06257a71aa
And document it in the manual page. PR: 244139 Submitted by: Keith White <kwhite AT site.uottawa.ca> (earlier version)
82 lines
2.6 KiB
C
82 lines
2.6 KiB
C
/*
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* Copyright (C) 2003 Sean Chittenden <seanc@FreeBSD.org>
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* 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 PROJECT 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 PROJECT 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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#ifndef __RANDOMIZE_FD__
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#define __RANDOMIZE_FD__
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#define RANDOM_TYPE_UNSET 0
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#define RANDOM_TYPE_LINES 1
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#define RANDOM_TYPE_WORDS 2
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/* The multiple instance single integer key */
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struct rand_node {
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u_char *cp;
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u_int len;
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struct rand_node *next;
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};
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int randomize_fd(int fd, int type, int unique, double denom);
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/*
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* Generates a random number uniformly in the range [0.0, 1.0).
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*/
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static inline double
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random_unit_float(void)
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{
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static const uint64_t denom = (1ull << 53);
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static const uint64_t mask = denom - 1;
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uint64_t rand64;
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/*
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* arc4random_buf(...) in this use generates integer outputs in [0,
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* UINT64_MAX].
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*
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* The double mantissa only has 53 bits, so we uniformly mask off the
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* high 11 bits and then floating-point divide by 2^53 to achieve a
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* result in [0, 1).
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*
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* We are not allowed to emit 1.0, so denom must be one greater than
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* the possible range of the preceeding step.
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*/
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arc4random_buf(&rand64, sizeof(rand64));
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rand64 &= mask;
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return ((double)rand64 / denom);
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}
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/*
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* Returns true with probability 1 / denom (a floating point number >= 1).
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* Otherwise, returns false.
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*/
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static inline bool
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random_uniform_denom(double denom)
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{
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return ((uint64_t)(denom * random_unit_float()) == 0);
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}
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#endif
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