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Annotation of OpenXM_contrib/gmp/mpz/sizeinbase.c, Revision 1.1.1.1

1.1       maekawa     1: /* mpz_sizeinbase(x, base) -- return an approximation to the number of
                      2:    character the integer X would have printed in base BASE.  The
                      3:    approximation is never too small.
                      4:
                      5: Copyright (C) 1991, 1993, 1994, 1995 Free Software Foundation, Inc.
                      6:
                      7: This file is part of the GNU MP Library.
                      8:
                      9: The GNU MP Library is free software; you can redistribute it and/or modify
                     10: it under the terms of the GNU Library General Public License as published by
                     11: the Free Software Foundation; either version 2 of the License, or (at your
                     12: option) any later version.
                     13:
                     14: The GNU MP Library is distributed in the hope that it will be useful, but
                     15: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
                     16: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
                     17: License for more details.
                     18:
                     19: You should have received a copy of the GNU Library General Public License
                     20: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     21: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     22: MA 02111-1307, USA. */
                     23:
                     24: #include "gmp.h"
                     25: #include "gmp-impl.h"
                     26: #include "longlong.h"
                     27:
                     28: size_t
                     29: #if __STDC__
                     30: mpz_sizeinbase (mpz_srcptr x, int base)
                     31: #else
                     32: mpz_sizeinbase (x, base)
                     33:      mpz_srcptr x;
                     34:      int base;
                     35: #endif
                     36: {
                     37:   mp_size_t size = ABS (x->_mp_size);
                     38:   int lb_base, cnt;
                     39:   size_t totbits;
                     40:
                     41:   /* Special case for X == 0.  */
                     42:   if (size == 0)
                     43:     return 1;
                     44:
                     45:   /* Calculate the total number of significant bits of X.  */
                     46:   count_leading_zeros (cnt, x->_mp_d[size - 1]);
                     47:   totbits = size * BITS_PER_MP_LIMB - cnt;
                     48:
                     49:   if ((base & (base - 1)) == 0)
                     50:     {
                     51:       /* Special case for powers of 2, giving exact result.  */
                     52:
                     53:       count_leading_zeros (lb_base, base);
                     54:       lb_base = BITS_PER_MP_LIMB - lb_base - 1;
                     55:
                     56:       return (totbits + lb_base - 1) / lb_base;
                     57:     }
                     58:   else
                     59:     return (size_t) (totbits * __mp_bases[base].chars_per_bit_exactly) + 1;
                     60: }