nflags=klass()
function nflags:init(o)
 self.c = o.c or 0  -- custom
 self.e = o.e or 0 -- effect
 self.v = o.v or 0 -- volume
 self.w = o.w or 0 -- waveform
 self.p = o.p or 0 -- pitch

 self:validate()
end

function nflags:validate()
 local c,e,v,w,p
  =self.c,self.e,self.v,self.w,self.p

 assert_range(c,0,2,"custom")
 assert_range(e,0,8,"effect")
 assert_range(v,0,8,"volume")
 assert_range(w,0,8,"waveform")
 assert_range(p,0,64,"pitch")
end

function nflags:encode()
 self:validate()
 local c,e,v,w,p
  =self.c,self.e,self.v,self.w,self.p

 c &= 0xffff
 e &= 0xffff
 v &= 0xffff
 w &= 0xffff
 p &= 0xffff

 return (
  (c << 15) |
  (e << 12) |
  (v << 9) |
  (w << 6) |
  (p)
 )
end