<?php

/**
* @version $Id: bad.php,v 1.2 2006/02/26 13:20:44 harryf Exp $
* Tools for locating / replacing bad bytes in UTF-8 strings
* The Original Code is Mozilla Communicator client code.
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1998
* the Initial Developer. All Rights Reserved.
* Ported to PHP by Henri Sivonen (http://hsivonen.iki.fi)
* Slight modifications to fit with phputf8 library by Harry Fuecks (hfuecks gmail com)
* @see http://lxr.mozilla.org/seamonkey/source/intl/uconv/src/nsUTF8ToUnicode.cpp
* @see http://lxr.mozilla.org/seamonkey/source/intl/uconv/src/nsUnicodeToUTF8.cpp
* @see http://hsivonen.iki.fi/php-utf8/
* @package utf8
* @subpackage bad
* @see utf8_is_valid
*/

/**
* Locates the first bad byte in a UTF-8 string returning it's
* byte index in the string
* PCRE Pattern to locate bad bytes in a UTF-8 string
* Comes from W3 FAQ: Multilingual Forms
* Note: modified to include full ASCII range including control chars
* @see http://www.w3.org/International/questions/qa-forms-utf-8
* @param string
* @return mixed integer byte index or FALSE if no bad found
* @package utf8
* @subpackage bad
*/
function utf8_bad_find($str)
{
	$UTF8_BAD =
		'([\x00-\x7F]'.                          # ASCII (including control chars)
		'|[\xC2-\xDF][\x80-\xBF]'.               # Non-overlong 2-byte
		'|\xE0[\xA0-\xBF][\x80-\xBF]'.           # Excluding overlongs
		'|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}'.    # Straight 3-byte
		'|\xED[\x80-\x9F][\x80-\xBF]'.           # Excluding surrogates
		'|\xF0[\x90-\xBF][\x80-\xBF]{2}'.        # Planes 1-3
		'|[\xF1-\xF3][\x80-\xBF]{3}'.            # Planes 4-15
		'|\xF4[\x80-\x8F][\x80-\xBF]{2}'.        # Plane 16
		'|(.{1}))';                              # Invalid byte
	$pos = 0;
	$badList = array();

	while (preg_match('/'.$UTF8_BAD.'/S', $str, $matches))
	{
		$bytes = strlen($matches[0]);

		if (isset($matches[2]))
			return $pos;

		$pos += $bytes;
		$str = substr($str,$bytes);
	}

	return false;
}

/**
* Locates all bad bytes in a UTF-8 string and returns a list of their
* byte index in the string
* PCRE Pattern to locate bad bytes in a UTF-8 string
* Comes from W3 FAQ: Multilingual Forms
* Note: modified to include full ASCII range including control chars
* @see http://www.w3.org/International/questions/qa-forms-utf-8
* @param string
* @return mixed array of integers or FALSE if no bad found
* @package utf8
* @subpackage bad
*/
function utf8_bad_findall($str)
{
	$UTF8_BAD =
		'([\x00-\x7F]'.                          # ASCII (including control chars)
		'|[\xC2-\xDF][\x80-\xBF]'.               # Non-overlong 2-byte
		'|\xE0[\xA0-\xBF][\x80-\xBF]'.           # Excluding overlongs
		'|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}'.    # Straight 3-byte
		'|\xED[\x80-\x9F][\x80-\xBF]'.           # Excluding surrogates
		'|\xF0[\x90-\xBF][\x80-\xBF]{2}'.        # Planes 1-3
		'|[\xF1-\xF3][\x80-\xBF]{3}'.            # Planes 4-15
		'|\xF4[\x80-\x8F][\x80-\xBF]{2}'.        # Plane 16
		'|(.{1}))';                              # Invalid byte
	$pos = 0;
	$badList = array();

	while (preg_match('/'.$UTF8_BAD.'/S', $str, $matches))
	{
		$bytes = strlen($matches[0]);

		if (isset($matches[2]))
			$badList[] = $pos;

		$pos += $bytes;
		$str = substr($str,$bytes);
	}

	if (count($badList) > 0)
		return $badList;

	return false;
}

/**
* Strips out any bad bytes from a UTF-8 string and returns the rest
* PCRE Pattern to locate bad bytes in a UTF-8 string
* Comes from W3 FAQ: Multilingual Forms
* Note: modified to include full ASCII range including control chars
* @see http://www.w3.org/International/questions/qa-forms-utf-8
* @param string
* @return string
* @package utf8
* @subpackage bad
*/
function utf8_bad_strip($str)
{
	$UTF8_BAD =
		'([\x00-\x7F]'.                          # ASCII (including control chars)
		'|[\xC2-\xDF][\x80-\xBF]'.               # Non-overlong 2-byte
		'|\xE0[\xA0-\xBF][\x80-\xBF]'.           # Excluding overlongs
		'|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}'.    # Straight 3-byte
		'|\xED[\x80-\x9F][\x80-\xBF]'.           # Excluding surrogates
		'|\xF0[\x90-\xBF][\x80-\xBF]{2}'.        # Planes 1-3
		'|[\xF1-\xF3][\x80-\xBF]{3}'.            # Planes 4-15
		'|\xF4[\x80-\x8F][\x80-\xBF]{2}'.        # Plane 16
		'|(.{1}))';                              # Invalid byte

	ob_start();

	while (preg_match('/'.$UTF8_BAD.'/S', $str, $matches))
	{
		if (!isset($matches[2]))
			echo $matches[0];

