/**
* 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<*****@*****.**>
* @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();
// trivial byte index, character offset pair
$prev = array(0, 0);
// use a short piece of str to estimate bytes per character
// $i (& $j) -> byte indexes into $str
$i = utf8_locate_next_chr($str, 300);
// $c -> character offset into $str
$c = strlen(utf8_decode(substr($str, 0, $i)));
// deal with arguments from lowest to highest
sort($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]));
// correct to utf8 character boundary
$j = utf8_locate_next_chr($str, $j);
// save the index, offset for use next iteration
$prev = array($i, $c);
if ($j > $i) {
// determine new character offset
$c += strlen(utf8_decode(substr($str, $i, $j - $i)));
} else {
// ditto
$c -= strlen(utf8_decode(substr($str, $j, $i - $j)));
}
$error = abs($c - $offset);
// ready for next time around
$i = $j;
// from 7 it is faster to iterate over the string
} while ($error > 7 && --$safety_valve);
if ($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;
}
function test_bounds()
{
// bounds checking
$tests = array();
$tests[] = array('aaживπά우리をあöä', -2, 0);
$tests[] = array('aaживπά우리をあöä', 128, 29);
foreach ($tests as $test) {
$this->assertIdentical(utf8_locate_current_chr($test[0], $test[1]), $test[2]);
}
$tests[] = array('aaживπά우리をあöä', -2, 0);
$tests[] = array('aaживπά우리をあöä', 128, 29);
foreach ($tests as $test) {
$this->assertIdentical(utf8_locate_next_chr($test[0], $test[1]), $test[2]);
}
}
