layout_id 0.2.4

// Copyright (c) 2016 Jonathan Nilsson
//
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. All files in the project carrying such notice may not be copied,
// modified, or distributed except according to those terms.

#![feature(core_intrinsics)]

extern crate regex;
extern crate twox_hash;

use regex::{Captures, Regex};
use std::hash::{Hash, Hasher};
use std::intrinsics;
use twox_hash::XxHash;

pub fn layout_id<T>() -> u64 {

    let mut s = XxHash::with_seed(0);
    
    get_type_name(unsafe { intrinsics::type_name::<T>() }).hash(&mut s);
    unsafe { intrinsics::min_align_of::<T>() }.hash(&mut s);
    unsafe { intrinsics::pref_align_of::<T>() }.hash(&mut s);
    unsafe { intrinsics::size_of::<T>() }.hash(&mut s);

    s.finish()
}

fn get_type_name(name: &str) -> String {

    let inner = Regex::new(r#"<(.*)>"#).unwrap();
    let last_name = Regex::new(r#"[::]?([^:]*)$"#).unwrap();

    let replaced_children = inner.replace_all(&name, |caps: &Captures| {
        format!("<{}>", get_type_name(&caps.at(1).unwrap()))
    });

    let caps = last_name.captures(&replaced_children).unwrap();

    String::from(caps.at(1).unwrap())
}

#[test]
fn test_get_type_name() {
    assert_eq!(&get_type_name("persistent_hashmap::HashmapEntry<user::User>"),
              "HashmapEntry<User>");
    assert_eq!(&get_type_name("persistent_hashmap::HashmapEntry<meus_iot::user::User>"),
               "HashmapEntry<User>");
    assert_eq!(&get_type_name("persistent_hashmap::HashmapEntry<meus_iot::user::User<test::Type>>"),
               "HashmapEntry<User<Type>>");
    assert_eq!(&get_type_name("HashmapEntry<User>"),
               "HashmapEntry<User>");
}