moodle/lib/moodlelib.php

<?PHP // $Id$

///////////////////////////////////////////////////////////////////////////
//                                                                       //
// moodlelib.php                                                         //
//                                                                       //
// Main library file of miscellaneous general-purpose Moodle functions   //
//                                                                       //
// Other main libraries:                                                 //
//                                                                       //
//   weblib.php      - functions that produce web output                 //
//   datalib.php     - functions that access the database                //
//                                                                       //
///////////////////////////////////////////////////////////////////////////
//                                                                       //
// NOTICE OF COPYRIGHT                                                   //
//                                                                       //
// Moodle - Modular Object-Oriented Dynamic Learning Environment         //
//          http://moodle.com                                            //
//                                                                       //
// Copyright (C) 2001-2003  Martin Dougiamas  http://dougiamas.com       //
//                                                                       //
// This program is free software; you can redistribute it and/or modify  //
// it under the terms of the GNU General Public License as published by  //
// the Free Software Foundation; either version 2 of the License, or     //
// (at your option) any later version.                                   //
//                                                                       //
// This program is distributed in the hope that it will be useful,       //
// but WITHOUT ANY WARRANTY; without even the implied warranty of        //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         //
// GNU General Public License for more details:                          //
//                                                                       //
//          http://www.gnu.org/copyleft/gpl.html                         //
//                                                                       //
///////////////////////////////////////////////////////////////////////////


/// PARAMETER HANDLING ////////////////////////////////////////////////////

function require_variable($var) {
/// Variable must be present
    if (! isset($var)) {
        error("A required parameter was missing");
    }
}

function optional_variable(&$var, $default=0) {
/// Variable may be present, if not then set a default
    if (! isset($var)) {
        $var = $default;
    }
}


function set_config($name, $value) {
/// No need for get_config because they are usually always available in $CFG

    if (get_field("config", "name", "name", $name)) {
        return set_field("config", "value", $value, "name", $name);
    } else {
        $config->name = $name;
        $config->value = $value;
        return insert_record("config", $config);
    }
}


/// FUNCTIONS FOR HANDLING TIME ////////////////////////////////////////////

function make_timestamp($year, $month=1, $day=1, $hour=0, $minute=0, $second=0) {
/// Given date parts in user time, produce a GMT timestamp

    return mktime((int)$hour,(int)$minute,(int)$second,(int)$month,(int)$day,(int)$year);
}

function format_time($totalsecs, $str=NULL) {
/// Given an amount of time in seconds, returns string
/// formatted nicely as months, days, hours etc as needed

    $totalsecs = abs($totalsecs);

    if (!$str) {  // Create the str structure the slow way
        $str->day   = get_string("day");
        $str->days  = get_string("days");
        $str->hour  = get_string("hour");
        $str->hours = get_string("hours");
        $str->min   = get_string("min");
        $str->mins  = get_string("mins");
        $str->sec   = get_string("sec");
        $str->secs  = get_string("secs");
    }

    $days      = floor($totalsecs/86400);
    $remainder = $totalsecs - ($days*86400);
    $hours     = floor($remainder/3600);
    $remainder = $remainder - ($hours*3600);
    $mins      = floor($remainder/60);
    $secs      = $remainder - ($mins*60);

    $ss = ($secs == 1)  ? $str->sec  : $str->secs;
    $sm = ($mins == 1)  ? $str->min  : $str->mins;
    $sh = ($hours == 1) ? $str->hour : $str->hours;
    $sd = ($days == 1)  ? $str->day  : $str->days;

    $odays = "";
    $ohours = "";
    $omins = "";
    $osecs = "";

    if ($days)  $odays  = "$days $sd";
    if ($hours) $ohours = "$hours $sh";
    if ($mins)  $omins  = "$mins $sm";
    if ($secs)  $osecs  = "$secs $ss";

    if ($days)  return "$odays $ohours";
    if ($hours) return "$ohours $omins";
    if ($mins)  return "$omins $osecs";
    if ($secs)  return "$osecs";
    return get_string("now");
}

function userdate($date, $format="", $timezone=99) {
/// Returns a formatted string that represents a date in user time
/// WARNING: note that the format is for strftime(), not date().
/// Because of a bug in most Windows time libraries, we can't use 
/// the nicer %e, so we have to use %d which has leading zeroes.
/// A lot of the fuss below is just getting rid of these leading 
/// zeroes as efficiently as possible.

