Contributor: LEE ARONER
{
I've been puzzling over Share myself the last week. Here's some
tips from what I've found:
1. Remember, if you are trying to write to the same region from
both processes, you will *still* get a sharing violation with
access denied to the last one to ask ! There is a subfunc, (440Bh
I think) for changing the default number of tries that share will
retry for access. You might want to look into that. Otherwise you
could use something like the OpenTxtFile routine below, modified
for use on non-text files, or both. (You aren't trying to share
text files are you? If so, there IS a way to do it, let me know).
2. Also note that you set the filemode AFTER assignment, and
BEFORE a reset, rewrite or append.
3. The following are 2 functions I've put together to handle my
stuff. Note that the first is for non-text files, the second is
for text files. The text file routine uses an external TFDD unit
to set up the filemode variable so it works with text files.
Holler if you want the unit also.........
(* Call this to lock or unlock the ENTIRE file
****** use lock =00ドル & unlock = 01ドル constants for action *********
***** SHARE.EXE MUST be loaded ! *******
Do NOT use on Text Files ! will NOT work !
You could modify this to only lock certain regions by passing values
for a start and stop region. Load CX/DX and DI/SI as done below. *)
}
Function LockFile(var f; action:byte):boolean;
Var
fsize : longint;
Begin
if GotShare then (* Share loaded ? *)
begin
fsize := longint(filesize(file(f))); (* Get filesize *)
Regs.AH := 5ドルC; (* Subfunc *)
Regs.AL := Action; (* 00ドル=Lock or 01ドル=unlock *)
Regs.BX := FileRec(f).Handle; (* Git the handle *)
Regs.CX := Hi(00ドル); (* Start of file *)
Regs.DX := Lo(00ドル);
Regs.DI := Lo(fsize); (* Compute end of file *)
Regs.SI := Hi(fsize);
Intr(21,ドル Regs);
if ((Regs.FLAGS and 01ドル) = 0) then LockFile := true
else
begin
IORes := regs.AX; (* If fails, errcode is in AX *)
LockFile := false; (* IORes is a global that gets *)
end; (* used in IOReport if an error *)
end;
End;
(*-------------------------------------------------------------*)
(* Share compatable Will retry if access denied, tries times
5 Tries is equivilent to a 1/2 second wait
----- Sharing Method -----
Access Compatibility Deny Deny Deny Deny
Method Mode Both Write Read None
---------------------------------------------------------
Read Only 0 16 32 48 64
Write Only 1 17 33 49 65
Read/Write 2* 18 34 50 66
* = default *)
FUNCTION OpenTxtFile(var f; fname:string; tries:word):boolean;
VAR
i : word;
Begin
i := 0;
if GotShare then (* Share loaded ? *)
begin
AssignText(text(f),Fname); (* From TxtShare unit *)
FileMode := 34; (* Open in r/w-deny write mode *)
end
else Assign(text(f),Fname);
Repeat
{$I-} Reset(text(f));
IORes := IoResult; {$I+}
if IORes = 5 then (* Only repeat if denied access *)
begin
wait(100); (* Wait 1/10 second before retry *)
INC(i); (* Use your own delay routine here *)
end
else i := tries; (* Quit if not a sharing deny *)
Until (IORes = 0) OR (i>= tries);
if GotShare then FileMode := 2; (* Set FileMode to default *)
OpenTxtFile := IORes = 0;
End;
{ ****** Here's a quick SHARE detect routine ********* }
Function ShareInstalled : boolean; assembler;
asm
mov ax,1000ドル
int 2ドルf
end;