1 /* mpn_scan0 -- Scan from a given bit position for the next clear bit.
3 Copyright (C) 1994, 1996 Free Software Foundation, Inc.
5 This file is part of the GNU MP Library.
7 The GNU MP Library is free software; you can redistribute it and/or modify
8 it under the terms of the GNU Library General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or (at your
10 option) any later version.
12 The GNU MP Library is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
15 License for more details.
17 You should have received a copy of the GNU Library General Public License
18 along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19 the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20 MA 02111-1307, USA. */
27 1. What if starting_bit is not within U? Caller's problem?
28 2. Bit index should be 'unsigned'?
31 1. U must sooner ot later have a limb with a clear bit.
36 mpn_scan0 (register mp_srcptr up,
37 register unsigned long int starting_bit)
39 mpn_scan0 (up, starting_bit)
40 register mp_srcptr up;
41 register unsigned long int starting_bit;
44 mp_size_t starting_word;
49 /* Start at the word implied by STARTING_BIT. */
50 starting_word = starting_bit / BITS_PER_MP_LIMB;
51 p = up + starting_word;
54 /* Mask off any bits before STARTING_BIT in the first limb. */
55 alimb &= - (mp_limb_t) 1 << (starting_bit % BITS_PER_MP_LIMB);
60 count_leading_zeros (cnt, alimb & -alimb);
61 return (p - up) * BITS_PER_MP_LIMB - 1 - cnt;