cdefines 0.1.4

A proc macro that translates c #define constants to rust consts
Documentation 
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extern crate proc_macro;
extern crate quote;

use proc_macro::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
use quote::quote;
use std::collections::BTreeMap;
use std::usize;

fn try_parse_c_const(value: &str) -> Option<usize> {
    if value.starts_with("0x") {
        usize::from_str_radix(value.trim_start_matches("0x"), 16).ok()
    } else if value.starts_with("0b") {
        usize::from_str_radix(value.trim_start_matches("0b"), 2).ok()
    } else if value.starts_with("0") {
        usize::from_str_radix(value.trim_start_matches("0"), 8).ok()
    } else {
        usize::from_str_radix(value, 10).ok()
    }
}

#[proc_macro_attribute]
pub fn preprocessor(_attr: TokenStream, item: TokenStream) -> TokenStream {
    let iters: Vec<TokenTree> = item.into_iter().collect();
    let mut enum_name: Option<String> = None;
    let mut gen_tokens: Vec<TokenTree> = Vec::new();
    let mut enum_tokens: Vec<TokenTree> = Vec::new();
    let mut mapping: BTreeMap<String, String> = BTreeMap::new();
    for it in iters {
        match it {
            TokenTree::Ident(ref ident) => {
                if ident.to_string() == "const" || ident.to_string() == "str" {
                    continue;
                }
                if enum_name.is_some() {
                    panic!("more than only name found");
                }
                enum_name = Some(ident.to_string());
            }
            TokenTree::Literal(ref literal) => {
                let mut data = literal.to_string();
                // remove quotes
                data.remove(data.len() - 1);
                data.remove(0);
                for line in data.split("\n") {
                    let tokens: Vec<&str> = line
                        .split(|ch| ch == ' ' || ch == '\t')
                        .filter(|s| s.len() > 0)
                        .collect();
                    if tokens.len() == 0 {
                        continue;
                    }
                    if tokens.len() != 3 {
                        // no supported
                        panic!("unsupported line: {}", line);
                    }
                    if tokens[0] == "#define" {
                        let name = tokens[1];
                        let value = tokens[2];
                        mapping.insert(String::from(name), String::from(value));

                        if let Some(value_usize) = try_parse_c_const(value) {
                            // constants
                            gen_tokens
                                .push(TokenTree::Ident(Ident::new("const", Span::call_site())));
                            gen_tokens.push(TokenTree::Ident(Ident::new(
                                &format!("{}_{}", enum_name.as_ref().expect("no name found"), name),
                                Span::call_site(),
                            )));
                            gen_tokens.push(TokenTree::Punct(Punct::new(':', Spacing::Alone)));
                            gen_tokens
                                .push(TokenTree::Ident(Ident::new("usize", Span::call_site())));
                            gen_tokens.push(TokenTree::Punct(Punct::new('=', Spacing::Alone)));
                            gen_tokens
                                .push(TokenTree::Literal(Literal::usize_unsuffixed(value_usize)));
                            gen_tokens.push(TokenTree::Punct(Punct::new(';', Spacing::Alone)));

                            // enum
                            enum_tokens.push(TokenTree::Ident(Ident::new(name, Span::call_site())));
                            enum_tokens.push(TokenTree::Punct(Punct::new('=', Spacing::Alone)));
                            enum_tokens
                                .push(TokenTree::Literal(Literal::usize_unsuffixed(value_usize)));
                            enum_tokens.push(TokenTree::Punct(Punct::new(',', Spacing::Alone)));
                        } else if let Some(_) = mapping.get(value) {
                            // #define A ...
                            // #define B A

                            // constants
                            gen_tokens
                                .push(TokenTree::Ident(Ident::new("const", Span::call_site())));
                            gen_tokens.push(TokenTree::Ident(Ident::new(
                                &format!("{}_{}", enum_name.as_ref().expect("no name found"), name),
                                Span::call_site(),
                            )));
                            gen_tokens.push(TokenTree::Punct(Punct::new(':', Spacing::Alone)));
                            gen_tokens
                                .push(TokenTree::Ident(Ident::new("usize", Span::call_site())));
                            gen_tokens.push(TokenTree::Punct(Punct::new('=', Spacing::Alone)));
                            gen_tokens.push(TokenTree::Ident(Ident::new(
                                &format!(
                                    "{}_{}",
                                    enum_name.as_ref().expect("no name found"),
                                    value
                                ),
                                Span::call_site(),
                            )));
                            gen_tokens.push(TokenTree::Punct(Punct::new(';', Spacing::Alone)));

                            // no enum
                        }
                    }
                }
            }
            _ => {}
        }
    }
    let mut enum_stream = TokenStream::new();
    enum_stream.extend(enum_tokens);
    let group = Group::new(Delimiter::Brace, enum_stream);

    let debug: TokenStream =
        quote!(#[repr(usize)]#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]).into();
    gen_tokens.extend(debug);
    gen_tokens.push(TokenTree::Ident(Ident::new("enum", Span::call_site())));
    gen_tokens.push(TokenTree::Ident(Ident::new(
        enum_name.as_ref().expect("no name found"),
        Span::call_site(),
    )));
    gen_tokens.push(TokenTree::Group(group));

    let mut result = TokenStream::new();
    result.extend(gen_tokens);
    result.into()
}