new_contents: #!/usr/bin/env python
  from cffi import FFI as _FFI
  import fcntl
  import array
  
  _ffi = _FFI()
  _ffi.cdef("""
  #define FIONREAD ...
  """)
  
  _C = _ffi.verify("""
  #include <sys/ioctl.h>
  """, libraries=[])
  
  def get_buffered_length(fd):
      buf = array.array("I", [0])
      fcntl.ioctl(fd, _C.FIONREAD, buf)
      return buf[0]
              
  
subject: Add function to read length of bytes in the buffer from the kernel