to_shmem_derive/
to_shmem.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5use crate::util::{add_predicate, fmap2_match, parse_field_attrs, parse_input_attrs};
6use darling::{FromDeriveInput, FromField};
7use proc_macro2::TokenStream;
8use quote::quote;
9use syn::{self, parse_quote};
10use synstructure::{BindStyle, Structure};
11
12pub fn derive(mut input: syn::DeriveInput) -> TokenStream {
13    let mut where_clause = input.generics.where_clause.take();
14    let attrs = parse_input_attrs::<ShmemInputAttrs>(&input);
15    if !attrs.no_bounds {
16        for param in input.generics.type_params() {
17            add_predicate(&mut where_clause, parse_quote!(#param: ::to_shmem::ToShmem));
18        }
19    }
20    for variant in Structure::new(&input).variants() {
21        for binding in variant.bindings() {
22            let attrs = parse_field_attrs::<ShmemFieldAttrs>(&binding.ast());
23            if attrs.field_bound {
24                let ty = &binding.ast().ty;
25                add_predicate(&mut where_clause, parse_quote!(#ty: ::to_shmem::ToShmem))
26            }
27        }
28    }
29
30    input.generics.where_clause = where_clause;
31
32    // Do all of the `to_shmem()?` calls before the `ManuallyDrop::into_inner()`
33    // calls, so that we don't drop a value in the shared memory buffer if one
34    // of the `to_shmem`s fails.
35    let match_body = fmap2_match(
36        &input,
37        BindStyle::Ref,
38        |binding| {
39            quote! {
40                ::to_shmem::ToShmem::to_shmem(#binding, builder)?
41            }
42        },
43        |binding| {
44            Some(quote! {
45                ::std::mem::ManuallyDrop::into_inner(#binding)
46            })
47        },
48    );
49
50    let name = &input.ident;
51    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
52
53    quote! {
54        impl #impl_generics ::to_shmem::ToShmem for #name #ty_generics #where_clause {
55            #[allow(unused_variables, unreachable_code)]
56            fn to_shmem(
57                &self,
58                builder: &mut ::to_shmem::SharedMemoryBuilder,
59            ) -> ::to_shmem::Result<Self> {
60                Ok(::std::mem::ManuallyDrop::new(
61                    match *self {
62                        #match_body
63                    }
64                ))
65            }
66        }
67    }
68}
69
70#[derive(Default, FromDeriveInput)]
71#[darling(attributes(shmem), default)]
72pub struct ShmemInputAttrs {
73    pub no_bounds: bool,
74}
75
76#[derive(Default, FromField)]
77#[darling(attributes(shmem), default)]
78pub struct ShmemFieldAttrs {
79    pub field_bound: bool,
80}
to_shmem_derive/to_shmem.rs

to_shmem_derive/
to_shmem.rs
