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//! Intermediate representation for the physical layout of some type.
use super::derive::CanDerive;
use super::ty::{Type, TypeKind, RUST_DERIVE_IN_ARRAY_LIMIT};
use crate::clang;
use crate::ir::context::BindgenContext;
use std::cmp;
/// A type that represents the struct layout of a type.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) struct Layout {
/// The size (in bytes) of this layout.
pub(crate) size: usize,
/// The alignment (in bytes) of this layout.
pub(crate) align: usize,
/// Whether this layout's members are packed or not.
pub(crate) packed: bool,
}
#[test]
fn test_layout_for_size() {
use std::mem;
let ptr_size = mem::size_of::<*mut ()>();
assert_eq!(
Layout::for_size_internal(ptr_size, ptr_size),
Layout::new(ptr_size, ptr_size)
);
assert_eq!(
Layout::for_size_internal(ptr_size, 3 * ptr_size),
Layout::new(3 * ptr_size, ptr_size)
);
}
impl Layout {
/// Gets the integer type name for a given known size.
pub(crate) fn known_type_for_size(
ctx: &BindgenContext,
size: usize,
) -> Option<syn::Type> {
Some(match size {
16 if ctx.options().rust_features.i128_and_u128 => {
syn::parse_quote! { u128 }
}
8 => syn::parse_quote! { u64 },
4 => syn::parse_quote! { u32 },
2 => syn::parse_quote! { u16 },
1 => syn::parse_quote! { u8 },
_ => return None,
})
}
/// Construct a new `Layout` with the given `size` and `align`. It is not
/// packed.
pub(crate) fn new(size: usize, align: usize) -> Self {
Layout {
size,
align,
packed: false,
}
}
fn for_size_internal(ptr_size: usize, size: usize) -> Self {
let mut next_align = 2;
while size % next_align == 0 && next_align <= ptr_size {
next_align *= 2;
}
Layout {
size,
align: next_align / 2,
packed: false,
}
}
/// Creates a non-packed layout for a given size, trying to use the maximum
/// alignment possible.
pub(crate) fn for_size(ctx: &BindgenContext, size: usize) -> Self {
Self::for_size_internal(ctx.target_pointer_size(), size)
}
/// Get this layout as an opaque type.
pub(crate) fn opaque(&self) -> Opaque {
Opaque(*self)
}
}
/// When we are treating a type as opaque, it is just a blob with a `Layout`.
#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) struct Opaque(pub(crate) Layout);
impl Opaque {
/// Construct a new opaque type from the given clang type.
pub(crate) fn from_clang_ty(
ty: &clang::Type,
ctx: &BindgenContext,
) -> Type {
let layout = Layout::new(ty.size(ctx), ty.align(ctx));
let ty_kind = TypeKind::Opaque;
let is_const = ty.is_const();
Type::new(None, Some(layout), ty_kind, is_const)
}
/// Return the known rust type we should use to create a correctly-aligned
/// field with this layout.
pub(crate) fn known_rust_type_for_array(
&self,
ctx: &BindgenContext,
) -> Option<syn::Type> {
Layout::known_type_for_size(ctx, self.0.align)
}
/// Return the array size that an opaque type for this layout should have if
/// we know the correct type for it, or `None` otherwise.
pub(crate) fn array_size(&self, ctx: &BindgenContext) -> Option<usize> {
if self.known_rust_type_for_array(ctx).is_some() {
Some(self.0.size / cmp::max(self.0.align, 1))
} else {
None
}
}
/// Return `true` if this opaque layout's array size will fit within the
/// maximum number of array elements that Rust allows deriving traits
/// with. Return `false` otherwise.
pub(crate) fn array_size_within_derive_limit(
&self,
ctx: &BindgenContext,
) -> CanDerive {
if self
.array_size(ctx)
.map_or(false, |size| size <= RUST_DERIVE_IN_ARRAY_LIMIT)
{
CanDerive::Yes
} else {
CanDerive::Manually
}
}
}