1 files changed, 262 insertions, 0 deletions
diff --git a/rust/qemu-api-macros/src/lib.rs b/rust/qemu-api-macros/src/lib.rs
new file mode 100644
index 0000000..c18bb4e
--- /dev/null
+++ b/rust/qemu-api-macros/src/lib.rs
@@ -0,0 +1,262 @@
+// Copyright 2024, Linaro Limited
+// Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{
+    parse_macro_input, parse_quote, punctuated::Punctuated, spanned::Spanned, token::Comma, Data,
+    DeriveInput, Field, Fields, FieldsUnnamed, Ident, Meta, Path, Token, Variant,
+};
+
+mod utils;
+use utils::MacroError;
+
+mod bits;
+use bits::BitsConstInternal;
+
+fn get_fields<'a>(
+    input: &'a DeriveInput,
+    msg: &str,
+) -> Result<&'a Punctuated<Field, Comma>, MacroError> {
+    let Data::Struct(ref s) = &input.data else {
+        return Err(MacroError::Message(
+            format!("Struct required for {msg}"),
+            input.ident.span(),
+        ));
+    };
+    let Fields::Named(ref fs) = &s.fields else {
+        return Err(MacroError::Message(
+            format!("Named fields required for {msg}"),
+            input.ident.span(),
+        ));
+    };
+    Ok(&fs.named)
+}
+
+fn get_unnamed_field<'a>(input: &'a DeriveInput, msg: &str) -> Result<&'a Field, MacroError> {
+    let Data::Struct(ref s) = &input.data else {
+        return Err(MacroError::Message(
+            format!("Struct required for {msg}"),
+            input.ident.span(),
+        ));
+    };
+    let Fields::Unnamed(FieldsUnnamed { ref unnamed, .. }) = &s.fields else {
+        return Err(MacroError::Message(
+            format!("Tuple struct required for {msg}"),
+            s.fields.span(),
+        ));
+    };
+    if unnamed.len() != 1 {
+        return Err(MacroError::Message(
+            format!("A single field is required for {msg}"),
+            s.fields.span(),
+        ));
+    }
+    Ok(&unnamed[0])
+}
+
+fn is_c_repr(input: &DeriveInput, msg: &str) -> Result<(), MacroError> {
+    let expected = parse_quote! { #[repr(C)] };
+
+    if input.attrs.iter().any(|attr| attr == &expected) {
+        Ok(())
+    } else {
+        Err(MacroError::Message(
+            format!("#[repr(C)] required for {msg}"),
+            input.ident.span(),
+        ))
+    }
+}
+
+fn is_transparent_repr(input: &DeriveInput, msg: &str) -> Result<(), MacroError> {
+    let expected = parse_quote! { #[repr(transparent)] };
+
+    if input.attrs.iter().any(|attr| attr == &expected) {
+        Ok(())
+    } else {
+        Err(MacroError::Message(
+            format!("#[repr(transparent)] required for {msg}"),
+            input.ident.span(),
+        ))
+    }
+}
+
+fn derive_object_or_error(input: DeriveInput) -> Result<proc_macro2::TokenStream, MacroError> {
+    is_c_repr(&input, "#[derive(Object)]")?;
+
+    let name = &input.ident;
+    let parent = &get_fields(&input, "#[derive(Object)]")?[0].ident;
+
+    Ok(quote! {
+        ::qemu_api::assert_field_type!(#name, #parent,
+            ::qemu_api::qom::ParentField<<#name as ::qemu_api::qom::ObjectImpl>::ParentType>);
+
+        ::qemu_api::module_init! {
+            MODULE_INIT_QOM => unsafe {
+                ::qemu_api::bindings::type_register_static(&<#name as ::qemu_api::qom::ObjectImpl>::TYPE_INFO);
+            }
+        }
+    })
+}
+
+#[proc_macro_derive(Object)]
+pub fn derive_object(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    let expanded = derive_object_or_error(input).unwrap_or_else(Into::into);
+
+    TokenStream::from(expanded)
+}
+
+fn derive_opaque_or_error(input: DeriveInput) -> Result<proc_macro2::TokenStream, MacroError> {
+    is_transparent_repr(&input, "#[derive(Wrapper)]")?;
+
+    let name = &input.ident;
+    let field = &get_unnamed_field(&input, "#[derive(Wrapper)]")?;
+    let typ = &field.ty;
+
+    // TODO: how to add "::qemu_api"?  For now, this is only used in the
+    // qemu_api crate so it's not a problem.
