Function pad_80 

pub fn pad_80(
    data: &mut Vec<u8>,
    block_size: usize,
) -> Result<(), Box<dyn Error>>

Apply 0x80 padding to a given byte array, in-place.

This function pads the input byte array so that its length is a multiple of the specified block size. The padding starts with a single 0x80 byte followed by 0x00 bytes.

Arguments

• data : A mutable reference to the byte array (Vec<u8>) to be padded.
• block_size : The block size (usize) for padding.

Returns

• Ok(()) if the padding is successfully applied.
• Err(Box<dyn Error>) if the block size is invalid.