#string #data-structures


A possibly-stack-allocated string with generic bytes storage

9 releases

Uses old Rust 2015

0.3.0 May 30, 2017
0.2.0 Feb 16, 2017
0.1.7 Jan 19, 2017
0.1.5 Nov 5, 2015
0.1.3 Oct 30, 2015

#1027 in Data structures

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string_wrapper is a crate which provides StringWrapper, which is a usually* stack-allocated UTF-8 string type. Features:

  • Array-backed StringWrappers can be entirely stored on the stack
  • The Copy trait can be implemented, unlike for standard Strings
  • Serde Serialization and Deserialization traits are implemented to act exactly like String


Docs are at http://docs.rs/string-wrapper


First, add this to your Cargo.toml:

string-wrapper = "0.2"

If you want to use Serde support, you have to enable the use_serde feature and use Rust 1.15 or higher.

string-wrapper = {version = "0.1.6", features = ["use_serde"]}

Make sure to use extern crate in your "crate root" module (usually either lib.rs or main.rs)

extern crate string_wrapper;

Finally, to actually use the StringWrapper type:

use string_wrapper::StringWrapper;

fn foo() {
  // `from_str` may panic; use `from_str_safe` if you're using arbitrary input
  let s: StringWrapper<[u8; 32]> = StringWrapper::from_str("foo");

  // a StringWrapper can be converted back to a String with `to_string`:
  println!("{}", s.to_string());
  // However, it also supports the Display trait directly:
  println!("{}", s);

Note that the type parameter MUST be made up of u8s, usually* as a [u8; N] array. Possible array sizes for arrays are listed in the Implementors section of the Buffer trait documentation: https://docs.rs/string-wrapper/*/string_wrapper/trait.Buffer.html.

Many other traits are supported by StringWrapper. See the http://docs.rs/string-wrapper/.

"Usually*"? Heap-allocated StringWrappers

Vec<u8> is also supported as a backing buffer instead of [u8; N]. Using a Vec<u8> means your string will be on the heap.

When is it useful?

This can be useful if you have tons of small strings that fit within a fixed length, and the overhead of dealing with pointers to those small strings is detrimental to your programs. If you're unsure, you should probably just use String since it's more flexible and convenient.

Is this SSO (Small-String Optimization)?

Note that this is not what is typically called "SSO String", which is a dynamically-sized string that is either stored directly on the stack (if it's small) or on the heap (if it's large). Such a string would not be able to implement the Copy trait.


Thanks to @SimonSapin, the original author of this code.



string-wrapper is dual-licensed under the MIT license and the Apache 2.0 license. All contributions must be made under the terms of both of these licenses.