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// Copyright (c) 2017 Doug Goldstein <cardoe@cardoe.com> // Permission is hereby granted, free of charge, to any person obtaining // a copy of this software and associated documentation files (the // “Software”), to deal in the Software without restriction, including // without limitation the rights to use, copy, modify, merge, publish, // distribute, sublicense, and/or sell copies of the Software, and to // permit persons to whom the Software is furnished to do so, subject to // the following conditions: // The above copyright notice and this permission notice shall be // included in all copies or substantial portions of the Software. // THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. // IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY // CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, // TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE // SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. //! This crate provides a custom derive `Primitive` that helps people //! providing native Rust bindings to C code by allowing a C-like `enum` //! declaration to convert to its primitve values and back from them. You //! can selectively include `num_traits::ToPrimitive` and //! `num_traits::FromPrimitive` to get these features. //! //! # Example //! //! ```rust //! use enum_primitive_derive::Primitive; //! use num_traits::{FromPrimitive, ToPrimitive}; //! //! #[derive(Debug, Eq, PartialEq, Primitive)] //! enum Foo { //! Bar = 32, //! Dead = 42, //! Beef = 50, //! } //! //! fn main() { //! assert_eq!(Foo::from_i32(32), Some(Foo::Bar)); //! assert_eq!(Foo::from_i32(42), Some(Foo::Dead)); //! assert_eq!(Foo::from_i64(50), Some(Foo::Beef)); //! assert_eq!(Foo::from_isize(17), None); //! //! let bar = Foo::Bar; //! assert_eq!(bar.to_i32(), Some(32)); //! //! let dead = Foo::Dead; //! assert_eq!(dead.to_isize(), Some(42)); //! } //! ``` //! //! # Complex Example //! //! ```rust //! use enum_primitive_derive::Primitive; //! use num_traits::{FromPrimitive, ToPrimitive}; //! //! pub const ABC: ::std::os::raw::c_uint = 1; //! pub const DEF: ::std::os::raw::c_uint = 2; //! pub const GHI: ::std::os::raw::c_uint = 4; //! //! #[derive(Clone, Copy, Debug, Eq, PartialEq, Primitive)] //! enum BindGenLike { //! ABC = ABC as isize, //! DEF = DEF as isize, //! GHI = GHI as isize, //! } //! //! fn main() { //! assert_eq!(BindGenLike::from_isize(4), Some(BindGenLike::GHI)); //! assert_eq!(BindGenLike::from_u32(2), Some(BindGenLike::DEF)); //! assert_eq!(BindGenLike::from_u32(8), None); //! //! let abc = BindGenLike::ABC; //! assert_eq!(abc.to_u32(), Some(1)); //! } //! ``` extern crate proc_macro; use proc_macro::TokenStream; /// Provides implementation of `num_traits::ToPrimitive` and /// `num_traits::FromPrimitive` #[proc_macro_derive(Primitive)] pub fn primitive(input: TokenStream) -> TokenStream { let ast = syn::parse_macro_input!(input as syn::DeriveInput); impl_primitive(&ast) } fn impl_primitive(ast: &syn::DeriveInput) -> TokenStream { let name = &ast.ident; // Check if derive(Primitive) was specified for a struct if let syn::Data::Enum(ref variant) = ast.data { let (var_u64, dis_u64): (Vec<_>, Vec<_>) = variant .variants .iter() .map(|v| { match v.fields { syn::Fields::Unit => (), _ => panic!("#[derive(Primitive) can only operate on C-like enums"), } if v.discriminant.is_none() { panic!( "#[derive(Primitive) requires C-like enums with \ discriminants for all enum variants" ); } let discrim = match v.discriminant.clone().map(|(_eq, expr)| expr).unwrap() { syn::Expr::Cast(real) => *real.expr, orig => orig, }; (v.ident.clone(), discrim) }) .unzip(); // quote!{} needs this to be a vec since its in #( )* let enum_u64 = vec![name.clone(); variant.variants.len()]; // can't reuse variables in quote!{} body let var_i64 = var_u64.clone(); let dis_i64 = dis_u64.clone(); let enum_i64 = enum_u64.clone(); let to_name = name.clone(); let to_enum_u64 = enum_u64.clone(); let to_var_u64 = var_u64.clone(); let to_dis_u64 = dis_u64.clone(); let to_enum_i64 = enum_u64.clone(); let to_var_i64 = var_u64.clone(); let to_dis_i64 = dis_u64.clone(); TokenStream::from(quote::quote! { impl ::num_traits::FromPrimitive for #name { fn from_u64(val: u64) -> Option<Self> { match val as _ { #( #dis_u64 => Some(#enum_u64::#var_u64), )* _ => None, } } fn from_i64(val: i64) -> Option<Self> { match val as _ { #( #dis_i64 => Some(#enum_i64::#var_i64), )* _ => None, } } } impl ::num_traits::ToPrimitive for #to_name { fn to_u64(&self) -> Option<u64> { match *self { #( #to_enum_u64::#to_var_u64 => Some(#to_dis_u64 as u64), )* } } fn to_i64(&self) -> Option<i64> { match *self { #( #to_enum_i64::#to_var_i64 => Some(#to_dis_i64 as i64), )* } } } }) } else { panic!("#[derive(Primitive)] is only valid for C-like enums"); } }