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// SPDX-FileCopyrightText: 2021 - 2022 Kamila Borowska <kamila@borowska.pw>
// SPDX-FileCopyrightText: 2021 Bruno Corrêa Zimmermann <brunoczim@gmail.com>
//
// SPDX-License-Identifier: MIT OR Apache-2.0
use crate::type_length;
use proc_macro2::TokenStream;
use quote::quote;
use syn::{DataStruct, Fields, FieldsNamed, FieldsUnnamed, Ident, Index};
pub fn generate(name: Ident, data_struct: DataStruct) -> TokenStream {
StructGenerator::from_fields(&data_struct.fields).finish(&name)
}
/// Total length is the product of each member's length. To represent a struct, one can
/// think of this as representing a little-endian number. First member is simply added, but
/// next members are multiplied before being added.
#[derive(Debug)]
struct StructGenerator {
length: TokenStream,
from_usize: TokenStream,
into_usize: TokenStream,
}
impl StructGenerator {
fn from_fields(fields: &Fields) -> Self {
match fields {
Fields::Unit => Self::from_unit_fields(),
Fields::Unnamed(fields_data) => Self::from_unnamed_fields(fields_data),
Fields::Named(fields_data) => Self::from_named_fields(fields_data),
}
}
fn from_unit_fields() -> Self {
Self {
length: quote! { 1usize },
from_usize: quote! { Self },
into_usize: quote! { 0usize },
}
}
fn from_unnamed_fields(fields: &FieldsUnnamed) -> Self {
let mut params_from = quote! {};
let mut into_usize = quote! { 0usize };
let mut length = quote! { 1usize };
for (i, field) in fields.unnamed.iter().enumerate() {
let ty = &field.ty;
let index_ident = Index::from(i);
let field_length = type_length(ty);
into_usize = quote! {
(#into_usize + #length * ::enum_map::Enum::into_usize(self.#index_ident))
};
params_from = quote! {
#params_from <#ty as ::enum_map::Enum>::from_usize(
value / #length % #field_length
),
};
length = quote! { (#length * #field_length) };
}
let from_usize = quote! { Self(#params_from) };
Self {
length,
from_usize,
into_usize,
}
}
fn from_named_fields(fields: &FieldsNamed) -> Self {
let mut params_from = quote! {};
let mut into_usize = quote! { 0usize };
let mut length = quote! { 1usize };
for field in fields.named.iter() {
let ty = &field.ty;
let ident = field.ident.as_ref().unwrap();
let field_length = type_length(ty);
into_usize = quote! {
(#into_usize + #length * ::enum_map::Enum::into_usize(self.#ident))
};
params_from = quote! {
#params_from #ident: <#ty as ::enum_map::Enum>::from_usize(
value / #length % #field_length
),
};
length = quote! { (#field_length * #length) };
}
let from_usize = quote! { Self { #params_from } };
Self {
length,
from_usize,
into_usize,
}
}
fn finish(&self, name: &Ident) -> TokenStream {
let length = &self.length;
let from_usize = &self.from_usize;
let into_usize = &self.into_usize;
quote! {
#[automatically_derived]
impl ::enum_map::Enum for #name {
const LENGTH: ::enum_map::usize = #length;
#[inline]
fn from_usize(value: ::enum_map::usize) -> Self {
#from_usize
}
#[inline]
fn into_usize(self) -> ::enum_map::usize {
#into_usize
}
}
#[automatically_derived]
impl<V> ::enum_map::EnumArray<V> for #name {
type Array = [V; #length];
}
}
}
}