lineGetID returns a NULL handle

[kobi]

Hi everybody
I tried to achieve a handle for readFile/writeFile operations using lineGetID.
The call to the function passed without errors. My problem is that the handle that I get is 0..., and I should make IO operations some how... :(
My code:
lRet := lineGetID( FLineHandle, 0, 0, LINECALLSELECT_LINE, PVarString, szClassType );
if lRet = 0 then
begin
FDevHandle := (LPHANDLE(PByte(PVarString) + PVarString^.dwStringOffset ))^;
// some more non relevant code which checks the validity of FDevHandle....
end;
The call to lineGetID is done after successful call to lineGetOpen. I test my application on i-mate jam with WM2003.

Thanks ahead
Kobi

[kobi]

Hi everybody
For those who encounters the same problem as mine here is the solution that I finally found:

1. The Handle is NULL if we call the lineGetID using LINECALLSELECT_LINE. We should call lineGetID after getting into the LINECALLSTATE_CONNECTED state and use the LINECALLSTATE_CALL parameter. This information was found in the MSDN.

2. The lineGetID (as well as other line functions) doesn't report (I use TAPI 2.0 with WM-2003 on i-mate jam - the cellular line channel) the error LINEERR_STRUCTURETOOSMALL, so immediately after calling the lineGetID I added the following line (I use free pascal compiler):
if (Result = 0) and (PVarString^.dwTotalSize < PVarString^.dwNeededSize) then
Result := integer(LINEERR_STRUCTURETOOSMALL);
After this line comes the characteristic TAPI code which checks if either we should reallocate the previous block, or we can already use the data that call should have given to us.

Just after considering these 2 issues I got a vaild Handle...
Kobi

[eefendi]

Hi Kobi,
I also having difficulties creating handle to write data on this TAPI Line, Can you please help me translate your code in VB.NET or C#, I am using VB and C# on developing application in WM2003.
Many thanks in Advance,
Eefendi

[kobi]

Hi Eefendi
I neither know VB.NET nor C#, so it will be in Pascal, but I will add comments.
The code itself should be activated after you received the LINE_CALLSTATECONNECTED message/event (depends on the mechanism you selected when you called lineInitialize).
The CallHandle is a variable holds the handle of the call you want to achieve a handle to its stream (you achieve CallHandle, in incoming call for example, using LINE_CALLSTATEOFFERING message/event). The final result we want is stored in Handle. The line itself should be opened using "comm" or "comm/datamodem" class type.

var
VarSize,
Res : integer;
PVarString : LPVARSTRING;
szClassType : PWideChar = 'comm/datamodem';
// these variables definitions is equivalent to the following C code:
// int VarSize, Res;
// LPVARSTRING PVarString;
// TCHAR *szClassType = "comm/datamodem";
begin
VarSize := sizeof(VARSTRING);
Handle := 0;
repeat
GetMem( PVarString, VarSize ); // alloc VarSize bytes
PVarString^.TotalSize := VarSize;
Res := lineGetID( 0, 0, CallHandle, LINECALLSELECT_CALL, PVarString, szClassType );
if (Res = 0) and (PVarString^.TotalSize < PVarString^.NeededSize) then
Res := LINEERR_STRUCTURETOOSMALL;
if Res = LINEERR_STRUCTURETOOSMALL then
VarSize := PVarString^.NeededSize
else
if Res = 0 then // no error
Handle := LPHANDLE(PByte(PVarString) + PVarString^.dwStringOffset)^;
FreeMem( PVarString, PVarString^.TotalSize ); // free memory
until Res <> LINEERR_STRUCTURETOOSMALL; // finish the repeat until loop if this condition is TRUE
if (Handle <> 0) and (Handle <> INVALID_HANDLE_VALUE) then
//;use it as you wish....
end;

Some help to you for conversion:
1. PVarString^.TotalSize using C means PVarString->TotalSize
2. PByte using C means char*
3. type cast for example to PByte is done by PByte(...) while using C it is done by (PByte)...
4. Refering to a value which is referenced by the pointer P and storing it in variable X is done by "X := P^;". using C it is done by "X = *P;".
5. The operator <> means not equal. in C it is !=.
I hope it will be easy to you to translate it to C or any other language you want.
Good luck with your project.
Kobi

[vangelderp]

TAPI does seem to pop up a lot.

Have you looked at my code I posted a while back here ?
http://forum.xda-developers.com/viewtopic.php?t=18978

[eefendi]

Hi Vangelderp and Kobi,
thanks for spending your time answering my questions and also thanks for the code provided. I use VB.Net 2003 on programming my pocket PC 2003, you guys provide me the code using pointer data type which is not supported in VB.net, so I am having trouble converting it. ( When I was learning C++, pointer is always make me confuse :roll: ). I wish you guys will be kind enough helping me convert it to VB.Net, just for small part to get Handle. :wink:

Mant Thanks in advance,
Eefendi