Function decode 

pub fn decode(
    code: &LdpcCode,
    llr: &mut [i16],
    max_iters: usize,
) -> Result<usize, LdpcError>

Decodes using layered min-sum belief propagation.

llr must have at least code.n + code.punctured entries. The first code.n are channel LLRs (positive = likely 0, negative = likely 1). The remaining code.punctured entries should be 0 (no channel information for punctured bits).

Returns Ok(iterations) on success (0 = already valid). After return, hard decision for bit i: 0 if llr[i] >= 0, 1 if llr[i] < 0. The first code.k bits are decoded info.

Currently supports k=1024 codes only.