/include/utf8/utils/position.php
PHP | 171 lines | 80 code | 25 blank | 66 comment | 25 complexity | 03eb213f6b767a4f1137c6f9e242e572 MD5 | raw file
Possible License(s): GPL-2.0
- <?php
- /**
- * Locate a byte index given a UTF-8 character index
- * @version $Id: position.php,v 1.1 2006/10/01 00:01:31 harryf Exp $
- * @package utf8
- * @subpackage position
- */
- /**
- * Given a string and a character index in the string, in
- * terms of the UTF-8 character position, returns the byte
- * index of that character. Can be useful when you want to
- * PHP's native string functions but we warned, locating
- * the byte can be expensive
- * Takes variable number of parameters - first must be
- * the search string then 1 to n UTF-8 character positions
- * to obtain byte indexes for - it is more efficient to search
- * the string for multiple characters at once, than make
- * repeated calls to this function
- *
- * @author Chris Smith<chris@jalakai.co.uk>
- * @param string string to locate index in
- * @param int (n times)
- * @return mixed - int if only one input int, array if more
- * @return boolean TRUE if it's all ASCII
- * @package utf8
- * @subpackage position
- */
- function utf8_byte_position()
- {
- $args = func_get_args();
- $str =& array_shift($args);
- if (!is_string($str))
- return false;
- $result = array();
- $prev = array(0, 0); // Trivial byte index, character offset pair
- $i = utf8_locate_next_chr($str, 300); // Use a short piece of str to estimate bytes per character. $i (& $j) -> byte indexes into $str
- $c = strlen(utf8_decode(substr($str, 0, $i))); // $c -> character offset into $str
- // Deal with arguments from lowest to highest
- sort($args);
- foreach ($args as $offset)
- {
- // Sanity checks FIXME
- // 0 is an easy check
- if ($offset == 0)
- {
- $result[] = 0; continue;
- }
- // Ensure no endless looping
- $safety_valve = 50;
- do
- {
- if (($c - $prev[1]) == 0)
- {
- // Hack: gone past end of string
- $error = 0;
- $i = strlen($str);
- break;
- }
- $j = $i + (int)(($offset-$c) * ($i - $prev[0]) / ($c - $prev[1]));
- $j = utf8_locate_next_chr($str, $j); // Correct to utf8 character boundary
- $prev = array($i,$c); // Save the index, offset for use next iteration
- if ($j > $i)
- $c += strlen(utf8_decode(substr($str, $i, $j-$i))); // Determine new character offset
- else
- $c -= strlen(utf8_decode(substr($str, $j, $i-$j))); // Ditto
- $error = abs($c-$offset);
- $i = $j; // Ready for next time around
- }
- while (($error > 7) && --$safety_valve); // From 7 it is faster to iterate over the string
- if ($error && $error <= 7)
- {
- if ($c < $offset)
- {
- // Move up
- while ($error--)
- $i = utf8_locate_next_chr($str, ++$i);
- }
- else
- {
- // Move down
- while ($error--)
- $i = utf8_locate_current_chr($str, --$i);
- }
- // Ready for next arg
- $c = $offset;
- }
- $result[] = $i;
- }
- if (count($result) == 1)
- return $result[0];
- return $result;
- }
- /**
- * Given a string and any byte index, returns the byte index
- * of the start of the current UTF-8 character, relative to supplied
- * position. If the current character begins at the same place as the
- * supplied byte index, that byte index will be returned. Otherwise
- * this function will step backwards, looking for the index where
- * curent UTF-8 character begins
- * @author Chris Smith<chris@jalakai.co.uk>
- * @param string
- * @param int byte index in the string
- * @return int byte index of start of next UTF-8 character
- * @package utf8
- * @subpackage position
- */
- function utf8_locate_current_chr( &$str, $idx )
- {
- if ($idx <= 0)
- return 0;
- $limit = strlen($str);
- if ($idx >= $limit)
- return $limit;
- // Binary value for any byte after the first in a multi-byte UTF-8 character
- // will be like 10xxxxxx so & 0xC0 can be used to detect this kind
- // of byte - assuming well formed UTF-8
- while ($idx && ((ord($str[$idx]) & 0xC0) == 0x80))
- $idx--;
- return $idx;
- }
- /**
- * Given a string and any byte index, returns the byte index
- * of the start of the next UTF-8 character, relative to supplied
- * position. If the next character begins at the same place as the
- * supplied byte index, that byte index will be returned.
- * @author Chris Smith<chris@jalakai.co.uk>
- * @param string
- * @param int byte index in the string
- * @return int byte index of start of next UTF-8 character
- * @package utf8
- * @subpackage position
- */
- function utf8_locate_next_chr(&$str, $idx)
- {
- if ($idx <= 0)
- return 0;
- $limit = strlen($str);
- if ($idx >= $limit)
- return $limit;
- // Binary value for any byte after the first in a multi-byte UTF-8 character
- // will be like 10xxxxxx so & 0xC0 can be used to detect this kind
- // of byte - assuming well formed UTF-8
- while (($idx < $limit) && ((ord($str[$idx]) & 0xC0) == 0x80))
- $idx++;
- return $idx;
- }