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use crate::attribute::BitcodeAttrs;
use crate::private;
use crate::shared::{remove_lifetimes, replace_lifetimes, variant_index};
use proc_macro2::{Ident, Span, TokenStream};
use quote::{quote, ToTokens};
use syn::{parse_quote, Generics, Path, Type};
#[derive(Copy, Clone)]
pub enum Item {
Type,
Default,
Encode,
EncodeVectored,
CollectInto,
Reserve,
}
impl Item {
const ALL: [Self; 6] = [
Self::Type,
Self::Default,
Self::Encode,
Self::EncodeVectored,
Self::CollectInto,
Self::Reserve,
];
const COUNT: usize = Self::ALL.len();
}
impl crate::shared::Item for Item {
fn field_impl(
self,
crate_name: &Path,
field_name: TokenStream,
global_field_name: TokenStream,
real_field_name: TokenStream,
field_type: &Type,
field_attrs: &BitcodeAttrs,
) -> TokenStream {
match self {
Self::Type => {
let mut static_type = replace_lifetimes(field_type, "static").to_token_stream();
if field_attrs.skip {
static_type = quote! { ::core::marker::PhantomData<#static_type> };
}
let private = private(crate_name);
quote! {
#global_field_name: <#static_type as #private::Encode>::Encoder,
}
}
Self::Default => quote! {
#global_field_name: Default::default(),
},
Self::Encode | Self::EncodeVectored => {
let static_type = replace_lifetimes(field_type, "static");
let value = if field_attrs.skip {
quote! {
{
let _ = #field_name;
&::core::marker::PhantomData::<#static_type>
}
}
} else if &static_type != field_type {
let underscore_type = replace_lifetimes(field_type, "_");
// HACK: Since encoders don't have lifetimes we can't reference <T<'a> as Encode>::Encoder since 'a
// does not exist. Instead we replace this with <T<'static> as Encode>::Encoder and transmute it to
// T<'a>. No encoder actually encodes T<'static> any differently from T<'a> so this is sound.
quote! {
unsafe { ::core::mem::transmute::<&#underscore_type, &#static_type>(#field_name) }
}
} else {
quote! { #field_name }
};
if matches!(self, Self::EncodeVectored) {
quote! {
self.#global_field_name.encode_vectored(i.clone().map(|me| {
let #field_name = &me.#real_field_name;
#value
}));
}
} else {
quote! {
self.#global_field_name.encode(#value);
}
}
}
Self::CollectInto => quote! {
self.#global_field_name.collect_into(out);
},
Self::Reserve => quote! {
self.#global_field_name.reserve(__additional);
},
}
}
fn struct_impl(
self,
ident: &Ident,
destructure_fields: &TokenStream,
do_fields: &TokenStream,
) -> TokenStream {
match self {
Self::Encode => {
quote! {
let #ident #destructure_fields = v;
#do_fields
}
}
_ => quote! { #do_fields },
}
}
fn enum_impl(
self,
crate_name: &Path,
variant_count: usize,
pattern: impl Fn(usize) -> TokenStream,
inner: impl Fn(Self, usize) -> TokenStream,
) -> TokenStream {
// if variant_count is 0 or 1 variants don't have to be encoded.
let encode_variants = variant_count > 1;
match self {
Self::Type => {
let variants = encode_variants
.then(|| {
let private = private(crate_name);
quote! { variants: #private::VariantEncoder<#variant_count>, }
})
.unwrap_or_default();
let inners: TokenStream = (0..variant_count).map(|i| inner(self, i)).collect();
quote! {
#variants
#inners
}
}
Self::Default => {
let variants = encode_variants
.then(|| quote! { variants: Default::default(), })
.unwrap_or_default();
let inners: TokenStream = (0..variant_count).map(|i| inner(self, i)).collect();
quote! {
#variants
#inners
}
}
Self::Encode => {
let variants = encode_variants
.then(|| {
let variants: TokenStream = (0..variant_count)
.map(|i| {
let pattern = pattern(i);
let i = variant_index(i);
quote! {
#pattern => #i,
}
})
.collect();
quote! {
#[allow(unused_variables, unused_assignments)]
self.variants.encode(&match v {
#variants
});
}
})
.unwrap_or_default();
let inners: TokenStream = (0..variant_count)
.map(|i| {
// We don't know the exact number of this variant since there is more than
// one, so we have to reserve one at a time.
