diff options
Diffstat (limited to 'Build/source/libs/gmp/gmp-6.0.0/rand/randmui.c')
-rw-r--r-- | Build/source/libs/gmp/gmp-6.0.0/rand/randmui.c | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/Build/source/libs/gmp/gmp-6.0.0/rand/randmui.c b/Build/source/libs/gmp/gmp-6.0.0/rand/randmui.c new file mode 100644 index 00000000000..2d4ef86aa32 --- /dev/null +++ b/Build/source/libs/gmp/gmp-6.0.0/rand/randmui.c @@ -0,0 +1,86 @@ +/* gmp_urandomm_ui -- uniform random number 0 to N-1 for ulong N. + +Copyright 2003, 2004 Free Software Foundation, Inc. + +This file is part of the GNU MP Library. + +The GNU MP Library is free software; you can redistribute it and/or modify +it under the terms of either: + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your + option) any later version. + +or + + * the GNU General Public License as published by the Free Software + Foundation; either version 2 of the License, or (at your option) any + later version. + +or both in parallel, as here. + +The GNU MP Library is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received copies of the GNU General Public License and the +GNU Lesser General Public License along with the GNU MP Library. If not, +see https://www.gnu.org/licenses/. */ + +#include "gmp.h" +#include "gmp-impl.h" +#include "longlong.h" + + +/* If n is a power of 2 then the test ret<n is always true and the loop is + unnecessary, but there's no need to add special code for this. Just get + the "bits" calculation correct and let it go through normally. + + If n is 1 then will have bits==0 and _gmp_rand will produce no output and + we always return 0. Again there seems no need for a special case, just + initialize a[0]=0 and let it go through normally. */ + +#define MAX_URANDOMM_ITER 80 + +unsigned long +gmp_urandomm_ui (gmp_randstate_ptr rstate, unsigned long n) +{ + mp_limb_t a[LIMBS_PER_ULONG]; + unsigned long ret, bits, leading; + int i; + + if (UNLIKELY (n == 0)) + DIVIDE_BY_ZERO; + + /* start with zeros, since if bits==0 then _gmp_rand will store nothing at + all (bits==0 arises when n==1), or if bits <= GMP_NUMB_BITS then it + will store only a[0]. */ + a[0] = 0; +#if LIMBS_PER_ULONG > 1 + a[1] = 0; +#endif + + count_leading_zeros (leading, (mp_limb_t) n); + bits = GMP_LIMB_BITS - leading - (POW2_P(n) != 0); + + for (i = 0; i < MAX_URANDOMM_ITER; i++) + { + _gmp_rand (a, rstate, bits); +#if LIMBS_PER_ULONG == 1 + ret = a[0]; +#else + ret = a[0] | (a[1] << GMP_NUMB_BITS); +#endif + if (LIKELY (ret < n)) /* usually one iteration suffices */ + goto done; + } + + /* Too many iterations, there must be something degenerate about the + rstate algorithm. Return r%n. */ + ret -= n; + ASSERT (ret < n); + + done: + return ret; +} |