This example shows how to use the following:
Interop.Call
Interop.Allocate

code:

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function GetUserName(){
   /*
      Allocate memory needed to store the returned username.
      Why do we need to use (2*(100)+2) for the size of the allocated memory?
          We do this because the maximum length of the returned string is
          100 characters (changes with different APIs). Since these are
          handled in Unicode we need to multiply the size by 2. Now the
          reason we add 2 is for a null character in unicode.

                     (Unicode*(MaxLength)+NullTerminatedString)
   */

// Thanks Cookie for pointing out that its actually UNLEN+1 and UNLEN is 256
   var sBuffer = Interop.Allocate(2*(256)+2);
// Thanks LJ I forgot I needed this.
   var lBuffer = Interop.Allocate(4);
   lBuffer.WriteDWORD(0, 255);
   Interop.Call('advapi32.dll', 'GetUserNameW', sBuffer, lBuffer);

   Debug.Trace('sBuffer: '+sBuffer.ReadString(0));

// Free the memory we allocated
   sBuffer.Size = 0;
   lBuffer.Size = 0;
}

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theres a lsight spelling mistake

code:

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var sBuffer = Interop.Allocate(2*(100+2));

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quote:

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Originally posted by JonnyT
theres a lsight spelling mistake

code:

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var sBuffer = Interop.Allocate(2*(100+2));

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and in the debug i get nothing just "sBuffer: "

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not as nicely styled as matty's but at least mine works

code:

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function GetUserName()
{
    var sBuffer = Interop.Allocate((255+1) * 2);
    var nBufferLength = Interop.Allocate(4);
    nBufferLength.WriteDWORD(0, 255);
    Interop.Call('advapi32.dll', 'GetUserNameW', sBuffer, nBufferLength);
    Debug.Trace('sBuffer: ' + sBuffer.ReadString(0));
}

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quote:

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Originally posted by Eljay
not as nicely styled as matty's but at least mine works

code:

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function GetUserName()
{
    var sBuffer = Interop.Allocate((255+1) * 2);
    var nBufferLength = Interop.Allocate(4);
    nBufferLength.WriteDWORD(0, 255);
    Interop.Call('advapi32.dll', 'GetUserNameW', sBuffer, nBufferLength);
    Debug.Trace('sBuffer: ' + sBuffer.ReadString(0));
}

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PS: A buffer size of (UNLEN + 1) characters will hold the maximum length user name including the terminating null character. UNLEN is defined in Lmcons.h.

And Lmcons.h defines UNLEN as being 256 characters. So I suppose the correct length for the (unicode) buffer should be 2*(256+1)

PS2:

quote:

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// Free the memory we allocated
   sBuffer.Size = 0;
   lBuffer.Size = 0;

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ah yeah that one works

so what else could this be used for?

quote:

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Originally posted by CookieRevised
PS:
A buffer size of (UNLEN + 1) characters will hold the maximum length user name including the terminating null character. UNLEN is defined in Lmcons.h.

and Lmcons.h defines UNLEN as being 256 characters. So I suppose the correct length for the buffer should be 2*256+2

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quote:

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Originally posted by JonnyT
ah yeah that one works

so what else could this be used for?

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quote:

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Originally posted by CookieRevised
PS2: Will be done automatically as soon as the function ends since the two are local variables though.

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code:

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function TraceWin32Error(){
    var LastError = Interop.GetLastError();
    if(LastError != 0){
        var MsgBuffer = Interop.Allocate(1024);
        Interop.Call("Kernel32", "FormatMessageW", 0x1000, 0, LastError, 0, MsgBuffer, 1024, 0);
        Debug.Trace(MsgBuffer.ReadString(0));
        MsgBuffer.Size = 0; //Release the allocated memory now
    }
}

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