balmet.com

random_int.php (6262B)

---

 <?php
 
 if (!is_callable('random_int')) {
     /**
      * Random_* Compatibility Library
      * for using the new PHP 7 random_* API in PHP 5 projects
      *
      * The MIT License (MIT)
      *
      * Copyright (c) 2015 - 2017 Paragon Initiative Enterprises
      *
      * Permission is hereby granted, free of charge, to any person obtaining a copy
      * of this software and associated documentation files (the "Software"), to deal
      * in the Software without restriction, including without limitation the rights
      * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
      * copies of the Software, and to permit persons to whom the Software is
      * furnished to do so, subject to the following conditions:
      *
      * The above copyright notice and this permission notice shall be included in
      * all copies or substantial portions of the Software.
      *
      * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
      * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
      * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
      * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
      * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
      * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
      * SOFTWARE.
      */
 
     /**
      * Fetch a random integer between $min and $max inclusive
      *
      * @param int $min
      * @param int $max
      *
      * @throws Exception
      *
      * @return int
      */
     function random_int($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 (int) $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;
         }
 
         $val = 0;
         /**
          * 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);
 
             /**
              * 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;
     }
 }