Crate yencoding_multi 

Multi-part yEnc Usenet article reassembly.

Background

Large binary files on Usenet are split across multiple articles. Each article is independently yEnc-encoded and carries =ypart begin=N end=M headers that declare exactly which byte range of the final file this article contains. After collecting all articles and decoding each with the yencoding crate, the decoded parts can be assembled back into the original file.

How this crate differs from uuencoding-multi

uuencoding-multi tracks parts by part number (1-based integer from the subject line) because UUencode articles carry no byte-range headers. yEnc articles carry explicit byte-range headers (=ypart begin=/end=), so this crate tracks parts by byte range instead. This enables:

• Immediate overlap/gap detection without knowing the total part count.
• Out-of-order assembly without sorting.
• Byte-accurate missing-range reporting.

What this crate does NOT do

• NZB parsing — NZB is an XML format describing which articles carry each file. Use a dedicated NZB parser to extract the article list before passing decoded parts here.
• NNTP transport — fetching articles is the caller’s responsibility.
• Subject-line parsing — use uuencoding-multi::parse_subject or similar for subject parsing if needed; this crate operates on decoded bytes only.
• yEnc decoding — use the yencoding crate to decode individual articles before passing them to Assembler.

Security

Reassembled data may represent a compressed archive (.tar.gz, .zip, .rar, etc.). This crate never decompresses the output. Any subsequent decompression is the caller’s responsibility and must be independently guarded against decompression-bomb attacks before beginning decompression.

Quick start

use yencoding_multi::Assembler;
use yencoding::decode;

// Imagine these raw article bytes come from an NNTP server.
let raw_articles: Vec<Vec<u8>> = todo!("fetch from NNTP");
let total_file_size: u64 = todo!("from =ybegin size= or NZB");
let whole_file_crc32_from_nzb: Option<u32> = todo!("from NZB; parts carry their own CRC");

let mut assembler = Assembler::new(total_file_size).expect("total_size too large");
// CRC from parts is extracted automatically by add_part(); call set_expected_crc32()
// only when you have the CRC from an out-of-band source such as an NZB file.
if let Some(crc) = whole_file_crc32_from_nzb {
    assembler.set_expected_crc32(crc);
}

for raw in &raw_articles {
    let part = decode(raw).expect("decode failed");
    assembler.add_part(&part).expect("assembly error");
}

if assembler.is_complete() {
    let file_bytes = assembler.finish().expect("CRC mismatch");
    // IMPORTANT: apply size/resource limits before decompressing file_bytes.
} else {
    eprintln!("still missing: {:?}", assembler.missing_ranges());
}

Structs

Assembler

Reassembles multi-part yEnc articles into a complete file.

Enums

AssemblyError

Errors produced by crate::Assembler operations.

Constants

MAX_TOTAL_SIZE

Maximum total_size accepted by Assembler::new.