Proyectos de Subversion Moodle

<?php

// This file is part of Moodle - http://moodle.org/

//

// Moodle 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 3 of the License, or

// (at your option) any later version.

//

// Moodle 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.

//

// You should have received a copy of the GNU General Public License

// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**

 * Defines string apis

 *

 * @package    core

 * @copyright  (C) 2001-3001 Eloy Lafuente (stronk7) {@link http://contiento.com}

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

defined('MOODLE_INTERNAL') || die();

/**

 * defines string api's for manipulating strings

 *

 * This class is used to manipulate strings under Moodle 1.6 an later. As

 * utf-8 text become mandatory a pool of safe functions under this encoding

 * become necessary. The name of the methods is exactly the

 * same than their PHP originals.

 *

 * This class was previously based on Typo3 which has now been removed and uses

 * native functions now.

 *

 * @package   core

 * @category  string

 * @copyright 1999 onwards Martin Dougiamas  {@link http://moodle.com}

 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class core_text {

    /** @var string Byte order mark for UTF-8 */

    const UTF8_BOM = "\xef\xbb\xbf";

    /**

     * @var string[] Array of strings representing Unicode non-characters

     */

    protected static $noncharacters;

    /**

     * Check whether the charset is supported by mbstring.

     * @param string $charset Normalised charset

     * @return bool

     */

    public static function is_charset_supported(string $charset): bool {

        static $cache = null;

        if (!$cache) {

            $cache = array_flip(array_map('strtolower', mb_list_encodings()));

        }

        if (isset($cache[strtolower($charset)])) {

            return true;

        }

        // We haven't found the charset, check if mb has aliases for the charset.

        try {

            return mb_encoding_aliases($charset) !== false;

        } catch (Throwable $e) {

            // A ValueError will be thrown if unsupported.

        }

        return false;

    }

    /**

     * Reset internal textlib caches.

     * @static

     * @deprecated since Moodle 4.0. See MDL-53544.

     * @todo To be removed in Moodle 4.4 - MDL-71748

     */

    public static function reset_caches() {

        debugging("reset_caches() is deprecated. Typo3 has been removed and caches aren't used anymore.", DEBUG_DEVELOPER);

    }

    /**

     * Standardise charset name

     *

     * Please note it does not mean the returned charset is actually supported.

     *

     * @static

     * @param string $charset raw charset name

     * @return string normalised lowercase charset name

     */

    public static function parse_charset($charset) {

        $charset = strtolower($charset ?? '');

        if ($charset === 'utf8' or $charset === 'utf-8') {

            return 'utf-8';

        }

        if (preg_match('/^(cp|win|windows)-?(12[0-9]{2})$/', $charset, $matches)) {

            return 'windows-'.$matches[2];

        }

        if (preg_match('/^iso-8859-[0-9]+$/', $charset, $matches)) {

            return $charset;

        }

        if ($charset === 'euc-jp') {

            return 'euc-jp';

        }

        if ($charset === 'iso-2022-jp') {

            return 'iso-2022-jp';

        }

        if ($charset === 'shift-jis' or $charset === 'shift_jis') {

            return 'shift_jis';

        }

        if ($charset === 'gb2312') {

            return 'gb2312';

        }

        if ($charset === 'gb18030') {

            return 'gb18030';

        }

        if ($charset === 'ms-ansi') {

            return 'windows-1252';

        }

        // We have reached this stage and haven't matched with anything. Return the original.

        return $charset;

    }

    /**

     * Converts the text between different encodings. It uses iconv extension with //TRANSLIT parameter.

     * If both source and target are utf-8 it tries to fix invalid characters only.

     *

     * @param string $text

     * @param string $fromCS source encoding

     * @param string $toCS result encoding

     * @return string|bool converted string or false on error

     */

    public static function convert($text, $fromCS, $toCS='utf-8') {

        $fromCS = self::parse_charset($fromCS);

        $toCS   = self::parse_charset($toCS);

        $text = (string)$text; // we can work only with strings

        if ($text === '') {

            return '';

        }

        if ($fromCS === 'utf-8') {

            $text = fix_utf8($text);

            if ($toCS === 'utf-8') {

                return $text;

            }

        }

        if ($toCS === 'ascii') {

            // Try to normalize the conversion a bit if the target is ascii.

            return self::specialtoascii($text, $fromCS);

        }

        // Prevent any error notices, do not use //IGNORE so that we get

        // consistent result if iconv fails.

        return @iconv($fromCS, $toCS.'//TRANSLIT', $text);

