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{%mainunit fpgfx.pas}
// fpGFX internal message queue implementation
type
// a simlpe linked list implementation
TMessageListElement = class
protected
Next: TMessageListElement;
Prev: TMessageListElement;
public
msg: TfpgMessageRec;
end;
var
// to make things easier we have a few global variable that will get set
UsedFirstMessage: TMessageListElement;
UsedLastMessage: TMessageListElement;
FreeFirstMessage: TMessageListElement;
FreeLastMessage: TMessageListElement;
procedure MsgListInsertElement(Elem: TMessageListElement; var First: TMessageListElement; var Last: TMessageListElement);
begin
Elem.Prev := nil;
Elem.Next := nil;
if First = nil then
begin
First := Elem;
Last := Elem;
end
else
begin
Last.Next := Elem;
Elem.Prev := Last;
Last := Elem;
end;
end;
procedure MsgListRemoveElement(Elem: TMessageListElement; var First: TMessageListElement; var Last: TMessageListElement);
begin
if Elem = First then
First := Elem.Next;
if Elem = Last then
Last := Elem.Prev;
if Elem.Next <> nil then
Elem.Next.Prev := Elem.Prev;
if Elem.Prev <> nil then
Elem.Prev.Next := Elem.Next;
end;
function pgfAllocateMessage: PfpgMessageRec;
var
e: TMessageListElement;
begin
e := FreeFirstMessage;
if e <> nil then
begin
MsgListRemoveElement(e, FreeFirstMessage, FreeLastMessage);
MsgListInsertElement(e, UsedFirstMessage, UsedLastMessage);
result := @(e.msg);
end
else
result := nil;
end;
procedure fpgDeleteFirstMessage;
var
e: TMessageListElement;
begin
e := UsedFirstMessage;
if e <> nil then
begin
MsgListRemoveElement(e, UsedFirstMessage, UsedLastMessage);
MsgListInsertElement(e, FreeFirstMessage, FreeLastMessage);
end;
end;
function fpgGetFirstMessage: PfpgMessageRec;
begin
if UsedFirstMessage <> nil then
Result := @(UsedFirstMessage.msg)
else
Result := nil;
end;
procedure fpgInitMsgQueue;
var
n: integer;
e: TMessageListElement;
begin
UsedFirstMessage := nil;
UsedLastMessage := nil;
FreeFirstMessage := nil;
FreeLastMessage := nil;
for n := 1 to cMessageQueueSize do
begin
e := TMessageListElement.Create;
MsgListInsertElement(e,FreeFirstMessage,FreeLastMessage);
end;
end;
procedure fpgPostMessage(Sender, Dest: TObject; MsgCode: integer; var aparams: TfpgMessageParams); overload;
var
p: PfpgMessageRec;
begin
if Dest = nil then
Exit; //==>
p := pgfAllocateMessage;
if p <> nil then
begin
p^.MsgCode := MsgCode;
p^.Sender := Sender;
p^.Dest := Dest;
p^.Params := aparams;
end
else
Writeln('THE MESSAGE QUEUE IS FULL.');
end;
procedure fpgPostMessage(Sender, Dest: TObject; MsgCode: integer); overload;
var
p: PfpgMessageRec;
begin
if Dest = nil then
Exit; //==>
p := pgfAllocateMessage;
if p <> nil then
begin
p^.MsgCode := MsgCode;
p^.Sender := Sender;
p^.Dest := Dest;
end
else
Writeln('THE MESSAGE QUEUE IS FULL.');
end;
procedure fpgSendMessage(Sender, Dest: TObject; MsgCode: integer; var aparams: TfpgMessageParams); overload;
var
m: TfpgMessageRec;
begin
if Dest = nil then
Exit; //==>
m.MsgCode := MsgCode;
m.Sender := Sender;
m.Dest := Dest;
m.Params := aparams;
m.Dest.Dispatch(m)
end;
procedure fpgSendMessage(Sender, Dest: TObject; MsgCode: integer); overload;
var
m: TfpgMessageRec;
begin
if Dest = nil then
Exit; //==>
m.MsgCode := MsgCode;
m.Sender := Sender;
m.Dest := Dest;
m.Dest.Dispatch(m)
end;
procedure fpgDeliverMessage(var msg: TfpgMessageRec);
begin
if msg.MsgCode = FPGM_KILLME then
msg.Dest.Free
else
msg.Dest.Dispatch(msg);
end;
procedure fpgDeliverMessages;
var
mp: PfpgMessageRec;
m: TfpgMessageRec;
begin
repeat
mp := fpgGetFirstMessage;
if mp <> nil then
begin
m := mp^;
fpgDeleteFirstMessage;
fpgDeliverMessage(m);
end;
until mp = nil;
end;
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