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// Copyright 2024 Gabriel Bjørnager Jensen.
//
// This file is part of bzipper.
//
// bzipper is free software: you can redistribute
// it and/or modify it under the terms of the GNU
// Lesser General Public License as published by
// the Free Software Foundation, either version 3
// of the License, or (at your option) any later
// version.
//
// bzipper is distributed in the hope that it will
// be useful, but WITHOUT ANY WARRANTY; without
// even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Less-
// er General Public License along with bzipper. If
// not, see <https://www.gnu.org/licenses/>.
use crate::Capture;
use proc_macro2::{Span, TokenStream};
use quote::quote;
use syn::{DataEnum, Fields, Ident, Token};
use syn::punctuated::Punctuated;
#[must_use]
pub fn serialise_enum(data: &DataEnum) -> TokenStream {
let mut sizes = Vec::new();
let mut match_arms = Punctuated::<TokenStream, Token![,]>::new();
for (index, variant) in data.variants.iter().enumerate() {
let mut serialised_size = Punctuated::<TokenStream, Token![+]>::new();
let name = &variant.ident;
let discriminant = u32::try_from(index)
.expect("enumeration discriminants must be representable in `u32`");
// Discriminant size:
serialised_size.push(quote! { <u32 as ::bzipper::Serialise>::SERIALISED_SIZE });
let arm = if matches!(variant.fields, Fields::Unit) {
quote! { Self::#name => stream.append(&#discriminant)? }
} else {
let mut captures = Punctuated::<Capture, Token![,]>::new();
let mut chain_commands = Punctuated::<TokenStream, Token![;]>::new();
chain_commands.push(quote! { stream.append(&#discriminant)? });
for (index, field) in variant.fields.iter().enumerate() {
let field_ty = &field.ty;
let field_name = field.ident
.as_ref()
.map_or_else(|| Ident::new(&format!("v{index}"), Span::call_site()), Clone::clone);
serialised_size.push(quote! { <#field_ty as ::bzipper::Serialise>::SERIALISED_SIZE });
captures.push(Capture {
ref_token: Token),
ident: field_name.clone(),
});
chain_commands.push(quote! { stream.append(#field_name)? });
}
chain_commands.push_punct(Token));
match variant.fields {
Fields::Named( ..) => quote! { Self::#name { #captures } => { #chain_commands } },
Fields::Unnamed(..) => quote! { Self::#name(#captures) => { #chain_commands } },
Fields::Unit => unreachable!(),
}
};
sizes.push(serialised_size);
match_arms.push(arm);
}
let mut size_tests = Punctuated::<TokenStream, Token![else]>::new();
for size in &sizes {
let mut test = Punctuated::<TokenStream, Token![&&]>::new();
for other_size in &sizes { test.push(quote! { #size >= #other_size }) }
size_tests.push(quote! { if #test { #size } });
}
size_tests.push(quote! { { core::unreachable!(); } });
quote! {
const SERIALISED_SIZE: usize = const { #size_tests };
fn serialise(&self, buf: &mut [u8]) -> ::bzipper::Result<()> {
::core::debug_assert_eq!(buf.len(), Self::SERIALISED_SIZE);
let mut stream = ::bzipper::Sstream::new(buf);
match (*self) { #match_arms }
Ok(())
}
}
}
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