randbui.c
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上传日期:2022-08-06
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- /* gmp_urandomb_ui -- random bits returned in a ulong.
- 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 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.
- 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 Lesser General Public
- License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
- #include "gmp.h"
- #include "gmp-impl.h"
- /* Currently bits>=BITS_PER_ULONG is quietly truncated to BITS_PER_ULONG,
- maybe this should raise an exception or something. */
- unsigned long
- gmp_urandomb_ui (gmp_randstate_ptr rstate, unsigned long bits)
- {
- mp_limb_t a[LIMBS_PER_ULONG];
- /* start with zeros, since if bits==0 then _gmp_rand will store nothing at
- all, 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
- _gmp_rand (a, rstate, MIN (bits, BITS_PER_ULONG));
- #if LIMBS_PER_ULONG == 1
- return a[0];
- #else
- return a[0] | (a[1] << GMP_NUMB_BITS);
- #endif
- }