1 files changed, 143 insertions, 0 deletions
diff --git a/third_party/rust/bindgen/ir/layout.rs b/third_party/rust/bindgen/ir/layout.rs
new file mode 100644
index 0000000000..6f4503070a
--- /dev/null
+++ b/third_party/rust/bindgen/ir/layout.rs
@@ -0,0 +1,143 @@
+//! 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 struct Layout {
+    /// The size (in bytes) of this layout.
+    pub size: usize,
+    /// The alignment (in bytes) of this layout.
+    pub align: usize,
+    /// Whether this layout's members are packed or not.
+    pub 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 fn known_type_for_size(
+        ctx: &BindgenContext,
+        size: usize,
+    ) -> Option<&'static str> {
+        Some(match size {
+            16 if ctx.options().rust_features.i128_and_u128 => "u128",
+            8 => "u64",
+            4 => "u32",
+            2 => "u16",
+            1 => "u8",
+            _ => return None,
+        })
+    }
+
+    /// Construct a new `Layout` with the given `size` and `align`. It is not
+    /// packed.
+    pub 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 fn for_size(ctx: &BindgenContext, size: usize) -> Self {
+        Self::for_size_internal(ctx.target_pointer_size(), size)
+    }
+
+    /// Is this a zero-sized layout?
+    pub fn is_zero(&self) -> bool {
+        self.size == 0 && self.align == 0
+    }
+
+    /// Construct a zero-sized layout.
+    pub fn zero() -> Self {
+        Self::new(0, 0)
+    }
+
+    /// Get this layout as an opaque type.
+    pub 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 struct Opaque(pub Layout);
+
+impl Opaque {
+    /// Construct a new opaque type from the given clang type.
+    pub 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 fn known_rust_type_for_array(
+        &self,
+        ctx: &BindgenContext,
+    ) -> Option<&'static str> {
+        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 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 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
+        }
+    }
+}