byteyarn
byteyarn
- Space-efficient byte strings 🧶🐈⬛
A Yarn
is a highly optimized string type that provides a number of
useful properties over String
:
- Always two pointers wide, so it is always passed into and out of functions in registers.
- Small string optimization (SSO) up to 15 bytes on 64-bit architectures.
- Can be either an owned buffer or a borrowed buffer (like
Cow<str>
). - Can be upcast to
'static
lifetime if it was constructed from a known-static string.
The main caveat is that Yarn
s cannot be easily appended to, since they
do not track an internal capacity, and the slice returned by
Yarn::as_slice()
does not have the same pointer stability properties as
String
(these are rarely needed, though).
Yarns are useful for situations in which a copy-on-write string is necessary
and most of the strings are relatively small. Although Yarn
itself is
not Copy
, there is a separate YarnRef
type that is. These types
have equivalent representations, and can be cheaply cast between each other.
The easiest way to create a yarn is with the yarn!()
and byarn!()
macros, which are similar to format!()
.
// Create a new yarn via `fmt`ing.
let yarn = yarn!;
// Convert that yarn into a reference.
let ry: = yarn.as_ref;
// Try up-casting the yarn into an "immortal yarn" without copying.
let copy: = ry.immortalize.unwrap;
assert_eq!;
Yarns are intended for storing text, either as UTF-8 or as
probably-UTF-8 bytes; Yarn<str>
and Yarn<[u8]>
serve these purposes,
and can be inter-converted with each other. The Yarn::utf8_chunks()
function can be used to iterate over definitely-valid-UTF-8 chunks within
a string.
Both kinds of yarns can be Debug
ed and Display
ed, and will print out as
strings would. In particular, invalid UTF-8 is converted into either \xNN
escapes or replacement characters (for Debug
and Display
respectively).
let invalid = from_byte;
assert_eq!;
assert_eq!;
License: Apache-2.0