672e12255d
rand(3)'s standard C API is extremely limiting, but we can do better than the historical 32-bit state Park-Miller LCG we've shipped since 2001: r73156. The justification provided at the time for not using random(3) was that rand_r(3) could not be made to use the same algorithm. That is still true. However, the irrelevance of rand_r(3) is increasingly obvious. Since that time, POSIX has marked the interface obsolescent. rand_r(3) never became part of the standard C library. If not for API compatibility reasons, I would just remove rand_r(3) entirely. So, I do not believe it is a problem for rand_r(3) and rand(3) to diverge. The 12 ABI is maintained with compatibility definitions, but this revision does subtly change the API of rand(3). The sequences of pseudorandom numbers produced in programs built against new versions of libc will differ from programs built against prior versions of libc. Reviewed by: kevans, markm MFC after: no Relnotes: yes Differential Revision: https://reviews.freebsd.org/D23290
86 lines
2.9 KiB
C
86 lines
2.9 KiB
C
/*-
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* Copyright 2020 Conrad Meyer <cem@FreeBSD.org>. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#pragma once
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/*
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* For each of the currently supported random number generators, we have a
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* break value on the amount of state information (you need at least this
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* many bytes of state info to support this random number generator), a degree
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* for the polynomial (actually a trinomial) that the R.N.G. is based on, and
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* the separation between the two lower order coefficients of the trinomial.
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*/
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#define TYPE_0 0 /* linear congruential */
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#define BREAK_0 8
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#define DEG_0 0
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#define SEP_0 0
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#define TYPE_1 1 /* x**7 + x**3 + 1 */
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#define BREAK_1 32
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#define DEG_1 7
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#define SEP_1 3
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#define TYPE_2 2 /* x**15 + x + 1 */
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#define BREAK_2 64
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#define DEG_2 15
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#define SEP_2 1
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#define TYPE_3 3 /* x**31 + x**3 + 1 */
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#define BREAK_3 128
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#define DEG_3 31
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#define SEP_3 3
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#define TYPE_4 4 /* x**63 + x + 1 */
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#define BREAK_4 256
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#define DEG_4 63
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#define SEP_4 1
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/*
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* Array versions of the above information to make code run faster --
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* relies on fact that TYPE_i == i.
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*/
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#define MAX_TYPES 5 /* max number of types above */
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/* A full instance of the random(3) generator. */
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struct __random_state {
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uint32_t *rst_fptr;
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uint32_t *rst_rptr;
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uint32_t *rst_state;
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int rst_type;
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int rst_deg;
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int rst_sep;
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uint32_t *rst_end_ptr;
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/* Flexible array member must be last. */
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uint32_t rst_randtbl[];
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};
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struct __random_state *allocatestate(unsigned type);
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int initstate_r(struct __random_state *, unsigned, uint32_t *, size_t);
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long random_r(struct __random_state *);
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void srandom_r(struct __random_state *, unsigned);
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void srandomdev_r(struct __random_state *);
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