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Fri, 10 Jan 2025 10:46:49 -0800 (PST) X-Google-Smtp-Source: AGHT+IGZNtxcF55o60VmqOVUIE+KIBufqGCdUqcSEtMDqK+albPDR+2ofPFhcgVnrPoRnId0rX2fkQ== X-Received: by 2002:a05:6402:270d:b0:5d3:d4cf:fea0 with SMTP id 4fb4d7f45d1cf-5d972e4c62emr9669946a12.21.1736534808928; Fri, 10 Jan 2025 10:46:48 -0800 (PST) From: Paolo Bonzini To: qemu-devel@nongnu.org Cc: Zhao Liu Subject: [PULL 12/38] rust: qemu-api-macros: add automatic TryFrom/TryInto derivation Date: Fri, 10 Jan 2025 19:45:53 +0100 Message-ID: <20250110184620.408302-13-pbonzini@redhat.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250110184620.408302-1-pbonzini@redhat.com> References: <20250110184620.408302-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.432, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1736534995127019000 Content-Type: text/plain; charset="utf-8" This is going to be fairly common. Using a custom procedural macro provides better error messages and automatically finds the right type. Note that this is different from the same-named macro in the derive_more crate. That one provides conversion from e.g. tuples to enums with tuple variants, not from integers to enums. Reviewed-by: Zhao Liu Signed-off-by: Paolo Bonzini --- rust/hw/char/pl011/src/lib.rs | 28 +------------ rust/qemu-api-macros/src/lib.rs | 74 ++++++++++++++++++++++++++++++++- 2 files changed, 73 insertions(+), 29 deletions(-) diff --git a/rust/hw/char/pl011/src/lib.rs b/rust/hw/char/pl011/src/lib.rs index 69064d6929b..0a89d393e0f 100644 --- a/rust/hw/char/pl011/src/lib.rs +++ b/rust/hw/char/pl011/src/lib.rs @@ -45,7 +45,7 @@ #[doc(alias =3D "offset")] #[allow(non_camel_case_types)] #[repr(u64)] -#[derive(Debug)] +#[derive(Debug, qemu_api_macros::TryInto)] pub enum RegisterOffset { /// Data Register /// @@ -102,32 +102,6 @@ pub enum RegisterOffset { //Reserved =3D 0x04C, } =20 -impl core::convert::TryFrom for RegisterOffset { - type Error =3D u64; - - fn try_from(value: u64) -> Result { - macro_rules! case { - ($($discriminant:ident),*$(,)*) =3D> { - /* check that matching on all macro arguments compiles, wh= ich means we are not - * missing any enum value; if the type definition ever cha= nges this will stop - * compiling. - */ - const fn _assert_exhaustive(val: RegisterOffset) { - match val { - $(RegisterOffset::$discriminant =3D> (),)* - } - } - - match value { - $(x if x =3D=3D Self::$discriminant as u64 =3D> Ok(Sel= f::$discriminant),)* - _ =3D> Err(value), - } - } - } - case! { DR, RSR, FR, FBRD, ILPR, IBRD, LCR_H, CR, FLS, IMSC, RIS, = MIS, ICR, DMACR } - } -} - pub mod registers { //! Device registers exposed as typed structs which are backed by arbi= trary //! integer bitmaps. [`Data`], [`Control`], [`LineControl`], etc. diff --git a/rust/qemu-api-macros/src/lib.rs b/rust/qemu-api-macros/src/lib= .rs index 539c48df298..7ec218202f4 100644 --- a/rust/qemu-api-macros/src/lib.rs +++ b/rust/qemu-api-macros/src/lib.rs @@ -5,8 +5,8 @@ use proc_macro::TokenStream; use quote::quote; use syn::{ - parse_macro_input, parse_quote, punctuated::Punctuated, token::Comma, = Data, DeriveInput, Field, - Fields, Ident, Type, Visibility, + parse_macro_input, parse_quote, punctuated::Punctuated, spanned::Spann= ed, token::Comma, Data, + DeriveInput, Field, Fields, Ident, Meta, Path, Token, Type, Variant, V= isibility, }; =20 mod utils; @@ -98,3 +98,73 @@ pub fn derive_offsets(input: TokenStream) -> TokenStream= { =20 TokenStream::from(expanded) } + +#[allow(non_snake_case)] +fn get_repr_uN(input: &DeriveInput, msg: &str) -> Result= { + let repr =3D input.attrs.iter().find(|attr| attr.path().is_ident("repr= ")); + if let Some(repr) =3D repr { + let nested =3D repr.parse_args_with(Punctuated:::= :parse_terminated)?; + for meta in nested { + match meta { + Meta::Path(path) if path.is_ident("u8") =3D> return Ok(pat= h), + Meta::Path(path) if path.is_ident("u16") =3D> return Ok(pa= th), + Meta::Path(path) if path.is_ident("u32") =3D> return Ok(pa= th), + Meta::Path(path) if path.is_ident("u64") =3D> return Ok(pa= th), + _ =3D> {} + } + } + } + + Err(MacroError::Message( + format!("#[repr(u8/u16/u32/u64) required for {}", msg), + input.ident.span(), + )) +} + +fn get_variants(input: &DeriveInput) -> Result<&Punctuated= , MacroError> { + if let Data::Enum(e) =3D &input.data { + if let Some(v) =3D e.variants.iter().find(|v| v.fields !=3D Fields= ::Unit) { + return Err(MacroError::Message( + "Cannot derive TryInto for enum with non-unit variants.".t= o_string(), + v.fields.span(), + )); + } + Ok(&e.variants) + } else { + Err(MacroError::Message( + "Cannot derive TryInto for union or struct.".to_string(), + input.ident.span(), + )) + } +} + +#[rustfmt::skip::macros(quote)] +fn derive_tryinto_or_error(input: DeriveInput) -> Result { + let repr =3D get_repr_uN(&input, "#[derive(TryInto)]")?; + + let name =3D &input.ident; + let variants =3D get_variants(&input)?; + let discriminants: Vec<&Ident> =3D variants.iter().map(|f| &f.ident).c= ollect(); + + Ok(quote! { + impl core::convert::TryFrom<#repr> for #name { + type Error =3D #repr; + + fn try_from(value: #repr) -> Result { + #(const #discriminants: #repr =3D #name::#discriminants as= #repr;)*; + match value { + #(#discriminants =3D> Ok(Self::#discriminants),)* + _ =3D> Err(value), + } + } + } + }) +} + +#[proc_macro_derive(TryInto)] +pub fn derive_tryinto(input: TokenStream) -> TokenStream { + let input =3D parse_macro_input!(input as DeriveInput); + let expanded =3D derive_tryinto_or_error(input).unwrap_or_else(Into::i= nto); + + TokenStream::from(expanded) +} --=20 2.47.1