3 * Random_* Compatibility Library
4 * for using the new PHP 7 random_* API in PHP 5 projects
6 * The MIT License (MIT)
8 * Copyright (c) 2015 Paragon Initiative Enterprises
10 * Permission is hereby granted, free of charge, to any person obtaining a copy
11 * of this software and associated documentation files (the "Software"), to deal
12 * in the Software without restriction, including without limitation the rights
13 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
14 * copies of the Software, and to permit persons to whom the Software is
15 * furnished to do so, subject to the following conditions:
17 * The above copyright notice and this permission notice shall be included in
18 * all copies or substantial portions of the Software.
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
23 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
24 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
25 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
30 * Fetch a random integer between $min and $max inclusive
39 function random_int($min, $max)
42 * Type and input logic checks
44 * If you pass it a float in the range (~PHP_INT_MAX, PHP_INT_MAX)
45 * (non-inclusive), it will sanely cast it to an int. If you it's equal to
46 * ~PHP_INT_MAX or PHP_INT_MAX, we let it fail as not an integer. Floats
47 * lose precision, so the <= and => operators might accidentally let a float
52 $min = RandomCompat_intval($min);
53 } catch (TypeError $ex) {
55 'random_int(): $min must be an integer'
60 $max = RandomCompat_intval($max);
61 } catch (TypeError $ex) {
63 'random_int(): $max must be an integer'
68 * Now that we've verified our weak typing system has given us an integer,
69 * let's validate the logic then we can move forward with generating random
70 * integers along a given range.
74 'Minimum value must be less than or equal to the maximum value'
83 * Initialize variables to 0
86 * $bytes => the number of random bytes we need
87 * $mask => an integer bitmask (for use with the &) operator
88 * so we can minimize the number of discards
90 $attempts = $bits = $bytes = $mask = $valueShift = 0;
93 * At this point, $range is a positive number greater than 0. It might
94 * overflow, however, if $max - $min > PHP_INT_MAX. PHP will cast it to
95 * a float and we will lose some precision.
100 * Test for integer overflow:
102 if (!is_int($range)) {
105 * Still safely calculate wider ranges.
106 * Provided by @CodesInChaos, @oittaa
108 * @ref https://gist.github.com/CodesInChaos/03f9ea0b58e8b2b8d435
110 * We use ~0 as a mask in this case because it generates all 1s
112 * @ref https://eval.in/400356 (32-bit)
113 * @ref http://3v4l.org/XX9r5 (64-bit)
115 $bytes = PHP_INT_SIZE;
121 * $bits is effectively ceil(log($range, 2)) without dealing with
125 if ($bits % 8 === 0) {
130 $mask = $mask << 1 | 1;
136 * Now that we have our parameters set up, let's begin generating
137 * random integers until one falls between $min and $max
141 * The rejection probability is at most 0.5, so this corresponds
142 * to a failure probability of 2^-128 for a working RNG
144 if ($attempts > 128) {
146 'random_int: RNG is broken - too many rejections'
151 * Let's grab the necessary number of random bytes
153 $randomByteString = random_bytes($bytes);
154 if ($randomByteString === false) {
156 'Random number generator failure'
161 * Let's turn $randomByteString into an integer
163 * This uses bitwise operators (<< and |) to build an integer
164 * out of the values extracted from ord()
166 * Example: [9F] | [6D] | [32] | [0C] =>
167 * 159 + 27904 + 3276800 + 201326592 =>
171 for ($i = 0; $i < $bytes; ++$i) {
172 $val |= ord($randomByteString[$i]) << ($i * 8);
183 * If $val overflows to a floating point number,
184 * ... or is larger than $max,
185 * ... or smaller than $min,
188 } while (!is_int($val) || $val > $max || $val < $min);