+    Ok(quote! {
+        unsafe impl crate::cell::Wrapper for #name {
+            type Wrapped = <#typ as crate::cell::Wrapper>::Wrapped;
+        }
+        impl #name {
+            pub unsafe fn from_raw<'a>(ptr: *mut <Self as crate::cell::Wrapper>::Wrapped) -> &'a Self {
+                let ptr = ::std::ptr::NonNull::new(ptr).unwrap().cast::<Self>();
+                unsafe { ptr.as_ref() }
+            }
+
+            pub const fn as_mut_ptr(&self) -> *mut <Self as crate::cell::Wrapper>::Wrapped {
+                self.0.as_mut_ptr()
+            }
+
+            pub const fn as_ptr(&self) -> *const <Self as crate::cell::Wrapper>::Wrapped {
+                self.0.as_ptr()
+            }
+
+            pub const fn as_void_ptr(&self) -> *mut ::core::ffi::c_void {
+                self.0.as_void_ptr()
+            }
+
+            pub const fn raw_get(slot: *mut Self) -> *mut <Self as crate::cell::Wrapper>::Wrapped {
+                slot.cast()
+            }
+        }
+    })
+}
+
+#[proc_macro_derive(Wrapper)]
+pub fn derive_opaque(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    let expanded = derive_opaque_or_error(input).unwrap_or_else(Into::into);
+
+    TokenStream::from(expanded)
+}
+
+#[allow(non_snake_case)]
+fn get_repr_uN(input: &DeriveInput, msg: &str) -> Result<Path, MacroError> {
+    let repr = input.attrs.iter().find(|attr| attr.path().is_ident("repr"));
+    if let Some(repr) = repr {
+        let nested = repr.parse_args_with(Punctuated::<Meta, Token![,]>::parse_terminated)?;
+        for meta in nested {
+            match meta {
+                Meta::Path(path) if path.is_ident("u8") => return Ok(path),
+                Meta::Path(path) if path.is_ident("u16") => return Ok(path),
+                Meta::Path(path) if path.is_ident("u32") => return Ok(path),
+                Meta::Path(path) if path.is_ident("u64") => return Ok(path),
+                _ => {}
+            }
+        }
+    }
+
+    Err(MacroError::Message(
+        format!("#[repr(u8/u16/u32/u64) required for {msg}"),
+        input.ident.span(),
+    ))
+}
+
+fn get_variants(input: &DeriveInput) -> Result<&Punctuated<Variant, Comma>, MacroError> {
+    let Data::Enum(ref e) = &input.data else {
+        return Err(MacroError::Message(
+            "Cannot derive TryInto for union or struct.".to_string(),
+            input.ident.span(),
+        ));
+    };
+    if let Some(v) = e.variants.iter().find(|v| v.fields != Fields::Unit) {
+        return Err(MacroError::Message(
+            "Cannot derive TryInto for enum with non-unit variants.".to_string(),
+            v.fields.span(),
+        ));
+    }
+    Ok(&e.variants)
+}
+
+#[rustfmt::skip::macros(quote)]
+fn derive_tryinto_body(
+    name: &Ident,
+    variants: &Punctuated<Variant, Comma>,
+    repr: &Path,
+) -> Result<proc_macro2::TokenStream, MacroError> {
+    let discriminants: Vec<&Ident> = variants.iter().map(|f| &f.ident).collect();
+
+    Ok(quote! {
+        #(const #discriminants: #repr = #name::#discriminants as #repr;)*;
+        match value {
+            #(#discriminants => core::result::Result::Ok(#name::#discriminants),)*
+            _ => core::result::Result::Err(value),
+        }
+    })
+}
+
+#[rustfmt::skip::macros(quote)]
+fn derive_tryinto_or_error(input: DeriveInput) -> Result<proc_macro2::TokenStream, MacroError> {
+    let repr = get_repr_uN(&input, "#[derive(TryInto)]")?;
+    let name = &input.ident;
+    let body = derive_tryinto_body(name, get_variants(&input)?, &repr)?;
+    let errmsg = format!("invalid value for {name}");
+
+    Ok(quote! {
+        impl #name {
+            #[allow(dead_code)]
+            pub const fn into_bits(self) -> #repr {
+                self as #repr
+            }
+
+            #[allow(dead_code)]
+            pub const fn from_bits(value: #repr) -> Self {
+                match ({
+                    #body
+                }) {
+                    Ok(x) => x,
+                    Err(_) => panic!(#errmsg)
+                }
+            }
+        }
+        impl core::convert::TryFrom<#repr> for #name {
+            type Error = #repr;
+
+            #[allow(ambiguous_associated_items)]
+            fn try_from(value: #repr) -> Result<Self, #repr> {
+                #body
+            }
+        }
+    })
+}
+
+#[proc_macro_derive(TryInto)]
+pub fn derive_tryinto(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    let expanded = derive_tryinto_or_error(input).unwrap_or_else(Into::into);
+
+    TokenStream::from(expanded)
+}
+
+#[proc_macro]
+pub fn bits_const_internal(ts: TokenStream) -> TokenStream {
+    let ts = proc_macro2::TokenStream::from(ts);
+    let mut it = ts.into_iter();
+
+    let expanded = BitsConstInternal::parse(&mut it).unwrap_or_else(Into::into);
+    TokenStream::from(expanded)
+}