Array of Strings and DllStruct

[wegstar]

Hello,

I am currently making a mysql UDF which directly calls functions in libmysql.dll. However, I am having trouble handling an array of strings (char**, char*[], char [][]) that is returned by the mysql_fetch_row() function.

As you can see in my code, I've figured out how to deal with returned char* strings...:

CODE

Func mysqlQuery($query)

$queryprep = DllStructCreate("char[" & (StringLen($query)+1) & "]")

DllStructSetData($queryprep, 1, $query)

$queryptr =DllStructGetPtr($queryprep, 1)

# we'll add on 100 to be sure

$bufferprep = DllStructCreate("char[" & (StringLen($query)+100) & "]")

$buffer =DllStructGetPtr($bufferprep, 1)

Local $temp = DllCall($dll, "int", "mysql_real_escape_string", "ptr", $fd, "ptr", $buffer, "ptr", $queryptr, "int", StringLen($query)+1)

; now, we have the real size, so fix up the data

; I wonder why I have to subtract 1 to get rid of extra stuff at end of string...

$bufferfix = DllStructCreate("char[" & ($temp[0]-1) & "]")

; copy string over, which will truncate extra 100

DllStructSetData($bufferfix, 1, DllStructGetData($bufferprep, 1))

However, I am unable to 'process' char** array of strings. Here is what I have tried so far:

CODE

Func mysqlFetchRow()

Local $temp = DllCall($dll, "ptr", "mysql_fetch_row", "ptr", $res)

MsgBox(1, "hmm", $temp[0])

$datastruct = DllStructCreate($temp[0]) ; $temp is char**

MsgBox(1, "hmm", DllStructGetData($datastruct, 1))

Local $datatemp = DllStructCreate(DllStructGetData($datastruct, 1))

MsgBox(1, "hmm", DllStructGetData($datatemp, 1))

EndFunc

As you can see, I assumed that DllStructGetData would form an array of char* pointers accessible by by DllStructGetData($datastruct, 1-2-3..etc.). But this does not seem to be the case.

Any ideas how to implement this? Thanks in advance.

[martin]

CODE

Func mysqlFetchRow()

Local $temp = DllCall($dll, "ptr", "mysql_fetch_row", "ptr", $res)

MsgBox(1, "hmm", $temp[0])

$datastruct = DllStructCreate($temp[0]) ; $temp is char**

MsgBox(1, "hmm", DllStructGetData($datastruct, 1))

Local $datatemp = DllStructCreate(DllStructGetData($datastruct, 1))

MsgBox(1, "hmm", DllStructGetData($datatemp, 1))

EndFunc

As you can see, I assumed that DllStructGetData would form an array of char* pointers accessible by by DllStructGetData($datastruct, 1-2-3..etc.). But this does not seem to be the case.

Any ideas how to implement this? Thanks in advance.

That doesn't make sense to me.

Local $temp = DllCall($dll, "ptr", "mysql_fetch_row", "ptr", $res)

You are expecting a ptr to be retured

$datastruct = DllStructCreate($temp[0]) ; $temp is char**;- no, it's a pointer, but anyway you don't create a struct like that

what you mean here is perhaps

$datastruct = DllStructCreate('ptr',$temp[0])

But if you knew there were 3 items you could say

$datastruct = DllStructCreate('ptr[3]',$temp[0])

But I would expect that the return is a pointer to the sructure for the array of strings. What you need to find out is how the structure is formed so you can read it. Presumably this is well known but not by me I'm afraid. If I couldn't find out I would read the memory location starting at $Temp[0] and see if I could understand it. The structure could be an array of strings, an array of pointers to strings (which is what I think you expect, but how do you know how many elements?), a value of the number of strings followed by pointers etc etc.

So what I think will be needed is

DllStructCreate($Structure,$Temp[0]) ;once you know the structure

Edited December 20, 2007 by martin

[piccaso]

here's a concept that should work...

#include<sqlite.au3>
$ppszRow = ;mysql_fetch_row(res)
$uiLen = ;mysql_num_fields(res)
dim $aRow[$uiLen],$vPointers = DllStructCreate("ptr[" & $uiLen & "]",$ppszRow)
Do
   $uiLen -= 1
   $aRow[$uiLen] = _szStringRead(DllStructGetData($vPointers,1,$uiLen+1))
Until $uiLen = 0


Func _szStringRead($pszString, $uiLen = -1)
    Local $aStrLen, $vszString
    If $pszString = 0 Then Return ""
    If $uiLen < 1 Then
        $aStrLen = DllCall("msvcrt.dll", "int:cdecl", "strlen", "ptr", $pszString)
        If @error Then Return SetError(1, 0, "")
        $uiLen = $aStrLen[0] + 1
    EndIf
    $vszString = DllStructCreate("char[" & $uiLen & "]", $pszString)
    If @error Then Return SetError(2, 0, "")
    Return SetError(0, $iLen, DllStructGetData($vszString, 1))
EndFunc

Edited December 20, 2007 by piccaso

[wegstar]

Thank you martin and picasso! It seems to work here