    global $USER;

    if ($format == "") {
        $format      = "%A, %d %B %Y, %I:%M %p";
        $formatnoday = "%A, DD %B %Y, %I:%M %p";
        $fixday = true;
    } else {
        $formatnoday = str_replace("%d", "DD", $format);
        $fixday = ($formatnoday != $format);
    }

    if ($timezone == 99) {
        if (isset($USER->timezone)) {
            $timezone = (float)$USER->timezone;
        }
    }
    if (abs($timezone) > 13) {
        if ($fixday) {
            $datestring = strftime($formatnoday, $date);
            $daystring  = str_replace(" 0", "", strftime(" %d", $date));
            $datestring = str_replace("DD", $daystring, $datestring);
        } else {
            $datestring = strftime($format, $date);
        }
    } else {
        if ($fixday) {
            $datestring = gmstrftime($formatnoday, $date + (int)($timezone * 3600));
            $daystring  = str_replace(" 0", "", gmstrftime(" %d", $date));
            $datestring = str_replace("DD", $daystring, $datestring);
        } else {
            $datestring = gmstrftime($format, $date + (int)($timezone * 3600));
        }
    }

    return $datestring;
}

function usergetdate($date, $timezone=99) {
/// Given a $date timestamp in GMT, returns an array 
/// that represents the date in user time

    global $USER;

    if ($timezone == 99) {
        $timezone = (float)$USER->timezone;
    }
    if (abs($timezone) > 13) {
        return getdate($date);
    }
    //There is no gmgetdate so I have to fake it...
    $date = $date + (int)($timezone * 3600);
    $getdate["seconds"] = gmstrftime("%S", $date);
    $getdate["minutes"] = gmstrftime("%M", $date);
    $getdate["hours"]   = gmstrftime("%H", $date);
    $getdate["mday"]    = gmstrftime("%d", $date);
    $getdate["wday"]    = gmstrftime("%u", $date);
    $getdate["mon"]     = gmstrftime("%m", $date);
    $getdate["year"]    = gmstrftime("%Y", $date);
    $getdate["yday"]    = gmstrftime("%j", $date);
    $getdate["weekday"] = gmstrftime("%A", $date);
    $getdate["month"]   = gmstrftime("%B", $date);
    return $getdate;
}

function usertime($date, $timezone=99) {
/// Given a GMT timestamp (seconds since epoch), offsets it by 
/// the timezone.  eg 3pm in India is 3pm GMT - 7 * 3600 seconds
    global $USER;

    if ($timezone == 99) {
        $timezone = (float)$USER->timezone;
    }
    if (abs($timezone) > 13) {
        return $date;
    }
    return $date - (int)($timezone * 3600);
}

function usergetmidnight($date, $timezone=99) {
/// Given a time, return the GMT timestamp of the most recent midnight
/// for the current user.
    global $USER;

    if ($timezone == 99) {
        $timezone = (float)$USER->timezone;
    }

    $userdate = usergetdate($date, $timezone);

    if (abs($timezone) > 13) {
        return mktime(0, 0, 0, $userdate["mon"], $userdate["mday"], $userdate["year"]);
    }

    $timemidnight = gmmktime (0, 0, 0, $userdate["mon"], $userdate["mday"], $userdate["year"]);
    return usertime($timemidnight, $timezone); // Time of midnight of this user's day, in GMT

}

function usertimezone($timezone=99) {
/// Returns a string that prints the user's timezone
    global $USER;

    if ($timezone == 99) {
        $timezone = (float)$USER->timezone;
    }
    if (abs($timezone) > 13) {
        return "server time";
    }
    if (abs($timezone) < 0.5) {
        return "GMT";
    }
    if ($timezone > 0) {
        return "GMT+$timezone";
    } else {
        return "GMT$timezone";
    }
}


/// USER AUTHENTICATION AND LOGIN ////////////////////////////////////////

function require_login($courseid=0) {
/// This function checks that the current user is logged in, and optionally
/// whether they are "logged in" or allowed to be in a particular course.
/// If not, then it redirects them to the site login or course enrolment.

    global $CFG, $SESSION, $USER, $FULLME, $HTTP_REFERER, $PHPSESSID;
      
    // First check that the user is logged in to the site.
    if (! (isset($USER->loggedin) and $USER->confirmed and ($USER->site == $CFG->wwwroot)) ) { // They're not
        $SESSION->wantsurl = $FULLME;
        $SESSION->fromurl  = $HTTP_REFERER;
        save_session("SESSION");
        $USER = NULL;
        save_session("USER");
        if ($PHPSESSID) { // Cookies not enabled.
            redirect("$CFG->wwwroot/login/index.php?PHPSESSID=$PHPSESSID");
        } else {
            redirect("$CFG->wwwroot/login/index.php");
        }
        die;
    }

