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nichy is a Rust type layout and niche optimization visualizer.

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# nichy

Rust type memory layout and niche optimization visualizer, powered by `rustc` internals.

nichy links directly against `rustc` via `#![feature(rustc_private)]` to query `layout_of` for every struct, enum, union, and type alias in your code. It reports exact sizes, alignments, field offsets, padding bytes, discriminant encoding, and niche optimization details. You get the same information the compiler uses, presented in a readable form.

Live instance: [niche.rs](https://niche.rs)

Or install locally:

```sh
curl --proto '=https' --tlsv1.2 -fsSL https://niche.rs/install.sh | sh
```

## Usage

### CLI

```
# analyze a type expression
nichy -t 'Option<&u64>'

# analyze a file
nichy src/types.rs

# pipe a snippet
echo 'struct Foo { a: u8, b: u64, c: u8 }' | nichy
```

JSON output for tooling:

```
nichy -t 'Result<u32, bool>' --json
```

Cross-target analysis:

```
nichy -t 'usize' --target aarch64-unknown-linux-gnu
```

### Web

The web service serves a browser UI and a JSON API:

| route | purpose |
| --- | --- |
| `POST /api/analyze` | Analyze `{code, target}` or `{type, target}`; returns layouts |
| `GET /api/health` | return "ok" |
| `POST /api/shorten` | Persist a snippet, returns a short id |
| `GET /api/snippet/{id}` | Fetch a previously shortened snippet |
| `GET /s/{id}` | Browser-loadable shortlink for a snippet |
| `GET /api/stats` / `/stats` | Aggregate request stats (JSON / page) |
| `GET /about` | Background reading on niche layouts |

```
cargo run -p nichy-web    # serves on 127.0.0.1:3873
```

Configuration is in `nichy-web.toml`:

```toml
site_name = "niche.rs"
listen = ["0.0.0.0:3873"]
timeout_secs = 2.0
db_path = "nichy-web.db"
```

## Install

`install.sh` writes a small launcher binary to `~/.local/bin/nichy`. On
each invocation the launcher reads `rustc -V` and runs a worker binary
matched to that exact rustc release, downloading it to `~/.cache/nichy/`
the first time. Any stable or beta toolchain on PATH works; `rustup` is
the easy way to get one.

```sh
curl --proto '=https' --tlsv1.2 -fsSL https://niche.rs/install.sh | sh
```

Override the install location:

```sh
curl --proto '=https' --tlsv1.2 -fsSL https://niche.rs/install.sh \
    | NICHY_PREFIX=/usr/local sh
```

## Building from source

You only need this path for local development on nichy itself, or to target a rustc release that's missing prebuilt artifacts.
For everything else, prefer the install script above.

### Local dev

```sh
git submodule update --init rust
cd rust
python3 x.py build library --stage 2 --target x86_64-unknown-linux-gnu
# build library for other targets you want to analyze
# python3 x.py build library --stage 2 \
#   --target aarch64-unknown-linux-gnu,i686-unknown-linux-gnu,wasm32-unknown-unknown
cd ..
cargo build -p nichy-cli -p nichy-web
```

### Docker
Downloads prebuilt rustc tarballs from `ci-artifacts.rust-lang.org`.

```sh
DOCKER_BUILDKIT=1 docker build -f Dockerfile.ci-local \
    --build-arg RUST_VERSION=1.95.0 -t nichy-ci-local .
```

For rustc versions that aren't on ci-artifacts. Builds rustc from
rust-lang/rust at the requested tag; takes tens of minutes or longer,
depending on your machine.

```sh
docker build -f Dockerfile.rust-stable \
    --build-arg RUST_TAG=1.95.0 -t nichy-rust-stable:1.95.0 .
docker build -f Dockerfile.stable -t nichy-stable-test .
```

#### Web service

```sh
docker build -f Dockerfile.rust -t nichy-rust:main .   # once, or on rustc bump
docker build -t nichy-web .
docker run -p 3873:3873 nichy-web
```

## License

[MIT](LICENSE)

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