About getting datahandle from datablock

[ronnielin]

MDataHandle inputHandle = datablock.inputValue( xxxxx, &stat );

How does Maya will handle the above line of code internally? Will Maya return a pointer pointing "directly" to the data my xxxxx plug holds, OR it will "copy" the data my xxxxx plug holds into somewhere and then return a pointer pointing to that copy?

The reason why I have this question is because I've found that more data xxxxx plug holds, slower this line of code would run. If it just return the pointer directly to the data, the running speed shouldn't have any difference no matter how much data there is.

BTW, the data i mean here is implemented from MPxData, which is a block of custom data I defined.

Thanks for any idea in advance

[joojaa]

Well it really depneds on the state of your data, and wether ist caching or not. See the datablock issues the data to compute if the plug is not clean (also it much chek if its clean too and multi attributes are a bit weird). And yes that means even if its a inernal connectible attribute it will call your won compute yet a second time if the datas not set to be clean.* Also if the plug is caching then obviously it needs to do a copy at some point.

Will Maya return a pointer pointing "directly" to the data my xxxxx plug holds,
OR it will "copy" the data my xxxxx plug holds into somewhere and then return
a pointer pointing to that copy?

Well its an api ist non of our business really. Not that it would matter one bit in anycase ist not up to us anyway.

• this means thet you can make nodes within nodes, and indeed nodes between actions inside nodes (one example is the aim constraint where you have time to inject your own stuff before it makes a complete run out of its values). This si also the reason why all examples ask for the asking plug when updating because you might never know what the order of evalueation may be.