||||
&"perfect derive is not supported for unions",
|
||||
));
|
||||
}
|
||||
syn::Data::Enum(_) => {
|
||||
return Err(syn::Error::new_spanned(
|
||||
trait_,
|
||||
&"perfect derive is not supported for enums",
|
||||
));
|
||||
}
|
||||
};
|
||||
|
||||
for field in fields {
|
||||
let ty = field.ty;
|
||||
predicates.push(syn::parse_quote!(
|
||||
#ty: #trait_
|
||||
));
|
||||
}
|
||||
} else {
|
||||
// No explicit bounds were given.
|
||||
// Enforce trait bound on all type generics.
|
||||
add_trait_marker(&mut input.generics, &trait_);
|
||||
}
|
||||
} else {
|
||||
// This trait does not allow explicit bounds.
|
||||
// Enforce trait bound on all type generics.
|
||||
add_trait_marker(&mut input.generics, &trait_);
|
||||
}
|
||||
|
||||
let name = &input.ident;
|
||||
|
||||
@ -339,11 +511,8 @@ fn derive_marker_trait_inner<Trait: Derivable>(
|
||||
quote!()
|
||||
};
|
||||
|
||||
let where_clause = if Trait::requires_where_clause() {
|
||||
where_clause
|
||||
} else {
|
||||
None
|
||||
};
|
||||
let where_clause =
|
||||
if Trait::requires_where_clause() { where_clause } else { None };
|
||||
|
||||
Ok(quote! {
|
||||
#asserts
|
||||
@ -364,9 +533,12 @@ fn add_trait_marker(generics: &mut syn::Generics, trait_name: &syn::Path) {
|
||||
let type_params = generics
|
||||
.type_params()
|
||||
.map(|param| ¶m.ident)
|
||||
.map(|param| syn::parse_quote!(
|
||||
#param: #trait_name
|
||||
)).collect::<Vec<syn::WherePredicate>>();
|
||||
.map(|param| {
|
||||
syn::parse_quote!(
|
||||
#param: #trait_name
|
||||
)
|
||||
})
|
||||
.collect::<Vec<syn::WherePredicate>>();
|
||||
|
||||
generics.make_where_clause().predicates.extend(type_params);
|
||||
}
|
||||
|
||||
@ -35,6 +35,9 @@ pub trait Derivable {
|
||||
fn requires_where_clause() -> bool {
|
||||
true
|
||||
}
|
||||
fn explicit_bounds_attribute_name() -> Option<&'static str> {
|
||||
None
|
||||
}
|
||||
}
|
||||
|
||||
pub struct Pod;
|
||||
@ -126,6 +129,10 @@ impl Derivable for Zeroable {
|
||||
Data::Enum(_) => bail!("Deriving Zeroable is not supported for enums"),
|
||||
}
|
||||
}
|
||||
|
||||
fn explicit_bounds_attribute_name() -> Option<&'static str> {
|
||||
Some("zeroable")
|
||||
}
|
||||
}
|
||||
|
||||
pub struct NoUninit;
|
||||
@ -532,12 +539,13 @@ fn generate_assert_no_padding(input: &DeriveInput) -> Result<TokenStream> {
|
||||
let size_rest =
|
||||
quote_spanned!(span => #( + ::core::mem::size_of::<#field_types>() )*);
|
||||
|
||||
quote_spanned!(span => #size_first#size_rest)
|
||||
quote_spanned!(span => #size_first #size_rest)
|
||||
} else {
|
||||
quote_spanned!(span => 0)
|
||||
};
|
||||
|
||||
Ok(quote_spanned! {span => const _: fn() = || {
|
||||
#[doc(hidden)]
|
||||
struct TypeWithoutPadding([u8; #size_sum]);
|
||||
let _ = ::core::mem::transmute::<#struct_type, TypeWithoutPadding>;
|
||||
};})
|
||||
@ -554,6 +562,7 @@ fn generate_fields_are_trait(
|
||||
let field_types = get_field_types(&fields);
|
||||
Ok(quote_spanned! {span => #(const _: fn() = || {
|
||||
#[allow(clippy::missing_const_for_fn)]
|
||||
#[doc(hidden)]
|
||||
fn check #impl_generics () #where_clause {
|
||||
fn assert_impl<T: #trait_>() {}
|
||||
assert_impl::<#field_types>();
|
||||
|
||||
@ -685,4 +685,5 @@ pub trait TransparentWrapperAlloc<Inner: ?Sized>:
|
||||
}
|
||||
}
|
||||
}
|
||||
impl<I: ?Sized, T: TransparentWrapper<I>> TransparentWrapperAlloc<I> for T {}
|
||||
|
||||
impl<I: ?Sized, T: ?Sized + TransparentWrapper<I>> TransparentWrapperAlloc<I> for T {}
|
||||
|
||||
@ -170,6 +170,7 @@ unsafe impl CheckedBitPattern for bool {
|
||||
}
|
||||
}
|
||||
|
||||
// Rust 1.70.0 documents that NonZero[int] has the same layout as [int].
