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<?php
/**
* Class that handles operations involving percent-encoding in URIs.
*
* @warning
* Be careful when reusing instances of PercentEncoder. The object
* you use for normalize() SHOULD NOT be used for encode(), or
* vice-versa.
*/
class HTMLPurifier_PercentEncoder
{
/**
* Reserved characters to preserve when using encode().
* @type array
*/
protected $preserve = array();
/**
* String of characters that should be preserved while using encode().
* @param bool $preserve
*/
public function __construct($preserve = false)
{
// unreserved letters, ought to const-ify
for ($i = 48; $i <= 57; $i++) { // digits
$this->preserve[$i] = true;
}
for ($i = 65; $i <= 90; $i++) { // upper-case
$this->preserve[$i] = true;
}
for ($i = 97; $i <= 122; $i++) { // lower-case
$this->preserve[$i] = true;
}
$this->preserve[45] = true; // Dash -
$this->preserve[46] = true; // Period .
$this->preserve[95] = true; // Underscore _
$this->preserve[126]= true; // Tilde ~
// extra letters not to escape
if ($preserve !== false) {
for ($i = 0, $c = strlen($preserve); $i < $c; $i++) {
$this->preserve[ord($preserve[$i])] = true;
}
}
}
/**
* Our replacement for urlencode, it encodes all non-reserved characters,
* as well as any extra characters that were instructed to be preserved.
* @note
* Assumes that the string has already been normalized, making any
* and all percent escape sequences valid. Percents will not be
* re-escaped, regardless of their status in $preserve
* @param string $string String to be encoded
* @return string Encoded string.
*/
public function encode($string)
{
$ret = '';
for ($i = 0, $c = strlen($string); $i < $c; $i++) {
if ($string[$i] !== '%' && !isset($this->preserve[$int = ord($string[$i])])) {
$ret .= '%' . sprintf('%02X', $int);
} else {
$ret .= $string[$i];
}
}
return $ret;
}
/**
* Fix up percent-encoding by decoding unreserved characters and normalizing.
* @warning This function is affected by $preserve, even though the
* usual desired behavior is for this not to preserve those
* characters. Be careful when reusing instances of PercentEncoder!
* @param string $string String to normalize
* @return string
*/
public function normalize($string)
{
if ($string == '') {
return '';
}
$parts = explode('%', $string);
$ret = array_shift($parts);
foreach ($parts as $part) {
$length = strlen($part);
if ($length < 2) {
$ret .= '%25' . $part;
continue;
}
$encoding = substr($part, 0, 2);
$text = substr($part, 2);
if (!ctype_xdigit($encoding)) {
$ret .= '%25' . $part;
continue;
}
$int = hexdec($encoding);
if (isset($this->preserve[$int])) {
$ret .= chr($int) . $text;
continue;
}
$encoding = strtoupper($encoding);
$ret .= '%' . $encoding . $text;
}
return $ret;
}
}
// vim: et sw=4 sts=4