<?php
/**
* Implementation for UTF-8 strings.
*
* The subscript operator in PHP, when used with string will return a byte
* and not a character. Because in UTF-8 strings a character may occupy more
* than one byte, the subscript operator may return an invalid character.
*
* Because the lexer relies on the subscript operator this class had to be
* implemented.
*
* @package SqlParser
*/
namespace SqlParser;
/**
* Implements array-like access for UTF-8 strings.
*
* In this library, this class should be used to parse UTF-8 queries.
*
* @category Misc
* @package SqlParser
* @author Dan Ungureanu <udan1107@gmail.com>
* @license http://opensource.org/licenses/GPL-2.0 GNU Public License
*/
class UtfString implements \ArrayAccess
{
/**
* The raw, multi-byte string.
*
* @var string
*/
public $str = '';
/**
* The index of current byte.
*
* For ASCII strings, the byte index is equal to the character index.
*
* @var int
*/
public $byteIdx = 0;
/**
* The index of current character.
*
* For non-ASCII strings, some characters occupy more than one byte and
* the character index will have a lower value than the byte index.
*
* @var int
*/
public $charIdx = 0;
/**
* The length of the string (in bytes).
*
* @var int
*/
public $byteLen = 0;
/**
* The length of the string (in characters).
*
* @var int
*/
public $charLen = 0;
/**
* Constructor.
*
* @param string $str The string.
*/
public function __construct($str)
{
$this->str = $str;
$this->byteIdx = 0;
$this->charIdx = 0;
// TODO: `strlen($str)` might return a wrong length when function
// overloading is enabled.
// https://php.net/manual/ro/mbstring.overload.php
$this->byteLen = strlen($str);
$this->charLen = mb_strlen($str, 'UTF-8');
}
/**
* Checks if the given offset exists.
*
* @param int $offset The offset to be checked.
*
* @return bool
*/
public function offsetExists($offset)
{
return ($offset >= 0) && ($offset < $this->charLen);
}
/**
* Gets the character at given offset.
*
* @param int $offset The offset to be returned.
*
* @return string
*/
public function offsetGet($offset)
{
if (($offset < 0) || ($offset >= $this->charLen)) {
return null;
}
$delta = $offset - $this->charIdx;
if ($delta > 0) {
// Fast forwarding.
while ($delta-- > 0) {
$this->byteIdx += static::getCharLength($this->str[$this->byteIdx]);
++$this->charIdx;
}
} elseif ($delta < 0) {
// Rewinding.
while ($delta++ < 0) {
do {
$byte = ord($this->str[--$this->byteIdx]);
} while ((128 <= $byte) && ($byte < 192));
--$this->charIdx;
}
}
$bytesCount = static::getCharLength($this->str[$this->byteIdx]);
$ret = '';
for ($i = 0; $bytesCount-- > 0; ++$i) {
$ret .= $this->str[$this->byteIdx + $i];
}
return $ret;
}
/**
* Sets the value of a character.
*
* @param int $offset The offset to be set.
* @param string $value The value to be set.
*
* @throws \Exception Not implemented.
*
* @return void
*/
public function offsetSet($offset, $value)
{
throw new \Exception('Not implemented.');
}
/**
* Unsets an index.
*
* @param int $offset The value to be unset.
*
* @throws \Exception Not implemented.
*
* @return void
*/
public function offsetUnset($offset)
{
throw new \Exception('Not implemented.');
}
/**
* Gets the length of an UTF-8 character.
*
* According to RFC 3629, a UTF-8 character can have at most 4 bytes.
* However, this implementation supports UTF-8 characters containing up to 6
* bytes.
*
* @param string $byte The byte to be analyzed.
*
* @see http://tools.ietf.org/html/rfc3629
*
* @return int
*/
public static function getCharLength($byte)
{
$byte = ord($byte);
if ($byte < 128) {
return 1;
} elseif ($byte < 224) {
return 2;
} elseif ($byte < 240) {
return 3;
} elseif ($byte < 248) {
return 4;
} elseif ($byte < 252) {
return 5; // unofficial
}
return 6; // unofficial
}
/**
* Returns the length in characters of the string.
*
* @return int
*/
public function length()
{
return $this->charLen;
}
/**
* Returns the contained string.
*
* @return string
*/
public function __toString()
{
return $this->str;
}
}
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