1 files changed, 91 insertions, 0 deletions
diff --git a/src/ir/layout.rs b/src/ir/layout.rs
new file mode 100644
index 00000000..033fff62
--- /dev/null
+++ b/src/ir/layout.rs
@@ -0,0 +1,91 @@
+//! Intermediate representation for the physical layout of some type.
+
+use std::cmp;
+use super::context::BindgenContext;
+use super::derive::{CanDeriveCopy, CanDeriveDebug};
+use super::ty::RUST_DERIVE_IN_ARRAY_LIMIT;
+
+/// A type that represents the struct layout of a type.
+#[derive(Debug, Clone, Copy)]
+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,
+}
+
+impl Layout {
+    /// Construct a new `Layout` with the given `size` and `align`. It is not
+    /// packed.
+    pub fn new(size: usize, align: usize) -> Self {
+        Layout {
+            size: size,
+            align: align,
+            packed: false,
+        }
+    }
+
+    /// 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`.
+pub struct Opaque(pub Layout);
+
+impl Opaque {
+    /// 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) -> Option<&'static str> {
+        Some(match self.0.align {
+            8 => "u64",
+            4 => "u32",
+            2 => "u16",
+            1 => "u8",
+            _ => return None,
+        })
+    }
+
+    /// 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) -> Option<usize> {
+        if self.known_rust_type_for_array().is_some() {
+            Some(self.0.size / cmp::max(self.0.align, 1))
+        } else {
+            None
+        }
+    }
+}
+
+impl CanDeriveDebug for Opaque {
+    type Extra = ();
+
+    fn can_derive_debug(&self, _: &BindgenContext, _: ()) -> bool {
+        self.array_size().map_or(false, |size| size <= RUST_DERIVE_IN_ARRAY_LIMIT)
+    }
+}
+
+impl<'a> CanDeriveCopy<'a> for Opaque {
+    type Extra = ();
+
+    fn can_derive_copy(&self, _: &BindgenContext, _: ()) -> bool {
+        self.array_size().map_or(false, |size| size <= RUST_DERIVE_IN_ARRAY_LIMIT)
+    }
+
+    fn can_derive_copy_in_array(&self, ctx: &BindgenContext, _: ()) -> bool {
+        self.can_derive_copy(ctx, ())
+    }
+}