Annotation of OpenXM_contrib/gmp/mpz/urandomm.c, Revision 1.1.1.2
1.1 maekawa 1: /* mpz_urandomm (rop, state, n) -- Generate a uniform pseudorandom
2: integer in the range 0 to N-1, using STATE as the random state
3: previously initialized by a call to gmp_randinit().
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: #include "longlong.h"
27:
28: void
29: #if __STDC__
30: mpz_urandomm (mpz_t rop, gmp_randstate_t rstate, mpz_t n)
31: #else
32: mpz_urandomm (rop, rstate, n)
33: mpz_t rop;
34: gmp_randstate_t rstate;
35: mpz_t n;
36: #endif
37: {
38: mpz_t t, p, m;
39: mp_ptr tp;
40: mp_size_t nbits, size;
41: int count;
1.1.1.2 ! maekawa 42: TMP_DECL (marker);
! 43:
! 44: TMP_MARK (marker);
1.1 maekawa 45:
46: /* FIXME: Should check for n == 0 and report error */
47:
48: size = SIZ (n);
49: count_leading_zeros (count, PTR (n)[size - 1]);
50: nbits = size * BITS_PER_MP_LIMB - count;
51:
52: /* Allocate enough for any mpz function called since a realloc of
53: these will fail. */
54: MPZ_TMP_INIT (t, size);
55: MPZ_TMP_INIT (m, size + 1);
56: MPZ_TMP_INIT (p, size + 1);
57:
58: /* Let m = highest possible random number plus 1. */
59: mpz_set_ui (m, 0);
60: mpz_setbit (m, nbits);
61:
62: /* Let p = floor(m / n) * n. */
63: mpz_fdiv_q (p, m, n);
64: mpz_mul (p, p, n);
65:
66: tp = PTR (t);
67: do
68: {
69: _gmp_rand (tp, rstate, nbits);
70: MPN_NORMALIZE (tp, size); /* FIXME: Really necessary? */
71: SIZ (t) = size;
72: }
73: while (mpz_cmp (t, p) >= 0);
74:
75: mpz_mod (rop, t, n);
1.1.1.2 ! maekawa 76:
! 77: TMP_FREE (marker);
1.1 maekawa 78: }
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