Simple macro for nice looking JNI signatures

lib.rs

extern crate proc_macro;

use quote::quote;
use proc_macro::TokenStream;

// this macro is dumb in a lot of ways, this is just a prototype
#[proc_macro_attribute]
pub fn java(attr: TokenStream, item: TokenStream) -> TokenStream {
    let mut name = String::new();
    name += "Java_";

    for tt in attr {
        let string = tt.to_string();
        if &string == "." {
            name.push('_');
        } else {
            name += &string;
        }
    }

    name += "_";

    let input = syn::parse_macro_input!(item as syn::ItemFn);

    let mut flag = false;
    for ch in input.sig.ident.to_string().chars() {
        if ch == '_' {
            flag = true;
        } else if flag {
            flag = false;
            name.push(ch.to_ascii_uppercase());
        } else {
            name.push(ch);
        }
    }

    let name = syn::Ident::new(&name, proc_macro2::Span::call_site());
    let params = input.sig.inputs;
    let ret = input.sig.output;
    let body = input.block;

    quote![
        #[no_mangle]
        pub extern fn #name(env: jni::JNIEnv, this: jni::objects::JObject, #params) #ret {
            #body
        }
    ].into()
}