    // Check that the user account is properly set up
    if (user_not_fully_set_up($USER)) {
        $site = get_site();
        redirect("$CFG->wwwroot/user/edit.php?id=$USER->id&course=$site->id");
        die;
    }
    
    // Next, check if the user can be in a particular course
    if ($courseid) {
        if (!empty($USER->student[$courseid]) or !empty($USER->teacher[$courseid]) or !empty($USER->admin)) {
            if (isset($USER->realuser)) {   // Make sure the REAL person can also access this course
                if (!isteacher($courseid, $USER->realuser)) {
                    print_header();
                    notice(get_string("studentnotallowed", "", "$USER->firstname $USER->lastname"), $CFG->wwwroot);
                }

            } else {  // just update their last login time
                update_user_in_db();
            }
            if (!$USER->email) {            // User logged in, but has not set up profile!
                                            // This can occur with external authentication
                redirect("$CFG->wwwroot/user/edit.php?id=$USER->id&course=$courseid");
                die;
            }
            return;   // user is a member of this course.
        }
        if (! $course = get_record("course", "id", $courseid)) {
            error("That course doesn't exist");
        }
        if ($USER->username == "guest") {
            switch ($course->guest) {
                case 0: // Guests not allowed
                    print_header();
                    notice(get_string("guestsnotallowed", "", $course->fullname));
                    break;
                case 1: // Guests allowed
                    update_user_in_db();
                    return;
                case 2: // Guests allowed with key (drop through)
                    break;
            }
        }

        // Currently not enrolled in the course, so see if they want to enrol
        $SESSION->wantsurl = $FULLME;
        save_session("SESSION");
        redirect("$CFG->wwwroot/course/enrol.php?id=$courseid");
        die;
    }
}

function update_user_login_times() {
    global $USER;

    $USER->lastlogin = $user->lastlogin = $USER->currentlogin;
    $USER->currentlogin = $user->currentlogin = time();
    save_session("USER");

    $user->id = $USER->id;

    return update_record("user", $user);
}

function user_not_fully_set_up($user) {
    return (empty($user->firstname) or empty($user->lastname) or empty($user->email));
}

function update_login_count() {
/// Keeps track of login attempts

    global $SESSION;

    $max_logins = 10;

    if (empty($SESSION->logincount)) {
        $SESSION->logincount = 1;
    } else {
        $SESSION->logincount++;
    }
    save_session("SESSION");

    if ($SESSION->logincount > $max_logins) {
        unset($SESSION->wantsurl);
        save_session("SESSION");
        error(get_string("errortoomanylogins"));
    }
}

function reset_login_count() {
/// Resets login attempts
    global $SESSION;

    $SESSION->logincount = 0;
    save_session("SESSION");
}


function isadmin($userid=0) {
/// Is the user an admin?
    global $USER;

    if (empty($USER)) {
        return false;
    }

    if (empty($userid)) {
        return record_exists("user_admins", "userid", $USER->id);
    }

    return record_exists("user_admins", "userid", $userid);
}


function isteacher($courseid, $userid=0) {
/// Is the user a teacher or admin?
    global $USER;

    if (isadmin($userid)) {  // admins can do anything the teacher can
        return true;
    }

    if (!$userid) {
        return !empty($USER->teacher[$courseid]);
    }

    return record_exists("user_teachers", "userid", $userid, "course", $courseid);
}


function isstudent($courseid, $userid=0) {
/// Is the user a student in this course?
    global $USER;

    if (!$userid) {
        return !empty($USER->student[$courseid]);
    }

  //  $timenow = time();   // todo:  add time check below

    return record_exists("user_students", "userid", $userid, "course", $courseid);
}

function isguest($userid=0) {
/// Is the user a guest?
    global $USER;

    if (!$userid) {
        return ($USER->username == "guest");
    }

    return record_exists("user", "id", $userid, "username", "guest");
}


function isediting($courseid, $user=NULL) {
/// Is the current user in editing mode?
    global $USER;
    if (!$user){
        $user = $USER;
    }
    if (empty($user->editing)) {
        return false;
    }
    return ($user->editing and isteacher($courseid, $user->id));
}


function set_moodle_cookie($thing) {
/// Sets a moodle cookie with an encrypted string
    global $CFG;

    $cookiename = "MOODLEID{$CFG->prefix}";

