[xml] Function xmlOutputBufferWriteEscape seems to slow down on big xml

[Alexandre Macard <amacard arkeia com>]

Hi everyone.

I developped a webservice with libcsoap api. This one use libxml2, of 
course.

I use libxml2 version 2.6.32 on Linux Gentoo.

We are doing some tests on this webservice and we have a very long time 
to get a response with a big XML.
(nearly 7mo xml).

We tried gprof to find why it takes more than 20secs ! and we found that 
all the 20secs are spent
in libxml2, function xmlNodeDump().

So I tried to define which function inside xmlNodeDump is in charge. And 
I found, if I patched libxml2 to use exclusively
function  xmlOutputBufferWriteString() instead of 
xmlOutputBufferWriteEscape(), the return takes only 1sec !

The source I patched to get this result is in xmlsave.c file in function 
xmlNodeDumpOutputInternal(). This function parse everything in the node. 
All nodes types are XML_TEXT_NODE and are encoded into base64. So, I 
don't need to escape
characters in these strings.

The function xmlOutputBufferWriteEscape() is always called because the 
node name (cur->name in source code) is always equal to the global const 
xmlStringText.

I tried to build my xml with a node name equal to xmlStringTextNoenc 
instead of xmlStringText but nothing changed.

Is there a known issue with xmlOutputBufferWriteEscape() function ?

Is there a solution to get node->name equal to xmlStringTextNoenc 
instead of xmlStringText, and how ?

Thanks in advance for your help.