Any advantages of using DllOpen ??

[Rickname]

Do you guys know why or when to use "DllOpen" ( opening the needed dll ) before calling a function via DllCall ?

Why I think that its still a good idea :

- because errors or problems can appear when multiple calls of the same function ( eg. in a loop ) are made

- because next time when calling the same function or other functions from the same dll can be more faster ?

Am I right ?

Edited April 6, 2013 by Rickname

[jchd]

DllOpen may have to perform a full load of things behind the hood and it's a slow operation. While it won't make any difference for basic system DLLs already loaded (~ no work to do) or if you DllCall a named DLL only once in a while, it makes a dramatic difference when DllCalling repeatedly a DLL by name which isn't already in use by the process.

[FireFox]

Your topic reminds me

[Rickname]

DllOpen may have to perform a full load of things behind the hood and it's a slow operation. While it won't make any difference for basic system DLLs already loaded (~ no work to do) or if you DllCall a named DLL only once in a while, it makes a dramatic difference when DllCalling repeatedly a DLL by name which isn't already in use by the process.

Your topic reminds me

So if I have

While $timerdiff < 5000
DllCall("user32.dll".....)
Wend

its still a better (faster) idea to put DllOpen a dll before that "While" loop ? Or the PC will have more things to process and will be slower ? I'm little confused

Edited April 7, 2013 by Rickname

[jchd]

user32.dll is one of the system DLLs which are always loaded for AFAIK every process, at least those doing significant work.

Here the only difference will be to parse the DLL path, look it up in the list of loaded DLLs and retrieving the handle it has (gory details skipped). That means almost nothing.

[JohnOne]

So if I have

While $timerdiff < 5000
DllCall("user32.dll".....)
Wend

its still a better (faster) idea to put DllOpen a dll before that "While" loop ? Or the PC will have more things to process and will be slower ? I'm little confused

Yes it is.

[Rickname]

Yes it is.

But just like @jchd said , the user32 library is used by absolutely so many processes, then its almost useless to open it with autoit too, no ?

Edited April 7, 2013 by Rickname

[UEZ]

I assume that a DllOpen() will load the full or a part from the DLL into the memory which is faster to call instead of loading the DLL each time on a DLLCall.

But I don't know how the os handle DLLs which are permantly used by apps. It might be that those DLLs are also cached in the memory.

Br,

UEZ

Edited April 7, 2013 by UEZ

[JohnOne]

But just like @jchd said , the user32 library is used by absolutely so many processes, then its almost useless to open it with autoit too, no ?

Yes, but as jchd also said, if you don't open it first, autoit will have to look through a list of already loaded dll files to see if it is open and retrieve a handle to it each time you call it.

[jchd]

Ummm, I believe it's rather the OS job to do that. It's also responsible for invoking the DLL init function and such.

[JohnOne]

Whoever job it is, I'm sure it's quicker, no matter how much for multiplr calls when I handle is used.