# jstring

## JavaString
The JavaString uses short string optimizations and a lack of a "capacity"
field to reduce struct size and heap fragmentation in certain cases.

### Features

- Supports String API (very little at the moment but steadily growing)
- Smaller size than standard string (16 vs 24 bytes on 64-bit platforms)
- String interning for up to 15 bytes on 64-bit architectures (or 7 bytes on 32-bit)

### How it works
Here's how it works:

1. We store `len`, the length of the string, and `data`, the pointer to the
   string itself.
2. We maintain the invariant that `data` is a valid pointer if and only if
   it points to something that's aligned to 2 bytes.
3. Now, any time we wanna read the string, we first check the lowest significance
   bit on `data`, and use that to see whether or not to dereference it.
4. Since `data` only uses one bit for its flag, we can use the entire lower
   order byte for length information when it's interned. We do this with a
   bitshift right.
5. When interning, we have `std::mem::size_of::<usize>() * 2 - 1` bytes of space.
   On x64, this is 15 bytes, and on 32-bit architectures, this is 7 bytes.

License: MIT