WordPress/wp-includes/sodium_compat/autoload.php

<?php

if (!is_callable('sodiumCompatAutoloader')) {
    /**
     * Sodium_Compat autoloader.
     *
     * @param string $class Class name to be autoloaded.
     *
     * @return bool         Stop autoloading?
     */
    function sodiumCompatAutoloader($class)
    {
        $namespace = 'ParagonIE_Sodium_';
        // Does the class use the namespace prefix?
        $len = strlen($namespace);
        if (strncmp($namespace, $class, $len) !== 0) {
            // no, move to the next registered autoloader
            return false;
        }

        // Get the relative class name
        $relative_class = substr($class, $len);

        // Replace the namespace prefix with the base directory, replace namespace
        // separators with directory separators in the relative class name, append
        // with .php
        $file = dirname(__FILE__) . '/src/' . str_replace('_', '/', $relative_class) . '.php';
        // if the file exists, require it
        if (file_exists($file)) {
            require_once $file;
            return true;
        }
        return false;
    }

    // Now that we have an autoloader, let's register it!
    spl_autoload_register('sodiumCompatAutoloader');
}

require_once dirname(__FILE__) . '/src/SodiumException.php';
if (PHP_VERSION_ID >= 50300) {
    // Namespaces didn't exist before 5.3.0, so don't even try to use this
    // unless PHP >= 5.3.0
    require_once dirname(__FILE__) . '/lib/namespaced.php';
    require_once dirname(__FILE__) . '/lib/sodium_compat.php';
} else {
    require_once dirname(__FILE__) . '/src/PHP52/SplFixedArray.php';
}
if (PHP_VERSION_ID < 70200 || !extension_loaded('sodium')) {
    if (PHP_VERSION_ID >= 50300 && !defined('SODIUM_CRYPTO_SCALARMULT_BYTES')) {
        require_once dirname(__FILE__) . '/lib/php72compat_const.php';
    }
    if (PHP_VERSION_ID >= 70000) {
        assert(class_exists('ParagonIE_Sodium_Compat'), 'Possible filesystem/autoloader bug?');
    } else {
        assert(class_exists('ParagonIE_Sodium_Compat'));
    }
    require_once (dirname(__FILE__) . '/lib/php72compat.php');
}