Get string from pointer to memory [Solved]

[c.haslam]

I am using _GuiCtrlTreeview_SetItemParam() to store a string associated with a treeview item. (I am not calling GuiCtrlCreateTreeViewItem partly because this function stores the control ID of the item there.) Because $iParam is an lparam, I actually call _WinAPI_CreateString() and then store the pointer it returns by calling _GuiCtrlTreeview_SetItemParam().

Now my question: in my case, _GuiCtrlTreeview_GetItemParam(0 returns a pointer. How can I get the string from the pointer?

Or is there a simpler way?

Edited December 10, 2018 by c.haslam

[Iczer]

basically, beside pointer you need length of string in characters, then:

$sString = DllStructGetData(DllStructCreate("WCHAR[" & $iStringLen & "]",$pPointer),1)

 

[c.haslam]

Thanks, but ...

I will have many of strings of various lengths, and I don't want to have to track them, so how do I get the length of each string?

[Nine]

Are the strings 0 ended ?

[InnI]

22 hours ago, c.haslam said:

Or is there a simpler way?

Create array of strings and keep array index like ItemParam.

[Iczer]

you can try this:

$hDLL = DllOpen("c:\windows\system32\msvcrt.dll")

$aRet = DllCall($hDLL,"long","wcslen", "PTR", $StringWPTR)
$sString = DllStructGetData(DllStructCreate("WCHAR[" & $aRet[0] & "]",$pStringWPTR),1)

$aRet = DllCall($hDLL,"long","strlen", "PTR", $StringAPTR)
$sString = DllStructGetData(DllStructCreate("CHAR[" & $aRet[0] & "]",$pStringAPTR),1)

but string should be zero-terminated and MS VC libraries should be installed

Edited December 8, 2018 by Iczer

[UEZ]

@c.haslam: a small demo script available?

[c.haslam]

I have found a solution. I will describe the relevant parts of the project -- for the benefit of others

I use Pegasus Mail and back up the settings and data daily: just the files that have changed, i.e. have the archive bit set. Pegasus organizes saved emails into what it calls "folders" (but which are actually files). The "folders' are organized into a tree structure.

Very occasionally a Pegasus "folder" disappears, and when it does, it needs to be retrieved from back ups. But to retrieve a "folder" one needs to know its filename, and the name of the file is FOL followed by seemingly random hex-looking digits.

Pegasus maintains a file, hierarch.pm. It is in CSV format and contains the tree structure including the name of the "folder" and the filename. It is, of course, flat,

My project is to show hierarch.pm in a treeview so the user can select a "folder" and have the script tell him the name of the corresponding file.

So the treeview needs a string to be associated with each "folder" item.

To do this, I avoided using GuiTreeviewCreateItem() so I, not calling this native AutoIt funcion, get to store the file name in the $iParam parameter of the treeview struct. So I created the treeview by calling _GuiCtrlTreeview_Add() and _GuiCtrlTreeview_AddChild().

I thought of calling _GuiCtrlTreeview_SetItemParam() to store the file name with each treeview item. But $iParam cannot be used directly to store a string.

In Structureconstants.au3, $iParam is a 4-byte integer. In 32-bit AutoIt, a pointer is also 4 bytes. I decided to try storing a pointer to a string there.

To allocate memory and get a pointer back, I call _WinAPI_CreateString(). To get the string back, I call PointerToStringW():

Func _PointerToStringW($ptr)
    Return DllStructGetData(DllStructCreate("wchar[" & _WinAPI_StringLenW($ptr) & "]", $ptr), 1)
EndFunc

To store the string with the treeview item, I coded;

$pStr = _WinAPI_CreateString(StringInStr($a20[$i][$kFull],':FOL') ? $a20[$i][$kFull] : '')
_GUICtrlTreeView_SetItemParam($g_hTV,$hItem,$pStr)

To retrieve a string I coded:

Local $ptr = _GUICtrlTreeView_GetItemParam($g_hTV,$hItem)
Local $s = _PointerToStringW($ptr)
.
.
.
Func _PointerToStringW($ptr)
    Return DllStructGetData(DllStructCreate("wchar[" & _WinAPI_StringLenW($ptr) & "]", $ptr), 1)
EndFunc

I also keep track of these pointers in an array, and when the script is ending I free the memory:

OnAutoItExitRegister('FreePointersToParamStrings')


Func FreePointersToParamStrings()
    For $i = 0 To $g_iqPointers
        _WinAPI_FreeMemory($g_pointers[$i])
    Next
EndFunc

This works in x86 AutoIt. It may not work in AutoIt x64.

Edited December 10, 2018 by c.haslam
Added retrieval code

[c.haslam]

I have been looking at the Param element on Microsoft. I see there that it is an LPARAM. StructureConstants.au3 has:

Global Const $tagTVITEM = "struct;uint Mask;handle hItem;uint State;uint StateMask;ptr Text;int TextMax;int Image;int SelectedImage;" & _
        "int Children;lparam Param;endstruct"

_GuiCtrlTreeview_SetItemParam() creates a $tagTVITEMEX structure.

This suggest that the last parameter to _GuiCtrlTreeview_SetItemParam() and  _GuiCtrlTreeview_GetItemParam() should be a pointer ($pParam).

Did I find 2 bugs?

(The Help for $tagTVITEMEX has Param as a Param. BTW the Help for DllStructCreate las LPARAM amd WPARAM but not PARAM.)