rfc:rng_extension

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rfc:rng_extension [2021/06/01 13:59] – drop RANDOM_USER, add RandomNumberGenerator interface. zeriyoshirfc:rng_extension [2022/02/14 10:42] – update 4.0 zeriyoshi
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-====== PHP RFC: Add Random class ====== +====== PHP RFC: Random Extension 4.0 ====== 
-  * Version: 1.1 +  * Version: 4.0 
-  * Date: 2021-05-18 +  * Date: 2022-02-14 
-  * Author: Go Kudo <zeriyoshi@gmail.com> +  * Author: Go Kudo <zeriyoshi@gmail.com> <g-kudo@colopl.co.jp> 
-  * Status: Draft +  * Status: Under Discussion 
-  * Implementation: https://github.com/php/php-src/pull/7079+  * Implementation: https://github.com/php/php-src/pull/XXXX
   * First Published at: http://wiki.php.net/rfc/object_scope_prng   * First Published at: http://wiki.php.net/rfc/object_scope_prng
  
 ===== Introduction ===== ===== Introduction =====
-PHP is currently having problems with RNG reproducibility. 
  
-PHP's RNG has been unified into an implementation using the Mersenne twister, with the rand() and srand() functions becoming aliases for mt_rand() and mt_srand() respectively in PHP 7.1.+PHP implements several useful RNGs. However, they are currently only available in the global scope.
  
-But, these functions still store the state in the global state of PHP and are not easily reproducible. Look at the following example.+Mersenne Twister, PHP's default RNG, provides a function mt_srand() to initialize with a user-specified seed value, but the scope is global, which may cause unintended user behavior.
  
-<code php> +When a user executes mt_srand(), one would expect it to only affect result of mt_rand(), however, the following functions implicitly affect the result of mt_rand()
-echo foo(1234, function (): void {}) . PHP_EOL; // Result: 1480009472 +
-echo foo(1234, function (): void { mt_rand(); }) . PHP_EOL; // Result: 1747253290+
  
-function foo(int $seed, callable $bar): int { +  * shuffle() 
-    mt_srand($seed); +  * str_shuffle() 
-    $result = mt_rand(); +  * array_rand()
-    $bar(); +
-    $result += mt_rand(); +
-    return $result; +
-} +
-</code>+
  
-As mentioned above, the reproducibility of random numbers can easily be lost if additional processing is added later. +For example, in the following code, the result of the second mt_rand() is not reproducible. This is because shuffle() uses a MT RNG internally, which changes the state.
- +
-In addition, the fiber extension was introduced in PHP 8.1. This makes it more difficult to keep track of the execution order. However, this problem has existed since the introduced of Generator. +
- +
-There is also the problem of functions that implicitly use the state stored in PHP's global state. shuffle(), str_shuffle(), and array_rand() functions implicitly advance the state of a random number. This means that the following code is not reproducible, but it is difficult for the user to notice this.+
  
 <code php> <code php>
 mt_srand(1234); mt_srand(1234);
-echo mt_rand() . PHP_EOL; // Result: 411284887+$next = mt_rand();
  
 mt_srand(1234); mt_srand(1234);
-str_shuffle('foobar'); +$arr = range(0, 9); 
-echo mt_rand() . PHP_EOL; // Result: 1314500282+shuffle($arr); 
 +$next2 = mt_rand(); 
 + 
 +die("next: ${next}, next2: ${next2}"); // next: 411284887, next2: 1848274264
 </code> </code>
  
-===== Proposal ===== +These behaviors were unintuitive and often led to unintended execution results, but were not that problematic for general web application use.
-Implements Random class and RandomNumberGenerator interface.+
  
-These class / interface implement in ext/standard, always bundled PHP core.+However, in more complex and repeatable applications (such as games), this can be a problem.
  
