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Diff for /OpenXM_contrib/gmp/mpz/Attic/scan0.c between version 1.1 and 1.1.1.3

version 1.1, 2000/01/10 15:35:27 version 1.1.1.3, 2003/08/25 16:06:33
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 /* mpz_scan0(op, startbit) -- Scan for the next set bit, starting at startbit.  /* mpz_scan0 -- search for a 0 bit.
   
 Copyright (C) 1996 Free Software Foundation, Inc.  Copyright 2000, 2001, 2002 Free Software Foundation, Inc.
   
 This file is part of the GNU MP Library.  This file is part of the GNU MP Library.
   
 The GNU MP Library is free software; you can redistribute it and/or modify  The GNU MP Library is free software; you can redistribute it and/or modify
 it under the terms of the GNU Library General Public License as published by  it under the terms of the GNU Lesser General Public License as published by
 the Free Software Foundation; either version 2 of the License, or (at your  the Free Software Foundation; either version 2.1 of the License, or (at your
 option) any later version.  option) any later version.
   
 The GNU MP Library is distributed in the hope that it will be useful, but  The GNU MP Library is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 License for more details.  License for more details.
   
 You should have received a copy of the GNU Library General Public License  You should have received a copy of the GNU Lesser General Public License
 along with the GNU MP Library; see the file COPYING.LIB.  If not, write to  along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
 the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,  the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 MA 02111-1307, USA. */  MA 02111-1307, USA. */
   
 #include "gmp.h"  #include "gmp.h"
 #include "gmp-impl.h"  #include "gmp-impl.h"
   #include "longlong.h"
   
 unsigned long int  
 #if __STDC__  /* mpn_scan0 can't be used for the u>0 search since there might not be a 0
 mpz_scan0 (mpz_srcptr u, unsigned long int starting_bit)     bit before the end of the data.  mpn_scan1 could be used for the inverted
 #else     search under u<0, but usually the search won't go very far so it seems
 mpz_scan0 (u, starting_bit)     reasonable to inline that code.  */
      mpz_srcptr u;  
      unsigned long int starting_bit;  unsigned long
 #endif  mpz_scan0 (mpz_srcptr u, unsigned long starting_bit)
 {  {
   return mpn_scan0 (u->_mp_d, starting_bit);    mp_srcptr      u_ptr = PTR(u);
     mp_size_t      size = SIZ(u);
     mp_size_t      abs_size = ABS(size);
     mp_srcptr      u_end = u_ptr + abs_size;
     unsigned long  starting_limb = starting_bit / GMP_NUMB_BITS;
     mp_srcptr      p = u_ptr + starting_limb;
     mp_limb_t      limb;
     int            cnt;
   
     /* When past end, there's an immediate 0 bit for u>=0, or no 0 bits for
        u<0.  Notice this test picks up all cases of u==0 too. */
     if (starting_limb >= abs_size)
       return (size >= 0 ? starting_bit : ULONG_MAX);
   
     limb = *p;
   
     if (size >= 0)
       {
         /* Mask to 1 all bits before starting_bit, thus ignoring them. */
         limb |= (CNST_LIMB(1) << (starting_bit % GMP_NUMB_BITS)) - 1;
   
         /* Search for a limb which isn't all ones.  If the end is reached then
            the zero bit immediately past the end is returned.  */
         while (limb == GMP_NUMB_MAX)
           {
             p++;
             if (p == u_end)
               return (unsigned long) abs_size * GMP_NUMB_BITS;
             limb = *p;
           }
   
         /* Now seek low 1 bit. */
         limb = ~limb;
       }
     else
       {
         mp_srcptr  q;
   
         /* If there's a non-zero limb before ours then we're in the ones
            complement region.  Search from *(p-1) downwards since that might
            give better cache locality, and since a non-zero in the middle of a
            number is perhaps a touch more likely than at the end.  */
         q = p;
         while (q != u_ptr)
           {
             q--;
             if (*q != 0)
               goto inverted;
           }
   
         /* Adjust so ~limb implied by searching for 1 bit below becomes -limb.
            If limb==0 here then this isn't the beginning of twos complement
            inversion, but that doesn't matter because limb==0 is a zero bit
            immediately (-1 is all ones for below).  */
         limb--;
   
       inverted:
         /* Now seeking a 1 bit. */
   
         /* Mask to 0 all bits before starting_bit, thus ignoring them. */
         limb &= (MP_LIMB_T_MAX << (starting_bit % GMP_NUMB_BITS));
   
         if (limb == 0)
           {
             /* If the high limb is zero after masking, then no 1 bits past
                starting_bit.  */
             p++;
             if (p == u_end)
               return ULONG_MAX;
   
             /* Search further for a non-zero limb.  The high limb is non-zero,
                if nothing else.  */
             for (;;)
               {
                 limb = *p;
                 if (limb != 0)
                   break;
                 p++;
                 ASSERT (p < u_end);
               }
           }
       }
   
     /* Mask to 0 all bits above the lowest 1 bit. */
     ASSERT (limb != 0);
     limb &= -limb;
   
     count_leading_zeros (cnt, limb);
     return (p - u_ptr) * GMP_NUMB_BITS + GMP_LIMB_BITS - 1 - cnt;
 }  }
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  Added in v.1.1.1.3
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