fn from_instructions(
    instructions: &mut Instructions,
    input: usize,
    offset: usize,
  ) -> Result<Option<Self>> {
    if instructions.next().transpose()? != Some(Instruction::Op(opcodes::all::OP_IF)) {
      return Ok(None);
    }

    if instructions.next().transpose()? != Some(Instruction::PushBytes((&PROTOCOL_ID).into())) {
      return Ok(None);
    }

    let mut pushnum = false;

    let mut payload = Vec::new();

    loop {
      match instructions.next().transpose()? {
        None => return Ok(None),
        Some(Instruction::Op(opcodes::all::OP_ENDIF)) => {
          return Ok(Some(Envelope {
            input: input.try_into().unwrap(),
            offset: offset.try_into().unwrap(),
            payload,
            pushnum,
          }));
        }
        Some(Instruction::Op(opcodes::all::OP_PUSHNUM_NEG1)) => {
          pushnum = true;
          payload.push(vec![0x81]);
        }
        Some(Instruction::Op(opcodes::all::OP_PUSHNUM_1)) => {
          pushnum = true;
          payload.push(vec![1]);