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/*
* Copyright (C) 2003 Sean Chittenden <seanc@FreeBSD.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef __RANDOMIZE_FD__
#define __RANDOMIZE_FD__
#define RANDOM_TYPE_UNSET 0
#define RANDOM_TYPE_LINES 1
#define RANDOM_TYPE_WORDS 2
/* The multiple instance single integer key */
struct rand_node {
u_char *cp;
u_int len;
struct rand_node *next;
};
int randomize_fd(int fd, int type, int unique, double denom);
/*
* Generates a random number uniformly in the range [0.0, 1.0).
*/
static inline double
random_unit_float(void)
{
static const uint64_t denom = (1ull << 53);
static const uint64_t mask = denom - 1;
uint64_t rand64;
/*
* arc4random_buf(...) in this use generates integer outputs in [0,
* UINT64_MAX].
*
* The double mantissa only has 53 bits, so we uniformly mask off the
* high 11 bits and then floating-point divide by 2^53 to achieve a
* result in [0, 1).
*
* We are not allowed to emit 1.0, so denom must be one greater than
* the possible range of the preceeding step.
*/
arc4random_buf(&rand64, sizeof(rand64));
rand64 &= mask;
return ((double)rand64 / denom);
}
/*
* Returns true with probability 1 / denom (a floating point number >= 1).
* Otherwise, returns false.
*/
static inline bool
random_uniform_denom(double denom)
{
return ((uint64_t)(denom * random_unit_float()) == 0);
}
#endif
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