module NHC.Binary
  ( clearBits
  ) where

import NHC.GreenCard
import BinHandle ({-type-}BinHandle(..))
import BinPtr    ({-type-}BinPtr(..))

%-#include "cLowBinary.h"
    -- %-#include <stdio.h>

%fun clearBits :: BinHandle -> Int -> IO BinPtr
%call (binHandle bh) (int width)
%code	/* code based closely on putBits */
%  p = (bh->file ? vtell(bh) : mtell(bh));
%  if (bh->highwater < p+width) bh->highwater = p+width;
%  while (width > 0) {
%    int byte    = bh->cptr / 8;
%    int avail   = 8 - (bh->cptr % 8);
%    if  (width >= avail) {
%      bh->cache[byte] = lhs(8-avail,bh->cache[byte]);
%      bh->cptr += avail;
%      width    -= avail;
%      bh->w     = ((bh->w > byte+1) ? bh->w : byte+1);
%      if ((byte+1) == CACHESIZE) nextcache(bh);
%    } else {
%      int rsegment = avail-width;
%      bh->cache[byte] = lhs(8-avail,bh->cache[byte])
%                      | rhs(rsegment,bh->cache[byte]); 
%      bh->cptr += width;
%      width     = 0;
%      bh->w     = ((bh->w > byte+1) ? bh->w : byte+1);
%    }
%  }
%result (binPtr p)