|
||||
macro_rules! impl_checked_for_nonzero {
|
||||
($($nonzero:ty: $primitive:ty),* $(,)?) => {
|
||||
$(
|
||||
@ -178,14 +179,7 @@ macro_rules! impl_checked_for_nonzero {
|
||||
|
||||
#[inline]
|
||||
fn is_valid_bit_pattern(bits: &Self::Bits) -> bool {
|
||||
// Note(zachs18): The size and alignment check are almost certainly
|
||||
// not necessary, but Rust currently doesn't explicitly document that
|
||||
// NonZero[int] has the same layout as [int], so we check it to be safe.
|
||||
// In a const to reduce debug-profile overhead.
|
||||
const LAYOUT_SAME: bool =
|
||||
core::mem::size_of::<$nonzero>() == core::mem::size_of::<$primitive>()
|
||||
&& core::mem::align_of::<$nonzero>() == core::mem::align_of::<$primitive>();
|
||||
LAYOUT_SAME && *bits != 0
|
||||
*bits != 0
|
||||
}
|
||||
}
|
||||
)*
|
||||
|
||||
@ -113,6 +113,11 @@ pub use pod::*;
|
||||
mod pod_in_option;
|
||||
pub use pod_in_option::*;
|
||||
|
||||
#[cfg(feature = "must_cast")]
|
||||
mod must;
|
||||
#[cfg(feature = "must_cast")]
|
||||
pub use must::*;
|
||||
|
||||
mod no_uninit;
|
||||
pub use no_uninit::*;
|
||||
|
||||
|
||||
203
src/must.rs
Normal file
203
src/must.rs
Normal file
@ -0,0 +1,203 @@
|
||||
#![allow(clippy::module_name_repetitions)]
|
||||
#![allow(clippy::let_unit_value)]
|
||||
#![allow(clippy::let_underscore_untyped)]
|
||||
#![allow(clippy::ptr_as_ptr)]
|
||||
|
||||
use crate::{AnyBitPattern, NoUninit};
|
||||
use core::mem::{align_of, size_of};
|
||||
|
||||
struct Cast<A, B>((A, B));
|
||||
impl<A, B> Cast<A, B> {
|
||||
const ASSERT_ALIGN_GREATER_THAN_EQUAL: () =
|
||||
assert!(align_of::<A>() >= align_of::<B>());
|
||||
const ASSERT_SIZE_EQUAL: () = assert!(size_of::<A>() == size_of::<B>());
|
||||
const ASSERT_SIZE_MULTIPLE_OF: () = assert!(
|
||||
(size_of::<A>() == 0) == (size_of::<B>() == 0)
|
||||
&& (size_of::<A>() % size_of::<B>() == 0)
|
||||
);
|
||||
}
|
||||
|
||||
// Workaround for https://github.com/rust-lang/miri/issues/2423.
|
||||
// Miri currently doesn't see post-monomorphization errors until runtime,
|
||||
// so `compile_fail` tests relying on post-monomorphization errors don't
|
||||
// actually fail. Instead use `should_panic` under miri as a workaround.
|
||||
#[cfg(miri)]
|
||||
macro_rules! post_mono_compile_fail_doctest {
|
||||
() => {
|
||||
"```should_panic"
|
||||
};
|
||||
}
|
||||
#[cfg(not(miri))]
|
||||
macro_rules! post_mono_compile_fail_doctest {
|
||||
() => {
|
||||
"```compile_fail,E0080"
|
||||
};
|
||||
}
|
||||
|
||||
/// Cast `A` into `B` if infalliable, or fail to compile.
|
||||
///
|
||||
/// Note that for this particular type of cast, alignment isn't a factor. The
|
||||
/// input value is semantically copied into the function and then returned to a
|
||||
/// new memory location which will have whatever the required alignment of the
|
||||
/// output type is.