    }

    /**

     * Multibyte safe substr() function, uses mbstring or iconv

     *

     * @param string $text string to truncate

     * @param int $start negative value means from end

     * @param int $len maximum length of characters beginning from start

     * @param string $charset encoding of the text

     * @return string portion of string specified by the $start and $len

     */

    public static function substr($text, $start, $len=null, $charset='utf-8') {

        $charset = self::parse_charset($charset);

        // Check whether the charset is supported by mbstring. CP1250 is not supported. Fall back to iconv.

        if (self::is_charset_supported($charset)) {

            $result = mb_substr($text ?? '', $start, $len, $charset);

        } else {

            $result = (string)iconv_substr($text ?? '', $start, $len, $charset);

        }

        return $result;

    }

    /**

     * Truncates a string to no more than a certain number of bytes in a multi-byte safe manner.

     * UTF-8 only!

     *

     * @param string $string String to truncate

     * @param int $bytes Maximum length of bytes in the result

     * @return string Portion of string specified by $bytes

     * @since Moodle 3.1

     */

    public static function str_max_bytes($string, $bytes) {

        return mb_strcut($string ?? '', 0, $bytes, 'UTF-8');

    }

    /**

     * Finds the last occurrence of a character in a string within another.

     * UTF-8 ONLY safe mb_strrchr().

     *

     * @param string $haystack The string from which to get the last occurrence of needle.

     * @param string $needle The string to find in haystack.

     * @param boolean $part If true, returns the portion before needle, else return the portion after (including needle).

     * @return string|false False when not found.

     * @since Moodle 2.4.6, 2.5.2, 2.6

     */

    public static function strrchr($haystack, $needle, $part = false) {

        if (is_null($haystack)) {

            // Compatibility with behavior in PHP before version 8.1.

            return false;

        }

        return mb_strrchr($haystack, $needle, $part, 'UTF-8');

    }

    /**

     * Multibyte safe strlen() function, uses mbstring or iconv

     *

     * @param string $text input string

     * @param string $charset encoding of the text

     * @return int number of characters

     */

    public static function strlen($text, $charset='utf-8') {

        $charset = self::parse_charset($charset);

        if (self::is_charset_supported($charset)) {

            return mb_strlen($text ?? '', $charset);

        }

        return iconv_strlen($text ?? '', $charset);

    }

    /**

     * Multibyte safe strtolower() function, uses mbstring.

     *

     * @param string $text input string

     * @param string $charset encoding of the text (may not work for all encodings)

     * @return string lower case text

     */

    public static function strtolower($text, $charset='utf-8') {

        $charset = self::parse_charset($charset);

        // Confirm mbstring can handle the charset.

        if (self::is_charset_supported($charset)) {

            return mb_strtolower($text ?? '', $charset);

        }

        // The mbstring extension cannot handle the charset. Convert to UTF-8.

        $convertedtext = self::convert($text, $charset, 'utf-8');

        $result = mb_strtolower($convertedtext);

        $result = self::convert($result, 'utf-8', $charset);

        return $result;

    }

    /**

     * Multibyte safe strtoupper() function, uses mbstring.

     *

     * @param string $text input string

     * @param string $charset encoding of the text (may not work for all encodings)

     * @return string upper case text

     */

    public static function strtoupper($text, $charset='utf-8') {

        $charset = self::parse_charset($charset);

        // Confirm mbstring can handle the charset.

        if (self::is_charset_supported($charset)) {

            return mb_strtoupper($text ?? '', $charset);

        }

        // The mbstring extension cannot handle the charset. Convert to UTF-8.

        $convertedtext = self::convert($text, $charset, 'utf-8');

        $result = mb_strtoupper($convertedtext);

        $result = self::convert($result, 'utf-8', $charset);

        return $result;

    }

    /**

     * Find the position of the first occurrence of a substring in a string.

     * UTF-8 ONLY safe strpos(), uses mbstring

     *

     * @param string $haystack the string to search in

     * @param string $needle one or more charachters to search for

     * @param int $offset offset from begining of string

     * @return int the numeric position of the first occurrence of needle in haystack.

