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Subject: domDoc class uses flock()
From: tk.lists@fastmail.fm (Terence)

I'v already started developing an object wrapper to DOM XML for my own 
usage (but freely available to anyone as with all my stuff) which 
provides a central point where I can control the way all this file 
accessing is done.

Here is the constructor method alone plus the constant definitions 
preceeding the class. This code has not been tested yet.


     /**
     * Constructor method
     *
     * Create the objDoc instance property and associated ndRoot 
property based
     * on the user-selected mode of document creation. In the process, 
establish
     * the blnIsReadOnly property.
     *
     * @param    mixed   information required to create a DOM document
     * @param    int     constant specifying how the document is to be 
created
     * @return   void
     */
     function domDoc(&$Starter,$intUse = DOMDOC_AS_NEW) {
         $this->objErr = new xmlErrorLog($this);
         $this->intMode = $intUse;
         $this->blnIsReadOnly = true;
                                     // for more info on each case 
block, see
                                     // comments in the constant definitions
                                     // at the top of this file.
         switch ($intUse) {
             case DOMDOC_AS_NEW:
                 $this->blnIsReadOnly = false;
                 $this->objDoc = domxml_new_doc("1.0");
                 $elRoot = $this->objDoc->create_element($Starter);
                 $this->ndRoot = $this->objDoc->append_child($elRoot);
             break;
             case DOMDOC_AS_READFILE:
                 $fp = fopen($Starter,"r")
                     OR $this->objErr->throw(
                         "could not open ".$Starter." for reading."
                     );
                                     // attempt thread safety by using flock
                 flock($fp,LOCK_SH);
                 $xmlData = fread($fp,filesize($Starter));
                 flock($fp,LOCK_UN);
                 fclose($fp);
                                     // finish working with the file as
                                     // quickly as possible and THEN worry
                                     // about making a DOM doc from it.
                 $this->_domOpenFromData($xmlData);
             break;
             case DOMDOC_AS_WRITEFILE:
                 $this->blnIsReadOnly = false;
                 $this->fp = fopen($Starter,"bw+")
                     OR $this->objErr->throw(
                         "could not open ".$Starter." for writing."
                     );
                 flock($this->fp,LOCK_EX);
                 $xmlData = fread($this->fp,filesize($Starter));
                 $this->_domOpenFromData($xmlData);
             break;
             case DOMDOC_AS_REMOTEFILE:
                 $fp = fopen($Starter,"r")
                     OR $this->objErr->throw(
                         "could not open ".$Starter." for reading."
                     );
                 $xmlData = fread($fp,filesize($Starter));
                 fclose($fp);
                 $this->_domOpenFromData($xmlData);
             break;
             case DOMDOC_AS_REFERENCE:
                 $this->objDoc =& $Starter;
             break;
             case DOMDOC_AS_DATA:
                 $this->_domOpenFromData($Starter);
             break;
             default:
                 $this->objErr->throw(
                     "second argument to domDoc constructor is invalid"
                 );
         }
     }