yencoding

yEnc encoding and decoding for Usenet binary posts.

yEnc (2001) replaced UUencode and Base64 on Usenet by passing most bytes through with only a +42 offset, giving ~1–2% overhead instead of 33%. This crate provides a pure-Rust, no-filesystem, no-unsafe implementation.

Features

• decode(input) — decode a yEnc article from raw bytes, with CRC32 verification
• encode(data, filename, line_length) — encode bytes as a single-part article
• encode_part(...) — encode one part of a multi-part series
• Handles preamble text before =ybegin (NNTP article headers, etc.)
• Accepts both LF and CRLF line endings
• Handles NNTP dot-stuffing
• total_parts exposed on YencMetadata for multi-part reassembly
• No filesystem I/O — all operations on &[u8] / Vec<u8>
• No unsafe code
• MSRV: 1.75

Usage

use yencoding::{decode, encode, DEFAULT_LINE_LENGTH};

// Decode a yEnc article (preamble/NNTP headers are skipped automatically)
let article: &[u8] = b"=ybegin line=128 size=3 name=hi.bin\r\n},-\r\n=yend size=3 crc32=b63cfbcd\r\n";
let part = decode(article).unwrap();
assert_eq!(part.data, &[0u8, 1, 2]);
assert_eq!(part.metadata.filename, "hi.bin");
assert!(part.crc32_verified);

// Encode bytes as a single-part article
let encoded = encode(b"Hello", "hello.bin", DEFAULT_LINE_LENGTH);
assert!(encoded.starts_with(b"=ybegin"));

Multi-part articles

For multi-part Usenet posts, decode each article individually with decode(), then reassemble using the companion yencoding-multi crate. DecodedPart::metadata.total_parts and part_begin/part_end carry the information needed for reassembly without separately parsing subject lines.

Error types

pub enum YencError {
    NoHeader,                            // no =ybegin line found
    InvalidHeader { field: String },     // required field missing or unparsable
    CrcMismatch { expected: u32, actual: u32 },
    UnexpectedEof,                       // =yend line never found
}

Security

Decoded bytes may represent a compressed archive. Any decompression is the caller's responsibility and must be independently guarded against decompression-bomb attacks. This crate does not decompress.

License

MIT OR Apache-2.0