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// SPDX-License-Identifier: MIT OR Apache-2.0
use std::fmt::Debug;
/// A C type.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Type<I: Layout> {
/// The layout of the type.
pub layout: I::TypeLayout,
/// The annotations on this type.
pub annotations: Vec<Annotation>,
/// The variant of the type.
pub variant: TypeVariant<I>,
}
impl<I: Layout> Type<I> {
/// Returns the identical type with the [`Layout`] converted.
pub fn into<J: Layout>(self) -> Type<J>
where
I::TypeLayout: Into<J::TypeLayout>,
I::FieldLayout: Into<J::FieldLayout>,
I::OpaqueLayout: Into<J::OpaqueLayout>,
{
Type {
layout: self.layout.into(),
annotations: self.annotations,
variant: self.variant.into(),
}
}
}
/// An annotation of a type or field.
///
/// Builtin types, arrays, and opaque types cannot be annotated.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum Annotation {
/// The `PragmaPack` annotation.
///
/// This cannot be used on fields. At most one of these can be used on a type.
///
/// If the argument is `n`, it corresponds to `#pragma pack(n/8)` in C.
/// If `n` is not a multiple of 8, this annotation will be ignored.
PragmaPack(u64),
/// The `AttrPacked` annotation.
///
/// This corresponds to `__attribute__((packed))` in C. On MSVC targets, the behavior
/// is the behavior of Clang.
AttrPacked,
/// The `Aligned` annotation.
///
/// If the argument is `Some(n)`, `n` must be a power of two and at least 8. It is the
/// corresponding C argument but in bits instead of bytes.
///
/// If the argument is `Some(n)`, it corresponds to `__declspec(align(n/8))` on MSVC
/// targets and `__attribute__((aligned(n/8)))` otherwise.
///
/// If the argument is `None`, it corresponds to `__attribute__((aligned))`. On MSVC
/// targets, the behavior is the behavior of Clang.
Align(Option<u64>),
}
/// A collection of types encoding the layout of a type.
pub trait Layout {
/// The type used to encode the layout of the type itself.
type TypeLayout: Copy + Default + Debug + Eq + PartialEq;
/// The type used to encode the layout of a field in a record.
type FieldLayout: Copy + Default + Debug + Eq + PartialEq;
/// The type used to encode the layout of an opaque type.
type OpaqueLayout: Copy + Default + Debug + Eq + PartialEq;
}
/// The computed layout of a type.
#[derive(Copy, Clone, Debug, Eq, PartialEq, Default)]
pub struct TypeLayout {
/// The size of the type in bits.
///
/// This is the value returned by `sizeof` and C and `std::mem::size_of` in Rust
/// (but in bits instead of bytes). This is a multiple of `pointer_alignment_bits`.
pub size_bits: u64,
/// The alignment of the type, in bits, when used as a field in a record.
///
/// This is usually the value returned by `_Alignof` in C, but there are some edge
/// cases in GCC where `_Alignof` returns a smaller value.
pub field_alignment_bits: u64,
/// The alignment, in bits, of valid pointers to this type.
///
/// This is the value returned by `std::mem::align_of` in Rust
/// (but in bits instead of bytes). `size_bits` is a multiple of this value.
pub pointer_alignment_bits: u64,
/// The required alignment of the type in bits.
///
/// This value is only used by MSVC targets. It is 8 on all other
/// targets. On MSVC targets, this value restricts the effects of `#pragma pack` except
/// in some cases involving bit-fields.
pub required_alignment_bits: u64,
}
/// The layout of a field.
#[derive(Copy, Clone, Debug, Eq, PartialEq, Default)]
pub struct FieldLayout {
/// The offset of the struct, in bits, from the start of the struct.
pub offset_bits: u64,
/// The size, in bits, of the field.
///
/// For bit-fields, this is the width of the field.
pub size_bits: u64,
}
impl Layout for TypeLayout {
type TypeLayout = TypeLayout;
type FieldLayout = FieldLayout;
type OpaqueLayout = TypeLayout;
}
impl Layout for () {
type TypeLayout = ();
type FieldLayout = ();
type OpaqueLayout = TypeLayout;
}
impl Into<()> for TypeLayout {
fn into(self) {}
}
impl Into<()> for FieldLayout {
fn into(self) {}
}
/// An enum of all available types.
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum TypeVariant<I: Layout> {
/// A builtin type.
Builtin(BuiltinType),
/// A record. Struct or union.
Record(Record<I>),
/// A typedef.
///
/// The box contains the target type.
Typedef(Box<Type<I>>),
/// An array.
Array(Array<I>),
/// An enum.
///
/// The vector contains the values of the variants.
Enum(Vec<i128>),
/// An opaque type.
///
/// This does not correspond to anything in C. It is useful if the layout of a nested
/// type is already known and should not be recomputed. On all supported targets,
/// substituting a type for the opaque type with the same layout leads to the same
/// layout for the containing type.