-The PHP code that represents the implementation is as follows:+There is also the issue of state management difficulties with Fiber, which was added in PHP 8.1. Nikita had this to say:
  
-<code php> +https://externals.io/message/115918#115959
-const RANDOM_XORSHIFT128PLUS = 'xorshift128plus'; // 64-bit, fast, default +
-const RANDOM_MT19937 = 'mt19937'; // 32-bit, for backward compatibility +
-const RANDOM_SECURE = 'secure'; // Cryptographically-Secure PRNG+
  
-interface RandomNumberGenerator +In addition, the Mersenne Twister, can only generate 32-bit values. 
-{ +In recent years, many of the environments where PHP runs have been migrating to 64-bit platforms. 
-    /** +In order to generate more secure values, an RNG that can generate 64-bit wide values should be provided by the language.
-      * Generate a number. +
-      */ +
-    public function generate(): int; +
-}+
  
-final class Random +===== Proposal =====
-{ +
-    private ?RandomNumberGenerator $rng;+
  
-    /** +Implement the XorShift128Plus algorithm for generating new 64-bit wide random numbers, along with a random extension that includes an object scope RNG, and bundle it with PHP. 
-     * Get registered algorithm string in array. +XorShift128Plus is a fast, high-quality RNG that is proven in major web browsers.  
-     */ +Many of the major hardware architectures are now 64-bit, so it makes sense to use this RNG.
-    public static function getAlgos(): array; +
-     +
-    /** +
-     * Get algorithm information in array. +
-     * if not registered, returns null. +
-     */ +
-    public static function getAlgoInfo(string $algo): ?array;+
  
-    /** +In addition to the new algorithm, the following classes will be added to fix the global scope issue.
-     * Constructor. +
-     * if $seed is null, generating seed by php_random_bytes(), but whether to use depends to algo. +
-     */ +
-    public function __construct(string|RandomNumberGenerator $algo = RANDOM_XORSHIFT128PLUS, ?int $seed = null) {}+
  
-    /** +  * class Random\NumberGenerator\XorShift128Plus 
-     * Returns raw generated number by RNG. +  * class Random\NumberGenerator\MersenneTwister 
-     * if on the 32-bit machine, least 32-bit will be truncated. +  * class Random\NumberGenerator\CombinedLCG 
-     */ +  * class Random\NumberGenerator\Secure (aka php_random_bytes())
-    public function nextInt(): int {}+
  
-    /** +These classes will hold independent RNG state and will not affect the global scope.
-     * Generates a number within a given range. +
-     * similar random_int() function. +
-     */ +
-    public function getInt(int $min, int $max): int {}+
  
-    /** +An interface Random\NumberGenerator is also added and are implmeneted by the classes above.  
-     * Generates a string within a given range. +This interface has only a single generate() method which makes it possible to switch between RNG implementations depending on the situation, 
-     * similar random_bytes() function. +allowing alternative implementations to be done by PHP in userland. This is useful, for example, for running tests.
-     */ +
-    public function getBytes(int $length): string {}+
  
-    /** +RNGs other than XorShift128Plus are based on the RNGs currently implemented in PHP.
-     * Shuffling the given array items. +
-     * similar shuffle(), but non-pass-by-reference. +
-     */ +
-    public function shuffleArray(array $array): array {}+
  
-    /** +The Random\Randomizer class will be added to manipulate data using these RNGs. 
-     * Shuffling the given string characters. +
-     * similar str_shuffle(). +
-     */ +
-    public function shuffleString(string $string): string {}+
  
-    /** +This class provides the following methods:
-     * Serializing state to string if algo's supported. +
-     */ +
-    public function __serialize(): array {}+
  
-    /** +  * __constructor(\Random\NumberGenerator $generator = null) [defaults to XorShift128Plus if null] 
-     * Unseriialize state from string in algo's supported. +  * getInt(int $min, int $max): int [replacement for mt_rand() / rand()] 
-     */ +  * getBytes(int $length): string [replacement for random_bytes()] 
-    public function __unserialize(array $data): void {} +  * shuffleArray(array $array): array [replacement for shuffle()] 
-}+  * shuffleString(string $string): string [replacement for str_shuffle()]
  
-</code>+Method equivalent to array_rand() was not implemented at this time because the implementation is complex and can be easily implemented in userland if necessary.
  
