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Annotation of OpenXM/src/kan96xx/gmp-2.0.2-ssh-2/mpn/generic/lshift.c, Revision 1.1.1.1

1.1       takayama    1: /* mpn_lshift -- Shift left low level.
                      2:
                      3: Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
                      4:
                      5: This file is part of the GNU MP Library.
                      6:
                      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.
                     11:
                     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.
                     16:
                     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. */
                     21:
                     22: #include "gmp.h"
                     23: #include "gmp-impl.h"
                     24:
                     25: /* Shift U (pointed to by UP and USIZE digits long) CNT bits to the left
                     26:    and store the USIZE least significant digits of the result at WP.
                     27:    Return the bits shifted out from the most significant digit.
                     28:
                     29:    Argument constraints:
                     30:    1. 0 < CNT < BITS_PER_MP_LIMB
                     31:    2. If the result is to be written over the input, WP must be >= UP.
                     32: */
                     33:
                     34: mp_limb_t
                     35: #if __STDC__
                     36: mpn_lshift (register mp_ptr wp,
                     37:            register mp_srcptr up, mp_size_t usize,
                     38:            register unsigned int cnt)
                     39: #else
                     40: mpn_lshift (wp, up, usize, cnt)
                     41:      register mp_ptr wp;
                     42:      register mp_srcptr up;
                     43:      mp_size_t usize;
                     44:      register unsigned int cnt;
                     45: #endif
                     46: {
                     47:   register mp_limb_t high_limb, low_limb;
                     48:   register unsigned sh_1, sh_2;
                     49:   register mp_size_t i;
                     50:   mp_limb_t retval;
                     51:
                     52: #ifdef DEBUG
                     53:   if (usize == 0 || cnt == 0)
                     54:     abort ();
                     55: #endif
                     56:
                     57:   sh_1 = cnt;
                     58: #if 0
                     59:   if (sh_1 == 0)
                     60:     {
                     61:       if (wp != up)
                     62:        {
                     63:          /* Copy from high end to low end, to allow specified input/output
                     64:             overlapping.  */
                     65:          for (i = usize - 1; i >= 0; i--)
                     66:            wp[i] = up[i];
                     67:        }
                     68:       return 0;
                     69:     }
                     70: #endif
                     71:
                     72:   wp += 1;
                     73:   sh_2 = BITS_PER_MP_LIMB - sh_1;
                     74:   i = usize - 1;
                     75:   low_limb = up[i];
                     76:   retval = low_limb >> sh_2;
                     77:   high_limb = low_limb;
                     78:   while (--i >= 0)
                     79:     {
                     80:       low_limb = up[i];
                     81:       wp[i] = (high_limb << sh_1) | (low_limb >> sh_2);
                     82:       high_limb = low_limb;
                     83:     }
                     84:   wp[i] = high_limb << sh_1;
                     85:
                     86:   return retval;
                     87: }