Analyzing in-memory source

big-code-analysis never requires source to live on disk. The recommended entry point analyze takes a Source carrying the language, source bytes, and an optional caller-supplied display name; no filesystem path is involved unless the C/C++ preprocessor lookup needs one (Source::preproc_path).

This is useful for:

• Scoring generated code before it is written out.
• Scoring pre-processed or bundled source (e.g. after a template expansion).
• Driving the analyzer from a language server or editor plugin that already holds the buffer in memory.
• Stdin pipelines and unit tests that should not touch the filesystem.

Reading from a buffer

#![allow(unused)]
fn main() {
use big_code_analysis::{analyze, MetricsOptions, Source, LANG};

fn analyze_buffer(source: &[u8]) -> Option<u64> {
    // `Source::name` is the display identifier baked into the
    // top-level `FuncSpace`. Pick whatever is meaningful for
    // downstream consumers (logs, JSON output); pass `None` if
    // you have nothing useful to attach.
    let space = analyze(
        Source::new(LANG::Python, source).with_name(Some("<stdin>".to_owned())),
        MetricsOptions::default(),
    )
    .ok()?;

    Some(space.metrics.cognitive.cognitive_sum())
}
}

Source::new borrows the source bytes — the caller retains ownership. If your downstream pipeline needs to highlight findings on the same bytes, you can keep using the original buffer after analyze returns.

Reading from stdin

use std::io::{self, Read};

use big_code_analysis::{analyze, MetricsOptions, Source, LANG};

fn main() -> io::Result<()> {
    let mut source = Vec::new();
    io::stdin().read_to_end(&mut source)?;

    let space = match analyze(
        Source::new(LANG::Javascript, &source)
            .with_name(Some("<stdin>".to_owned())),
        MetricsOptions::default(),
    ) {
        Ok(space) => space,
        Err(err) => {
            eprintln!("parse failed: {err}");
            std::process::exit(1);
        }
    };

    println!("{}", space.metrics.cyclomatic.cyclomatic_sum());
    Ok(())
}

Picking the language from content

If you do not know the language up front, combine guess_language with analyze. guess_language peeks at the path extension, an Emacs mode-line, and the shebang in that order:

#![allow(unused)]
fn main() {
use std::path::PathBuf;

use big_code_analysis::{analyze, guess_language, MetricsOptions, Source};

fn analyze_unknown(path: PathBuf, source: Vec<u8>) -> Option<()> {
    let (lang, _name) = guess_language(&source, &path);
    let lang = lang?;
    // `.ok()?` collapses `MetricsError` into `None` so this helper's
    // `Option` return shape is preserved. See `error-handling.md` for
    // a richer mapping that preserves the variant.
    let _space = analyze(
        Source::new(lang, &source)
            .with_name(path.to_str().map(str::to_owned)),
        MetricsOptions::default(),
    )
    .ok()?;
    Some(())
}
}

guess_language returns (None, _) for unrecognised extensions — treat that as "skip" rather than as a hard error.

Watch out for these

• Name identity matters. Top-level FuncSpace::name is whatever string you put in Source::name. Two analyses sharing the same name will look identical to a downstream consumer that keys on it. Use distinct labels for distinct buffers.
• Source::name is Option<String>. Passing None leaves the top-level FuncSpace::name as None — useful for ad-hoc snippets that have no meaningful identity. Downstream consumers that require a stable identifier should check for None explicitly.
• No filesystem fallback. Unlike the CLI, the library does not read sibling files, follow #includes, or interpret a .gitignore. Feed it exactly the bytes you want analyzed.

Reusing one parse for several passes

analyze is the one-shot entry point: bytes in, FuncSpace out. When you need more than metrics from a single parse — operators and operands, an AST dump, a function-span list — parse once with Ast::parse and call the per-pass methods on the returned handle (metrics, ops, dump, functions, …). See Parse once, run metrics many times.