aa9bc17601
BMakefiles and other bits will follow. Requested by: Andrey Chernov Made world by: Chuck Robey
63 lines
1.9 KiB
C
63 lines
1.9 KiB
C
/* mpn_scan0 -- Scan from a given bit position for the next clear bit.
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Copyright (C) 1994, 1996 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Library General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
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License for more details.
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You should have received a copy of the GNU Library General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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/* Design issues:
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1. What if starting_bit is not within U? Caller's problem?
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2. Bit index should be 'unsigned'?
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Argument constraints:
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1. U must sooner ot later have a limb with a clear bit.
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*/
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unsigned long int
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#if __STDC__
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mpn_scan0 (register mp_srcptr up,
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register unsigned long int starting_bit)
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#else
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mpn_scan0 (up, starting_bit)
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register mp_srcptr up;
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register unsigned long int starting_bit;
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#endif
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{
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mp_size_t starting_word;
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mp_limb_t alimb;
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int cnt;
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mp_srcptr p;
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/* Start at the word implied by STARTING_BIT. */
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starting_word = starting_bit / BITS_PER_MP_LIMB;
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p = up + starting_word;
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alimb = ~*p++;
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/* Mask off any bits before STARTING_BIT in the first limb. */
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alimb &= - (mp_limb_t) 1 << (starting_bit % BITS_PER_MP_LIMB);
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while (alimb == 0)
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alimb = ~*p++;
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count_leading_zeros (cnt, alimb & -alimb);
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return (p - up) * BITS_PER_MP_LIMB - 1 - cnt;
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}
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