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/*!
*/
use quote::quote;
use syn::spanned::Spanned;
/// Defines a COM interface to call or implement.
///
/// # Example
/// ```rust,ignore
/// #[interface("094d70d6-5202-44b8-abb8-43860da5aca2")]
/// unsafe trait IValue: IUnknown {
/// fn GetValue(&self, value: *mut i32) -> HRESULT;
/// }
///
/// #[implement(IValue)]
/// struct Value(i32);
///
/// impl IValue_Impl for Value {
/// unsafe fn GetValue(&self, value: *mut i32) -> HRESULT {
/// *value = self.0;
/// HRESULT(0)
/// }
/// }
///
/// fn main() {
/// let object: IValue = Value(123).into();
/// // Call interface methods...
/// }
/// ```
#[proc_macro_attribute]
pub fn interface(
attributes: proc_macro::TokenStream,
original_type: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
let guid = syn::parse_macro_input!(attributes as Guid);
let interface = syn::parse_macro_input!(original_type as Interface);
let tokens = match interface.gen_tokens(&guid) {
Ok(t) => t,
Err(e) => return e.to_compile_error().into(),
};
tokens.into()
}
macro_rules! bail {
($item:expr, $($msg:tt),*) => {
return Err(syn::Error::new($item.span(), std::fmt::format(format_args!($($msg),*))));
};
}
macro_rules! unexpected_token {
($item:expr, $msg:expr) => {
if let Some(i) = $item {
bail!(i, "unexpected {}", $msg);
}
};
}
macro_rules! expected_token {
($sig:tt.$item:tt(), $msg:expr) => {
if let None = $sig.$item() {
bail!($sig, "expected {}", $msg);
}
};
}
/// Parsed interface
///
/// ```rust,ignore
/// #[windows_interface::interface("8CEEB155-2849-4ce5-9448-91FF70E1E4D9")]
/// unsafe trait IUIAnimationVariable: IUnknown {
/// //^ parses this
/// fn GetValue(&self, value: *mut f64) -> HRESULT;
/// }
/// ```
struct Interface {
visibility: syn::Visibility,
name: syn::Ident,
parent: Option<syn::Path>,
methods: Vec<InterfaceMethod>,
docs: Vec<syn::Attribute>,
}
impl Interface {
/// Generates all the code needed for a COM interface
fn gen_tokens(&self, guid: &Guid) -> syn::Result<proc_macro2::TokenStream> {
let vis = &self.visibility;
let name = &self.name;
let docs = &self.docs;
let parent = self.parent_type();
let vtable_name = quote::format_ident!("{}_Vtbl", name);
let guid = guid.to_tokens()?;
let implementation = self.gen_implementation();
let com_trait = self.get_com_trait();
let vtable = self.gen_vtable(&vtable_name);
let conversions = self.gen_conversions();
Ok(quote! {
#[repr(transparent)]
#(#docs)*
#vis struct #name(#parent);
#implementation
unsafe impl ::windows_core::Interface for #name {
type Vtable = #vtable_name;
const IID: ::windows_core::GUID = #guid;
}
impl ::windows_core::RuntimeName for #name {}
impl ::core::ops::Deref for #name {
type Target = #parent;
fn deref(&self) -> &Self::Target {
unsafe { ::core::mem::transmute(self) }
}
}
#com_trait
#vtable
#conversions
})
}
/// Generates the methods users can call on the COM interface pointer
fn gen_implementation(&self) -> proc_macro2::TokenStream {
let name = &self.name;
let methods = self
.methods
.iter()
.map(|m| {
let vis = &m.visibility;
let name = &m.name;
let generics = m.gen_consume_generics();
let params = m.gen_consume_params();
let args = m.gen_consume_args();
let ret = &m.ret;
if m.is_result() {
quote! {
#[inline(always)]
#vis unsafe fn #name<#(#generics),*>(&self, #(#params),*) #ret {
(::windows_core::Interface::vtable(self).#name)(::windows_core::Interface::as_raw(self), #(#args),*).ok()
}
}
} else {
quote! {
#[inline(always)]
