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Angel

Pass by reference to DllCall

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Hi,

I am trying to call a Dll using DllCall. Some of the parameters that are passed to some of the functions in the dll are modified (i.e. passed by reference, as pointers).

I cannot test my program as to run it I must use a PC which is on a lab to wich I do not have access all the time, so I'd like to write my code beforehand.

So my question is, is it possible to call such a Dll? which kind of parameter type should I pass, a "ptr" or an "int" (in C it is a pointer to int).

I could not get the answer to these questions in the docs or in the forum, so I apologize if this has been covered before.

Thanks in advance,

Angel

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The reason DllCall() returns an array is for just this reason. Any parameters that are changed can be accessed from that array. As for the type, that depends on what the function expects. The answer actually is in the helpfile, review it some.

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Valik, off topic, but do you have any idea if Jon is planning to add str_ptr support? Some apis request it, and cannot be controlled with regular str.


Who else would I be?

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A pointer to string could be a couple different things. It could be a pointer to a string or it could be a pointer to an array of strings. Very likely if a function wants a pointer to a string, then its wanting to make it an array, because otherwise, it could just write over the string normally (Since C-style strings are pointers, already). Therefore, you run into the problem of access anything beyond the first element in an array/structure.

I'm not saying Jon won't add it or anything, I'm just saying what I suspect these functions may be doing and why they want a pointer to string.

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You are right Valike. After re-reading it is actually very clear. I think that I actually was not expecting for this to be possible, so I read what I wanted to read, if you know what I mean.

Sorry for the unnecessary post...

However I still have a doubt. If the function is supposed to modify the integer parameter, then I should use a "int_ptr" type, right?

Angel

Edited by Angel

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I see what you mean Valik. I had some examples around here somewhere, maybe I can find them again and see if they really want an array.


Who else would I be?

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You are right Valike. After re-reading it is actually very clear. I think that I actually was not expecting for this to be possible, so I read what I wanted to read, if you know what I mean.

Sorry for the unnecessary post...

However I still have a doubt. If the function is supposed to modify the integer parameter, then I should use a "int_ptr" type, right?

Angel

<{POST_SNAPBACK}>

You'll want to use the *_ptr version of the closest matching type to what the function expects.

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You'll want to use the *_ptr version of the closest matching type to what the function expects.

<{POST_SNAPBACK}>

Thanks a lot!!! :lmao:

Angel

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Another question:

In the help file it says:

If the function call fails then @error is set to 1. Otherwise an array is returned that contains the function return value and a copy of all the parameters (including parameters that the function may have modified).

Does this mean that if there is no error the returned value will always be an array, independently of the number of arguments that were modified? Or will it return a non array value if there are no modified arguments?

What would happen, for instance if the return type is void but there is one modified parameter?

Angel

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It always returns an array on success. It will return back to you the same parameters you passed in as well, whether they were modified or not. $array[0] = Return value from the function, $array[1] - $array[n] are the parameters passed to the function, some of which the function could of modified.

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