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COM QueryInterface

Started by Guest , Dec 10 2011 03:08 AM

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46 replies to this topic
maul.esel
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Sorry for my absence (no internet access). As you wanted an example, here it is: <!-- m -->https://github.com/m... ... ample1.ahk<!-- m --> (for use with CCF). It uses IShellLinkW + IPersistFile and creates + saves a shell link.

Btw: to ensure your IShellLinkW code works with ANSI builds, pass strings with the "wstr" type.
#31 - Posted 16 December 2011 - 04:58 PM
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I just followed the maul.esel's tutorial.

Reading only the excerpt which you quoted, it seems to me that maul.esel was showing code which produces a similar result, not telling you to use that code. Note the following:

If an IID is specified, an interface pointer is returned. (...)
Otherwise, a wrapper object usable by script is returned.

You were passing an IID and therefore do not need to "unwrap" an object.
#32 - Posted 17 December 2011 - 12:09 AM
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Btw: to ensure your IShellLinkW code works with ANSI builds, pass strings with the "wstr" type.

Changing Str to WStr in the all DllCall lines just gives n in the result with the ANSI build.

By the way, although I appreciate your effort, there should be an example in here and there. They wouldn't be called a tutorial unless there is at least one working example. In fact, it caused lots of confusion when I was following it.

Reading only the excerpt which you quoted, it seems to me that maul.esel was showing code which produces a similar result, not telling you to use that code

There isn't a working example so it is hard to tell what he meant.

By the way, any thoughts why the code produces only a file name? I expected it returns a full path. I tried the other flags for the GetPath method, LGP_SHORTPATH and SLGP_UNCPRIORITY but the same. Also should I add ObjRelease(pIPersistFile) before returning from the function?
#33 - Posted 17 December 2011 - 02:54 AM
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Changing Str to WStr in the all DllCall lines just gives n in the result with the ANSI build.

In addition to it, in order to support the ANSI build, I found that the last line of the function had to be changed to:
Return StrGet(&WIN32_FIND_DATA + 44, A_IsUnicode ? "utf-16" : "cp1200")
By the way, If I put UTF-8 instead of UTF-16 in the Unicode builds, is started not returning the correct string. Does that mean IShellLinkW internally encodes strings as UTF-16?
#34 - Posted 17 December 2011 - 04:32 AM
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Return StrGet(&WIN32_FIND_DATA + 44, A_IsUnicode ? "[color=green]utf-16[/color]" : "[color=darkred]cp1200[/color]")

FileEncoding
[*:x7c4pj88]UTF-16: Unicode UTF-16, little endian byte order. This is equivalent to CP1200.


#35 - Posted 17 December 2011 - 09:04 AM
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Ah, so it's only enough to specify either utf-16 or cp-1200 for the ANSI build. Thanks.
Return StrGet(&WIN32_FIND_DATA + 44, "utf-16")

Any idea why the function only returns a file name, not the full path?
#36 - Posted 17 December 2011 - 09:18 AM
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HRESULT GetPath(

  [[color=red]out[/color]]      LPTSTR pszFile,

  [in]       int cchMaxPath,

  [in, out]  WIN32_FIND_DATA *pfd,

  [in]       DWORD fFlags

);

#37 - Posted 17 December 2011 - 11:38 AM
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Ah, thanks.

Here is the update. It works well. 
lnkpath := A_ScriptDIr "\notepad.lnk"
FileCreateShortcut, %A_WIndir%\notepad.exe, % lnkpath
if target := IShellLinkResolve(lnkpath)
	msgbox % target
else
	msgbox not found
FileDelete, % lnkpath
Return
	
IShellLinkResolve(FilePath) {

	static	IID_IShellLinkW := "{000214F9-0000-0000-C000-000000000046}"
	static CLSID_ShellLink := "{00021401-0000-0000-C000-000000000046}"	
	static IID_IPersistFile := "{0000010b-0000-0000-C000-000000000046}"
	
	if !(pCOM_IShellLink := ComObjCreate(CLSID_ShellLink, IID_IShellLinkW))
        return False		
	if !(pIPersistFile := ComObjQuery(pCOM_IShellLink, IID_IPersistFile)) 
		Return False
	
	vtIShellLink := NumGet(pCOM_IShellLink + 0) ;pointer to the vTable 
	pIShellLink_GetPath := NumGet(vtIShellLink + 03 * A_PtrSize)	
	pIShellLink_Resolve := NumGet(vtIShellLink + 19 * A_PtrSize)	
	
	vtPersistFile := NumGet(pIPersistFile+0)
	pIPersistFile_Load := NumGet(vtPersistFile + 05 * A_PtrSize)	;defined in ObjIdl.h 

	;IPersistFile::Load http://msdn.microsoft.com/en-us/library/windows/desktop/ms687284%28v=vs.85%29.aspx
	;Flags http://msdn.microsoft.com/en-us/library/windows/desktop/aa380337%28v=vs.85%29.aspx
	if hresult := DllCall(pIPersistFile_Load
		, "Ptr", pIPersistFile
		, "wStr", FilePath
		, "Uint", 0x00000000)	;STGM_Read
		return false