#vis unsafe fn #name<#(#generics),*>(&self, #(#params),*) #ret {
(::windows_core::Interface::vtable(self).#name)(::windows_core::Interface::as_raw(self), #(#args),*)
}
}
}
})
.collect::<Vec<_>>();
quote! {
impl #name {
#(#methods)*
}
}
}
fn get_com_trait(&self) -> proc_macro2::TokenStream {
let name = quote::format_ident!("{}_Impl", self.name);
let vis = &self.visibility;
let methods = self
.methods
.iter()
.map(|m| {
let name = &m.name;
let docs = &m.docs;
let args = m.gen_args();
let ret = &m.ret;
quote! {
#(#docs)*
unsafe fn #name(&self, #(#args),*) #ret;
}
})
.collect::<Vec<_>>();
let parent = self.parent_trait_constraint();
quote! {
#[allow(non_camel_case_types)]
#vis trait #name: Sized + #parent {
#(#methods)*
}
}
}
/// Generates the vtable for a COM interface
fn gen_vtable(&self, vtable_name: &syn::Ident) -> proc_macro2::TokenStream {
let vis = &self.visibility;
let name = &self.name;
let trait_name = quote::format_ident!("{}_Impl", name);
let implvtbl_name = quote::format_ident!("{}_ImplVtbl", name);
let vtable_entries = self
.methods
.iter()
.map(|m| {
let name = &m.name;
let ret = &m.ret;
let args = m.gen_args();
if m.is_result() {
quote! {
pub #name: unsafe extern "system" fn(this: *mut ::core::ffi::c_void, #(#args),*) -> ::windows_core::HRESULT,
}
} else {
quote! {
pub #name: unsafe extern "system" fn(this: *mut ::core::ffi::c_void, #(#args),*) #ret,
}
}
})
.collect::<Vec<_>>();
let parent_vtable_generics = quote!(Identity, OFFSET);
let parent_vtable = self.parent_vtable();
// or_parent_matches will be `|| parent::matches(iid)` if this interface inherits from another
// interface (except for IUnknown) or will be empty if this is not applicable. This is what allows
// QueryInterface to work correctly for all interfaces in an inheritance chain, e.g.
// IFoo3 derives from IFoo2 derives from IFoo.
//
// We avoid matching IUnknown because object identity depends on the uniqueness of the IUnknown pointer.
let or_parent_matches = match parent_vtable.as_ref() {
Some(parent) if !self.parent_is_iunknown() => quote! (|| <#parent>::matches(iid)),
_ => quote!(),
};
let functions = self
.methods
.iter()
.map(|m| {
let name = &m.name;
let args = m.gen_args();
let params = &m
.args
.iter()
.map(|a| {
let pat = &a.pat;
quote! { #pat }
})
.collect::<Vec<_>>();
let ret = &m.ret;
let ret = if m.is_result() {
quote! { -> ::windows_core::HRESULT }
} else {
quote! { #ret }
};
if parent_vtable.is_some() {
quote! {
unsafe extern "system" fn #name<
Identity: ::windows_core::IUnknownImpl,
const OFFSET: isize
>(
this: *mut ::core::ffi::c_void, // <-- This is the COM "this" pointer, which is not the same as &T or &T_Impl.
#(#args),*
) #ret
where
Identity : #trait_name
{
// This step is essentially a virtual dispatch adjustor thunk. Its purpose is to adjust
// the "this" pointer from the address used by the COM interface to the root of the
// MyApp_Impl object. Since a given MyApp_Impl may implement more than one COM interface
// (and more than one COM interface chain), we need to know how to get from COM's "this"
// back to &MyApp_Impl. The OFFSET constant gives us the value (in pointer-sized units).
let this_outer: &Identity = &*((this as *const *const ()).offset(OFFSET) as *const Identity);
// Last, we invoke the implementation function.
// We use explicit <Impl as IFoo_Impl> so that we can select the correct method
// for situations where IFoo3 derives from IFoo2 and both declare a method with
// the same name.
