pub fn padded_block(message: &[u8], block_index: usize) -> Option<[u8; 64]>Expand description
Produces one padded SHA-256 block from an immutable byte stream.
This is the canonical block-stream contract used by the fixed HashSigs
sizes. It inserts 0x80, zero fill, and the 64-bit big-endian message length.
None is returned for an out-of-range block or a message whose bit length
does not fit SHA-256’s 64-bit length field.