source-lang 0.2.0

<h1 align="center">
    <img width="99" alt="Rust logo" src="https://raw.githubusercontent.com/jamesgober/rust-collection/72baabd71f00e14aa9184efcb16fa3deddda3a0a/assets/rust-logo.svg">
    <br>
    <b>source-lang</b>
    <br>
    <sub><sup>SOURCE FILES & MAPS</sup></sub>
</h1>

<div align="center">
    <a href="https://crates.io/crates/source-lang"><img alt="Crates.io" src="https://img.shields.io/crates/v/source-lang"></a>
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    <a href="https://github.com/rust-lang/rfcs/blob/master/text/2495-min-rust-version.md"><img alt="MSRV" src="https://img.shields.io/badge/MSRV-1.85%2B-blue"></a>
</div>

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<div align="left">
    <p>
        source-lang manages the text a compiler front-end reads: it loads files and buffers, assigns each a stable id, and maps a global position back to the specific file and local offset it came from. It is the multi-file coordinate layer that sits above raw spans, so a diagnostic can say not just where in a buffer an error is, but which file.
    </p>
    <br>
    <hr>
    <p>
        <strong>MSRV is 1.85+</strong> (Rust 2024 edition).
    </p>
    <blockquote>
        <strong>Status: pre-1.0, in active development.</strong> The public API is being designed across the 0.x series and frozen at <code>1.0.0</code>. See <a href="./CHANGELOG.md"><code>CHANGELOG.md</code></a>.
    </blockquote>
</div>

<hr>
<br>

## Installation

```toml
[dependencies]
source-lang = "0.2"
```

Or from the terminal:

```bash
cargo add source-lang
```

<br>

## Usage

Add sources to a map and resolve a global position back to the file and local
offset it came from.

```rust
use source_lang::{BytePos, SourceMap};

let mut map = SourceMap::new();
let main = map.add("main.rs", "fn main() {}")?;   // global 0..12
let util = map.add("util.rs", "fn helper() {}")?; // global 12..26

// Which file does global position 13 belong to, and where inside it?
let (id, local) = map.locate(BytePos::new(13)).expect("inside util.rs");
assert_eq!(id, util);
assert_eq!(local, BytePos::new(1)); // 13 - 12

// The id is a stable handle back to the source for the life of the map.
assert_eq!(map.source(main).unwrap().name(), "main.rs");
# Ok::<(), source_lang::SourceMapError>(())
```

Read the located text back out of the resolved source:

```rust
use source_lang::{BytePos, SourceMap};

let mut map = SourceMap::new();
map.add("a", "let x = 1;")?;
let two = map.add("b", "let y = 2;")?;

let (id, local) = map.locate(BytePos::new(14)).expect("in range");
assert_eq!(id, two);
let file = map.source(id).unwrap();
assert_eq!(&file.text()[local.to_usize()..], "y = 2;");
# Ok::<(), source_lang::SourceMapError>(())
```

Walk every loaded source in order — id order is also global-offset order:

```rust
use source_lang::SourceMap;

let mut map = SourceMap::new();
map.add("a.txt", "one")?;
map.add("b.txt", "two")?;

let names: Vec<_> = map.iter().map(|(_, f)| f.name()).collect();
assert_eq!(names, ["a.txt", "b.txt"]);
# Ok::<(), source_lang::SourceMapError>(())
```

See <a href="./docs/API.md"><code>docs/API.md</code></a> for the full reference.

<br>

## How it works

Sources are placed end to end in the order they are added: the first occupies
global offsets `0..len₀`, the next `len₀..len₀ + len₁`, and so on. The ranges never
overlap, and because each base is the running total of all earlier sources, the
internal list stays sorted by offset — so <code>locate</code> is a binary search,
<code>O(log files)</code>, that borrows the resolved source rather than copying it.
The shared space is 32 bits wide (the same envelope a single <code>BytePos</code>
addresses), so the combined length of every source is capped at 4&nbsp;GiB;
overrunning it is a defined error, never a silent wrap into a neighbour's range.

<br>

## Status

<code>v0.2.0</code> implements the core: the <code>SourceMap</code>, stable
<code>SourceId</code>s, the non-overlapping global position space, and the
<code>O(log files)</code> resolver — each invariant property-tested against a naive
linear scan. File loading from disk, line/column integration, and <code>serde</code>
land across the rest of the 0.x series per the
<a href="./dev/ROADMAP.md"><code>ROADMAP</code></a>; the public API is frozen at
<code>1.0.0</code>.

<hr>
<br>

## Contributing

See <a href="./dev/DIRECTIVES.md"><code>dev/DIRECTIVES.md</code></a> for engineering standards and the definition of done. Before a PR: `cargo fmt --all`, `cargo clippy --all-targets --all-features -- -D warnings`, and `cargo test --all-features` must be clean.

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<div id="license">
    <h2>License</h2>
    <p>Licensed under either of</p>
    <ul>
        <li><b>Apache License, Version 2.0</b> &mdash; <a href="./LICENSE-APACHE">LICENSE-APACHE</a></li>
        <li><b>MIT License</b> &mdash; <a href="./LICENSE-MIT">LICENSE-MIT</a></li>
    </ul>
    <p>at your option.</p>
</div>

<div align="center">
  <h2></h2>
  <sup>COPYRIGHT <small>&copy;</small> 2026 <strong>James Gober <me@jamesgober.com>.</strong></sup>
</div>