		$str = substr($str, strlen($matches[0]));
	}

	$result = ob_get_contents();
	ob_end_clean();

	return $result;
}

/**
* Replace bad bytes with an alternative character - ASCII character
* recommended is replacement char
* PCRE Pattern to locate bad bytes in a UTF-8 string
* Comes from W3 FAQ: Multilingual Forms
* Note: modified to include full ASCII range including control chars
* @see http://www.w3.org/International/questions/qa-forms-utf-8
* @param string to search
* @param string to replace bad bytes with (defaults to '?') - use ASCII
* @return string
* @package utf8
* @subpackage bad
*/
function utf8_bad_replace($str, $replace='?')
{
	$UTF8_BAD =
		'([\x00-\x7F]'.                          # ASCII (including control chars)
		'|[\xC2-\xDF][\x80-\xBF]'.               # Non-overlong 2-byte
		'|\xE0[\xA0-\xBF][\x80-\xBF]'.           # Excluding overlongs
		'|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}'.    # Straight 3-byte
		'|\xED[\x80-\x9F][\x80-\xBF]'.           # Excluding surrogates
		'|\xF0[\x90-\xBF][\x80-\xBF]{2}'.        # Planes 1-3
		'|[\xF1-\xF3][\x80-\xBF]{3}'.            # Planes 4-15
		'|\xF4[\x80-\x8F][\x80-\xBF]{2}'.        # Plane 16
		'|(.{1}))';                              # Invalid byte

	ob_start();

	while (preg_match('/'.$UTF8_BAD.'/S', $str, $matches))
	{
		if (!isset($matches[2]))
			echo $matches[0];
		else
			echo $replace;

		$str = substr($str, strlen($matches[0]));
	}

	$result = ob_get_contents();
	ob_end_clean();

	return $result;
}

/**
* Return code from utf8_bad_identify() when a five octet sequence is detected.
* Note: 5 octets sequences are valid UTF-8 but are not supported by Unicode so
* do not represent a useful character
* @see utf8_bad_identify
* @package utf8
* @subpackage bad
*/
define('UTF8_BAD_5OCTET', 1);

/**
* Return code from utf8_bad_identify() when a six octet sequence is detected.
* Note: 6 octets sequences are valid UTF-8 but are not supported by Unicode so
* do not represent a useful character
* @see utf8_bad_identify
* @package utf8
* @subpackage bad
*/
define('UTF8_BAD_6OCTET', 2);

/**
* Return code from utf8_bad_identify().
* Invalid octet for use as start of multi-byte UTF-8 sequence
* @see utf8_bad_identify
* @package utf8
* @subpackage bad
*/
define('UTF8_BAD_SEQID', 3);

/**
* Return code from utf8_bad_identify().
* From Unicode 3.1, non-shortest form is illegal
* @see utf8_bad_identify
* @package utf8
* @subpackage bad
*/
define('UTF8_BAD_NONSHORT', 4);

/**
* Return code from utf8_bad_identify().
* From Unicode 3.2, surrogate characters are illegal
* @see utf8_bad_identify
* @package utf8
* @subpackage bad
*/
define('UTF8_BAD_SURROGATE', 5);

/**
* Return code from utf8_bad_identify().
* Codepoints outside the Unicode range are illegal
* @see utf8_bad_identify
* @package utf8
* @subpackage bad
*/
define('UTF8_BAD_UNIOUTRANGE', 6);

/**
* Return code from utf8_bad_identify().
* Incomplete multi-octet sequence
* Note: this is kind of a "catch-all"
* @see utf8_bad_identify
* @package utf8
* @subpackage bad
*/
define('UTF8_BAD_SEQINCOMPLETE', 7);

/**
* Reports on the type of bad byte found in a UTF-8 string. Returns a
* status code on the first bad byte found
* @author <hsivonen@iki.fi>
* @param string UTF-8 encoded string
* @return mixed integer constant describing problem or FALSE if valid UTF-8
* @see utf8_bad_explain
* @see http://hsivonen.iki.fi/php-utf8/
* @package utf8
* @subpackage bad
*/
function utf8_bad_identify($str, &$i)
{
	$mState = 0;	// Cached expected number of octets after the current octet
					// until the beginning of the next UTF8 character sequence
	$mUcs4  = 0;	// Cached Unicode character
	$mBytes = 1;	// Cached expected number of octets in the current sequence