    $days = 60;
    $seconds = 60*60*24*$days;

    setCookie($cookiename, "", time() - 3600, "/");
    setCookie($cookiename, rc4encrypt($thing), time()+$seconds, "/");
}


function get_moodle_cookie() {
/// Gets a moodle cookie with an encrypted string
    global $CFG;

    $cookiename = "MOODLEID{$CFG->prefix}"; 

    global $$cookiename;

    return rc4decrypt($$cookiename);
}


function save_session($VAR) {
/// Copies temporary session variable to permanent session variable
/// eg $_SESSION["USER"] = $USER;
    global $$VAR;
    $_SESSION[$VAR] = $$VAR;
}


function create_user_record($username, $password) {
/// Creates a bare-bones user record 
    global $REMOTE_ADDR, $CFG;

    if (function_exists(auth_get_userinfo)) {
        if ($newinfo = auth_get_userinfo($username)) {
            foreach ($newinfo as $key => $value){
                $newuser->$key = $value;
            }
        }
    }

    $newuser->username = $username;
    $newuser->password = md5($password);
    $newuser->lang = $CFG->lang;
    $newuser->confirmed = 1;
    $newuser->lastIP = $REMOTE_ADDR;
    $newuser->timemodified = time();

    if (insert_record("user", $newuser)) {
        return get_user_info_from_db("username", $username);
    }
    return false;
}

function authenticate_user_login($username, $password) {
/// Given a username and password, this function looks them 
/// up using the currently selected authentication mechanism,
/// and if the authentication is successful, it returns a 
/// valid $user object from the 'user' table.
///
/// Uses auth_ functions from the currently active auth module

    global $CFG;

    $md5password = md5($password);

    if (!isset($CFG->auth)) {
        $CFG->auth = "email";    // Default authentication module
    }

    if ($username == "guest") {
        $CFG->auth = "none";     // Guest account always internal
    }

    // If this is the admin, then just use internal methods
    // Doing this first (even though it's less efficient) because 
    // the chosen authentication method might hang and lock the 
    // admin out.
    if (adminlogin($username, $md5password)) {
        return get_user_info_from_db("username", $username);
    }

    // OK, the user is a normal user, so try and authenticate them
    require_once("$CFG->dirroot/auth/$CFG->auth/lib.php");

    if (auth_user_login($username, $password)) {  // Successful authentication

        if ($user = get_user_info_from_db("username", $username)) {
            if ($md5password <> $user->password) {   // Update local copy of password for reference
                set_field("user", "password", $md5password, "username", $username);
            }
            return $user;

        } else {
            return create_user_record($username, $password);
        }
    }

    return false;
}


function enrol_student($user, $course) {
/// Enrols a student in a given course
    global $db;

    $record->userid = $user;
    $record->course = $course;
    $record->start = 0;
    $record->end = 0;
    $record->time = time();

    return insert_record("user_students", $record);
}

function unenrol_student($user, $course=0) {
/// Unenrols a student from a given course
    global $db;

    if ($course) {
        /// First delete any crucial stuff that might still send mail
        if ($forums = get_records("forum", "course", $course)) {
            foreach ($forums as $forum) {
                delete_records("forum_subscriptions", "forum", $forum->id, "userid", $user);
            }
        }
        return delete_records("user_students", "userid", $user, "course", $course);

    } else {
        delete_records("forum_subscriptions", "userid", $user);
        return delete_records("user_students", "userid", $user);
    }
}

function remove_teacher($user, $course=0) {
/// Removes a teacher from a given course (or ALL courses)
/// Does not delete the user account
    global $db;

    if ($course) {
        /// First delete any crucial stuff that might still send mail
        if ($forums = get_records("forum", "course", $course)) {
            foreach ($forums as $forum) {
                delete_records("forum_subscriptions", "forum", $forum->id, "userid", $user);
            }
        }
        return delete_records("user_teachers", "userid", $user, "course", $course);
    } else {
        delete_records("forum_subscriptions", "userid", $user);
        return delete_records("user_teachers", "userid", $user);
    }
}

function remove_admin($user) {
/// Removes an admin from a site
    global $db;

    return delete_records("user_admins", "userid", $user);
}



/// CORRESPONDENCE  ////////////////////////////////////////////////

function email_to_user($user, $from, $subject, $messagetext, $messagehtml="", $attachment="", $attachname="") {
///  user        - a user record as an object
///  from        - a user record as an object
///  subject     - plain text subject line of the email
///  messagetext - plain text version of the message
///  messagehtml - complete html version of the message (optional)
///  attachment  - a file on the filesystem, relative to $CFG->dataroot
///  attachname  - the name of the file (extension indicates MIME)

    global $CFG, $_SERVER;

    include_once("$CFG->libdir/phpmailer/class.phpmailer.php");

    if (!$user) {
        return false;
    }
    
    $mail = new phpmailer;

