/*
 * bitio.c -- bit based I/O package
 * (C)Copyright 1998, 99 by Hiroshi Takekawa
 * This file is part of Enfle.
 *
 * Last Modified: Sat Oct 16 22:29:01 1999.
 * $Id: bitio.c,v 1.1 1999/10/18 12:30:33 sian Exp $
 *
 * Enfle is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Enfle is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include <stdlib.h>
#include "bitio.h"

Bit_stream *
bitio_init(Archive *ar)
{
  Bit_stream *st;

  if ((st = calloc(1, sizeof(Bit_stream))) == NULL)
    return NULL;
  st->left = st->buf = 0;
  st->ar = ar;

  return st;
}

int
bitio_getbit(Bit_stream *p)
{
  if (p->left == 0) {
    if ((p->buf = archive_getc(p->ar)) == EOF)
      return -1;
    p->left = 8;
  }
  p->left--;

  return (p->buf >> p->left) & 1;
}

int
bitio_getbits(Bit_stream *p, int bits)
{
  int c;

  if (!bits)
    return 0;
  while (bits > p->left) {
    if ((c = archive_getc(p->ar)) == EOF)
      return -1;
    p->buf = (p->buf << 8) | c;
    p->left += 8;
  }
  p->left -= bits;

  return (p->buf >> p->left) & ((1 << bits) - 1);
}