-This class retrieves and uses the RNG algorithm registered in the core, based on the string passed in the constructor argument $algo. +Examples of these uses are as follows:
- +
-The bundled RNGs are as follows: +
- +
-  * XorShift128+: 64-bit, reproducible, PRNG. +
-  * MT19937: 32-bit, reproducible, PRNG, compatible mt_srand() / mt_rand(). +
-  * secure: 64-bit, non-reproducible, CSPRNG, uses php_random_bytes() internally. +
- +
-By default, XorShift128+ is used. It can generate 64-bit values, is used by major browsers, and is fast and reliable. On the other hand, MT19937 is retained for compatibility. +
- +
-"secure" is practically equivalent to random_int(), but can be used to shuffle arrays and strings. Also, since it is an object, it is easy to exchange implementations. +
- +
-This class also supports RNGs defined in userland. It can be used by passing an instance of a class that implements the RandomNumberGenerator interface provided at the same time as the first argument.This is useful for unit testing or when you want to use a fixed number.+
  
 <code php> <code php>
 +// Use different RNGs for different environments.
 +$rng = $is_production
 +    ? new Random\NumberGenerator\Secure()
 +    : new Random\NumberGenerator\XorShift128Plus(1234);
  
-class UserDefinedRNG implements RandomNumberGenerator +$randomizer = new Random\Randomizer($rng); 
-{ +$randomizer->shuffleString('foobar');
-    protected int $current = 0; +
-     +
-    public function generate(): int +
-    { +
-        return ++$this->current; +
-    } +
-} +
- +
-function foobar(Random $random): void { +
-    for ($i = 0; $i < 9; $i++) { +
-        echo $random->nextInt(); +
-    } +
-} +
- +
-foobar(new Random(new UserDefinedRNG())); // Results: 123456789+
 </code> </code>
  
-Algorithms can be registered and unregistered using PHP's C API, and new implementations can be added via Extension. The following APIs are provided:+<code php> 
 +// Safely migrate the existing mt_rand() state.
  
-<code c> +// before 
-/* Register new RNG algo */ +mt_srand(1234, MT_RAND_PHP); 
-int php_random_class_algo_register(const php_random_class_algo *algo);+foobar(); 
 +$result = str_shuffle('foobar');
  
-/* Unregister RNG algo */ +// after 
-void php_random_class_algo_unregister(const char *ident); +$randomizer = new Random\Randomizer(new Random\NumberGenerator\MersenneTwister(1234, MT_RAND_PHP)); 
- +foobar(); 
-/* Find and get registered algo */ +$result = $randomizer->stringShuffle('foobar');
-const php_random_class_algo* php_random_class_algo_find(const zend_string *ident);+
 </code> </code>
  
-Also, as with MT, various alternative APIs using object scope RNGs will be provided.+As a side effect of this RFC, the following PHP functions have been moved to the new ext/random extension
  
-<code c> +This is because ext/standard/random.c reserves the name RANDOM and cannot be used by the extension. 
-/* similar php_mt_rand() */ +In addition, all RNG-related implementations will be moved to the new random extension in order to standardize the RNG implementation.
-uint64_t php_random_class_next(php_random_class *random_class);+
  
-/* similar php_mt_rand_range() */ +  * lcg_value() 
-zend_long php_random_class_range(php_random_class *random_class, zend_long min, zend_long max);+  * srand() 
 +  * rand() 
 +  * mt_srand() 
 +  * mt_rand() 
 +  * random_int() 
 +  * random_bytes()
  
-/* similar php_array_data_shuffle() */ +The following internal APIs will also be moved to the ext/random extension:
-void php_random_class_array_data_shuffle(php_random_class *random_class, zval *array);+
  
-/* similar php_string_shuffle() */ +  * php_random_int_throw() 
-void php_random_class_string_shuffle(php_random_class *random_class, char *str, zend_long len); +  * php_random_int_silent() 
-</code>+  * php_combined_lcg() 
 +  * php_mt_srand() 
 +  * php_mt_rand() 
 +  * php_mt_rand_range() 
 +  * php_mt_rand_common() 
 +  * php_srand() 
 +  * php_rand() 
 +  * php_random_bytes() 
 +  * php_random_int()
  
