cb9cadad57
Change-Id: Ib246f1fbfce93274020ee93ce461e3d8bd8b9f17 Signed-off-by: Ed Warnicke <eaw@cisco.com>
157 lines
4.6 KiB
C
157 lines
4.6 KiB
C
/*
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* Copyright (c) 2015 Cisco and/or its affiliates.
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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Copyright (c) 2001, 2002, 2003 Eliot Dresselhaus
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef included_random_h
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#define included_random_h
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#include <vppinfra/clib.h>
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#include <vppinfra/vec.h> /* for vec_resize */
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#include <vppinfra/format.h> /* for unformat_input_t */
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/** \file
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Linear Congruential Random Number Generator
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This specific random number generator is described in
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"Numerical Recipes in C", 2nd edition, page 284. If you need
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random numbers with really excellent statistics, take a look
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at Chapter 7...
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By definition, a linear congruential random number generator
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is of the form: rand[i+1] = a*rand[i] + c (mod m) for specific
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values of (a,c,m).
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In this case, choose m = 2**32 and use the low-order 32-bits of
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the 64-bit product a*N[i]. Knuth suggests the use of a=1664525,
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H.W. Lewis has tested C=1013904223 extensively. This routine is
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reputedly as good as any 32-bit LCRN, and costs only a single
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multiply-add.
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Several variants: 32/64-bit, machine word width,
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f64 on the closed interval [0,1].
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*/
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/** \brief 32-bit random number generator */
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always_inline u32 random_u32 (u32 * seed)
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{
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*seed = (1664525 * *seed) + 1013904223;
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return *seed;
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}
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/* External test routine. */
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int test_random_main (unformat_input_t * input);
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/** \brief Maximum value returned by random_u32() */
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always_inline u32 random_u32_max (void)
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{ return 0xffffffff; }
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#ifdef CLIB_UNIX
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#include <unistd.h> /* for getpid */
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/** \brief Default random seed (unix/linux user-mode) */
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always_inline uword random_default_seed (void)
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{ return getpid (); }
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#endif
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#ifdef CLIB_LINUX_KERNEL
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#include <linux/sched.h> /* for jiffies */
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/** \brief Default random seed (Linux kernel) */
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always_inline uword random_default_seed (void)
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{ return jiffies; }
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#endif
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#ifdef CLIB_STANDALONE
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extern u32 standalone_random_default_seed;
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always_inline u32 random_default_seed (void)
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{ return standalone_random_default_seed; }
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#endif
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/** \brief 64-bit random number generator
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created via two calls to random_u32(). Quick and dirty.
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*/
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always_inline u64
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random_u64 (u32 * seed)
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{
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u64 result;
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result = (u64) random_u32 (seed) << 32;
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result |= random_u32 (seed);
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return result;
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}
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/** \brief machine word size random number generator */
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always_inline uword
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random_uword (u32 * seed)
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{
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if (sizeof (uword) == sizeof (u64))
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return random_u64 (seed);
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else
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return random_u32 (seed);
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}
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/** \brief Generate f64 random number in the interval [0,1] */
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always_inline f64 random_f64 (u32 * seed)
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{ return (f64) random_u32 (seed) / (f64) random_u32_max (); }
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/** \brief Generate random character vector
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From the alphabet a-z, lower case.
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Returns a vector of the supplied length which is NOT guaranteed to be
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NULL-terminated. FIXME?
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*/
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always_inline u8 *
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random_string (u32 * seed, uword len)
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{
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u8 * alphabet = (u8 *) "abcdefghijklmnopqrstuvwxyz";
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u8 * s = 0;
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word i;
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vec_resize (s, len);
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for (i = 0; i < len; i++)
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s[i] = alphabet[random_u32 (seed) % 26];
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return s;
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}
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#endif /* included_random_h */
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