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#![recursion_limit = "1024"]
extern crate proc_macro;
extern crate syn;
#[macro_use]
extern crate quote;
use proc_macro::TokenStream;
use quote::Tokens;
use syn::MetaItem::*;
use syn::Lit::*;
use syn::Body::*;
use syn::NestedMetaItem::*;
struct VariantInfo {
rust_name: syn::Ident,
rust_variant: syn::Ident,
c_name: syn::Ident,
c_variant: syn::Ident,
}
impl VariantInfo {
fn from(variant: syn::Variant, c_name: syn::Ident, rust_name: syn::Ident) -> Self {
let c_variant: syn::Ident = variant_attr_val_for_str("c_variant", &variant).into();
VariantInfo {
rust_name: rust_name,
rust_variant: variant.ident,
c_name: c_name,
c_variant: c_variant,
}
}
fn tokens_for_as_c(&self) -> Tokens {
let ref rust_name = self.rust_name;
let ref rust_variant = self.rust_variant;
let ref c_name = self.c_name;
let ref c_variant = self.c_variant;
let c_joined = syn::Ident::new(c_name.to_string() + "_" +
&c_variant.to_string());
quote! {
#rust_name::#rust_variant => #c_joined,
}
}
fn tokens_for_from_c(&self) -> Tokens {
let ref rust_name = self.rust_name;
let ref rust_variant = self.rust_variant;
let ref c_name = self.c_name;
let ref c_variant = self.c_variant;
let c_joined = syn::Ident::new(c_name.to_string() + "_" +
&c_variant.to_string());
quote! {
#c_joined => #rust_name::#rust_variant,
}
}
fn tokens_for_try_from_c(&self) -> Tokens {
let ref rust_name = self.rust_name;
let ref rust_variant = self.rust_variant;
let ref c_name = self.c_name;
let ref c_variant = self.c_variant;
let c_joined = syn::Ident::new(c_name.to_string() + "_" +
&c_variant.to_string());
quote! {
#c_joined => Ok(#rust_name::#rust_variant),
}
}
}
#[proc_macro_derive(EnumWrapper, attributes(wrap))]
pub fn enum_wrapper(input: TokenStream) -> TokenStream {
let source = input.to_string();
let ast = syn::parse_derive_input(&source).expect("Could not parse derive input");
let expanded = wrap_enum(ast);
expanded.parse().expect("Could not parse expanded output")
}
fn wrap_enum(ast: syn::DeriveInput) -> Tokens {
let rust_name = &ast.ident;
let c_name: syn::Ident = attr_val_for_str("c_enum", &ast).unwrap().into();
let default_variant = attr_val_for_str("default", &ast);
match ast.body {
Enum(variant_vec) => {
let info_vec: Vec<VariantInfo> = variant_vec.iter().map(|v| {
VariantInfo::from(v.clone(), c_name.clone(), rust_name.clone())
}).collect();
if let Some(v) = default_variant {
gen_impl(&info_vec[..], Some(v.into()))
} else {
gen_impl(&info_vec[..], None)
}
},
Struct(_) => panic!("This derive macro does not support structs"),
}
}
fn gen_impl(variant_slice: &[VariantInfo], default_variant: Option<syn::Ident>) -> Tokens {
let ref c_name = variant_slice[0].c_name;
let ref rust_name = variant_slice[0].rust_name;
let for_arms: Vec<Tokens> = variant_slice.iter().map(|v| {
v.tokens_for_as_c()
}).collect();
let from_arms: Vec<Tokens> = variant_slice.iter().map(|v| {
v.tokens_for_from_c()
}).collect();
let try_from_arms: Vec<Tokens> = variant_slice.iter().map(|v| {
v.tokens_for_try_from_c()
}).collect();
if let Some(v) = default_variant {
quote! {
impl #rust_name {
pub fn as_c(&self) -> #c_name {
match *self {
#(#for_arms)*
}
}
}
impl From<#c_name> for #rust_name {
fn from(enum_: #c_name) -> Self {
match enum_ {
#(#from_arms)*
_ => #c_name::#v
}
}
}
}
} else {
quote! {
impl #rust_name {
pub fn as_c(&self) -> #c_name {
match *self {
#(#for_arms)*
}
}
pub fn try_from(enum_: #c_name) -> Result<Self> {
match enum_ {
#(#try_from_arms)*
_ => Err(Error::from_kind(ErrorKind::UnexpectedVariant)),
}
}
}
}
}
}
fn attr_val_for_str<S: AsRef<str>>(string: S, ast: &syn::DeriveInput) -> Option<String> {
let mut return_string: Option<String> = None;
ast.attrs.iter().find(|ref a| match a.value {
List(ref ident, ref nested_items_vec) => {
let mut real_return_val = false;
if ident == "wrap" {
let item = nested_items_vec.iter().find(|ref i| match i {
&&&MetaItem(ref item) => match item {
&NameValue(ref ident, ref lit) => {
let mut return_val = false;
if ident == string.as_ref() {
return_string = match lit {
&Str(ref the_value, _) => Some(the_value.to_string()),
_ => panic!("Attribute value was not a string")
};
return_val = true;
}
return_val
},
_ => panic!("Attribute was was not a namevalue"),
},
_ => false,
});
if let Some(_) = item {
real_return_val = true;
}
}
real_return_val
},
_ => false,
});
return_string
}
fn variant_attr_val_for_str<S: AsRef<str>>(string: S, variant: &syn::Variant) -> String {
let mut return_string = "this_is_not_to_be_returned".to_string();
variant.attrs.iter().find(|ref a| match a.value {
List(ref ident, ref nested_items_vec) => {
let mut real_return_val = false;
if ident == "wrap" {
let item = nested_items_vec.iter().find(|ref i| match i {
&&&MetaItem(ref item) => match item {
&NameValue(ref ident, ref lit) => {
let mut return_val = false;
if ident == string.as_ref() {
return_string = match lit {
&Str(ref the_value, _) => the_value.to_string(),
_ => panic!("Attribute value was not a string")
};
return_val = true;
}
return_val
},
_ => panic!("Attribute was was not a namevalue"),
},
_ => false,
});
if let Some(_) = item {
real_return_val = true;
}
}
real_return_val
},
_ => false,
});
if return_string != "this_is_not_supposed_to_be_returned" {
return_string
} else {
panic!("Could not find attribute for {:?}", string.as_ref())
}
}