X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/blobdiff_plain/ba6e6b64033b1f9de49feccb5c9cd438354481f7..0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a:/mprand.c?ds=sidebyside diff --git a/mprand.c b/mprand.c deleted file mode 100644 index c0f9675f..00000000 --- a/mprand.c +++ /dev/null @@ -1,140 +0,0 @@ -/* -*-c-*- - * - * $Id: mprand.c,v 1.5 2004/04/08 01:36:15 mdw Exp $ - * - * Generate a random multiprecision integer - * - * (c) 1999 Straylight/Edgeware - */ - -/*----- Licensing notice --------------------------------------------------* - * - * This file is part of Catacomb. - * - * Catacomb is free software; you can redistribute it and/or modify - * it under the terms of the GNU Library General Public License as - * published by the Free Software Foundation; either version 2 of the - * License, or (at your option) any later version. - * - * Catacomb 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 Library General Public License for more details. - * - * You should have received a copy of the GNU Library General Public - * License along with Catacomb; if not, write to the Free - * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, - * MA 02111-1307, USA. - */ - -/*----- Header files ------------------------------------------------------*/ - -#include - -#include "grand.h" -#include "mp.h" -#include "mprand.h" - -/*----- Main code ---------------------------------------------------------*/ - -/* --- @mprand@ --- * - * - * Arguments: @mp *d@ = destination integer - * @unsigned b@ = number of bits - * @grand *r@ = pointer to random number source - * @mpw or@ = mask to OR with low-order bits - * - * Returns: A random integer with the requested number of bits. - * - * Use: Constructs an arbitrarily large pseudorandom integer. - * Assuming that the generator @r@ is good, the result is - * uniformly distributed in the interval %$[2^{b - 1}, 2^b)$%. - * The result is then ORred with the given @or@ value. This - * will often be 1, to make the result odd. - */ - -mp *mprand(mp *d, unsigned b, grand *r, mpw or) -{ - size_t sz = (b + 7) >> 3; - arena *a = (d && (d->f & MP_BURN)) ? arena_secure : arena_global; - octet *v = x_alloc(a, sz); - unsigned m; - - /* --- Fill buffer with random data --- */ - - r->ops->fill(r, v, sz); - - /* --- Force into the correct range --- * - * - * This is slightly tricky. Oh, well. - */ - - b = (b - 1) & 7; - m = (1 << b); - v[0] = (v[0] & (m - 1)) | m; - - /* --- Mask, load and return --- */ - - d = mp_loadb(d, v, sz); - d->v[0] |= or; - memset(v, 0, sz); - x_free(a, v); - return (d); -} - -/* --- @mprand_range@ --- * - * - * Arguments: @mp *d@ = destination integer - * @mp *l@ = limit for random number - * @grand *r@ = random number source - * @mpw or@ = mask for low-order bits - * - * Returns: A pseudorandom integer, unformly distributed over the - * interval %$[0, l)$%. - * - * Use: Generates a uniformly-distributed pseudorandom number in the - * appropriate range. - */ - -mp *mprand_range(mp *d, mp *l, grand *r, mpw or) -{ - size_t b = mp_bits(l); - size_t sz = (b + 7) >> 3; - arena *a = (d && (d->f & MP_BURN)) ? arena_secure : arena_global; - octet *v = x_alloc(a, sz); - unsigned m; - - /* --- The algorithm --- * - * - * Rather simpler than most. Find the number of bits in the number %$l$% - * (i.e., the integer %$b$% such that %$2^{b - 1} \le l < 2^b$%), and - * generate pseudorandom integers with %$n$% bits (but not, unlike in the - * function above, with the top bit forced to 1). If the integer is - * greater than or equal to %$l$%, try again. - * - * This is similar to the algorithms used in @lcrand_range@ and friends, - * except that I've forced the `raw' range of the random numbers such that - * %$l$% itself is the largest multiple of %$l$% in the range (since, by - * the inequality above, %$2^b \le 2l$%). This removes the need for costly - * division and remainder operations. - * - * As usual, the number of iterations expected is two. - */ - - b = ((b - 1) & 7) + 1; - m = (1 << b) - 1; - do { - r->ops->fill(r, v, sz); - v[0] &= m; - d = mp_loadb(d, v, sz); - d->v[0] |= or; - } while (MP_CMP(d, >=, l)); - - /* --- Done --- */ - - memset(v, 0, sz); - x_free(a, v); - return (d); -} - -/*----- That's all, folks -------------------------------------------------*/