     */

    public static function strpos($haystack, $needle, $offset=0) {

        return mb_strpos($haystack ?? '', $needle, $offset, 'UTF-8');

    }

    /**

     * Find the position of the last occurrence of a substring in a string

     * UTF-8 ONLY safe strrpos(), uses mbstring

     *

     * @param string $haystack the string to search in

     * @param string $needle one or more charachters to search for

     * @return int the numeric position of the last occurrence of needle in haystack

     */

    public static function strrpos($haystack, $needle) {

        if (is_null($haystack)) {

            // Compatibility with behavior in PHP before version 8.1.

            return false;

        }

        return mb_strrpos($haystack, $needle, 0, 'UTF-8');

    }

    /**

     * Reverse UTF-8 multibytes character sets (used for RTL languages)

     * (We only do this because there is no mb_strrev or iconv_strrev)

     *

     * @param string $str the multibyte string to reverse

     * @return string the reversed multi byte string

     */

    public static function strrev($str) {

        preg_match_all('/./us', $str ?? '', $ar);

        return join('', array_reverse($ar[0]));

    }

    /**

     * Try to convert upper unicode characters to plain ascii,

     * the returned string may contain unconverted unicode characters.

     *

     * With the removal of typo3, iconv conversions was found to be the best alternative to Typo3's function.

     * However using the standard iconv call

     *      iconv($charset, 'ASCII//TRANSLIT//IGNORE', (string) $text);

     * resulted in invalid strings with special character from Russian/Japanese. To solve this, the transliterator was

     * used but this resulted in empty strings for certain strings in our test. It was decided to use a combo of the 2

     * to cover all our bases. Refer MDL-53544 for further information.

     *

     * @param string $text input string

     * @param string $charset encoding of the text

     * @return string converted ascii string

     */

    public static function specialtoascii($text, $charset='utf-8') {

        $charset = self::parse_charset($charset);

        $oldlevel = error_reporting(E_PARSE);

        // Always convert to utf-8, so transliteration can do its work always.

        if ($charset !== 'utf-8') {

            $text = iconv($charset, 'utf-8'.'//TRANSLIT', $text);

        }

        $text = transliterator_transliterate('Any-Latin; Latin-ASCII', (string) $text);

        // Still, apply iconv because some chars are not handled by transliterate.

        $result = iconv('utf-8', 'ASCII//TRANSLIT//IGNORE', (string) $text);

        error_reporting($oldlevel);

        return $result;

    }

    /**

     * Generate a correct base64 encoded header to be used in MIME mail messages.

     * This function seems to be 100% compliant with RFC1342. Credits go to:

     * paravoid (http://www.php.net/manual/en/function.mb-encode-mimeheader.php#60283).

     *

     * @param string $text input string

     * @param string $charset encoding of the text

     * @return string base64 encoded header

     */

    public static function encode_mimeheader($text, $charset='utf-8') {

        if (empty($text)) {

            return (string)$text;

        }

        // Normalize charset

        $charset = self::parse_charset($charset);

        // If the text is pure ASCII, we don't need to encode it

        if (self::convert($text, $charset, 'ascii') == $text) {

            return $text;

        }

        // Although RFC says that line feed should be \r\n, it seems that

        // some mailers double convert \r, so we are going to use \n alone

        $linefeed="\n";

        // Define start and end of every chunk

        $start = "=?$charset?B?";

        $end = "?=";

        // Accumulate results

        $encoded = '';

        // Max line length is 75 (including start and end)

        $length = 75 - strlen($start) - strlen($end);

        // Multi-byte ratio

        $multilength = self::strlen($text, $charset);

        // Detect if strlen and friends supported

        if ($multilength === false) {

            if ($charset == 'GB18030' or $charset == 'gb18030') {

                while (strlen($text)) {

                    // try to encode first 22 chars - we expect most chars are two bytes long

                    if (preg_match('/^(([\x00-\x7f])|([\x81-\xfe][\x40-\x7e])|([\x81-\xfe][\x80-\xfe])|([\x81-\xfe][\x30-\x39]..)){1,22}/m', $text, $matches)) {

                        $chunk = $matches[0];

                        $encchunk = base64_encode($chunk);

                        if (strlen($encchunk) > $length) {

                            // find first 11 chars - each char in 4 bytes - worst case scenario

                            preg_match('/^(([\x00-\x7f])|([\x81-\xfe][\x40-\x7e])|([\x81-\xfe][\x80-\xfe])|([\x81-\xfe][\x30-\x39]..)){1,11}/m', $text, $matches);

                            $chunk = $matches[0];

                            $encchunk = base64_encode($chunk);

                        }

                        $text = substr($text, strlen($chunk));

                        $encoded .= ' '.$start.$encchunk.$end.$linefeed;

                    } else {

                        break;

                    }

                }

                $encoded = trim($encoded);

                return $encoded;

            } else {

                return false;

            }

        }

        $ratio = $multilength / strlen($text);

        // Base64 ratio

        $magic = $avglength = floor(3 * $length * $ratio / 4);

        // basic infinite loop protection

        $maxiterations = strlen($text)*2;

