# `hipstr`

[![Rust](https://github.com/polazarus/hipstr/actions/workflows/basic.yml/badge.svg)](https://github.com/polazarus/hipstr/actions/workflows/basic.yml)
[![Clippy & Miri](https://github.com/polazarus/hipstr/actions/workflows/analysis.yml/badge.svg)](https://github.com/polazarus/hipstr/actions/workflows/analysis.yml)
[![codecov](https://codecov.io/gh/polazarus/hipstr/branch/main/graph/badge.svg?token=Z7YUHB4YUD)](https://codecov.io/gh/polazarus/hipstr)
[![Docs](https://img.shields.io/docsrs/hipstr)](https://docs.rs/hipstr)
![MIT OR Apache-2.0](https://img.shields.io/crates/l/hipstr)

Yet another string type for Rust 🦀

- no copy **borrow** via `borrowed` (a `const` constructor) or `from_static`
- no alloc **small strings** (_23 bytes_ on 64-bit platform)
- no copy **owned slices**
- a niche: `Option<HipStr>` and `HipStr` have the same size
- **zero dependency** and compatible `no_std` with `alloc`

Also byte strings, OS strings, and paths!

## ⚡ Examples

```rust
use hipstr::HipStr;

let simple_greetings = HipStr::from_static("Hello world");
let _clone = simple_greetings.clone(); // no copy

let user = "John";
let greetings = HipStr::from(format!("Hello {}", user));
let user = greetings.slice(6..): // no copy
drop(greetings); // the slice is owned, it exists even if greetings disappear

let chars = user.chars().count(); // "inherits" `&str` methods
```

## ✏️ Features

- `std` (default): uses `std` rather than `core` and `alloc`, and also provides more trait implementations (for comparison, conversions, and errors)
- `serde`: provides serialization/deserialization support with `serde` crate
- `unstable`: exposes internal `Backend` trait that may change at any moment

## ☣️ Safety of `hipstr`

This crate uses `unsafe` extensively. 🤷

It exploits the 2-bit alignment niche in pointers existing on most platforms (I think all Rustc supported platforms) to distinguish the inline representation from the other representations.

To make things safer, Rust is tested thoroughly on multiple platforms, normally and with [Miri] (the MIR interpreter).

## 🧪 Testing

### ☔ Coverage

This crate has **near full line coverage**:

```bash
cargo llvm-cov --all-features --html
# or
cargo tarpaulin --all-features --out html --engine llvm
```

Check out the current coverage on [Codecov]:

![Coverage grid](https://codecov.io/gh/polazarus/hipstr/branch/main/graphs/tree.svg?token=Z7YUHB4YUD)

### 🖥️ Cross-platform testing

You can easily run the test on various platforms with [`cross`]:

```bash
cross test --target s390x-unknown-linux-gnu         # 32-bit BE
cross test --target powerpc64-unknown-linux-gnu     # 64-bit BE
cross test --target i686-unknown-linux-gnu          # 32-bit LE
cross test --target x86_64-unknown-linux-gnu        # 64-bit LE
```

NB: previously I used MIPS targets for big endian, but due to some LLVM-related issue they are not working anymore… see [Rust issue #113065](https://github.com/rust-lang/rust/issues/113065)

### 🔍 [Miri]

This crate runs successfully with Miri:

```bash
MIRIFLAGS=-Zmiri-symbolic-alignment-check cargo +nightly miri test

for SEED in $(seq 0 10); do
  echo "Trying seed: $SEED"
  MIRIFLAGS="-Zmiri-seed=$SEED" cargo +nightly miri test || { echo "Failing seed: $SEED"; break; };
done
```

To check with different word size and endianness:

```bash
# Big endian, 64-bit
cargo +nightly miri test --target mips64-unknown-linux-gnuabi64
# Little endian, 32-bit
cargo +nightly miri test --target i686-unknown-linux-gnu
```