    $mail->Version = "Moodle $CFG->version";           // mailer version 
    $mail->PluginDir = "$CFG->libdir/phpmailer/";      // plugin directory (eg smtp plugin)


    if (current_language() != "en") {
        $mail->CharSet = get_string("thischarset");
    }

    if ($CFG->smtphosts) {
        $mail->IsSMTP();                               // use SMTP directly
        $mail->Host = "$CFG->smtphosts";               // specify main and backup servers

        if ($CFG->smtpuser) {                          // Use SMTP authentication
            $mail->SMTPAuth = true;
            $mail->Username = $CFG->smtpuser;
            $mail->Password = $CFG->smtppass;
        }
    } else {
        $mail->IsMail();                               // use PHP mail() = sendmail
    }

    $mail->From     = "$from->email";
    $mail->FromName = "$from->firstname $from->lastname";
    $mail->Subject  =  stripslashes($subject);

    $mail->AddAddress("$user->email", "$user->firstname $user->lastname"); 

    $mail->WordWrap = 70;                               // set word wrap

    if ($messagehtml) {
        $mail->IsHTML(true);
        $mail->Body    =  $messagehtml;
        $mail->AltBody =  "\n$messagetext\n";
    } else {
        $mail->IsHTML(false);
        $mail->Body =  "\n$messagetext\n";
    }

    if ($attachment && $attachname) {
        if (ereg( "\\.\\." ,$attachment )) {    // Security check for ".." in dir path
            $adminuser = get_admin();
            $mail->AddAddress("$adminuser->email", "$adminuser->firstname $adminuser->lastname");
            $mail->AddStringAttachment("Error in attachment.  User attempted to attach a filename with a unsafe name.", "error.txt", "8bit", "text/plain");
        } else {
            include_once("$CFG->dirroot/files/mimetypes.php");
            $mimetype = mimeinfo("type", $attachname);
            $mail->AddAttachment("$CFG->dataroot/$attachment", "$attachname", "base64", "$mimetype");
        }
    }

    if ($mail->Send()) {
        return true;
    } else {
        echo "ERROR: $mail->ErrorInfo\n";
        $site = get_site();
        add_to_log($site->id, "library", "mailer", $_SERVER["REQUEST_URI"], "ERROR: $mail->ErrorInfo");
        return false;
    }
}

function reset_password_and_mail($user) {

    global $CFG;

    $site  = get_site();
    $from = get_admin();

    $newpassword = generate_password();

    if (! set_field("user", "password", md5($newpassword), "id", $user->id) ) {
        error("Could not set user password!");
    }

    $a->firstname = $user->firstname;
    $a->sitename = $site->fullname;
    $a->username = $user->username;
    $a->newpassword = $newpassword;
    $a->link = "$CFG->wwwroot/login/change_password.php";
    $a->signoff = "$from->firstname $from->lastname ($from->email)";

    $message = get_string("newpasswordtext", "", $a);

    $subject  = "$site->fullname: ".get_string("changedpassword");

    return email_to_user($user, $from, $subject, $message);

}

function send_confirmation_email($user) {

    global $CFG;

    $site = get_site();
    $from = get_admin();

    $data->firstname = $user->firstname;
    $data->sitename = $site->fullname;
    $data->link = "$CFG->wwwroot/login/confirm.php?p=$user->secret&s=$user->username";
    $data->admin = "$from->firstname $from->lastname ($from->email)";

    $message = get_string("emailconfirmation", "", $data);
    $subject = "$site->fullname account confirmation";

    return email_to_user($user, $from, $subject, $message);

}



/// FILE HANDLING  /////////////////////////////////////////////

function make_upload_directory($directory) {
/// $directory = a string of directory names under $CFG->dataroot
/// eg  stuff/assignment/1
/// Returns full directory if successful, false if not

    global $CFG;

    $currdir = $CFG->dataroot;
    if (!file_exists($currdir)) {
        if (! mkdir($currdir, 0750)) {
            notify("ERROR: You need to create the directory $currdir with web server write access");
            return false;
        }
    }

    $dirarray = explode("/", $directory);

    foreach ($dirarray as $dir) {
        $currdir = "$currdir/$dir";
        if (! file_exists($currdir)) {
            if (! mkdir($currdir, 0750)) {
                notify("ERROR: Could not find or create a directory ($currdir)");
                return false;
            }
        }
    }

    return $currdir;
}

function make_mod_upload_directory($courseid) {
/// Makes an upload directory for a particular module
    global $CFG;

    if (! $moddata = make_upload_directory("$courseid/$CFG->moddata")) {
        return false;
    }

