获取$ min和$ max之间的随机整数

原型

random_int( int $min, int $max )

参数

$min (int) (Required)

$max (int) (Required)

返回值

(int)  

源文件

路径:wp-includes/random_compat/random_int.php

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
<?php
...
function random_int($min, $max)
{
    /**
     * Type and input logic checks
     * 
     * If you pass it a float in the range (~PHP_INT_MAX, PHP_INT_MAX)
     * (non-inclusive), it will sanely cast it to an int. If you it's equal to
     * ~PHP_INT_MAX or PHP_INT_MAX, we let it fail as not an integer. Floats 
     * lose precision, so the <= and => operators might accidentally let a float
     * through.
     */
    
    try {
        $min = RandomCompat_intval($min);
    } catch (TypeError $ex) {
        throw new TypeError(
            'random_int(): $min must be an integer'
        );
    }

    try {
        $max = RandomCompat_intval($max);
    } catch (TypeError $ex) {
        throw new TypeError(
            'random_int(): $max must be an integer'
        );
    }
    
    /**
     * Now that we've verified our weak typing system has given us an integer,
     * let's validate the logic then we can move forward with generating random
     * integers along a given range.
     */
    if ($min > $max) {
        throw new Error(
            'Minimum value must be less than or equal to the maximum value'
        );
    }

    if ($max === $min) {
        return $min;
    }

    /**
     * Initialize variables to 0
     * 
     * We want to store:
     * $bytes => the number of random bytes we need
     * $mask => an integer bitmask (for use with the &) operator
     *          so we can minimize the number of discards
     */
    $attempts = $bits = $bytes = $mask = $valueShift = 0;

    /**
     * At this point, $range is a positive number greater than 0. It might
     * overflow, however, if $max - $min > PHP_INT_MAX. PHP will cast it to
     * a float and we will lose some precision.
     */
    $range = $max - $min;

    /**
     * Test for integer overflow:
     */
    if (!is_int($range)) {

        /**
         * Still safely calculate wider ranges.
         * Provided by @CodesInChaos, @oittaa
         * 
         * @ref https://gist.github.com/CodesInChaos/03f9ea0b58e8b2b8d435
         * 
         * We use ~0 as a mask in this case because it generates all 1s
         * 
         * @ref https://eval.in/400356 (32-bit)
         * @ref http://3v4l.org/XX9r5  (64-bit)
         */
        $bytes = PHP_INT_SIZE;
        $mask = ~0;

    } else {

        /**
         * $bits is effectively ceil(log($range, 2)) without dealing with 
         * type juggling
         */
        while ($range > 0) {
            if ($bits % 8 === 0) {
               ++$bytes;
            }
            ++$bits;
            $range >>= 1;
            $mask = $mask << 1 | 1;
        }
        $valueShift = $min;
    }

    /**
     * Now that we have our parameters set up, let's begin generating
     * random integers until one falls between $min and $max
     */
    do {
        /**
         * The rejection probability is at most 0.5, so this corresponds
         * to a failure probability of 2^-128 for a working RNG
         */
        if ($attempts > 128) {
            throw new Exception(
                'random_int: RNG is broken - too many rejections'
            );
        }

        /**
         * Let's grab the necessary number of random bytes
         */
        $randomByteString = random_bytes($bytes);
        if ($randomByteString === false) {
            throw new Exception(
                'Random number generator failure'
            );
        }

        /**
         * Let's turn $randomByteString into an integer
         * 
         * This uses bitwise operators (<< and |) to build an integer
         * out of the values extracted from ord()
         * 
         * Example: [9F] | [6D] | [32] | [0C] =>
         *   159 + 27904 + 3276800 + 201326592 =>
         *   204631455
         */
        $val = 0;
        for ($i = 0; $i < $bytes; ++$i) {
            $val |= ord($randomByteString[$i]) << ($i * 8);
        }

        /**
         * Apply mask
         */
        $val &= $mask;
        $val += $valueShift;

        ++$attempts;
        /**
         * If $val overflows to a floating point number,
         * ... or is larger than $max,
         * ... or smaller than $min,
         * then try again.
         */
    } while (!is_int($val) || $val > $max || $val < $min);

    return (int) $val;
}

...
?>

其他

英文文档:https://developer.wordpress.org/reference/functions/random_int/