[Codecov]: https://app.codecov.io/gh/polazarus/hipstr
[`cross`]: https://github.com/cross-rs/cross
[Miri]: https://github.com/rust-lang/miri

## 📦 Similar crates

`#[non_exhaustive]`

| Name                                                           | Thread-safe cheap-clone | Local cheap-clone | Inline | Cheap slice | Bytes  | Cow<'a> | Comment                                                                                                |
| -------------------------------------------------------------- | ----------------------- | ----------------- | ------ | ----------- | ------ | ------- | :----------------------------------------------------------------------------------------------------- |
| `hipstr`                                                       | 🟢                      | 🟢                | 🟢     | 🟢          | 🟢     | 🟢      | obviously!                                                                                             |
| [`arcstr`](https://github.com/thomcc/arcstr)                   | 🟢\*                    | ❌                | ❌     | ❌\*\*      | ❌     | ❌      | \*use a custom thin `Arc`, \*\*heavy slice (with dedicated substring type)                             |
| [`flexstr`](https://github.com/nu11ptr/flexstr)                | 🟢\*                    | 🟢                | 🟢     | ❌          | ❌     | ❌      | \*use an `Arc<str>` instead of an `Arc<String>` (remove one level of indirection but use fat pointers) |
| [`imstr`](https://github.com/xfbs/imstr)                       | 🟢                      | 🟢                | ❌     | 🟢          | ❌     | ❌      |                                                                                                        |
| [`faststr`](https://github.com/volo-rs/faststr)                | 🟢                      | ❌                | 🟢     | 🟢          | ❌     | ❌      | zero-doc with complex API                                                                              |
| [`fast-str`](https://github.com/xxXyh1908/rust-fast-str)       | 🟢                      | ❌                | 🟢     | 🟢          | ❌     | ❌      | inline repr is opt-in                                                                                  |
| [`ecow`](https://github.com/typst/ecow)                        | 🟢\*                    | ❌                | 🟢     | ❌          | 🟢\*\* | ❌      | \*on two words only 🤤, \*\*even any `T`                                                               |
| [`cowstr`](https://git.pipapo.org/cehteh/cowstr.git)           | 🟢                      | ❌                | ❌     | ❌\*        | ❌     | ❌\*\*  | \*heavy slice, \*\*contrary to its name                                                                |
| [`compact_str`](https://github.com/parkmycar/compact_str)      | ❌                      | ❌                | 🟢     | ❌          | 🟢\*   | ❌      | \*opt-in via `smallvec`                                                                                |
| [`inline_string`](https://github.com/fitzgen/inlinable_string) | ❌                      | ❌                | 🟢     | ❌          | ❌     | ❌      |                                                                                                        |
| [`smartstring`](https://github.com/bodil/smartstring)          | ❌                      | ❌                | 🟢     | ❌          | ❌     | ❌      |                                                                                                        |
| [`smallstr`](https://github.com/murarth/smallstr)              | ❌                      | ❌                | 🟢     | ❌          | ❌     | ❌      |                                                                                                        |
| [`smol_str`](https://github.com/rust-analyzer/smol_str)        | ❌                      | ❌                | 🟢\*   | ❌          | ❌     | ❌      | \*but only inline string, here for reference                                                           |

skipping specialized string types like [`tinystr`](https://github.com/unicode-org/icu4x) (ASCII-only, bounded), or bstr, or bytestring, or...

In short, `HipStr`, one string type to rule them all 😉

[![How standards proliferate](https://imgs.xkcd.com/comics/standards.png)](https://xkcd.com/927/)

## 🏎️ Performances

While speed is not the main motivator for `hipstr`, it seems to be doing OK on that front.

On my i7-8550U, under Arch Linux over Windows 11/WSL 2 (yeah I know 😅), the creation of a `HipStr` from a slice is competitive with other crates and the `std`:

![string-comparison/chart.svg](string-comparison/chart.svg)

## 📖 Author and licenses

For now, just me PoLazarus 👻 \
Help welcome! 🚨

MIT + Apache