    $strreadme = get_string("readme");

    if (file_exists("$CFG->dirroot/lang/$CFG->lang/docs/module_files.txt")) {
        copy("$CFG->dirroot/lang/$CFG->lang/docs/module_files.txt", "$moddata/$strreadme.txt");
    } else {
        copy("$CFG->dirroot/lang/en/docs/module_files.txt", "$moddata/$strreadme.txt");
    }
    return $moddata;
}


function valid_uploaded_file($newfile) {
/// Returns current name of file on disk if true
    if (empty($newfile)) {
        return "";
    }
    if (is_uploaded_file($newfile['tmp_name']) and $newfile['size'] > 0) {
        return $newfile['tmp_name'];
    } else {
        return "";
    }
}

function get_max_upload_file_size() {
/// Returns the maximum size for uploading files
    if (! $filesize = ini_get("upload_max_filesize")) {
        $filesize = "5M";
    }
    return get_real_size($filesize);
}

function get_directory_list($rootdir, $excludefile="", $descend=true) {
/// Returns an array with all the filenames in 
/// all subdirectories, relative to the given rootdir.
/// If excludefile is defined, then that file/directory is ignored

    $dirs = array();
   
    $dir = opendir($rootdir);

    if (!$dir) {
        notify("Error: unable to read this directory! : $rootdir");
        return $dirs;
    }

    while ($file = readdir($dir)) {
        if ($file != "." and $file != ".." and $file != "CVS" and $file != $excludefile) {
            $fullfile = $rootdir."/".$file;
            if ($descend and filetype($fullfile) == "dir") {
                $subdirs = get_directory_list($fullfile, $excludefile, $descend);
                foreach ($subdirs as $subdir) {
                    $dirs[] = $file."/".$subdir;
                }
            } else {
                $dirs[] = $file;
            }
        }
    }
    closedir($dir);

    asort($dirs);

    return $dirs;
}

function get_real_size($size=0) {
/// Converts numbers like 10M into bytes
    if (!$size) {
        return 0; 
    }
    $scan['MB'] = 1048576;
    $scan['Mb'] = 1048576;
    $scan['M'] = 1048576;
    $scan['KB'] = 1024;
    $scan['Kb'] = 1024;
    $scan['K'] = 1024;

    while (list($key) = each($scan)) {
        if ((strlen($size)>strlen($key))&&(substr($size, strlen($size) - strlen($key))==$key)) {
            $size = substr($size, 0, strlen($size) - strlen($key)) * $scan[$key];
            break;
        }
    }
    return $size;
}

function display_size($size) {
/// Converts bytes into display form
    if ($size >= 1073741824) {
        $size = round($size / 1073741824 * 10) / 10 . "Gb";
    } else if ($size >= 1048576) {
        $size = round($size / 1048576 * 10) / 10 . "Mb";
    } else if ($size >= 1024) {
        $size = round($size / 1024 * 10) / 10 . "Kb";
    } else { 
        $size = $size . "b";
    }
    return $size;
}

function clean_filename($string) {
/// Cleans a given filename by removing suspicious or troublesome characters
    $string = stripslashes($string);
    $string = eregi_replace("\.\.", "", $string);
    $string = eregi_replace("[^([:alnum:]|\.)]", "_", $string);
    return    eregi_replace("_+", "_", $string);
}


/// STRING TRANSLATION  ////////////////////////////////////////

function current_language() {
/// Returns the code for the current language
    global $CFG, $USER;

    if (isset($USER->lang)) {    // User language can override site language
        return $USER->lang;
    } else {
        return $CFG->lang;
    }
}

function print_string($identifier, $module="", $a=NULL) {
/// Given a string to translate - prints it out.
    echo get_string($identifier, $module, $a);
}

function get_string($identifier, $module="", $a=NULL) {
/// Return the translated string specified by $identifier as 
/// for $module.  Uses the same format files as STphp.
/// $a is an object, string or number that can be used
/// within translation strings
///
/// eg "hello \$a->firstname \$a->lastname"
/// or "hello \$a"

    global $CFG;

