I am trying to create a multiuser environment by locking and unlocking
records.
However, I am having difficulty in locking record numbers 48 and above in
my
typed random access file. The last error returned is always
87 (Parameter Invalid). Record numbers 0 to 47 lock without a problem.
My record size is 1416.
Please, could someone tell me what I am doing wrong ?
If possible please mail me direct at:
infoafr...@dial.pipex.co.za
//I have declared these variables global
var
TestTypedFile_Handle: word;
error_no: longint;
//Click this button to open the file in sharing mode
procedure TForm1.ButtonOpenTypedShareClick(Sender: TObject);
var
fn_pchar: PChar;
A: array[0..127] of char; //Assume maximum 128 character path name
size_in_bytes: dword;
begin
//Open typed file in SHARE mode
new(fn_pchar);
TestTypedFile_Handle := CreateFile(StrPCopy(A,TestTyped_fn),
GENERIC_READ OR GENERIC_WRITE,
FILE_SHARE_READ OR FILE_SHARE_WRITE,
nil, //No security attributes
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL OR
FILE_FLAG_RANDOM_ACCESS,
0);
dispose(fn_pchar);
error_no := GetLastError;
end;
//Click this button to lock record number 48
procedure TForm1.ButtonLockClick(Sender: TObject);
var
locked: boolean;
begin
locked := LockTypedRec(48);
end;
//Lock specified record number in TestTypedFile with handle:
TestTypedFile_handle
function TForm1.LockTypedRec(rec: dword): boolean;
var
locked: boolean;
RecSize: dword;
RecOffset: dword;
begin
LockTypedRec := FALSE;
//Get size of record to be locked
RecSize := SizeOf(Client_RecType);
//Get offset of record to be locked
RecOffset := (rec-1)*RecSize;
//Lock record
locked := LockFile(TestTypedFile_Handle,
LoWord(RecOffset), HiWord(RecOffset),
LoWord(RecSize), HiWord(RecSize));
if NOT locked then begin
error_no := GetLastError;
ShowMessage(IntToStr(error_no));
//error_no is always 87 (Parameter invalid) if I attempt to lock
record
//number 48 and up. Record size is 1416.
end;
LockTypedRec := locked;
end;
