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#![recursion_limit = "192"] extern crate proc_macro; use std::iter; use std::mem; use std::str::FromStr; use proc_macro2::{Ident, Span, TokenStream}; use quote::{quote, ToTokens}; use syn::{ parse_macro_input, AttrStyle, Attribute, Data, DeriveInput, Expr, Fields, Meta, NestedMeta, Type, TypeGenerics, TypePath, }; #[proc_macro_derive(H5Type)] pub fn derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream { let input = parse_macro_input!(input as DeriveInput); let name = input.ident; let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl(); let body = impl_trait(&name, &input.data, &input.attrs, &ty_generics); let dummy = Ident::new(&format!("_IMPL_H5TYPE_FOR_{}", name), Span::call_site()); let expanded = quote! { #[allow(dead_code, unused_variables, unused_attributes)] const #dummy: () = { extern crate hdf5 as _h5; #[automatically_derived] unsafe impl #impl_generics _h5::types::H5Type for #name #ty_generics #where_clause { #[inline] fn type_descriptor() -> _h5::types::TypeDescriptor { #body } } }; }; proc_macro::TokenStream::from(expanded) } fn impl_compound<F>( ty: &Ident, ty_generics: &TypeGenerics, fields: &[F], names: &[String], types: &[Type], ) -> TokenStream where F: ToTokens, { quote! { let origin: *const #ty #ty_generics = ::std::ptr::null(); let mut fields = vec![#( _h5::types::CompoundField { name: #names.to_owned(), ty: <#types as _h5::types::H5Type>::type_descriptor(), offset: unsafe { &((*origin).#fields) as *const _ as _ }, index: 0, } ),*]; for i in 0..fields.len() { fields[i].index = i; } let size = ::std::mem::size_of::<#ty #ty_generics>(); _h5::types::TypeDescriptor::Compound(_h5::types::CompoundType { fields, size }) } } fn impl_enum(names: Vec<Ident>, values: Vec<Expr>, repr: &Ident) -> TokenStream { let size = Ident::new( &format!( "U{}", usize::from_str(&repr.to_string()[1..]).unwrap_or(mem::size_of::<usize>() * 8) / 8 ), Span::call_site(), ); let signed = repr.to_string().starts_with('i'); let repr = iter::repeat(repr); quote! { _h5::types::TypeDescriptor::Enum( _h5::types::EnumType { size: _h5::types::IntSize::#size, signed: #signed, members: vec![#( _h5::types::EnumMember { name: stringify!(#names).to_owned(), value: (#values) as #repr as _, } ),*], } ) } } fn is_phantom_data(ty: &Type) -> bool { match *ty { Type::Path(TypePath { qself: None, ref path }) => { path.segments.iter().last().map(|x| x.ident == "PhantomData").unwrap_or(false) } _ => false, } } fn find_repr(attrs: &[Attribute], expected: &[&str]) -> Option<Ident> { for attr in attrs.iter() { if attr.style == AttrStyle::Outer { if let Ok(Meta::List(ref list)) = attr.parse_meta() { if list.ident == "repr" { for item in list.nested.iter() { if let NestedMeta::Meta(Meta::Word(ref ident)) = *item { if expected.iter().any(|&s| *ident == s) { return Some(Ident::new(&ident.to_string(), Span::call_site())); } } } } } } } None } fn pluck<'a, I, F, T, S>(iter: I, func: F) -> Vec<S> where I: Iterator<Item = &'a T>, F: Fn(&'a T) -> S, T: 'a, { iter.map(func).collect() } fn impl_trait( ty: &Ident, data: &Data, attrs: &[Attribute], ty_generics: &TypeGenerics, ) -> TokenStream { match *data { Data::Struct(ref data) => match data.fields { Fields::Unit => { panic!("Cannot derive H5Type for unit structs"); } Fields::Named(ref fields) => { let fields: Vec<_> = fields.named.iter().filter(|f| !is_phantom_data(&f.ty)).collect(); if fields.is_empty() { panic!("Cannot derive H5Type for empty structs"); } find_repr(attrs, &["C"]).expect("H5Type requires #[repr(C)] for structs"); let types = pluck(fields.iter(), |f| f.ty.clone()); let fields = pluck(fields.iter(), |f| f.ident.clone().unwrap()); let names = fields.iter().map(|f| f.to_string()).collect::<Vec<_>>(); impl_compound(ty, ty_generics, &fields, &names, &types) } Fields::Unnamed(ref fields) => { let (index, fields): (Vec<usize>, Vec<_>) = fields .unnamed .iter() .enumerate() .filter(|&(_, f)| !is_phantom_data(&f.ty)) .unzip(); if fields.is_empty() { panic!("Cannot derive H5Type for empty tuple structs"); } find_repr(attrs, &["C"]).expect("H5Type requires #[repr(C)] for structs"); let names = (0..fields.len()).map(|f| f.to_string()).collect::<Vec<_>>(); let types = pluck(fields.iter(), |f| f.ty.clone()); impl_compound(ty, ty_generics, &index, &names, &types) } }, Data::Enum(ref data) => { let variants = &data.variants; if variants.iter().any(|v| v.fields != Fields::Unit || v.discriminant.is_none()) { panic!("H5Type can only be derived for enums with scalar discriminants"); } else if variants.is_empty() { panic!("Cannot derive H5Type for empty enums") } let enum_reprs = &["i8", "i16", "i32", "i64", "u8", "u16", "u32", "u64", "isize", "usize"]; let repr = find_repr(attrs, enum_reprs) .expect("H5Type can only be derived for enums with explicit representation"); let names = pluck(variants.iter(), |v| v.ident.clone()); let values = pluck(variants.iter(), |v| v.discriminant.clone().unwrap().1); impl_enum(names, values, &repr) } Data::Union(_) => { panic!("Cannot derive H5Type for tagged unions"); } } }