#tagged #pointer #64-bit

nightly tagged_ptr

A safe tagged union pointer datastructure for x64

1 unstable release

Uses old Rust 2015

0.1.0 Mar 1, 2017

#981 in Rust patterns


298 lines

Tagged union pointers

What is it?

This library is unstable and may contain bugs!

A safe library for tagged union pointers. This library supports putting up to 8 Packable3 types in a 64-bit word. A type can implement Packable3 if it supports a bijection to a 61-bit number. The supported operations are packing, unpacking, unpacked references for matching and mutation.

Provided types are (), bool, u16, u32, f32, &'a T', Rc<T>,Box<T>, *T, *mut T.


type ThinVal = Packed<Box<u64>, Box<u64>, f32, u32, bool>;
fn test_example() {
    let mut y : ThinVal = Unpacked::C(1.6f32).pack();
    match *y.unpack_mut() {
        Unpacked::A(ref mut b) => **b += 1,
        Unpacked::B(ref mut b) => **b += 5,
        Unpacked::C(ref mut f) => {*f += 4.8f32},
        Unpacked::D(ref mut u) => *u += 2,
        Unpacked::E(ref mut b) => *b ^= true,
        _ => panic!()
    println!("{:?}", y.unpack());

Planned features

  • Generalisations for variadic number of bits. (Generic heavy code using Peano.)
  • NAN-boxing.
  • Some documentation.
  • Move Packable implementations to other file.
  • Provide derived std traits: Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Debug, Display.


Add this to your Cargo.toml:

tagged_ptr = "0.1"

and this to your crate root:

extern crate tagged_ptr;


  • 0.1.0 Added 64-bit tagged union pointer without documentation.


Dual-licensed to be compatible with the Rust project.

Licensed under the Apache License, Version 2.0 http://www.apache.org/licenses/LICENSE-2.0 or the MIT license http://opensource.org/licenses/MIT, at your option. This file may not be copied, modified, or distributed except according to those terms.

No runtime deps