Iterator to Extract Message Headers from Bounced Messages

BouncedHeaders.php

<?php
/*
 *      BouncedHeaders.php
 *      
 *      Copyright 2011 mot <@fsfe.org>
 *      
 *      This program is free software; you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation; either version 2 of the License, or
 *      (at your option) any later version.
 *      
 *      This program is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU General Public License for more details.
 *      
 *      You should have received a copy of the GNU General Public License
 *      along with this program; if not, write to the Free Software
 *      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 *      MA 02110-1301, USA.
 */

/**
 * Iterator that extracts message headers from plain
 * text that is normally the body of a bounce-email-message.
 * 
 * Supports folded header field bodies.
 * 
 * Iterator value is the header-field-value or complete line if not
 *   a header.
 * Iterator key is the header-field-name or empty if not a header.
 *
 * To filter non-header lines, ignore zero-length keys.
 * 
 * As there can be duplicate header field names, there can be
 * duplicate keys.
 * 
 * If initialized with retobj set to true, value will be an object
 * containing detailed information and key will be a numerical index.
 */
class BouncedHeaders implements Iterator
{
    /**
     * @var string message body
     */
    private $body;
    /**
     * @var string line ending delimiter, "\r\n" by RFC (2)822
     */
    private $crlf;
    /**
     * @var bool return object instead of string
     */
    private $retobj;
    /**
     * @var current's line header field
     */
    private $yykey;
    /**
     * @var int current parser position
     */
    private $yypos;
    /**
     * @var int iterator index
     */
    private $yycount;
    /**
     * @var int next parser position
     */
    private $yynext;
    /**
     * @var int line pointer
     */
    private $yyline;
    /**
     * @var int currents element length of lines
     */
    private $yylines;
    /**
     * @param string $body message body
     * @param string $crlf (optional) line ending
     */
    public function __construct($body,$retobj=false,$crlf="\r\n") {
        $this->body=(string)$body;
        $this->crlf=(string)$crlf;
        $this->retobj=(bool)$retobj;
    }
    /**
     * get field-name from a line
     * 
     * @param string $line
     * @return string field name or zero-length string if not found.
     */
    public static function fieldName($line)
    {
        // Header Name per RFC: 33 and 126, inclusive, except 58 colon 
        $r=preg_match('(^([\x21-\x39\x3B-\x7F]+)([\t ]*:)(.+)$)',$line,$matches);
        if($r===false) throw new Exception('preg_match failed to process line.');
        return $r?$matches[1]:'';
    }
    private function getCurrentLine()
    {   
        $line='';
        $from=$this->yypos;
        $crlflen=strlen($this->crlf);
        $key='';
        $this->yylines=0;
        do
        {
            $next=strpos($this->body,$this->crlf,$from);
            $next===false&&$next=strlen($this->body);
            $length=$next-$from;
            $line.=substr($this->body,$from,$length);
            $from=$next+$crlflen;
            $this->yylines++;
        }
        while
        (
            (
                isset($key[0])
                ||strlen($key=self::fieldName($line))
            )
            &&isset($this->body[$from])
            &&strspn($this->body[$from],"\t ")
        );
        $this->yykey=$key;
        $this->yynext=$from;
        return $line;
    }
    public function current()
    {
        static $lastyypos=-1,$line;
        if ($lastyypos===$this->yypos) return $line;

        $lastyypos=$this->yypos;
        $line=$this->getCurrentLine();
        isset($this->yykey[0])&&$line=substr(strstr($line,':'),1);
        if($this->retobj)
        {
            $c = new stdClass;
            $c->isfield=isset($this->yykey[0]);
            $c->name=$this->yykey;
            $c->value=$line;
            $c->offset=$this->yypos;
            $c->line=$this->yyline;
            $c->lines=$this->yylines;
            $line=$c;
        }
        return $line;
    }
    /**
     * @return string
     */
    public function key()
    {
        return $this->retobj?$this->yycount:$this->yykey;
    }
    public function next()
    {
        $this->yypos=$this->yynext;
        $this->yyline+=$this->yylines;
        $this->yycount++;
    }
    public function rewind()
    {
        $this->yypos=$this->yynext=$this->yyline=0;
        $this->yycount=0;
        $this->yykey='';
    }
    public function valid()
    {
        return isset($this->body[$this->yypos]);
    }
}

/**
 * FilterIterator to remove normal lines and optionally
 * only return header with the name(s) given in the
 * $filter argument.
 */
class BouncedHeadersFiltered extends FilterIterator
{
    private $userFilter;
   
    public function __construct($body, $filter=array() )
    {
        $iterator=new BouncedHeaders($body);
        parent::__construct($iterator);
        $this->userFilter = $filter;
    }
   
    public function accept()
    {
        $key=$this->getInnerIterator()->key();
        if(is_int($key)) {
            $key=$this->getInnerIterator()->current()->name;
        }
        $isHeader=(bool) strlen($key);
        if ($isHeader && count($this->userFilter))
        {
            $isHeader = in_array($key, $this->userFilter);
        }
        return $isHeader;
    }
}