|
||||
///
|
||||
/// ## Failure
|
||||
///
|
||||
/// * If the types don't have the same size this fails to compile.
|
||||
///
|
||||
/// ## Examples
|
||||
/// ```
|
||||
/// // compiles:
|
||||
/// let bytes: [u8; 2] = bytemuck::must_cast(12_u16);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// // fails to compile (size mismatch):
|
||||
/// let bytes : [u8; 3] = bytemuck::must_cast(12_u16);
|
||||
/// ```
|
||||
#[inline]
|
||||
pub fn must_cast<A: NoUninit, B: AnyBitPattern>(a: A) -> B {
|
||||
let _ = Cast::<A, B>::ASSERT_SIZE_EQUAL;
|
||||
unsafe { transmute!(a) }
|
||||
}
|
||||
|
||||
/// Convert `&A` into `&B` if infalliable, or fail to compile.
|
||||
///
|
||||
/// ## Failure
|
||||
///
|
||||
/// * If the target type has a greater alignment requirement.
|
||||
/// * If the source type and target type aren't the same size.
|
||||
///
|
||||
/// ## Examples
|
||||
/// ```
|
||||
/// // compiles:
|
||||
/// let bytes: &[u8; 2] = bytemuck::must_cast_ref(&12_u16);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// // fails to compile (size mismatch):
|
||||
/// let bytes : &[u8; 3] = bytemuck::must_cast_ref(&12_u16);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// // fails to compile (alignment requirements increased):
|
||||
/// let bytes : &u16 = bytemuck::must_cast_ref(&[1u8, 2u8]);
|
||||
/// ```
|
||||
#[inline]
|
||||
pub fn must_cast_ref<A: NoUninit, B: AnyBitPattern>(a: &A) -> &B {
|
||||
let _ = Cast::<A, B>::ASSERT_SIZE_EQUAL;
|
||||
let _ = Cast::<A, B>::ASSERT_ALIGN_GREATER_THAN_EQUAL;
|
||||
unsafe { &*(a as *const A as *const B) }
|
||||
}
|
||||
|
||||
/// Convert a `&mut A` into `&mut B` if infalliable, or fail to compile.
|
||||
///
|
||||
/// As [`must_cast_ref`], but `mut`.
|
||||
///
|
||||
/// ## Examples
|
||||
/// ```
|
||||
/// let mut i = 12_u16;
|
||||
/// // compiles:
|
||||
/// let bytes: &mut [u8; 2] = bytemuck::must_cast_mut(&mut i);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// # let mut bytes: &mut [u8; 2] = &mut [1, 2];
|
||||
/// // fails to compile (alignment requirements increased):
|
||||
/// let i : &mut u16 = bytemuck::must_cast_mut(bytes);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// # let mut i = 12_u16;
|
||||
/// // fails to compile (size mismatch):
|
||||
/// let bytes : &mut [u8; 3] = bytemuck::must_cast_mut(&mut i);
|
||||
/// ```
|
||||
#[inline]
|
||||
pub fn must_cast_mut<
|
||||
A: NoUninit + AnyBitPattern,
|
||||
B: NoUninit + AnyBitPattern,
|
||||
>(
|
||||
a: &mut A,
|
||||
) -> &mut B {
|
||||
let _ = Cast::<A, B>::ASSERT_SIZE_EQUAL;
|
||||
let _ = Cast::<A, B>::ASSERT_ALIGN_GREATER_THAN_EQUAL;
|
||||
unsafe { &mut *(a as *mut A as *mut B) }
|
||||
}
|
||||
|
||||
/// Convert `&[A]` into `&[B]` (possibly with a change in length) if
|
||||
/// infalliable, or fail to compile.
|
||||
///
|
||||
/// * `input.as_ptr() as usize == output.as_ptr() as usize`
|
||||
/// * `input.len() * size_of::<A>() == output.len() * size_of::<B>()`
|
||||
///
|
||||
/// ## Failure
|
||||
///
|
||||
/// * If the target type has a greater alignment requirement.
|
||||
/// * If the target element type doesn't evenly fit into the the current element
|
||||
/// type (eg: 3 `u16` values is 1.5 `u32` values, so that's a failure).
|
||||
/// * Similarly, you can't convert between a [ZST](https://doc.rust-lang.org/nomicon/exotic-sizes.html#zero-sized-types-zsts)
|
||||
/// and a non-ZST.