-Random class can be serialized or cloned if the algorithm supports it. This is useful for storing and reusing state.+All of these features are available from the extension by simply including a single ext/random/php_random.h
  
-<code php> +The following header files are left in for extension compatibility. The contents all include ext/random/php_random.h.
-// serialize +
-$foo = new Random(); +
-for ($i = 0; $i < 10; $i++) { $foo->nextInt(); } +
-var_dump(unserialize(serialize($foo))->nextInt() === $foo->nextInt()); // true+
  
-// clone +  * ext/standard/php_lcg.h 
-$bar = new Random(); +  * ext/standard/php_rand.h 
-for ($i = 0; $i < 10; $i++) { $bar->nextInt(); } +  * ext/standard/php_mt_rand.h 
-$baz = clone $bar; +  * ext/standard/php_random.h
-var_dump($baz->nextInt() === $bar->nextInt()); // true +
-</code>+
  
-Using this feature, the first example can be rewritten as follows:+===== Future Scope =====
  
-<code php> +These are not within the scope of this RFC, but are worth considering in the future:
-echo foo(1234, function (): void {}) . PHP_EOL; // Result: 1480009472 +
-echo foo(1234, function (): void { mt_rand(); }) . PHP_EOL; // Result: 1480009472+
  
-function foo(int $seed, callable $bar): int { +  * Remove old header files for compatibility (php_lcg.h, php_rand.h, php_mt_rand.h, php_random.h) 
-    $random = new Random(RANDOM_MT19937, $seed); +  * Deprecate lcg_value(), mt_srand(), srand()
-    $result = $random->nextInt(); +
-    $bar(); +
-    $result += $random->nextInt(); +
-    return $result; +
-} +
-</code>+
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
-The following items will no longer be available: 
  
-  - "Random" class name +The following names have been reserved and will no longer be available 
-  - "RandomNumberGenerator" class (interface) name + 
-  - "RANDOM_XORSHIFT128PLUS" constant +  * "Random" 
-  - "RANDOM_MT19937" constant +  * "Random\NumberGenerator" 
-  - "RANDOM_SECURE" constant+  * "Random\NumberGenerator\XorShift128Plus" 
 +  * "Random\NumberGenerator\MersenneTwister" 
 +  * "Random\NumberGenerator\CombinedLCG" 
 +  * "Random\NumberGenerator\Secure"
  
 ===== Proposed PHP Version(s) ===== ===== Proposed PHP Version(s) =====
-8.1+8.2
  
 ===== RFC Impact ===== ===== RFC Impact =====
Line 237: Line 166:
  
 ==== To Existing Extensions ==== ==== To Existing Extensions ====
-none+In the future, it may be necessary to change the included header files to point to ext/random/php_random.h. However, compatibility will be maintained for now.
  
 ==== To Opcache ==== ==== To Opcache ====
Line 243: Line 172:
  
 ==== New Constants ==== ==== New Constants ====
-  * RANDOM_XORSHIFT128PLUS +none
-  * RANDOM_MT19937 +
-  * RANDOM_SECURE+
  
 ==== php.ini Defaults ==== ==== php.ini Defaults ====
Line 254: Line 181:
  
 ===== Vote ===== ===== Vote =====
-Voting opens 2021-MM-DD and 2021-MM-DD at 00:00:00 EDT. 2/3 required to accept.+Voting opens 2022-MM-DD and 2021-MM-DD at 00:00:00 EDT. 2/3 required to accept.
  
-<doodle title="Add Random class" auth="zeriyoshi" voteType="single" closed="true"> +<doodle title="Add Random extension" auth="zeriyoshi" voteType="single" closed="true"> 
    * Yes    * Yes
    * No    * No
Line 262: Line 189:
  
 ===== Patches and Tests ===== ===== Patches and Tests =====
-  * https://github.com/php/php-src/pull/7079+  * https://github.com/php/php-src/pull/XXXX
rfc/rng_extension.txt · Last modified: 2022/08/01 16:52 by timwolla

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