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<?php
namespace Aws;
use Aws\Api\Service;
use Psr\Http\Message\RequestInterface;
/**
* @internal Middleware that auto fills parameters with `idempotencyToken` trait
*/
class IdempotencyTokenMiddleware
{
/** @var Service */
private $service;
/** @var string */
private $bytesGenerator;
/** @var callable */
private $nextHandler;
/**
* Creates a middleware that populates operation parameter
* with trait 'idempotencyToken' enabled with a random UUIDv4
*
* One of following functions needs to be available
* in order to generate random bytes used for UUID
* (SDK will attempt to utilize function in following order):
* - random_bytes (requires PHP 7.0 or above)
* - openssl_random_pseudo_bytes (requires 'openssl' module enabled)
* - mcrypt_create_iv (requires 'mcrypt' module enabled)
*
* You may also supply a custom bytes generator as an optional second
* parameter.
*
* @param \Aws\Api\Service $service
* @param callable|null $bytesGenerator
*
* @return callable
*/
public static function wrap(
Service $service,
callable $bytesGenerator = null
) {
return function (callable $handler) use ($service, $bytesGenerator) {
return new self($handler, $service, $bytesGenerator);
};
}
public function __construct(
callable $nextHandler,
Service $service,
callable $bytesGenerator = null
) {
$this->bytesGenerator = $bytesGenerator
?: $this->findCompatibleRandomSource();
$this->service = $service;
$this->nextHandler = $nextHandler;
}
public function __invoke(
CommandInterface $command,
RequestInterface $request = null
) {
$handler = $this->nextHandler;
if ($this->bytesGenerator) {
$operation = $this->service->getOperation($command->getName());
$members = $operation->getInput()->getMembers();
foreach ($members as $member => $value) {
if ($value['idempotencyToken']) {
$bytes = call_user_func($this->bytesGenerator, 16);
// populating UUIDv4 only when the parameter is not set
$command[$member] = $command[$member]
?: $this->getUuidV4($bytes);
// only one member could have the trait enabled
break;
}
}
}
return $handler($command, $request);
}
/**
* This function generates a random UUID v4 string,
* which is used as auto filled token value.
*
* @param string $bytes 16 bytes of pseudo-random bytes
* @return string
* More information about UUID v4, see:
* https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_.28random.29
* https://tools.ietf.org/html/rfc4122#page-14
*/
private static function getUuidV4($bytes)
{
// set version to 0100
$bytes[6] = chr(ord($bytes[6]) & 0x0f | 0x40);
// set bits 6-7 to 10
$bytes[8] = chr(ord($bytes[8]) & 0x3f | 0x80);
return vsprintf('%s%s-%s-%s-%s-%s%s%s', str_split(bin2hex($bytes), 4));
}
/**
* This function decides the PHP function used in generating random bytes.
*
* @return callable|null
*/
private function findCompatibleRandomSource()
{
if (function_exists('random_bytes')) {
return 'random_bytes';
}
if (function_exists('openssl_random_pseudo_bytes')) {
return 'openssl_random_pseudo_bytes';
}
if (function_exists('mcrypt_create_iv')) {
return 'mcrypt_create_iv';
}
}
}
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