/**
* Inspect each character in a string, copying quoted characters, with
* their escaping, into the result. Look for unquoted non alphanumerics
* and if not "*" or "?", add escaping.
* @param $s
* @return
* @throws Exception representing parsing errors.
*/
private function addQuoting($s)
{
$result = "";
$idx = 0;
$embedded = false;
while ($idx < strlen($s)) {
$c = substr($s, $idx, 1);
if (Utilities::isAlphanum($c) || $c == "_") {
// Alphanumeric characters pass untouched.
$result = $result . $c;
$idx = $idx + 1;
$embedded = true;
continue;
}
if ($c == "\\") {
// Anything quoted in the bound string stays quoted in the
// unbound string.
$result = $result . substr($s, $idx, 2);
$idx = $idx + 2;
$embedded = true;
continue;
}
if ($c == "*") {
// An unquoted asterisk must appear at the beginning or the end
// of the string.
if ($idx == 0 || $idx == strlen($s) - 1) {
$result = $result . $c;
$idx = $idx + 1;
$embedded = true;
continue;
} else {
throw new Exception("Error! cannot have unquoted * embedded in formatted string.", 0);
}
}
if ($c == "?") {
// An unquoted question mark must appear at the beginning or
// end of the string, or in a leading or trailing sequence.
if ($idx == 0 || $idx == strlen($s) - 1 || !$embedded && substr($s, $idx - 1, 1) == "?" || $embedded && substr($s, $idx + 1, 1) == "?") {
$result = $result . $c;
$idx = $idx + 1;
$embedded = false;
continue;
} else {
throw new Exception("Error! cannot have unquoted ? embedded in formatted string.", 0);
}
}
// All other characters must be quoted.
$result = $result . "\\" . $c;
$idx = $idx + 1;
$embedded = true;
}
return $result;
}
/**
* Scans an input string and performs the following transformations:
* - Pass alphanumeric characters thru untouched
* - Percent-encode quoted non-alphanumerics as needed
* - Unquoted special characters are mapped to their special forms
* @param $s string to be transformed
* @return transformed string
*/
private function transformForURI($s)
{
$result = "";
$idx = 0;
while ($idx < strlen($s)) {
// Get the idx'th character of s.
$thischar = substr($s, $idx, 1);
// Alphanumerics (incl. underscore) pass untouched.
if (Utilities::isAlphanum($thischar)) {
$result = $result . $thischar;
$idx = $idx + 1;
continue;
}
// Check for escape character.
if ($thischar == "\\") {
$idx = $idx + 1;
$nxtchar = substr($s, $idx, 1);
$result = $result . $this->pctEncode($nxtchar);
$idx = $idx + 1;
continue;
}
// Bind the unquoted '?' special character to "%01".
if ($thischar == "?") {
$result = $result . "%01";
}
// Bind the unquoted '*' special character to "%02".
if ($thischar == "*") {
$result = $result . "%02";
}
$idx = $idx + 1;
}
return $result;
}
/**
* Searches a string for the backslash character
* @param $str string to search in
* @param $idx end index
* @return true if the number of backslash characters is even, false if odd
*/
private function isEvenWildcards($str, $idx)
{
$result = 0;
while ($idx > 0 && strpos($str, "\\", $idx - 1) !== false) {
$idx = $idx - 1;
$result = $result + 1;
}
return Utilities::isEvenNumber($result);
}