2 * Copyright (C) 2003 Sean Chittenden <seanc@FreeBSD.org>
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
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17 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 #ifndef __RANDOMIZE_FD__
30 #define __RANDOMIZE_FD__
32 #define RANDOM_TYPE_UNSET 0
33 #define RANDOM_TYPE_LINES 1
34 #define RANDOM_TYPE_WORDS 2
36 /* The multiple instance single integer key */
40 struct rand_node *next;
43 int randomize_fd(int fd, int type, int unique, double denom);
46 * Generates a random number uniformly in the range [0.0, 1.0).
49 random_unit_float(void)
51 static const uint64_t denom = (1ull << 53);
52 static const uint64_t mask = denom - 1;
57 * arc4random_buf(...) in this use generates integer outputs in [0,
60 * The double mantissa only has 53 bits, so we uniformly mask off the
61 * high 11 bits and then floating-point divide by 2^53 to achieve a
64 * We are not allowed to emit 1.0, so denom must be one greater than
65 * the possible range of the preceeding step.
67 arc4random_buf(&rand64, sizeof(rand64));
69 return ((double)rand64 / denom);
73 * Returns true with probability 1 / denom (a floating point number >= 1).
74 * Otherwise, returns false.
77 random_uniform_denom(double denom)
79 return ((uint64_t)(denom * random_unit_float()) == 0);