        $iteration = 0;

        // Iterate over the string in magic chunks

        for ($i=0; $i <= $multilength; $i+=$magic) {

            if ($iteration++ > $maxiterations) {

                return false; // probably infinite loop

            }

            $magic = $avglength;

            $offset = 0;

            // Ensure the chunk fits in length, reducing magic if necessary

            do {

                $magic -= $offset;

                $chunk = self::substr($text, $i, $magic, $charset);

                $chunk = base64_encode($chunk);

                $offset++;

            } while (strlen($chunk) > $length);

            // This chunk doesn't break any multi-byte char. Use it.

            if ($chunk)

                $encoded .= ' '.$start.$chunk.$end.$linefeed;

        }

        // Strip the first space and the last linefeed

        $encoded = substr($encoded, 1, -strlen($linefeed));

        return $encoded;

    }

    /**

     * Returns HTML entity transliteration table.

     * @return array with (html entity => utf-8) elements

     */

    protected static function get_entities_table() {

        static $trans_tbl = null;

        // Generate/create $trans_tbl

        if (!isset($trans_tbl)) {

            if (version_compare(phpversion(), '5.3.4') < 0) {

                $trans_tbl = array();

                foreach (get_html_translation_table(HTML_ENTITIES, ENT_COMPAT) as $val=>$key) {

                    $trans_tbl[$key] = self::convert($val, 'ISO-8859-1', 'utf-8');

                }

            } else if (version_compare(phpversion(), '5.4.0') < 0) {

                $trans_tbl = get_html_translation_table(HTML_ENTITIES, ENT_COMPAT, 'UTF-8');

                $trans_tbl = array_flip($trans_tbl);

            } else {

                $trans_tbl = get_html_translation_table(HTML_ENTITIES, ENT_COMPAT | ENT_HTML401, 'UTF-8');

                $trans_tbl = array_flip($trans_tbl);

            }

        }

        return $trans_tbl;

    }

    /**

     * Converts all the numeric entities &#nnnn; or &#xnnn; to UTF-8

     * Original from laurynas dot butkus at gmail at:

     * http://php.net/manual/en/function.html-entity-decode.php#75153

     * with some custom mods to provide more functionality

     *

     * @param string $str input string

     * @param boolean $htmlent convert also html entities (defaults to true)

     * @return string encoded UTF-8 string

     */

    public static function entities_to_utf8($str, $htmlent=true) {

        static $callback1 = null ;

        static $callback2 = null ;

        if (!$callback1 or !$callback2) {

            $callback1 = function($matches) {

                return core_text::code2utf8(hexdec($matches[1]));

            };

            $callback2 = function($matches) {

                return core_text::code2utf8($matches[1]);

            };

        }

        $result = (string)$str;

        $result = preg_replace_callback('/&#x([0-9a-f]+);/i', $callback1, $result);

        $result = preg_replace_callback('/&#([0-9]+);/', $callback2, $result);

        // Replace literal entities (if desired)

        if ($htmlent) {

            $trans_tbl = self::get_entities_table();

            // It should be safe to search for ascii strings and replace them with utf-8 here.

            $result = strtr($result, $trans_tbl);

        }

        // Return utf8-ised string

        return $result;

    }

    /**

     * Converts all Unicode chars > 127 to numeric entities &#nnnn; or &#xnnn;.

     *

     * @param string $str input string

     * @param boolean $dec output decadic only number entities

     * @param boolean $nonnum remove all non-numeric entities

     * @return string converted string

     */

    public static function utf8_to_entities($str, $dec=false, $nonnum=false) {

        static $callback = null ;

        if ($nonnum) {

            $str = self::entities_to_utf8($str, true);

        }

        $result = mb_strtolower(mb_encode_numericentity($str ?? '', [0xa0, 0xffff, 0, 0xffff], 'UTF-8', true));

        // We cannot use the decimal equivalent of the above call due to the unit test and our allowance for

        // entities to be entered within the provided $str. Refer to the correspond unit test for examples.

        if ($dec) {

            if (!$callback) {

                $callback = function($matches) {

                    return '&#' . hexdec($matches[1]) . ';';

                };

            }

            $result = preg_replace_callback('/&#x([0-9a-f]+);/i', $callback, $result);

        }

        return $result;

    }

    /**

     * Removes the BOM from unicode string {@link http://unicode.org/faq/utf_bom.html}

     *

     * @param string $str input string

     * @return string

     */

    public static function trim_utf8_bom($str) {

        if (is_null($str)) {

            return null;

        }

        $bom = self::UTF8_BOM;

        if (strpos($str, $bom) === 0) {

            return substr($str, strlen($bom));

        }

        return $str;

    }

    /**

     * There are a number of Unicode non-characters including the byte-order mark (which may appear

     * multiple times in a string) and also other ranges. These can cause problems for some

     * processing.

