webkit-dev - about hashmap staticDOMObjects

static DOMObjectMap& domObjects()
{
    // Don't use malloc here. Calling malloc from a mark function can
deadlock.
    static DOMObjectMap staticDOMObjects;
    return staticDOMObjects;
}

what kind of DOMObjects should be stored in it? And why?
I searched the source codes and I found that these classes below will do
that:

Document, Event, HTMLCollection, XMLHttpRequest, CanvasGradient,
CanvasPattern, CanvasRenderingContext2D, DOMCoreException,
DOMImplementation, DOMParser, EventException, History, NamedNodeMap,
NodeFilter, NodeIterator, NodeList, Range, RangeException, TreeWalker,
XMLHttpRequestException, XMLSerializer, Clipboard

but what's the reason? Is it because these classes are essentially simple
and just acting as a tool?

thanks a lot

br>=A0=A0=A0 static DOMObjectMap staticDOMObjects;<br>
=A0=A0=A0 return staticDOMObjects;<br>}<br><br>what kind of DOMObjects shou=
ld be stored in it? And why?<br>I searched the source codes and I found tha=
t these classes below will do that:<br><br>Document, Event, HTMLCollection,=
 XMLHttpRequest, CanvasGradient, CanvasPattern, CanvasRenderingContext2D, D=
OMCoreException, DOMImplementation, DOMParser, EventException, History, Nam=
edNodeMap, NodeFilter, NodeIterator, NodeList, Range, RangeException, TreeW=
alker, XMLHttpRequestException, XMLSerializer, Clipboard<br>
<br>but what&#39;s the reason? Is it because these classes are essentially =
simple and just acting as a tool?<br><br>thanks a lot<br>

stored in

static NodePerDocMap& domNodesPerDocument()
{
    ASSERT(JSLock::lockCount());
    static NodePerDocMap staticDOMNodesPerDocument;
    return staticDOMNodesPerDocument;
}




2009/4/22 ZHOU Xiao-bo <zhxb.ustc@gmail.com>

> hi all:
>      I still don't understand the purpose of the HashMap:
>
> static DOMObjectMap& domObjects()
> {
>     // Don't use malloc here. Calling malloc from a mark function can
> deadlock.
>     static DOMObjectMap staticDOMObjects;
>     return staticDOMObjects;
> }
>
> what kind of DOMObjects should be stored in it? And why?
> I searched the source codes and I found that these classes below will do
> that:
>
> Document, Event, HTMLCollection, XMLHttpRequest, CanvasGradient,
> CanvasPattern, CanvasRenderingContext2D, DOMCoreException,
> DOMImplementation, DOMParser, EventException, History, NamedNodeMap,
> NodeFilter, NodeIterator, NodeList, Range, RangeException, TreeWalker,
> XMLHttpRequestException, XMLSerializer, Clipboard
>
> but what's the reason? Is it because these classes are essentially simple
> and just acting as a tool?
>
> thanks a lot
>

br>
=A0=A0=A0 static NodePerDocMap staticDOMNodesPerDocument;<br>=A0=A0=A0 retu=
rn staticDOMNodesPerDocument;<br>}<br><br><br><br><br><div class=3D"gmail-q=
uote">2009/4/22 ZHOU Xiao-bo <span dir=3D"ltr">&lt;<a href=3D"mailto:zhxb.u=
stc@gmail.com">zhxb.ustc@gmail.com</a>&gt;</span><br>
<blockquote class=3D"gmail-quote" style=3D"border-left: 1px solid rgb(204, =
204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">hi all:<br>=A0=A0=
=A0=A0 I still don&#39;t understand the purpose of the HashMap:<br><br>stat=
ic DOMObjectMap&amp; domObjects()<br>
{ <br>=A0=A0=A0 // Don&#39;t use malloc here. Calling malloc from a mark fu=
nction can deadlock.<br>=A0=A0=A0 static DOMObjectMap staticDOMObjects;<br>
=A0=A0=A0 return staticDOMObjects;<br>}<br><br>what kind of DOMObjects shou=
ld be stored in it? And why?<br>I searched the source codes and I found tha=
t these classes below will do that:<br><br>Document, Event, HTMLCollection,=
 XMLHttpRequest, CanvasGradient, CanvasPattern, CanvasRenderingContext2D, D=
OMCoreException, DOMImplementation, DOMParser, EventException, History, Nam=
edNodeMap, NodeFilter, NodeIterator, NodeList, Range, RangeException, TreeW=
alker, XMLHttpRequestException, XMLSerializer, Clipboard<br>

<br>but what&#39;s the reason? Is it because these classes are essentially =
simple and just acting as a tool?<br><br>thanks a lot<br>
</blockquote></div><br>

On Apr 22, 2009, at 12:27 AM, ZHOU Xiao-bo wrote:

> hi all:
>      I still don't understand the purpose of the HashMap:
>
> static DOMObjectMap& domObjects()
> {
>     // Don't use malloc here. Calling malloc from a mark function  
> can deadlock.
>     static DOMObjectMap staticDOMObjects;
>     return staticDOMObjects;
> }
>
> what kind of DOMObjects should be stored in it? And why?
> I searched the source codes and I found that these classes below  
> will do that:
>
> Document, Event, HTMLCollection, XMLHttpRequest, CanvasGradient,  
> CanvasPattern, CanvasRenderingContext2D, DOMCoreException,  
> DOMImplementation, DOMParser, EventException, History, NamedNodeMap,  
> NodeFilter, NodeIterator, NodeList, Range, RangeException,  
> TreeWalker, XMLHttpRequestException, XMLSerializer, Clipboard
>
> but what's the reason? Is it because these classes are essentially  
> simple and just acting as a tool?

The hash map is to ensure that DOM wrappers are unique but created on  
demand, without consuming a pointer in the underlying C++ object. For  
DOM Nodes, we use a hash table in the Node's owner document, but in  
the case of non-Node objects and the Document itself (which has no  
owner document), we need this global hash table.

Regards,
Maciej