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

1.1       maekawa     1: /* mpz_rrandomb -- Generate a positive random mpz_t of specified bit size, with
                      2:    long runs of consecutive ones and zeros in the binary representation.
                      3:    Meant for testing of other MP routines.
                      4:
                      5: Copyright (C) 2000 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 Lesser General Public License as published by
                     11: the Free Software Foundation; either version 2.1 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 Lesser General Public
                     17: License for more details.
                     18:
                     19: You should have received a copy of the GNU Lesser 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:
                     27: static void gmp_rrandomb _PROTO ((mp_ptr rp, gmp_randstate_t rstate, unsigned long int nbits));
                     28:
                     29: void
                     30: #if __STDC__
                     31: mpz_rrandomb (mpz_ptr x, gmp_randstate_t rstate, unsigned long int nbits)
                     32: #else
                     33: mpz_rrandomb (x, rstate, nbits)
                     34:      mpz_ptr x;
                     35:      gmp_randstate_t rstate;
                     36:      unsigned long int nbits;
                     37: #endif
                     38: {
                     39:   mp_size_t nl = 0;
                     40:
                     41:   if (nbits != 0)
                     42:     {
                     43:       mp_ptr xp;
                     44:       nl = (nbits + BITS_PER_MP_LIMB - 1) / BITS_PER_MP_LIMB;
                     45:       if (x->_mp_alloc < nl)
                     46:        _mpz_realloc (x, nl);
                     47:
                     48:       xp = PTR(x);
                     49:       gmp_rrandomb (xp, rstate, nbits);
                     50:       MPN_NORMALIZE (xp, nl);
                     51:     }
                     52:
                     53:   SIZ(x) = nl;
                     54: }
                     55:
                     56: #define BITS_PER_CHUNK 4
                     57:
                     58: static void
                     59: #if __STDC__
                     60: gmp_rrandomb (mp_ptr rp, gmp_randstate_t rstate, unsigned long int nbits)
                     61: #else
                     62: gmp_rrandomb (rp, rstate, nbits)
                     63:      mp_ptr rp;
                     64:      gmp_randstate_t rstate;
                     65:      unsigned long int nbits;
                     66: #endif
                     67: {
                     68:   int nb;
                     69:   int bit_pos;
                     70:   mp_size_t limb_pos;
                     71:   mp_limb_t ran, ranm;
                     72:   mp_limb_t acc;
                     73:   mp_size_t n;
                     74:
                     75:   bit_pos = nbits % BITS_PER_MP_LIMB;
                     76:   limb_pos = nbits / BITS_PER_MP_LIMB;
                     77:   if (bit_pos == 0)
                     78:     {
                     79:       bit_pos = BITS_PER_MP_LIMB;
                     80:       limb_pos--;
                     81:     }
                     82:
                     83:   acc = 0;
                     84:   while (limb_pos >= 0)
                     85:     {
                     86:       _gmp_rand (&ranm, rstate, BITS_PER_CHUNK + 1);
                     87:       ran = ranm;
                     88:       nb = (ran >> 1) + 1;
                     89:       if ((ran & 1) != 0)
                     90:        {
                     91:          /* Generate a string of ones.  */
                     92:          if (nb > bit_pos)
                     93:            {
                     94:              rp[limb_pos--] = acc | ((((mp_limb_t) 1) << bit_pos) - 1);
                     95:              bit_pos += BITS_PER_MP_LIMB;
                     96:              bit_pos -= nb;
                     97:              acc = (~(mp_limb_t) 0) << bit_pos;
                     98:            }
                     99:          else
                    100:            {
                    101:              bit_pos -= nb;
                    102:              acc |= ((((mp_limb_t) 1) << nb) - 1) << bit_pos;
                    103:            }
                    104:        }
                    105:       else
                    106:        {
                    107:          /* Generate a string of zeroes.  */
                    108:          if (nb > bit_pos)
                    109:            {
                    110:              rp[limb_pos--] = acc;
                    111:              acc = 0;
                    112:              bit_pos += BITS_PER_MP_LIMB;
                    113:            }
                    114:          bit_pos -= nb;
                    115:        }
                    116:     }
                    117: }