let reserve = encode_variants
.then(|| {
let reserve = inner(Self::Reserve, i);
quote! {
let __additional = ::core::num::NonZeroUsize::MIN;
#reserve
}
})
.unwrap_or_default();
let inner = inner(self, i);
let pattern = pattern(i);
quote! {
#pattern => {
#reserve
#inner
}
}
})
.collect();
(variant_count != 0)
.then(|| {
quote! {
#variants
match v {
#inners
}
}
})
.unwrap_or_default()
}
// This is a copy of Encode::encode_vectored's default impl (which provides no speedup).
// TODO optimize enum encode_vectored.
Self::EncodeVectored => quote! {
for t in i {
self.encode(t);
}
},
Self::CollectInto => {
let variants = encode_variants
.then(|| {
quote! { self.variants.collect_into(out); }
})
.unwrap_or_default();
let inners: TokenStream = (0..variant_count).map(|i| inner(self, i)).collect();
quote! {
#variants
#inners
}
}
Self::Reserve => {
encode_variants
.then(|| {
quote! { self.variants.reserve(__additional); }
})
.or_else(|| {
(variant_count == 1).then(|| {
// We know the exact number of this variant since it's the only one so we can reserve it.
inner(self, 0)
})
})
.unwrap_or_default()
}
}
}
}
pub struct Encode;
impl crate::shared::Derive<{ Item::COUNT }> for Encode {
type Item = Item;
const ALL: [Self::Item; Item::COUNT] = Item::ALL;
fn bound(&self, crate_name: &Path) -> Path {
let private = private(crate_name);
parse_quote!(#private::Encode)
}
fn skip_bound(&self) -> Option<Path> {
None
}
fn derive_impl(
&self,
crate_name: &Path,
output: [TokenStream; Item::COUNT],
ident: Ident,
mut generics: Generics,
_any_static_borrow: bool,
) -> TokenStream {
let input_generics = generics.clone();
let (impl_generics, input_generics, where_clause) = input_generics.split_for_impl();
let input_ty = quote! { #ident #input_generics };
// Encoder can't contain any lifetimes from input (which would limit reuse of encoder).
remove_lifetimes(&mut generics);
let (encoder_impl_generics, encoder_generics, encoder_where_clause) =
generics.split_for_impl();
let [type_body, default_body, encode_body, encode_vectored_body, collect_into_body, reserve_body] =
output;
let encoder_ident = Ident::new(&format!("{ident}Encoder"), Span::call_site());
let encoder_ty = quote! { #encoder_ident #encoder_generics };
let private = private(crate_name);
quote! {
const _: () = {
impl #impl_generics #private::Encode for #input_ty #where_clause {
type Encoder = #encoder_ty;
}
#[allow(non_snake_case)]
pub struct #encoder_ident #encoder_impl_generics #encoder_where_clause {
#type_body
}
// Avoids bounding #impl_generics: Default.
impl #encoder_impl_generics ::core::default::Default for #encoder_ty #encoder_where_clause {
fn default() -> Self {
Self {
#default_body
}
}
}
impl #impl_generics #private::Encoder<#input_ty> for #encoder_ty #where_clause {
#[cfg_attr(not(debug_assertions), inline(always))]
fn encode(&mut self, v: &#input_ty) {
#[allow(unused_imports)]
use #private::Buffer as _;
#encode_body
}
// #[cfg_attr(not(debug_assertions), inline(always))]
// #[inline(never)]
fn encode_vectored<'__v>(&mut self, #[allow(unused)] i: impl Iterator<Item = &'__v #input_ty> + Clone) where #input_ty: '__v {
#[allow(unused_imports)]
use #private::Buffer as _;
#encode_vectored_body
}
}
impl #encoder_impl_generics #private::Buffer for #encoder_ty #encoder_where_clause {
fn collect_into(&mut self, #[allow(unused)] out: &mut #private::Vec<u8>) {
#collect_into_body
}
fn reserve(&mut self, __additional: ::core::num::NonZeroUsize) {
#reserve_body
}
}
};
}
}
}