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Annotation of OpenXM_contrib/gmp/mpz/rrandomb.c, Revision 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: }