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use proc_macro2::Ident;
use proc_macro2::Span;
use proc_macro2::TokenStream;
use syn::*;
use crate::config::Config;
use crate::endian::*;
use crate::enums::*;
use crate::gen::get_extra_args;
use crate::meta;
use crate::structs::get_pre_post_exec;
use crate::Result;
use super::Generator;
pub struct GenEnum {
pub name: Ident,
pub config: Config,
extra_args: Option<TokenStream>,
orig_generics: Generics,
tl_pre: Option<TokenStream>,
tl_post: Option<TokenStream>,
variants_defs: Vec<VariantParserTree>,
}
impl Generator for GenEnum {
fn from_ast(ast: &DeriveInput, endianness: ParserEndianness) -> Result<Self> {
match &ast.data {
syn::Data::Enum(data_enum) => GenEnum::from_data_enum(
&ast.ident,
data_enum,
&ast.attrs,
&ast.generics,
endianness,
),
_ => panic!("Wrong type for GenEnum::from_ast"),
}
}
#[inline]
fn name(&self) -> &Ident {
&self.name
}
fn set_debug(&mut self, debug_derive: bool) {
self.config.debug_derive |= debug_derive;
}
#[inline]
fn extra_args(&self) -> Option<&TokenStream> {
self.extra_args.as_ref()
}
#[inline]
fn orig_generics(&self) -> &Generics {
&self.orig_generics
}
#[inline]
fn config(&self) -> &Config {
&self.config
}
fn gen_fn_body(&self, endianness: ParserEndianness) -> Result<TokenStream> {
let orig_input = Ident::new(self.config.orig_input_name(), Span::call_site());
let input = Ident::new(self.config.input_name(), Span::call_site());
let (tl_pre, tl_post) = (&self.tl_pre, &self.tl_post);
// generate body
let (default_case_handled, variants_code) = self.gen_variants(endianness)?;
let default_case = if default_case_handled {
quote! {}
} else {
quote! { _ => Err(nom::Err::Error(nom::error_position!(#input, nom::error::ErrorKind::Switch))) }
};
let tokens = quote! {
let #input = #orig_input;
#tl_pre
let (#input, enum_def) = match selector {
#(#variants_code)*
#default_case
}?;
#tl_post
Ok((#input, enum_def))
};
Ok(tokens)
}
}
impl GenEnum {
pub fn from_data_enum(
name: &Ident,
data_enum: &DataEnum,
attrs: &[Attribute],
generics: &Generics,
endianness: ParserEndianness,
) -> Result<Self> {
let name = name.clone();
// parse top-level attributes and prepare tokens for each field parser
let meta = meta::parse_nom_top_level_attribute(attrs)?;
// eprintln!("top-level meta: {:?}", meta);
let mut config = Config::from_meta_list(name.to_string(), &meta)?;
// endianness must be set before parsing struct
set_object_endianness(name.span(), endianness, &meta, &mut config)?;
let extra_args = get_extra_args(&meta).map(Clone::clone);
// test endianness validity (not 2 or more)
validate_endianness(
endianness,
config.object_endianness,
config.global_endianness,
)?;
// save global pre/post exec
let (tl_pre, tl_post) = get_pre_post_exec(&meta, &config);
// fieldless enums should not be handled by this generator
assert!(config.selector_type().is_some());
// iter fields / variants and store info
let variants_defs = data_enum
.variants
.iter()
.map(|v| parse_variant(v, &mut config))
.collect::<Result<Vec<_>>>()?;
Ok(Self {
name,
config,
extra_args,
orig_generics: generics.clone(),
tl_pre,
tl_post,
variants_defs,
})
}
/// Generate parser code for every variant of the enum
///
/// Returns a boolean indicating if default case was handled, and the list of tokens for each variant
fn gen_variants(&self, endianness: ParserEndianness) -> Result<(bool, Vec<TokenStream>)> {
let name = &self.name;
let input = syn::Ident::new(self.config.input_name(), Span::call_site());
let mut default_case_handled = false;
let mut variants_code: Vec<_> = {
self.variants_defs
.iter()
.map(|def| {
if def.selector_type == "_" {
default_case_handled = true;
}
let m: proc_macro2::TokenStream =
def.selector_type.parse().expect("invalid selector value");
let variantname = &def.ident;
let (idents, parser_tokens): (Vec<_>, Vec<_>) = def
.struct_def
.parsers
.iter()
.map(|sp| {
let id = syn::Ident::new(&sp.name, Span::call_site());
// set current endianness for functions that do not specify it
let item = sp.item.with_endianness(endianness);
(id, item)
})
.unzip();
let (pre, post): (Vec<_>, Vec<_>) = def
.struct_def
.parsers
.iter()
.map(|sp| (sp.pre_exec.as_ref(), sp.post_exec.as_ref()))
.unzip();
let idents2 = idents.clone();
let struct_def = match (def.struct_def.empty, def.struct_def.unnamed) {
(true, _) => quote! { ( #name::#variantname ) },
(_, true) => quote! { ( #name::#variantname ( #(#idents2),* ) ) },
(_, false) => quote! { ( #name::#variantname { #(#idents2),* } ) },
};
//
// XXX this looks wrong: endianness does not appear in this function!
// XXX parser_tokens should specify endianness
// XXX
// XXX this is caused by quote!{} calling to_string()
quote! {
#m => {
#(
#pre
let (#input, #idents) = #parser_tokens (#input) ?;
#post
)*
let struct_def = #struct_def;
Ok((#input, struct_def))
// Err(nom::Err::Error(error_position!(#input_name, nom::ErrorKind::Switch)))
},
}
})
.collect()
};
// if we have a default case, make sure it is the last entry
if default_case_handled {
let pos = self
.variants_defs
.iter()
.position(|def| def.selector_type == "_")
.expect("default case is handled but couldn't find index");
let last_index = self.variants_defs.len() - 1;
if pos != last_index {
// self.variants_defs.swap(pos, last_index);
variants_code.swap(pos, last_index);
}
}
Ok((default_case_handled, variants_code))
}
}
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