uuencoding-multi

Multi-part UUencoded Usenet/email post reassembly.

Multi-part UUencoding was the standard way to post binary files to Usenet before MIME. A large file was split into numbered parts, each posted as a separate message with a subject line like filename.tar.gz (03/17). This crate reassembles those parts.

Depends on the uuencoding crate for decoding individual parts.

Features

• Parse 5 real-world subject line formats to extract part number and total
• Accumulate parts via PartCollection with gap detection and is_complete() check
• Best-effort TOC (table-of-contents) parsing for part-0 summary posts
• reassemble() — decode each part and concatenate into the original file bytes
• Partial reassembly when parts are missing (is_truncated flag, missing_parts list)
• No panics on any input
• No unsafe code
• MSRV: 1.75

Quick start

use uuencoding_multi::{PartCollection, PartEntry, parse_subject, reassemble};

// Step 1: parse subject lines to identify part number and grouping key
let sp = parse_subject("bigfile.tar.gz (02/05)").unwrap();
assert_eq!(sp.part_index, Some(2));
assert_eq!(sp.part_total, Some(5));
assert_eq!(sp.base_subject, "bigfile.tar.gz");

// Step 2: collect parts (body_bytes is the raw UU-encoded message body)
let mut coll = PartCollection::with_total(3);
coll.add(PartEntry { part_number: 1, body_bytes: part1_bytes, subject: None }).unwrap();
coll.add(PartEntry { part_number: 2, body_bytes: part2_bytes, subject: None }).unwrap();
coll.add(PartEntry { part_number: 3, body_bytes: part3_bytes, subject: None }).unwrap();

// Step 3: reassemble when complete
if coll.is_complete() {
    let file = reassemble(&coll).unwrap();
    // IMPORTANT: apply size/resource limits before decompressing file.data
    println!("{}: {} bytes (mode {:o})", file.filename, file.data.len(), file.mode);
}

Subject line formats supported

Re: and Fwd: prefixes are stripped before matching. yEnc subjects return None (distinct encoding, out of scope for this crate).

Partial reassembly

When parts are missing, reassemble() still returns Ok rather than an error:

let file = reassemble(&coll).unwrap();
if file.is_truncated {
    if !file.missing_parts.is_empty() {
        // Gap in the collection — these parts were absent
        eprintln!("missing parts: {:?}", file.missing_parts);
    } else {
        // All parts present but at least one had a truncated UU body
        eprintln!("per-part encoding problem");
    }
}

Error types

pub enum MultiUuError {
    /// reassemble() called with no parts (part_number >= 1).
    EmptyCollection,
    /// uuencoding::decode failed on one of the part bodies.
    DecodeError(uuencoding::UuError),
    /// Two parts with the same part_number were added.
    DuplicatePart { part_number: u32 },
}

Security

Reassembled data is raw bytes which may be a compressed archive. Any decompression is the caller's responsibility and must be independently guarded against decompression bombs. This crate does not decompress.

License

MIT OR Apache-2.0