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+<?php
+
+/**
+ * Class to safely store UTF-8 in a Filename
+ *
+ * Encodes a utf8 string using only the following characters 0-9a-z_.-%
+ * characters 0-9a-z in the original string are preserved, "plain".
+ * all other characters are represented in a substring that starts
+ * with '%' are "converted".
+ * The transition from converted substrings to plain characters is
+ * marked with a '.'
+ *
+ * @author Christopher Smith <chris@jalakai.co.uk>
+ * @date 2010-04-02
+ */
+class SafeFN {
+
+ // 'safe' characters are a superset of $plain, $pre_indicator and $post_indicator
+ private static $plain = '-./[_0123456789abcdefghijklmnopqrstuvwxyz'; // these characters aren't converted
+ private static $pre_indicator = '%';
+ private static $post_indicator = ']';
+
+ /**
+ * Convert an UTF-8 string to a safe ASCII String
+ *
+ * conversion process
+ * - if codepoint is a plain or post_indicator character,
+ * - if previous character was "converted", append post_indicator to output, clear "converted" flag
+ * - append ascii byte for character to output
+ * (continue to next character)
+ *
+ * - if codepoint is a pre_indicator character,
+ * - append ascii byte for character to output, set "converted" flag
+ * (continue to next character)
+ *
+ * (all remaining characters)
+ * - reduce codepoint value for non-printable ASCII characters (0x00 - 0x1f). Space becomes our zero.
+ * - convert reduced value to base36 (0-9a-z)
+ * - append $pre_indicator characater followed by base36 string to output, set converted flag
+ * (continue to next character)
+ *
+ * @param string $filename a utf8 string, should only include printable characters - not 0x00-0x1f
+ * @return string an encoded representation of $filename using only 'safe' ASCII characters
+ *
+ * @author Christopher Smith <chris@jalakai.co.uk>
+ */
+ public static function encode($filename) {
+ return self::unicodeToSafe(\dokuwiki\Utf8\Unicode::fromUtf8($filename));
+ }
+
+ /**
+ * decoding process
+ * - split the string into substrings at any occurrence of pre or post indicator characters
+ * - check the first character of the substring
+ * - if its not a pre_indicator character
+ * - if previous character was converted, skip over post_indicator character
+ * - copy codepoint values of remaining characters to the output array
+ * - clear any converted flag
+ * (continue to next substring)
+ *
+ * _ else (its a pre_indicator character)
+ * - if string length is 1, copy the post_indicator character to the output array
+ * (continue to next substring)
+ *
+ * - else (string length > 1)
+ * - skip the pre-indicator character and convert remaining string from base36 to base10
+ * - increase codepoint value for non-printable ASCII characters (add 0x20)
+ * - append codepoint to output array
+ * (continue to next substring)
+ *
+ * @param string $filename a 'safe' encoded ASCII string,
+ * @return string decoded utf8 representation of $filename
+ *
+ * @author Christopher Smith <chris@jalakai.co.uk>
+ */
+ public static function decode($filename) {
+ return \dokuwiki\Utf8\Unicode::toUtf8(self::safeToUnicode(strtolower($filename)));
+ }
+
+ public static function validatePrintableUtf8($printable_utf8) {
+ return !preg_match('#[\x01-\x1f]#',$printable_utf8);
+ }
+
+ public static function validateSafe($safe) {
+ return !preg_match('#[^'.self::$plain.self::$post_indicator.self::$pre_indicator.']#',$safe);
+ }
+
+ /**
+ * convert an array of unicode codepoints into 'safe_filename' format
+ *
+ * @param array int $unicode an array of unicode codepoints
+ * @return string the unicode represented in 'safe_filename' format
+ *
+ * @author Christopher Smith <chris@jalakai.co.uk>
+ */
+ private static function unicodeToSafe($unicode) {
+
+ $safe = '';
+ $converted = false;
+
+ foreach ($unicode as $codepoint) {
+ if ($codepoint < 127 && (strpos(self::$plain.self::$post_indicator,chr($codepoint))!==false)) {
+ if ($converted) {
+ $safe .= self::$post_indicator;
+ $converted = false;
+ }
+ $safe .= chr($codepoint);
+
+ } else if ($codepoint == ord(self::$pre_indicator)) {
+ $safe .= self::$pre_indicator;
+ $converted = true;
+ } else {
+ $safe .= self::$pre_indicator.base_convert((string)($codepoint-32),10,36);
+ $converted = true;
+ }
+ }
+ if($converted) $safe .= self::$post_indicator;
+ return $safe;
+ }
+
+ /**
+ * convert a 'safe_filename' string into an array of unicode codepoints
+ *
+ * @param string $safe a filename in 'safe_filename' format
+ * @return array int an array of unicode codepoints
+ *
+ * @author Christopher Smith <chris@jalakai.co.uk>
+ */
+ private static function safeToUnicode($safe) {
+
+ $unicode = array();
+ $split = preg_split('#(?=['.self::$post_indicator.self::$pre_indicator.'])#',$safe,-1,PREG_SPLIT_NO_EMPTY);
+
+ $converted = false;
+ foreach ($split as $sub) {
+ $len = strlen($sub);
+ if ($sub[0] != self::$pre_indicator) {
+ // plain (unconverted) characters, optionally starting with a post_indicator
+ // set initial value to skip any post_indicator
+ for ($i=($converted?1:0); $i < $len; $i++) {
+ $unicode[] = ord($sub[$i]);
+ }
+ $converted = false;
+ } else if ($len==1) {
+ // a pre_indicator character in the real data
+ $unicode[] = ord($sub);
+ $converted = true;
+ } else {
+ // a single codepoint in base36, adjusted for initial 32 non-printable chars
+ $unicode[] = 32 + (int)base_convert(substr($sub,1),36,10);
+ $converted = true;
+ }
+ }
+
+ return $unicode;
+ }
+
+}