<Identity as #trait_name>::#name(this_outer, #(#params),*).into()
}
}
} else {
quote! {
unsafe extern "system" fn #name<Impl: #trait_name>(this: *mut ::core::ffi::c_void, #(#args),*) #ret {
let this = (this as *mut *mut ::core::ffi::c_void) as *const ::windows_core::ScopedHeap;
let this = (*this).this as *const Impl;
(*this).#name(#(#params),*).into()
}
}
}
})
.collect::<Vec<_>>();
if let Some(parent_vtable) = parent_vtable {
let entries = self
.methods
.iter()
.map(|m| {
let name = &m.name;
quote!(#name: #name::<Identity, OFFSET>)
})
.collect::<Vec<_>>();
quote! {
#[repr(C)]
#[doc(hidden)]
#vis struct #vtable_name {
pub base__: #parent_vtable,
#(#vtable_entries)*
}
impl #vtable_name {
pub const fn new<
Identity: ::windows_core::IUnknownImpl,
const OFFSET: isize,
>() -> Self
where
Identity : #trait_name
{
#(#functions)*
Self { base__: #parent_vtable::new::<#parent_vtable_generics>(), #(#entries),* }
}
#[inline(always)]
pub fn matches(iid: &::windows_core::GUID) -> bool {
*iid == <#name as ::windows_core::Interface>::IID
#or_parent_matches
}
}
}
} else {
let entries = self
.methods
.iter()
.map(|m| {
let name = &m.name;
quote!(#name: #name::<Impl>)
})
.collect::<Vec<_>>();
quote! {
#[repr(C)]
#[doc(hidden)]
#vis struct #vtable_name {
#(#vtable_entries)*
}
impl #vtable_name {
pub const fn new<Impl: #trait_name>() -> Self {
#(#functions)*
Self { #(#entries),* }
}
}
struct #implvtbl_name<T: #trait_name> (::core::marker::PhantomData<T>);
impl<T: #trait_name> #implvtbl_name<T> {
const VTABLE: #vtable_name = #vtable_name::new::<T>();
}
impl #name {
fn new<'a, T: #trait_name>(this: &'a T) -> ::windows_core::ScopedInterface<'a, #name> {
let this = ::windows_core::ScopedHeap { vtable: &#implvtbl_name::<T>::VTABLE as *const _ as *const _, this: this as *const _ as *const _ };
let this = ::core::mem::ManuallyDrop::new(::windows_core::imp::Box::new(this));
unsafe { ::windows_core::ScopedInterface::new(::core::mem::transmute(&this.vtable)) }
}
}
}
}
}
/// Generates various conversions such as from and to `IUnknown`
fn gen_conversions(&self) -> proc_macro2::TokenStream {
let name = &self.name;
let name_string = format!("{name}");
quote! {
impl ::core::convert::From<#name> for ::windows_core::IUnknown {
fn from(value: #name) -> Self {
unsafe { ::core::mem::transmute(value) }
}
}
impl ::core::convert::From<&#name> for ::windows_core::IUnknown {
fn from(value: &#name) -> Self {
::core::convert::From::from(::core::clone::Clone::clone(value))
}
}
impl ::core::clone::Clone for #name {
fn clone(&self) -> Self {
Self(self.0.clone())
}
}
impl ::core::cmp::PartialEq for #name {
fn eq(&self, other: &Self) -> bool {
self.0 == other.0
}
}
impl ::core::cmp::Eq for #name {}
impl ::core::fmt::Debug for #name {
fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
f.debug_tuple(#name_string).field(&::windows_core::Interface::as_raw(self)).finish()
}
}
}
}
fn parent_type(&self) -> proc_macro2::TokenStream {
if let Some(parent) = &self.parent {
quote!(#parent)
} else {
quote!(::core::ptr::NonNull<::core::ffi::c_void>)
}
}
fn parent_vtable(&self) -> Option<proc_macro2::TokenStream> {
if let Some((ident, path)) = self.parent_path().split_last() {
let ident = quote::format_ident!("{}_Vtbl", ident);
Some(quote! { #(#path::)* #ident })
} else {
None
}
}
fn parent_is_iunknown(&self) -> bool {
if let Some(ident) = self.parent_path().last() {
ident == "IUnknown"
} else {
false
}
}
fn parent_path(&self) -> Vec<syn::Ident> {
if let Some(parent) = &self.parent {
parent
.segments
.iter()
.map(|segment| segment.ident.clone())
.collect()
} else {
vec![]
}
}
/// Gets the parent trait constrait which is nothing if the parent is IUnknown
