mirror of https://github.com/macssh/macssh.git
74 lines
2.0 KiB
C
Executable File
74 lines
2.0 KiB
C
Executable File
/* mpz_urandomm (rop, state, n) -- Generate a uniform pseudorandom
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integer in the range 0 to N-1, using STATE as the random state
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previously initialized by a call to gmp_randinit().
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Copyright (C) 2000 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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void
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#if __STDC__
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mpz_urandomm (mpz_t rop, gmp_randstate_t rstate, mpz_t n)
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#else
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mpz_urandomm (rop, rstate, n)
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mpz_t rop;
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gmp_randstate_t rstate;
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mpz_t n;
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#endif
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{
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mpz_t t, p, m;
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mp_ptr tp;
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mp_size_t nbits, size;
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int count;
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/* FIXME: Should check for n == 0 and report error */
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size = SIZ (n);
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count_leading_zeros (count, PTR (n)[size - 1]);
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nbits = size * BITS_PER_MP_LIMB - count;
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/* Allocate enough for any mpz function called since a realloc of
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these will fail. */
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MPZ_TMP_INIT (t, size);
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MPZ_TMP_INIT (m, size + 1);
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MPZ_TMP_INIT (p, size + 1);
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/* Let m = highest possible random number plus 1. */
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mpz_set_ui (m, 0);
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mpz_setbit (m, nbits);
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/* Let p = floor(m / n) * n. */
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mpz_fdiv_q (p, m, n);
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mpz_mul (p, p, n);
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tp = PTR (t);
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do
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{
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_gmp_rand (tp, rstate, nbits);
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MPN_NORMALIZE (tp, size); /* FIXME: Really necessary? */
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SIZ (t) = size;
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}
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while (mpz_cmp (t, p) >= 0);
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mpz_mod (rop, t, n);
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}
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