    $lang = current_language();

    if ($module == "") {
        $module = "moodle";
    }

    $langpath = "$CFG->dirroot/lang";
    $langfile = "$langpath/$lang/$module.php";

    if (!file_exists($langfile)) {                // try English instead
        $langfile = "$langpath/en/$module.php";
        if (!file_exists($langfile)) {
            return "ERROR: No lang file ($langpath/en/$module.php)!";
        }
    }

    if ($result = get_string_from_file($identifier, $langfile, "\$resultstring")) {

        eval($result);
        return $resultstring;

    } else {
        if ($lang == "en") {
            return "[['$identifier']]";

        } else {   // Try looking in the english file.
            $langfile = "$langpath/en/$module.php";
            if (!file_exists($langfile)) {
                return "ERROR: No lang file ($langpath/en/$module.php)!";
            }
            if ($result = get_string_from_file($identifier, $langfile, "\$resultstring")) {
                eval($result);
                return $resultstring;
            } else {
                return "[['$identifier']]";
            }
        }
    }
}


function get_string_from_file($identifier, $langfile, $destination) {
/// This function is only used from get_string().
    include ($langfile);

    if (!isset ($string[$identifier])) {
        return false;
    }

    return "$destination = sprintf(\"".$string[$identifier]."\");";
}


function get_list_of_languages() {
/// Returns a list of language codes and their full names
    global $CFG;

    if (!$langdirs = get_list_of_plugins("lang")) {
        return false;
    }

    foreach ($langdirs as $lang) {
        include("$CFG->dirroot/lang/$lang/moodle.php");
        $languages[$lang] = $string["thislanguage"]." ($lang)";
        unset($string);
    }
    return $languages;
}

function document_file($file, $include=true) {
/// Can include a given document file (depends on second
/// parameter) or just return info about it

    global $CFG, $SESSION;

    if (empty($file)) {
        echo "Error 404";
        return false;
    }

    if (!empty($SESSION->doclang)) {
        $lang = $SESSION->doclang;
    } else {
        $lang = current_language();
    }

    $file = clean_filename($file);

    $info->filepath = "$CFG->dirroot/lang/$lang/docs/$file";
    $info->urlpath  = "$CFG->wwwroot/lang/$lang/docs/$file";

    if (!file_exists($info->filepath)) {
        $info->filepath = "$CFG->dirroot/lang/en/docs/$file";
        $info->urlpath  = "$CFG->wwwroot/lang/en/docs/$file";
    }

    if ($include) {
        include($info->filepath);
    }

    return $info;
}


/// ENCRYPTION  ////////////////////////////////////////////////

function rc4encrypt($data) {
    $password = "nfgjeingjk";
    return endecrypt($password, $data, "");
}

function rc4decrypt($data) {
    $password = "nfgjeingjk";
    return endecrypt($password, $data, "de");
}

function endecrypt ($pwd, $data, $case) {
/// Based on a class by Mukul Sabharwal [mukulsabharwal@yahoo.com]

    if ($case == 'de') {
        $data = urldecode($data);
    }

    $key[] = "";
    $box[] = "";
    $temp_swap = "";
    $pwd_length = 0;

    $pwd_length = strlen($pwd);

    for ($i = 0; $i <= 255; $i++) {
        $key[$i] = ord(substr($pwd, ($i % $pwd_length), 1));
        $box[$i] = $i;
    }

    $x = 0;

    for ($i = 0; $i <= 255; $i++) {
        $x = ($x + $box[$i] + $key[$i]) % 256;
        $temp_swap = $box[$i];
        $box[$i] = $box[$x];
        $box[$x] = $temp_swap;
    }

    $temp = "";
    $k = "";

    $cipherby = "";
    $cipher = "";

    $a = 0;
    $j = 0;

    for ($i = 0; $i < strlen($data); $i++) {
        $a = ($a + 1) % 256;
        $j = ($j + $box[$a]) % 256;
        $temp = $box[$a];
        $box[$a] = $box[$j];
        $box[$j] = $temp;
        $k = $box[(($box[$a] + $box[$j]) % 256)];
        $cipherby = ord(substr($data, $i, 1)) ^ $k;
        $cipher .= chr($cipherby);
    }

    if ($case == 'de') {
        $cipher = urldecode(urlencode($cipher));
    } else {
        $cipher = urlencode($cipher);
    }

    return $cipher;
}


/// ENVIRONMENT CHECKING  ////////////////////////////////////////////////////////////

function get_list_of_plugins($plugin="mod") {
/// Lists plugin directories within some directory

    global $CFG;

