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Wed, 21 May 2025 01:18:55 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFcK8YTwPUKcO65rs2si2DQU9nhEw3TQ5CTI6CUM2IeHnAm8wcOmtgnkQnf+sn8QKK4TIOxHw== X-Received: by 2002:a05:600c:3e8d:b0:43d:174:2668 with SMTP id 5b1f17b1804b1-442f844e5d4mr208403745e9.0.1747815534893; Wed, 21 May 2025 01:18:54 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, qemu-rust@nongnu.org, manos.pitsidianakis@linaro.org Subject: [RFC PATCH 3/6] rust: qemu-api-macros: add from_bits and into_bits to #[derive(TryInto)] Date: Wed, 21 May 2025 10:18:42 +0200 Message-ID: <20250521081845.496442-4-pbonzini@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250521081845.496442-1-pbonzini@redhat.com> References: <20250521081845.496442-1-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: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.487, 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_H5=0.001, RCVD_IN_MSPIKE_WL=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=unavailable 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: 1747815595301116600 Content-Type: text/plain; charset="utf-8" These const functions make it possible to use enums easily together with the bitfield-struct crate. Signed-off-by: Paolo Bonzini --- rust/qemu-api-macros/src/lib.rs | 48 ++++++++++++++++++++++++++------- 1 file changed, 38 insertions(+), 10 deletions(-) diff --git a/rust/qemu-api-macros/src/lib.rs b/rust/qemu-api-macros/src/lib= .rs index ceb79f09f97..103470785e3 100644 --- a/rust/qemu-api-macros/src/lib.rs +++ b/rust/qemu-api-macros/src/lib.rs @@ -193,23 +193,51 @@ fn get_variants(input: &DeriveInput) -> Result<&Punct= uated, Macr } =20 #[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)?; +fn derive_tryinto_body( + name: &Ident, + variants: &Punctuated, + repr: &Path, +) -> Result { let discriminants: Vec<&Ident> =3D variants.iter().map(|f| &f.ident).c= ollect(); =20 Ok(quote! { + #(const #discriminants: #repr =3D #name::#discriminants as #repr;)= *; + match value { + #(#discriminants =3D> Ok(#name::#discriminants),)* + _ =3D> Err(value), + } + }) +} + +#[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 body =3D derive_tryinto_body(name, get_variants(&input)?, &repr)?; + let errmsg =3D 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) =3D> x, + Err(_) =3D> panic!(#errmsg) + } + } + } impl core::convert::TryFrom<#repr> for #name { type Error =3D #repr; =20 fn try_from(value: #repr) -> Result { - #(const #discriminants: #repr =3D #name::#discriminants as= #repr;)*; - match value { - #(#discriminants =3D> Ok(Self::#discriminants),)* - _ =3D> Err(value), - } + #body } } }) --=20 2.49.0