Re: WM_COPYDATA ... what's inside?
On 17 Jun., 17:02, David Wilkinson <no-re...@effisols.com> wrote:
.rhavin grobert wrote:
After reading something about WM_COPYDATA, i'm still unshure if i
should use it...
The question is: what does it do? M$ doesnt explaint this very well
(as expected ;-), so i see two possible ways how it is done:
#1 SendMessage(WM_COPYDATA, ...) copies the data in an internal buffer
and POSTS the message to the destination 'while' it returns (so it is
some kind of PostMessage anyway).
#2 SendMessage(WM_COPYDATA, ...) SENDS the pointer to the data or the
pointer to an internal copy of the data to the destination and returns
AFTER the message was processed (whitch would render it pretty useless
for me;-).
if #1 is true it would be easy to implement #2 atop of it, but if #2
is true, it would be completely useless for me, so perhaps someone
could please answer this...
.rhavin:
It's more like 2. Like any SendMessage() it does not return until the receiver
has handled the message. But why is this bad for you? If you want, your receiver
can copy the data, post a message to itself, and return immediately. The actual
work can be done in the PostMessage() handler.
--
David Wilkinson
Visual C++ MVP
because sender and receiver rest in different treads, so if i'd
implement it like you suggest that would be:
Data-> Sendmessage(WM_COPYDATA) = { malloc new buffer, copy data} -
// Threadborder // OnCopyData() = { malloc new buffer, copy data} ->
PostMessage() -> DataReceived.
So the data is actually copied twice!
what i want to implement is:
Data-> {malloc new buffer, copy data} ->PostMessage() //Threadborder//
-> DataReceivedUnfortunatelyInGUIThread() -> Process and delete
buffer.
I've already a working solution (see other thread in this group), but
that way leaks because sometime a message gets lost, so i thougt
WM_COPYDATA would automatically delete its buffer if the message is
lost because the window was meanwhile destroyed. I start to belive
that the only way of doing that correctly (sender POSTS and forgets,
receiver deletes) is a hook, isnt it?