Code shared from the Rust Playground

playground.rs

  fn ready_next_slice_from_idat(&mut self) -> Result<(), ZlibError> {
    debug_assert!(self.spare_slice.is_empty());
    match self.idat_iter.next() {
      Some(Ok(sli)) => Ok(self.spare_slice = sli),
      otherwise => Err(ZlibError::UnexpectedEndOfStream),
    }
  }

  fn ready_next_byte(&mut self) -> Result<(), ZlibError> {
    debug_assert!(self.spare_bits_count + 8 < 32);
    if self.spare_slice.is_empty() {
      self.ready_next_slice_from_idat()?
    }
    debug_assert!(!self.spare_slice.is_empty());
    self.spare_bits |= u32::from(self.spare_slice[0]) << self.spare_bits_count;
    self.spare_bits_count += 8;
    #[cfg(not(feature = "png_skip_adler_checks"))]
    {
      self.adler = update_adler32(self.adler, &self.spare_slice[0..1]);
    }
    Ok(self.spare_slice = &self.spare_slice[1..])
  }