	;http://msdn.microsoft.com/en-us/library/windows/desktop/bb774952%28v=vs.85%29.aspx
	if hresult := DllCall(pIShellLink_Resolve
		, "ptr", pCOM_IShellLink
		, "Ptr", A_ScriptHwnd
		, "Uint", 0x0001)	;SLR_NO_UI
		return false
	
	; IShellLink::GetPath http://msdn.microsoft.com/en-us/library/windows/desktop/bb774944%28v=VS.85%29.aspx
	VarSetCapacity(WIN32_FIND_DATA, 592)
	VarSetCapacity(target, 260)
	if hresult := DllCall(pIShellLink_GetPath
		, "ptr", pCOM_IShellLink
		, "wStr", target
		, "Int", 260
		, "Ptr", &WIN32_FIND_DATA 
		, "Uint", 0x4)	; SLGP_SHORTPATH = 0x1 SLGP_UNCPRIORITY = 0x2 SLGP_RAWPATH = 0x4
		return false
	
	ObjRelease(pIPersistFile)
	ObjRelease(pCOM_IShellLink)
	Return target 	
	
}

#38 - Posted 17 December 2011 - 01:03 PM
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VarSetCapacity(target, 260 [color=red]* 2[/color])
It's unicode!
#39 - Posted 17 December 2011 - 01:25 PM
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Does that mean also the number in the second parameter for IShellLink::GetPath (the third parameter in DllCall) has to be 260*2 ?

By the way, I noticed that it didn't run in the ANSI build regardless the suggested change.

Here is the updated function which also runs with the ANSI build.
IShellLinkResolve(FilePath) {

	static	IID_IShellLinkW := "{000214F9-0000-0000-C000-000000000046}"
	static CLSID_ShellLink := "{00021401-0000-0000-C000-000000000046}"	
	static IID_IPersistFile := "{0000010b-0000-0000-C000-000000000046}"
	
	if !(pCOM_IShellLink := ComObjCreate(CLSID_ShellLink, IID_IShellLinkW))
        return False		
	if !(pIPersistFile := ComObjQuery(pCOM_IShellLink, IID_IPersistFile)) 
		Return False
	

	;IPersistFile::Load http://msdn.microsoft.com/en-us/library/windows/desktop/ms687284%28v=vs.85%29.aspx
	;Flags http://msdn.microsoft.com/en-us/library/windows/desktop/aa380337%28v=vs.85%29.aspx
	if hresult := DllCall(NumGet(NumGet(pIPersistFile+0) + 05 * A_PtrSize)	;IPersistFile::Load
		, "Ptr", pIPersistFile
		, "wStr", FilePath
		, "Uint", 0x00000000)	;STGM_Read
		return false

	;http://msdn.microsoft.com/en-us/library/windows/desktop/bb774952%28v=vs.85%29.aspx
	if hresult := DllCall(NumGet(NumGet(pCOM_IShellLink + 0) + 19 * A_PtrSize)		;IShellLink:Resolve
		, "ptr", pCOM_IShellLink
		, "Ptr", A_ScriptHwnd
		, "Uint", 0x0001)	;SLR_NO_UI
		return false
	
	; IShellLink::GetPath http://msdn.microsoft.com/en-us/library/windows/desktop/bb774944%28v=VS.85%29.aspx
	VarSetCapacity(WIN32_FIND_DATA, 592)
	VarSetCapacity(target, 260 * 2)
	if hresult := DllCall(NumGet(NumGet(pCOM_IShellLink + 0) + 03 * A_PtrSize)		;IShellLink:GetPath
		, "ptr", pCOM_IShellLink
		, "ptr", &target
		, "Int", 260   ;[color=red]<-- not sure if it should be 260*2[/color]
		, "Ptr", &WIN32_FIND_DATA 
		, "Uint", 0x4)	; SLGP_SHORTPATH = 0x1 SLGP_UNCPRIORITY = 0x2 SLGP_RAWPATH = 0x4
		return false
	
	ObjRelease(pIPersistFile)
	ObjRelease(pCOM_IShellLink)
	Return StrGet(&target, "utf-16") 	
	
}

#40 - Posted 17 December 2011 - 02:34 PM
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VarSetCapacity()
Parameters
RequestedCapacity

Specify for RequestedCapacity the number of bytes that the variable should be able to hold after the adjustment. For Unicode strings, this should be the length times two.


#41 - Posted 17 December 2011 - 03:28 PM
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I'm talking about the part commented in red.
#42 - Posted 17 December 2011 - 03:39 PM
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IShellLink::GetPath method

cchMaxPath [in]
Type: int

The size, in characters, of the buffer pointed to by the pszFile parameter, including the terminating null character. The maximum path size that can be returned is MAX_PATH. This parameter is commonly set by calling ARRAYSIZE(pszFile). The ARRAYSIZE macro is defined in Winnt.h.


#43 - Posted 17 December 2011 - 03:47 PM
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OK, so it should be 260*2 as well. Thanks.
#44 - Posted 17 December 2011 - 03:52 PM
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No, it shouldn't: Unicode (UTF-16) -> 1 character = 2 bytes. :roll:
#45 - Posted 17 December 2011 - 04:28 PM
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