     *

     * This function removes the characters using string replace, so that the rest of the string

     * remains unchanged.

     *

     * @param string $value Input string

     * @return string Cleaned string value

     * @since Moodle 3.5

     */

    public static function remove_unicode_non_characters($value) {

        // Set up list of all Unicode non-characters for fast replacing.

        if (!self::$noncharacters) {

            self::$noncharacters = [];

            // This list of characters is based on the Unicode standard. It includes the last two

            // characters of each code planes 0-16 inclusive...

            for ($plane = 0; $plane <= 16; $plane++) {

                $base = ($plane === 0 ? '' : dechex($plane));

                self::$noncharacters[] = html_entity_decode('&#x' . $base . 'fffe;', ENT_COMPAT);

                self::$noncharacters[] = html_entity_decode('&#x' . $base . 'ffff;', ENT_COMPAT);

            }

            // ...And the character range U+FDD0 to U+FDEF.

            for ($char = 0xfdd0; $char <= 0xfdef; $char++) {

                self::$noncharacters[] = html_entity_decode('&#x' . dechex($char) . ';', ENT_COMPAT);

            }

        }

        // Do character replacement.

        return str_replace(self::$noncharacters, '', $value);

    }

    /**

     * Returns encoding options for select boxes, utf-8 and platform encoding first

     *

     * @return array encodings

     */

    public static function get_encodings() {

        $encodings = array();

        $encodings['UTF-8'] = 'UTF-8';

        $winenc = strtoupper(get_string('localewincharset', 'langconfig'));

        if ($winenc != '') {

            $encodings[$winenc] = $winenc;

        }

        $nixenc = strtoupper(get_string('oldcharset', 'langconfig'));

        $encodings[$nixenc] = $nixenc;

        $listedencodings = mb_list_encodings();

        foreach ($listedencodings as $enc) {

            $enc = strtoupper($enc);

            $encodings[$enc] = $enc;

        }

        return $encodings;

    }

    /**

     * Returns the utf8 string corresponding to the unicode value

     * (from php.net, courtesy - romans@void.lv)

     *

     * @param  int    $num one unicode value

     * @return string the UTF-8 char corresponding to the unicode value

     */

    public static function code2utf8($num) {

        if ($num < 128) {

            return chr($num);

        }

        if ($num < 2048) {

            return chr(($num >> 6) + 192) . chr(($num & 63) + 128);

        }

        if ($num < 65536) {

            return chr(($num >> 12) + 224) . chr((($num >> 6) & 63) + 128) . chr(($num & 63) + 128);

        }

        if ($num < 2097152) {

            return chr(($num >> 18) + 240) . chr((($num >> 12) & 63) + 128) . chr((($num >> 6) & 63) + 128) . chr(($num & 63) + 128);

        }

        return '';

    }

    /**

     * Returns the code of the given UTF-8 character

     *

     * @param  string $utf8char one UTF-8 character

     * @return int    the code of the given character

     */

    public static function utf8ord($utf8char) {

        if ($utf8char == '') {

            return 0;

        }

        $ord0 = ord($utf8char[0]);

        if ($ord0 >= 0 && $ord0 <= 127) {

            return $ord0;

        }

        $ord1 = ord($utf8char[1]);

        if ($ord0 >= 192 && $ord0 <= 223) {

            return ($ord0 - 192) * 64 + ($ord1 - 128);

        }

        $ord2 = ord($utf8char[2]);

        if ($ord0 >= 224 && $ord0 <= 239) {

            return ($ord0 - 224) * 4096 + ($ord1 - 128) * 64 + ($ord2 - 128);

        }

        $ord3 = ord($utf8char[3]);

        if ($ord0 >= 240 && $ord0 <= 247) {

            return ($ord0 - 240) * 262144 + ($ord1 - 128 )* 4096 + ($ord2 - 128) * 64 + ($ord3 - 128);

        }

        return false;

    }

    /**

     * Makes first letter of each word capital - words must be separated by spaces.

     * Use with care, this function does not work properly in many locales!!!

     *

     * @param string $text input string

     * @return string

     */

    public static function strtotitle($text) {

        if (empty($text)) {

            return $text;

        }

        return mb_convert_case($text, MB_CASE_TITLE, 'UTF-8');

    }

}