Function encode 

pub fn encode(
    chunk: &[u8],
    k: usize,
    n: usize,
) -> BpResult<Vec<EncodedFragment>>

Split chunk into k source symbols and produce n encoded fragments.

The first k fragments are systematic (identity coding vectors), so the original symbols can always be recovered from frags[..k] without any linear algebra. The remaining n-k fragments use random coefficients drawn from GF(2⁸) for redundancy.

Arguments

• chunk — raw bytes of the chunk to encode.
• k — number of source symbols (recovery threshold).
• n — total number of encoded fragments to produce (n ≥ k).

Errors

Returns an error if n < k or chunk is empty.