    $basedir = opendir("$CFG->dirroot/$plugin");
    while ($dir = readdir($basedir)) {
        if ($dir == "." || $dir == ".." || $dir == "CVS") {
            continue;
        }
        if (filetype("$CFG->dirroot/$plugin/$dir") != "dir") {
            continue;
        }
        $plugins[] = $dir;
    }
    if ($plugins) {
        asort($plugins);
    }
    return $plugins;
}

function check_php_version($version="4.1.0") {
/// Returns true is the current version of PHP is greater that the specified one
    $minversion = intval(str_replace(".", "", $version));
    $curversion = intval(str_replace(".", "", phpversion()));
    return ($curversion >= $minversion);
}

function check_browser_version($brand="MSIE", $version=5.5) {
/// Checks to see if is a browser matches the specified
/// brand and is equal or better version.
    global $HTTP_USER_AGENT;

    if (!$HTTP_USER_AGENT) {
        return false;
    }
    $string = explode(";", $HTTP_USER_AGENT);
    if (!isset($string[1])) {
        return false;
    }
    $string = explode(" ", trim($string[1]));
    if (!isset($string[0]) and !isset($string[1])) {
        return false;
    }
    if ($string[0] == $brand and (float)$string[1] >= $version ) {
        return true;
    }
    return false;
}

function can_use_richtext_editor() {
/// Is the richedit editor enabled?
    global $USER, $CFG;
    if ($USER->htmleditor and $CFG->htmleditor) {
        return check_browser_version("MSIE", 5.5);
    }
    return false;
}

function check_gd_version() {
/// Hack to find out the GD version by parsing phpinfo output
    ob_start();
    phpinfo(8);
    $phpinfo = ob_get_contents();
    ob_end_clean();

    $phpinfo = explode("\n",$phpinfo);

    $gdversion = 0;


    foreach ($phpinfo as $text) {
        $parts = explode('</td>',$text);
        foreach ($parts as $key => $val) {
            $parts[$key] = trim(strip_tags($val));
        }
        if ($parts[0] == "GD Version") {
            if (substr_count($parts[1], "2.0")) {
                $parts[1] = "2.0";
            }
            $gdversion = intval($parts[1]);
        }
    }

    return $gdversion;   // 1, 2 or 0
}


function moodle_needs_upgrading() {
/// Checks version numbers of Main code and all modules to see
/// if there are any mismatches ... returns true or false
    global $CFG;

    include_once("$CFG->dirroot/version.php");  # defines $version and upgrades
    if ($CFG->version) { 
        if ($version > $CFG->version) {
            return true;
        }
        if ($mods = get_list_of_plugins("mod")) {
            foreach ($mods as $mod) {
                $fullmod = "$CFG->dirroot/mod/$mod";
                unset($module);
                include_once("$fullmod/version.php");  # defines $module with version etc
                if ($currmodule = get_record("modules", "name", $mod)) {
                    if ($module->version > $currmodule->version) {
                        return true;
                    }
                }
            }
        }
    } else {
        return true;
    }
    return false;
}


/// MISCELLANEOUS ////////////////////////////////////////////////////////////////////

function count_words($string) {
/// Words are defined as things between whitespace
    $string = strip_tags($string);
    return count(preg_split("/\w\b/", $string)) - 1;
}

function random_string ($length=15) {
    $pool  = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $pool .= "abcdefghijklmnopqrstuvwxyz";
    $pool .= "0123456789";
    $poollen = strlen($pool);
    mt_srand ((double) microtime() * 1000000);
    $string = "";
    for ($i = 0; $i < $length; $i++) {
        $string .= substr($pool, (mt_rand()%($poollen)), 1);
    }
    return $string;
}


function getweek ($startdate, $thedate) {
/// Given dates in seconds, how many weeks is the date from startdate
/// The first week is 1, the second 2 etc ... 
    
    if ($thedate < $startdate) {   // error
        return 0;  
    }

    return floor(($thedate - $startdate) / 604800.0) + 1;
}

function generate_password($maxlen=10) {
/// returns a randomly generated password of length $maxlen.  inspired by
/// http://www.phpbuilder.com/columns/jesus19990502.php3 

    global $CFG;

    $fillers = "1234567890!$-+";
    $wordlist = file($CFG->wordlist);

    srand((double) microtime() * 1000000);
    $word1 = trim($wordlist[rand(0, count($wordlist) - 1)]);
    $word2 = trim($wordlist[rand(0, count($wordlist) - 1)]);
    $filler1 = $fillers[rand(0, strlen($fillers) - 1)];

    return substr($word1 . $filler1 . $word2, 0, $maxlen);
}

function format_float($num, $places=0) {
/// Given a float, prints it nicely
    return sprintf("%.$places"."f", $num);
}



?>