	$len = strlen($str);

	for($i=0; $i < $len; $i++)
	{
		$in = ord($str{$i});

		if ( $mState == 0)
		{
			// When mState is zero we expect either a US-ASCII character or a multi-octet sequence.
			if (0 == (0x80 & ($in)))
			{
				// US-ASCII, pass straight through.
				$mBytes = 1;
			}
			else if (0xC0 == (0xE0 & ($in)))
			{
				// First octet of 2 octet sequence
				$mUcs4 = ($in);
				$mUcs4 = ($mUcs4 & 0x1F) << 6;
				$mState = 1;
				$mBytes = 2;
			}
			else if (0xE0 == (0xF0 & ($in)))
			{
				// First octet of 3 octet sequence
				$mUcs4 = ($in);
				$mUcs4 = ($mUcs4 & 0x0F) << 12;
				$mState = 2;
				$mBytes = 3;
			}
			else if (0xF0 == (0xF8 & ($in)))
			{
				// First octet of 4 octet sequence
				$mUcs4 = ($in);
				$mUcs4 = ($mUcs4 & 0x07) << 18;
				$mState = 3;
				$mBytes = 4;
			}
			else if (0xF8 == (0xFC & ($in)))
			{
				/* First octet of 5 octet sequence.
				*
				* This is illegal because the encoded codepoint must be either
				* (a) not the shortest form or
				* (b) outside the Unicode range of 0-0x10FFFF.
				*/
				return UTF8_BAD_5OCTET;
			}
			else if (0xFC == (0xFE & ($in)))
			{
				// First octet of 6 octet sequence, see comments for 5 octet sequence.
				return UTF8_BAD_6OCTET;
			}
			else
			{
				// Current octet is neither in the US-ASCII range nor a legal first
				// octet of a multi-octet sequence.
				return UTF8_BAD_SEQID;
			}
		}
		else
		{
			// When mState is non-zero, we expect a continuation of the multi-octet sequence
			if (0x80 == (0xC0 & ($in)))
			{
				// Legal continuation.
				$shift = ($mState - 1) * 6;
				$tmp = $in;
				$tmp = ($tmp & 0x0000003F) << $shift;
				$mUcs4 |= $tmp;

				/**
				* End of the multi-octet sequence. mUcs4 now contains the final
				* Unicode codepoint to be output
				*/
				if (0 == --$mState)
				{
					// From Unicode 3.1, non-shortest form is illegal
					if (((2 == $mBytes) && ($mUcs4 < 0x0080)) ||
					((3 == $mBytes) && ($mUcs4 < 0x0800)) ||
					((4 == $mBytes) && ($mUcs4 < 0x10000)) )
						return UTF8_BAD_NONSHORT;
					else if (($mUcs4 & 0xFFFFF800) == 0xD800) // From Unicode 3.2, surrogate characters are illegal
						return UTF8_BAD_SURROGATE;
					else if ($mUcs4 > 0x10FFFF) // Codepoints outside the Unicode range are illegal
						return UTF8_BAD_UNIOUTRANGE;

					// Initialize UTF8 cache
					$mState = 0;
					$mUcs4  = 0;
					$mBytes = 1;
				}

			}
			else
			{
				// ((0xC0 & (*in) != 0x80) && (mState != 0))
				// Incomplete multi-octet sequence.
				$i--;
				return UTF8_BAD_SEQINCOMPLETE;
			}
		}
	}

	// Incomplete multi-octet sequence
	if ($mState != 0)
	{
		$i--;
		return UTF8_BAD_SEQINCOMPLETE;
	}

	// No bad octets found
	$i = null;
	return false;
}

/**
* Takes a return code from utf8_bad_identify() are returns a message
* (in English) explaining what the problem is.
* @param int return code from utf8_bad_identify
* @return mixed string message or FALSE if return code unknown
* @see utf8_bad_identify
* @package utf8
* @subpackage bad
*/
function utf8_bad_explain($code)
{
	switch ($code)
	{
		case UTF8_BAD_5OCTET:
		return 'Five octet sequences are valid UTF-8 but are not supported by Unicode';
		break;

		case UTF8_BAD_6OCTET:
		return 'Six octet sequences are valid UTF-8 but are not supported by Unicode';
		break;

		case UTF8_BAD_SEQID:
		return 'Invalid octet for use as start of multi-byte UTF-8 sequence';
		break;

		case UTF8_BAD_NONSHORT:
		return 'From Unicode 3.1, non-shortest form is illegal';
		break;

		case UTF8_BAD_SURROGATE:
		return 'From Unicode 3.2, surrogate characters are illegal';
		break;

		case UTF8_BAD_UNIOUTRANGE:
		return 'Codepoints outside the Unicode range are illegal';
		break;

		case UTF8_BAD_SEQINCOMPLETE:
		return 'Incomplete multi-octet sequence';
		break;
	}

	trigger_error('Unknown error code: '.$code, E_USER_WARNING);

	return false;
}