Keith Vetter 2005-03-21 : Recently I had to optimize some code that was using pure-tcl to extract out each element of an XML file in the order it appears in the file. My first step in optimization was simply to use tdom to build a dom tree. Then, the following code does a restartable pre-order traversal of that tree
The first call to :::WalkXML::NextNode with XML data initializes the dom tree. Each subsequent call to ::WalkXML::NextNode returns the next dom node.
Just this optimization alone, without redoing the code to utilize the dom tree, greatly speeded up the processing.
NEM 21Mar05: If you want to walk the elements in the order they appear in the file, might a SAX interface be just what you are after?
##+##########################################################################
#
# WalkXML -- walks an tdom XML tree with each call to NextNode returning
# the next node in a pre-order traversal of the dom tree.
# by Keith Vetter, March 2005
#
package require tdom
namespace eval ::WalkXML { variable stack}
proc ::WalkXML::NextNode {{XML ""}} {
variable stack ;# List of VISITED ancestors
if {$XML ne ""} { ;# Parse given xml
set doc [dom parse $XML]
set root [$doc documentElement]
set stack [list $root]
return $root
}
while {1} {
set last [lindex $stack end] ;# Last already visited node
set next [$last firstChild] ;# Try going down the tree
if {$next ne ""} break
set stack [lrange $stack 0 end-1]
set next [$last nextSibling] ;# Try going across the tree
if {$next ne ""} break
while {1} { ;# Must go up the tree
set next [lindex $stack end] ;# Parent
set stack [lrange $stack 0 end-1]
if {$next eq ""} break
set next [$next nextSibling] ;# Try parent's sibling
if {$next ne ""} break
}
break
}
if {$next ne ""} {
lappend stack $next
}
return $next
}
################################################################
#
# Demo code
#
set XML {<?xml version="1.0" encoding="ISO-8859-1"?>
<loc version="1.0" src="Groundspeak">
<waypoint>
<name id="GCGPXK"><![CDATA[Playing Poker with the Squirrels by Rino 'n Rinette]]></name>
<coord lat="40.1548166" lon="-82.5202833"/>
<type>Geocache</type>
<link text="Cache Details">http://www.geocaching.com/seek/cache_details.aspx?wp=GCGPXK</link>
</waypoint><waypoint>
<name id="GC19DF"><![CDATA[Great Playground Caper by Treasure Hunters Inc.]]></name>
<coord lat="40.0667166666667" lon="-82.5358"/>
<type>Geocache</type>
<link text="Cache Details">http://www.geocaching.com/seek/cache_details.aspx?wp=GC19DF</link>
</waypoint>
</loc>
}
set node [::WalkXML::NextNode $XML]
while {$node ne ""} {
if {[$node nodeType] eq "TEXT_NODE"} {
puts "\"[$node nodeValue]\""
} else {
puts "[$node nodeName]"
}
set node [::WalkXML::NextNode]
}