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: }
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