fn parent_trait_constraint(&self) -> proc_macro2::TokenStream {
if let Some((ident, path)) = self.parent_path().split_last() {
if ident != "IUnknown" {
let ident = quote::format_ident!("{}_Impl", ident);
return quote! { #(#path::)* #ident };
}
}
quote! {}
}
}
impl syn::parse::Parse for Interface {
fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
let attributes = input.call(syn::Attribute::parse_outer)?;
let mut docs = Vec::new();
for attr in attributes.into_iter() {
let path = attr.path();
if path.is_ident("doc") {
docs.push(attr);
} else {
return Err(syn::Error::new(path.span(), "Unrecognized attribute "));
}
}
let visibility = input.parse::<syn::Visibility>()?;
_ = input.parse::<syn::Token![unsafe]>()?;
_ = input.parse::<syn::Token![trait]>()?;
let name = input.parse::<syn::Ident>()?;
_ = input.parse::<syn::Token![:]>();
let parent = input.parse::<syn::Path>().ok();
let content;
syn::braced!(content in input);
let mut methods = Vec::new();
while !content.is_empty() {
methods.push(content.parse::<InterfaceMethod>()?);
}
Ok(Self {
visibility,
methods,
name,
parent,
docs,
})
}
}
/// Parsed interface guid attribute
///
/// ```rust,ignore
/// #[windows_interface::interface("8CEEB155-2849-4ce5-9448-91FF70E1E4D9")]
/// //^ parses this
/// unsafe trait IUIAnimationVariable: IUnknown {
/// fn GetValue(&self, value: *mut f64) -> HRESULT;
/// }
/// ```
struct Guid(Option<syn::LitStr>);
impl Guid {
fn to_tokens(&self) -> syn::Result<proc_macro2::TokenStream> {
fn hex_lit(num: &str) -> syn::LitInt {
syn::LitInt::new(&format!("0x{num}"), proc_macro2::Span::call_site())
}
fn ensure_length(
part: Option<&str>,
index: usize,
length: usize,
span: proc_macro2::Span,
) -> syn::Result<String> {
let part = match part {
Some(p) => p,
None => {
return Err(syn::Error::new(
span,
format!("The IID missing part at index {index}"),
))
}
};
if part.len() != length {
return Err(syn::Error::new(
span,
format!(
"The IID part at index {} must be {} characters long but was {} characters",
index,
length,
part.len()
),
));
}
Ok(part.to_owned())
}
if let Some(value) = &self.0 {
let guid_value = value.value();
let mut delimited = guid_value.split('-').fuse();
let chunks = [
ensure_length(delimited.next(), 0, 8, value.span())?,
ensure_length(delimited.next(), 1, 4, value.span())?,
ensure_length(delimited.next(), 2, 4, value.span())?,
ensure_length(delimited.next(), 3, 4, value.span())?,
ensure_length(delimited.next(), 4, 12, value.span())?,
];
let data1 = hex_lit(&chunks[0]);
let data2 = hex_lit(&chunks[1]);
let data3 = hex_lit(&chunks[2]);
let (data4_1, data4_2) = chunks[3].split_at(2);
let data4_1 = hex_lit(data4_1);
let data4_2 = hex_lit(data4_2);
let (data4_3, rest) = chunks[4].split_at(2);
let data4_3 = hex_lit(data4_3);
let (data4_4, rest) = rest.split_at(2);
let data4_4 = hex_lit(data4_4);
let (data4_5, rest) = rest.split_at(2);
let data4_5 = hex_lit(data4_5);
let (data4_6, rest) = rest.split_at(2);
let data4_6 = hex_lit(data4_6);
let (data4_7, data4_8) = rest.split_at(2);
let data4_7 = hex_lit(data4_7);
let data4_8 = hex_lit(data4_8);
Ok(quote! {
::windows_core::GUID {
data1: #data1,
data2: #data2,
data3: #data3,
data4: [#data4_1, #data4_2, #data4_3, #data4_4, #data4_5, #data4_6, #data4_7, #data4_8]
}
})
} else {
Ok(quote! {
::windows_core::GUID::zeroed()
})
}
}
}
impl syn::parse::Parse for Guid {
fn parse(cursor: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
let string: Option<syn::LitStr> = cursor.parse().ok();
Ok(Self(string))
}
}
/// A parsed interface method
///
/// ```rust,ignore
/// #[windows_interface::interface("8CEEB155-2849-4ce5-9448-91FF70E1E4D9")]
/// unsafe trait IUIAnimationVariable: IUnknown {
/// fn GetValue(&self, value: *mut f64) -> HRESULT;
