nom::length_value!

macro_rules! length_value(
  ($i:expr, $f:expr, $g:expr) => (
    {
      match $f($i) {
        $crate::IResult::Error(a)      => $crate::IResult::Error(a),
        $crate::IResult::Incomplete(i) => $crate::IResult::Incomplete(i),
        $crate::IResult::Done(i1,nb)   => {
          let length_token     = $i.len() - i1.len();
          let mut begin        = 0;
          let mut remaining    = i1.len();
          let mut res          = Vec::new();
          let mut err          = false;
          let mut inc          = $crate::Needed::Unknown;

          loop {
            if res.len() == nb as usize {
              break;
            }
            match $g(&i1[begin..]) {
              $crate::IResult::Done(i2,o2) => {
              res.push(o2);
                let parsed  = remaining - i2.len();
                begin      += parsed;
                remaining   = i2.len();
              },
              $crate::IResult::Error(_)      => {
                err = true;
              },
              $crate::IResult::Incomplete(a) => {
                inc = a;
                break;
              }
            }
          }
          if err {
            $crate::IResult::Error($crate::Err::Position($crate::ErrorCode::LengthValue as u32,$i))
          } else if res.len() < nb as usize {
            match inc {
              $crate::Needed::Unknown      => $crate::IResult::Incomplete($crate::Needed::Unknown),
              $crate::Needed::Size(length) => $crate::IResult::Incomplete($crate::Needed::Size(length_token + nb as usize * length))
            }
          } else {
            $crate::IResult::Done(&i1[begin..], res)
          }

        }
      }
    }
  );
  ($i:expr, $f:expr, $g:expr, $length:expr) => (
    {
      match $f($i) {
        $crate::IResult::Error(a)      => $crate::IResult::Error(a),
        $crate::IResult::Incomplete(i) => $crate::IResult::Incomplete(i),
        $crate::IResult::Done(i1,nb)   => {
          let length_token     = $i.len() - i1.len();
          let mut begin        = 0;
          let mut remaining    = i1.len();
          let mut res          = Vec::new();
          let mut err          = false;
          let mut inc          = $crate::Needed::Unknown;

          loop {
            if res.len() == nb as usize {
              break;
            }
            match $g(&i1[begin..]) {
              $crate::IResult::Done(i2,o2) => {
              res.push(o2);
                let parsed  = remaining - i2.len();
                begin      += parsed;
                remaining   = i2.len();
              },
              $crate::IResult::Error(_)      => {
                err = true;
              },
              $crate::IResult::Incomplete(a) => {
                inc = a;
                break;
              }
            }
          }
          if err {
            $crate::IResult::Error($crate::Err::Position($crate::ErrorCode::LengthValue as u32,$i))
          } else if res.len() < nb as usize {
            match inc {
              $crate::Needed::Unknown => $crate::IResult::Incomplete($crate::Needed::Unknown),
              $crate::Needed::Size(_) => $crate::IResult::Incomplete($crate::Needed::Size(length_token + nb as usize * $length))
            }
          } else {
            $crate::IResult::Done(&i1[begin..], res)
          }

        }
      }
    }
  );
);

length_value!(I -> IResult<I, nb>, I -> IResult<I,O>) => I -> IResult<I, Vec<O>> gets a number from the first parser, then applies the second parser that many times