1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164

#![recursion_limit = "256"]
extern crate proc_macro;

use quote::quote;

use proc_macro2::TokenStream;

#[proc_macro_derive(Trans, attributes(trans))]
pub fn derive_trans(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input: TokenStream = input.into();
    let result: TokenStream = {
        let ast: syn::DeriveInput = syn::parse_str(&input.to_string()).unwrap();
        let input_type = &ast.ident;
        let mut magic: Option<syn::Expr> = None;
        for attr in &ast.attrs {
            if let Ok(syn::Meta::List(syn::MetaList {
                path: ref meta_path,
                nested: ref nested,
                ..
            })) = attr.parse_meta()
            {
                if meta_path.is_ident("trans") {
                    for inner in nested {
                        if let syn::NestedMeta::Meta(syn::Meta::NameValue(syn::MetaNameValue {
                            path: ref meta_path,
                            lit: syn::Lit::Str(ref lit),
                            ..
                        })) = *inner
                        {
                            if meta_path.is_ident("magic") {
                                magic = Some(syn::parse_str(&lit.value()).unwrap());
                            }
                        }
                    }
                }
            }
        }
        let (magic_write, magic_read) = match magic {
            Some(magic) => (
                quote! {
                    trans::Trans::write_to(&#magic, &mut writer)?;
                },
                quote! {
                    assert_eq!(<i32 as trans::Trans>::read_from(&mut reader)?, #magic);
                },
            ),
            None => (quote! {}, quote! {}),
        };
        match ast.data {
            syn::Data::Struct(syn::DataStruct { ref fields, .. }) => {
                let field_tys: Vec<_> = fields.iter().map(|field| &field.ty).collect();
                let field_tys = &field_tys;
                let field_names: Vec<_> = fields
                    .iter()
                    .enumerate()
                    .map(|(index, field)| {
                        field.ident.clone().map_or_else(
                            || syn::Member::Unnamed(index.into()),
                            |ident| syn::Member::Named(ident),
                        )
                    })
                    .collect();
                let field_names = &field_names;
                let mut generics = ast.generics.clone();
                let extra_where_clauses = quote! {
                    where #(#field_tys: trans::Trans,)*
                };
                let extra_where_clauses: syn::WhereClause =
                    syn::parse_str(&extra_where_clauses.to_string()).unwrap();
                generics
                    .make_where_clause()
                    .predicates
                    .extend(extra_where_clauses.predicates);
                let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
                let expanded = quote! {
                    impl #impl_generics trans::Trans for #input_type #ty_generics #where_clause {
                        fn write_to(&self, mut writer: impl std::io::Write) -> std::io::Result<()> {
                            #magic_write
                            #(trans::Trans::write_to(&self.#field_names, &mut writer)?;)*
                            Ok(())
                        }
                        fn read_from(mut reader: impl std::io::Read) -> std::io::Result<Self> {
                            #magic_read
                            Ok(Self {
                                #(#field_names: trans::Trans::read_from(&mut reader)?),*
                            })
                        }
                    }
                };
                expanded.into()
            }
            syn::Data::Enum(syn::DataEnum { ref variants, .. }) => {
                let mut generics = ast.generics.clone();
                let all_field_tys = variants
                    .iter()
                    .map(|variant| variant.fields.iter().map(|field| &field.ty))
                    .flatten();
                let extra_where_clauses = quote! {
                    where #(#all_field_tys: trans::Trans + 'static,)*
                };
                let extra_where_clauses: syn::WhereClause =
                    syn::parse_str(&extra_where_clauses.to_string()).unwrap();
                generics
                    .make_where_clause()
                    .predicates
                    .extend(extra_where_clauses.predicates);
                let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
                let variant_writes = variants.iter().enumerate().map(|(discriminant, variant)| {
                    let discriminant = discriminant as i32;
                    let variant_name = &variant.ident;
                    let field_names: Vec<_> = variant
                        .fields
                        .iter()
                        .map(|field| field.ident.as_ref().unwrap())
                        .collect();
                    let field_names = &field_names;
                    let field_names_copy = field_names;
                    quote! {
                        #input_type::#variant_name { #(#field_names,)* } => {
                            trans::Trans::write_to(&#discriminant, &mut writer)?;
                            #(trans::Trans::write_to(#field_names_copy, &mut writer)?;)*
                        }
                    }
                });
                let variant_reads = variants.iter().enumerate().map(|(discriminant, variant)| {
                    let discriminant = discriminant as i32;
                    let variant_name = &variant.ident;
                    let field_names = variant
                        .fields
                        .iter()
                        .map(|field| field.ident.as_ref().unwrap());
                    quote! {
                        #discriminant => #input_type::#variant_name {
                            #(#field_names: trans::Trans::read_from(&mut reader)?,)*
                        },
                    }
                });
                let expanded = quote! {
                    impl #impl_generics trans::Trans for #input_type #ty_generics #where_clause {
                        fn write_to(&self, mut writer: impl std::io::Write) -> std::io::Result<()> {
                            match self {
                                #(#variant_writes)*
                            }
                            Ok(())
                        }
                        fn read_from(mut reader: impl std::io::Read) -> std::io::Result<Self> {
                            Ok(match <i32 as trans::Trans>::read_from(&mut reader)? {
                                #(#variant_reads)*
                                discriminant => {
                                    return Err(std::io::Error::new(
                                        std::io::ErrorKind::Other,
                                        format!("Unexpected discriminant {:?}", discriminant)));
                                }
                            })
                        }
                    }
                };
                expanded.into()
            }
            syn::Data::Union(_) => panic!("Unions not supported"),
        }
    };
    result.into()
}