Opaque(I::OpaqueLayout),
}
impl<I: Layout> TypeVariant<I> {
/// Returns the identical type variant with the [`Layout`] converted.
pub fn into<J: Layout>(self) -> TypeVariant<J>
where
I::TypeLayout: Into<J::TypeLayout>,
I::FieldLayout: Into<J::FieldLayout>,
I::OpaqueLayout: Into<J::OpaqueLayout>,
{
match self {
TypeVariant::Builtin(bi) => TypeVariant::Builtin(bi),
TypeVariant::Record(rt) => TypeVariant::Record(Record {
kind: rt.kind,
fields: rt.fields.into_iter().map(|v| v.into()).collect(),
}),
TypeVariant::Typedef(td) => TypeVariant::Typedef(Box::new((*td).into())),
TypeVariant::Array(at) => TypeVariant::Array(Array {
element_type: Box::new((*at.element_type).into()),
num_elements: at.num_elements,
}),
TypeVariant::Opaque(l) => TypeVariant::Opaque(l.into()),
TypeVariant::Enum(v) => TypeVariant::Enum(v),
}
}
}
/// A record.
///
/// This corresponds to a struct or a union in C.
///
/// # Example
///
/// ```c
/// #pragma pack(8)
/// struct {
/// int i __attribute__((aligned(16)));
/// char :1;
/// };
/// ```
///
/// ```
/// # use repc_impl::layout::{Record, RecordKind, RecordField, Annotation, Type, TypeVariant, BuiltinType};
/// Type::<()> {
/// layout: (),
/// annotations: vec!(Annotation::PragmaPack(64)),
/// variant: TypeVariant::Record(Record::<()> {
/// kind: RecordKind::Struct,
/// fields: vec![
/// RecordField {
/// layout: None,
/// annotations: vec!(Annotation::Align(Some(128))),
/// named: true,
/// bit_width: None,
/// ty: Type {
/// layout: (),
/// annotations: vec!(),
/// variant: TypeVariant::Builtin(BuiltinType::Int),
/// },
/// },
/// RecordField {
/// layout: None,
/// annotations: vec!(),
/// named: false,
/// bit_width: Some(1),
/// ty: Type {
/// layout: (),
/// annotations: vec!(),
/// variant: TypeVariant::Builtin(BuiltinType::Char),
/// },
/// },
/// ],
/// }),
/// };
/// ```
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Record<I: Layout> {
/// The type of the record. Struct or union.
pub kind: RecordKind,
/// The fields of the record.
pub fields: Vec<RecordField<I>>,
}
/// An array.
///
/// This corresponds to the type of `T var[N]` in C.
///
/// # Example
///
/// ```c
/// int i[1];
/// ```
///
/// ```
/// # use repc_impl::layout::{Type, TypeVariant, Array, BuiltinType};
/// Array::<()> {
/// element_type: Box::new(Type {
/// layout: (),
/// annotations: vec!(),
/// variant: TypeVariant::Builtin(BuiltinType::Int),
/// }),
/// num_elements: Some(1),
/// };
/// ```
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Array<I: Layout> {
/// The type of elements of the array.
pub element_type: Box<Type<I>>,
/// The number of elements in the array.
///
/// If this is `None`, it corresponds to a flexible array in C.
pub num_elements: Option<u64>,
}
/// A field of a record.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct RecordField<I: Layout> {
/// The layout of the field.
///
/// This is `None` for unnamed fields.
pub layout: Option<I::FieldLayout>,
/// The annotations on this field.
pub annotations: Vec<Annotation>,
/// Whether the field is named.
///
/// An unnamed field in C is always a bit-field and is declared like `T : N` where
/// `T` is the type of the field and `N` is the width of the bit-field.
pub named: bool,
/// If this is a bit-field, the width of the field.
///
/// The field is recognized as a bit-field if and only if this is `Some`.
pub bit_width: Option<u64>,
/// The type of the field.
pub ty: Type<I>,
}
impl<I: Layout> RecordField<I> {
/// Returns the identical record field with the [`Layout`] converted.
pub fn into<J: Layout>(self) -> RecordField<J>
where
I::TypeLayout: Into<J::TypeLayout>,
I::FieldLayout: Into<J::FieldLayout>,
I::OpaqueLayout: Into<J::OpaqueLayout>,
{
RecordField {
layout: self.layout.map(|v| v.into()),
annotations: self.annotations,
named: self.named,
bit_width: self.bit_width,
ty: self.ty.into(),
}
}
}
/// The type of a record. Either a struct or a union.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum RecordKind {
/// A struct.
Struct,
/// A union.
Union,
}
/// A builtin type.
///
/// This includes both builtin Rust and C types. The Rust types will be treated like the
/// corresponding C types if possible. If the type does not exist on the target, the
/// results might not be meaningful.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum BuiltinType {
/// `()`
Unit,
/// `bool`
Bool,
/// `u8`
U8,
/// `u16`
U16,
/// `u32`
U32,
/// `u64`
U64,
/// `u128`
U128,
/// `i8`
I8,
/// `i16`
I16,
/// `i32`
I32,
/// `i64`
I64,
/// `i128`
I128,
/// `c_char`
Char,
/// `c_schar`
SignedChar,
/// `c_uchar`
UnsignedChar,
/// `c_short`
Short,
/// `c_ushort`
UnsignedShort,
/// `c_int`
Int,
/// `c_uint`
UnsignedInt,
/// `c_long`
Long,
/// `c_ulong`
UnsignedLong,
/// `c_longlong`
LongLong,
/// `c_ulonglong`
UnsignedLongLong,
/// `f32`
F32,
/// `f64`
F64,
/// `c_float`
Float,
/// `c_double`
Double,
/// `*const T`,`*mut T`, `&T`, `&mut T` for sized `T`; `fn()`, `Option<fn()>`, etc.
Pointer,
}