/// //^ parses this
/// }
/// ```
struct InterfaceMethod {
pub name: syn::Ident,
pub visibility: syn::Visibility,
pub args: Vec<InterfaceMethodArg>,
pub ret: syn::ReturnType,
pub docs: Vec<syn::Attribute>,
}
impl InterfaceMethod {
fn is_result(&self) -> bool {
if let syn::ReturnType::Type(_, ty) = &self.ret {
if let syn::Type::Path(path) = &**ty {
if let Some(segment) = path.path.segments.last() {
let ident = segment.ident.to_string();
if ident == "Result" {
if let syn::PathArguments::AngleBracketed(args) = &segment.arguments {
if args.args.len() == 1 {
return true;
}
}
}
}
}
}
false
}
/// Generates arguments (of the form `$pat: $type`)
fn gen_args(&self) -> Vec<proc_macro2::TokenStream> {
self.args
.iter()
.map(|a| {
let pat = &a.pat;
let ty = &a.ty;
quote! { #pat: #ty }
})
.collect::<Vec<_>>()
}
fn gen_consume_generics(&self) -> Vec<proc_macro2::TokenStream> {
self.args
.iter()
.enumerate()
.filter_map(|(generic_index, a)| {
if let Some((ty, ident)) = a.borrow_type() {
let generic_ident = quote::format_ident!("P{generic_index}");
if ident == "Ref" {
Some(quote! { #generic_ident: ::windows_core::Param<#ty> })
} else {
Some(quote! { #generic_ident: ::windows_core::OutParam<#ty> })
}
} else {
None
}
})
.collect::<Vec<_>>()
}
fn gen_consume_params(&self) -> Vec<proc_macro2::TokenStream> {
self.args
.iter()
.enumerate()
.map(|(generic_index, a)| {
let pat = &a.pat;
if a.borrow_type().is_some() {
let generic_ident = quote::format_ident!("P{generic_index}");
quote! { #pat: #generic_ident }
} else {
let ty = &a.ty;
quote! { #pat: #ty }
}
})
.collect::<Vec<_>>()
}
fn gen_consume_args(&self) -> Vec<proc_macro2::TokenStream> {
self.args
.iter()
.map(|a| {
let pat = &a.pat;
if let Some((_, ident)) = a.borrow_type() {
if ident == "Ref" {
quote! { #pat.param().borrow() }
} else {
quote! { #pat.borrow_mut() }
}
} else {
quote! { #pat }
}
})
.collect::<Vec<_>>()
}
}
impl syn::parse::Parse for InterfaceMethod {
fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
let docs = input.call(syn::Attribute::parse_outer)?;
let visibility = input.parse::<syn::Visibility>()?;
let method = input.parse::<syn::TraitItemFn>()?;
unexpected_token!(docs.iter().find(|a| !a.path().is_ident("doc")), "attribute");
unexpected_token!(method.default, "default method implementation");
let sig = method.sig;
unexpected_token!(sig.abi, "abi declaration");
unexpected_token!(sig.asyncness, "async declaration");
unexpected_token!(sig.generics.params.iter().next(), "generics declaration");
unexpected_token!(sig.constness, "const declaration");
expected_token!(
sig.receiver(),
"the method to have &self as its first argument"
);
unexpected_token!(sig.variadic, "variadic args");
let args = sig
.inputs
.into_iter()
.filter_map(|a| match a {
syn::FnArg::Receiver(_) => None,
syn::FnArg::Typed(p) => Some(p),
})
.map(|p| {
Ok(InterfaceMethodArg {
ty: p.ty,
pat: p.pat,
})
})
.collect::<Result<Vec<InterfaceMethodArg>, syn::Error>>()?;
let ret = sig.output;
Ok(InterfaceMethod {
name: sig.ident,
visibility,
args,
ret,
docs,
})
}
}
/// An argument to an interface method
struct InterfaceMethodArg {
/// The type of the argument
pub ty: Box<syn::Type>,
/// The name of the argument
pub pat: Box<syn::Pat>,
}
impl InterfaceMethodArg {
fn borrow_type(&self) -> Option<(syn::Type, String)> {
if let syn::Type::Path(path) = &*self.ty {
if let Some(segment) = path.path.segments.last() {
let ident = segment.ident.to_string();
if matches!(ident.as_str(), "Ref" | "OutRef") {
if let syn::PathArguments::AngleBracketed(args) = &segment.arguments {
if args.args.len() == 1 {
if let Some(syn::GenericArgument::Type(ty)) = args.args.first() {
return Some((ty.clone(), ident));
}
}
}
}
}
}
None
}
}