motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-01 14:53:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

rust: qemu-api-macros: add from_bits and into_bits to #[derive(TryInto)]

Browse source 
These const functions make it possible to use enums easily together
with the bitfield-struct crate.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2025-05-13 13:04:41 +02:00
parent 9c8ff2a1ed
commit 214518614c
1 changed files with 38 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

48
rust/qemu-api-macros/src/lib.rs
View file

@ -193,23 +193,51 @@ fn get_variants(input: &DeriveInput) -> Result<&Punctuated<Variant, Comma>, Macr
}
#[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 variants = get_variants(&input)?;
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 => Ok(#name::#discriminants),)*
_ => 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;
fn try_from(value: #repr) -> Result<Self, Self::Error> {
#(const #discriminants: #repr = #name::#discriminants as #repr;)*;
match value {
#(#discriminants => Ok(Self::#discriminants),)*
_ => Err(value),
}
#body
}
}
})