|
||||
///
|
||||
/// ## Examples
|
||||
/// ```
|
||||
/// let indicies: &[u16] = &[1, 2, 3];
|
||||
/// // compiles:
|
||||
/// let bytes: &[u8] = bytemuck::must_cast_slice(indicies);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// # let bytes : &[u8] = &[1, 0, 2, 0, 3, 0];
|
||||
/// // fails to compile (bytes.len() might not be a multiple of 2):
|
||||
/// let byte_pairs : &[[u8; 2]] = bytemuck::must_cast_slice(bytes);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// # let byte_pairs : &[[u8; 2]] = &[[1, 0], [2, 0], [3, 0]];
|
||||
/// // fails to compile (alignment requirements increased):
|
||||
/// let indicies : &[u16] = bytemuck::must_cast_slice(byte_pairs);
|
||||
/// ```
|
||||
#[inline]
|
||||
pub fn must_cast_slice<A: NoUninit, B: AnyBitPattern>(a: &[A]) -> &[B] {
|
||||
let _ = Cast::<A, B>::ASSERT_SIZE_MULTIPLE_OF;
|
||||
let _ = Cast::<A, B>::ASSERT_ALIGN_GREATER_THAN_EQUAL;
|
||||
let new_len = if size_of::<A>() == size_of::<B>() {
|
||||
a.len()
|
||||
} else {
|
||||
a.len() * (size_of::<A>() / size_of::<B>())
|
||||
};
|
||||
unsafe { core::slice::from_raw_parts(a.as_ptr() as *const B, new_len) }
|
||||
}
|
||||
|
||||
/// Convert `&mut [A]` into `&mut [B]` (possibly with a change in length) if
|
||||
/// infalliable, or fail to compile.
|
||||
///
|
||||
/// As [`must_cast_slice`], but `&mut`.
|
||||
///
|
||||
/// ## Examples
|
||||
/// ```
|
||||
/// let mut indicies = [1, 2, 3];
|
||||
/// let indicies: &mut [u16] = &mut indicies;
|
||||
/// // compiles:
|
||||
/// let bytes: &mut [u8] = bytemuck::must_cast_slice_mut(indicies);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// # let mut bytes = [1, 0, 2, 0, 3, 0];
|
||||
/// # let bytes : &mut [u8] = &mut bytes[..];
|
||||
/// // fails to compile (bytes.len() might not be a multiple of 2):
|
||||
/// let byte_pairs : &mut [[u8; 2]] = bytemuck::must_cast_slice_mut(bytes);
|
||||
/// ```
|
||||
#[doc = post_mono_compile_fail_doctest!()]
|
||||
/// # let mut byte_pairs = [[1, 0], [2, 0], [3, 0]];
|
||||
/// # let byte_pairs : &mut [[u8; 2]] = &mut byte_pairs[..];
|
||||
/// // fails to compile (alignment requirements increased):
|
||||
/// let indicies : &mut [u16] = bytemuck::must_cast_slice_mut(byte_pairs);
|
||||
/// ```
|
||||
#[inline]
|
||||
pub fn must_cast_slice_mut<
|
||||
A: NoUninit + AnyBitPattern,
|
||||
B: NoUninit + AnyBitPattern,
|
||||
>(
|
||||
a: &mut [A],
|
||||
) -> &mut [B] {
|
||||
let _ = Cast::<A, B>::ASSERT_SIZE_MULTIPLE_OF;
|
||||
let _ = Cast::<A, B>::ASSERT_ALIGN_GREATER_THAN_EQUAL;
|
||||
let new_len = if size_of::<A>() == size_of::<B>() {
|
||||
a.len()
|
||||
} else {
|
||||
a.len() * (size_of::<A>() / size_of::<B>())
|
||||
};
|
||||
unsafe { core::slice::from_raw_parts_mut(a.as_mut_ptr() as *mut B, new_len) }
|
||||
}
|
||||
@ -60,7 +60,7 @@ unsafe impl<T: 'static> Pod for *const T {}
|
||||
#[cfg(feature = "unsound_ptr_pod_impl")]
|
||||
unsafe impl<T: 'static> PodInOption for NonNull<T> {}
|
||||
|
||||
unsafe impl<T: Pod> Pod for PhantomData<T> {}
|
||||
unsafe impl<T: ?Sized + 'static> Pod for PhantomData<T> {}
|
||||
unsafe impl Pod for PhantomPinned {}
|
||||
unsafe impl<T: Pod> Pod for ManuallyDrop<T> {}
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user