source-lang 1.0.0

Installation

[dependencies]
source-lang = "1.0"

Or from the terminal:

cargo add source-lang

Usage

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

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:

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>(())

Resolve a global position to its file and 1-based line/column in one step — what a diagnostic renderer needs to print file:line:col:

use source_lang::{BytePos, LineCol, SourceMap};

let mut map = SourceMap::new();
map.add("a.rs", "fn a() {}")?;                  // global 0..9
let b = map.add("b.rs", "let x = 1;\nlet y = 2;")?; // global 9..30

let (id, lc) = map.line_col(BytePos::new(20)).expect("in range");
assert_eq!(id, b);
assert_eq!(lc, LineCol::new(2, 1)); // second line of b.rs
# Ok::<(), source_lang::SourceMapError>(())

Load untrusted input — a file from disk or raw bytes from a buffer — through the same checks, so bad input is a defined error rather than a panic:

use source_lang::{SourceMap, SourceMapError};

let mut map = SourceMap::new();
map.set_max_source_len(1 << 20); // cap any single source at 1 MiB

// Raw bytes are validated as UTF-8 before they are stored.
let id = map.add_bytes("config.toml", b"name = \"demo\"")?;
assert_eq!(map.source(id).unwrap().text(), "name = \"demo\"");

// Non-UTF-8 input is rejected, naming the source.
let err = map.add_bytes("blob.bin", &[0xff, 0xfe]).unwrap_err();
assert!(matches!(err, SourceMapError::NotUtf8 { .. }));
# Ok::<(), source_lang::SourceMapError>(())

With the default std feature, map.add_file("src/main.rs") reads a path from disk through those same checks, rejecting an oversize file from its metadata before a byte is read.

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

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>(())

With the serde feature, a whole SourceMap round-trips through any serde format — its spans and ids are regenerated on load, so the layout is validated rather than trusted:

let mut map = SourceMap::new();
map.add("main.rs", "fn main() {}")?;
let json = serde_json::to_string(&map)?;
let restored: SourceMap = serde_json::from_str(&json)?;
assert_eq!(map, restored);

See docs/API.md for the full reference.

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 locate is a binary search, O(log files), that borrows the resolved source rather than copying it. The shared space is 32 bits wide (the same envelope a single BytePos addresses), so the combined length of every source is capped at 4 GiB; overrunning it is a defined error, never a silent wrap into a neighbour's range.

Status

v1.0.0 is the stable release: the public API is frozen and follows Semantic Versioning, with no breaking changes before 2.0. The surface is the full source map — the SourceMap, stable SourceIds, and the non-overlapping global position space with its O(log files) resolver, disk and buffer loading, line_col resolution, and optional serde — each invariant property-tested against a naive linear scan, verified on Linux, macOS, and Windows. See the SemVer promise.

Contributing

See dev/DIRECTIVES.md 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.