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//! Intermediate representation for the physical layout of some type.
use crate::ir::context::BindgenContext;
/// 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::size_of;
let ptr_size = 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(size: usize) -> Option<syn::Type> {
Some(match size {
16 => 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)
}
}