smarty中改进truncate使其支持中文的方法，smartytruncate

<&#63;php
/*
* Smarty plugin
* -------------------------------------------------------------
* Type:   modifier
* Name:   truncate
* Purpose: Truncate a string to a certain length if necessary,
*      optionally splitting in the middle of a word, and 
*      appending the $etc string.
* Update:  change substr to msubstr and add fun msubstr.so it
*      can bu used in chinese charset.
* -------------------------------------------------------------
*/
function smarty_modifier_truncate($string, $length = 80, $etc = '...', $break_words = false)
{
  if ($length == 0)
    return '';
  if (strlen($string) > $length) {
    $length -= strlen($etc);
    if (!$break_words)
      $string = preg_replace('//s+&#63;(/S+)&#63;$/', '', SubstrGB($string, 0, $length+1));
    return SubstrGB($string, 0, $length).$etc;
  } else
    return $string;
}
function SubstrGB($str,$start,$len){
  for($i=0;$i<$start+$len;$i++){
    $tmpstr=(ord($str[$i])>=161 && ord($str[$i])<=254&& ord($str[$i+1])>=161 && ord($str[$i+1])<=254)&#63;$str[$i].$str[++$i]:$tmpstr=$str[$i];
    if ($i>=$start&&$i<($start+$len))$tmp .=$tmpstr;
  }
  return $tmp;
}
/* vim: set expandtab: */
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