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OtlContainerObserver.pas
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OtlContainerObserver.pas
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///<summary>Observer pattern interface for the containers unit.
/// Part of the OmniThreadLibrary project.</summary>
///<author>Primoz Gabrijelcic</author>
///<license>
///This software is distributed under the BSD license.
///
///Copyright (c) 2009 Primoz Gabrijelcic
///All rights reserved.
///
///Redistribution and use in source and binary forms, with or without modification,
///are permitted provided that the following conditions are met:
///- Redistributions of source code must retain the above copyright notice, this
/// list of conditions and the following disclaimer.
///- Redistributions in binary form must reproduce the above copyright notice,
/// this list of conditions and the following disclaimer in the documentation
/// and/or other materials provided with the distribution.
///- The name of the Primoz Gabrijelcic may not be used to endorse or promote
/// products derived from this software without specific prior written permission.
///
///THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
///ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
///WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
///DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
///ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
///(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
///LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
///ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
///(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
///SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
///</license>
///<remarks><para>
/// Author : Primoz Gabrijelcic
/// Creation date : 2009-02-19
/// Last modification : 2010-07-01
/// Version : 1.04
///</para><para>
/// History:
/// 1.04: 2010-07-01
/// - Includes OTLOptions.inc.
/// 1.03: 2009-12-22
/// - TOmniContainerSubject moved here from OtlContainers because it will also be
/// used in OtlCollections.
/// 1.02: 2009-11-15
/// - Windows message observer exposes some of its internals.
/// 1.01: 2009-04-06
/// - External event can be provided in the TOmniContainerWindowsEventObserverImpl
/// constructor.
/// - Event is created in TOmniContainerWindowsEventObserverImpl constructor if external
/// event is not provided.
/// 1.0: 2009-03-30
/// - First official release.
///</para></remarks>
unit OtlContainerObserver;
{$I OtlOptions.inc}
{$WARN SYMBOL_PLATFORM OFF} // Win32Check
interface
uses
Classes,
OtlSync,
GpStuff;
type
///<summary>All possible actions observer can take interest in.</summary>
TOmniContainerObserverInterest = (
//Interests with permanent subscription:
coiNotifyOnAllInserts, coiNotifyOnAllRemoves,
//Interests with one-shot subscription:
coiNotifyOnPartlyEmpty, coiNotifyOnAlmostFull
);
///<summary>Container observer. Class based for performance.</summary>
TOmniContainerObserver = class
strict private
coIsActivated: TGp4AlignedInt;
public
constructor Create;
procedure Activate; inline;
function CanNotify: boolean; inline;
procedure Deactivate; inline;
procedure Notify; virtual; abstract;
end; { TOmniContainerObserver }
TOmniContainerWindowsEventObserver = class(TOmniContainerObserver)
public
function GetEvent: THandle; virtual; abstract;
end; { TOmniContainerWindowsEventObserver }
TOmniContainerWindowsMessageObserver = class(TOmniContainerObserver)
strict protected
function GetHandle: THandle; virtual; abstract;
public
procedure Send(aMessage: cardinal; wParam, lParam: integer); virtual; abstract;
property Handle: THandle read GetHandle;
end; { TOmniContainerWindowsMessageObserver }
TOmniContainerSubject = class
strict private
csListLocks : array [TOmniContainerObserverInterest] of TOmniMREW;
csObserverLists: array [TOmniContainerObserverInterest] of TList;
public
constructor Create;
destructor Destroy; override;
procedure Attach(const observer: TOmniContainerObserver;
interest: TOmniContainerObserverInterest);
procedure Detach(const observer: TOmniContainerObserver;
interest: TOmniContainerObserverInterest);
procedure Notify(interest: TOmniContainerObserverInterest);
procedure NotifyOnce(interest: TOmniContainerObserverInterest);
procedure Rearm(interest: TOmniContainerObserverInterest);
end; { TOmniContainerSubject }
function CreateContainerWindowsEventObserver(externalEvent: THandle = 0):
TOmniContainerWindowsEventObserver;
function CreateContainerWindowsMessageObserver(hWindow: THandle; msg: cardinal;
wParam, lParam: integer): TOmniContainerWindowsMessageObserver;
implementation
uses
Windows,
SysUtils,
{$IFDEF OTL_HasSystemTypes}
System.Types,
{$ENDIF}
DSiWin32,
OtlCommon;
type
TOmniContainerWindowsEventObserverImpl = class(TOmniContainerWindowsEventObserver)
strict private
cweoEvent : THandle;
cweoEventIsExternal: boolean;
public
constructor Create(externalEvent: THandle = 0);
destructor Destroy; override;
function GetEvent: THandle; override;
procedure Notify; override;
end; { TOmniContainerWindowsEventObserverImpl }
TOmniContainerWindowsMessageObserverImpl = class(TOmniContainerWindowsMessageObserver)
strict private
cwmoHandle : THandle;
cwmoLParam : integer;
cwmoMessage : cardinal;
cwmoWParam : integer;
strict protected
function GetHandle: THandle; override;
public
constructor Create(handle: THandle; aMessage: cardinal; wParam, lParam: integer);
procedure Send(aMessage: cardinal; wParam, lParam: integer); override;
procedure Notify; override;
end; { TOmniContainerWindowsMessageObserver }
{ exports }
function CreateContainerWindowsEventObserver(externalEvent: THandle):
TOmniContainerWindowsEventObserver;
begin
Result := TOmniContainerWindowsEventObserverImpl.Create(externalEvent);
end; { CreateContainerWindowsEventObserver }
function CreateContainerWindowsMessageObserver(hWindow: THandle; msg: cardinal; wParam,
lParam: integer): TOmniContainerWindowsMessageObserver;
begin
Result := TOmniContainerWindowsMessageObserverImpl.Create(hWindow, msg, wParam, lParam);
end; { CreateContainerWindowsMessageObserver }
{ TOmniContainerObserver }
constructor TOmniContainerObserver.Create;
begin
inherited;
Activate;
end; { TOmniContainerObserver.Create }
procedure TOmniContainerObserver.Activate;
begin
coIsActivated.Value := 1;
end; { TOmniContainerObserver.Activate }
function TOmniContainerObserver.CanNotify: boolean;
begin
Result := (InterlockedCompareExchange(PInteger(coIsActivated.Addr)^, 0, 1) = 1);
end; { TOmniContainerObserver.CanNotify }
procedure TOmniContainerObserver.Deactivate;
begin
coIsActivated.Value := 0;
end; { TOmniContainerObserver.Deactivate }
{ TOmniContainerWindowsEventObserverImpl }
constructor TOmniContainerWindowsEventObserverImpl.Create(externalEvent: THandle);
begin
if externalEvent <> 0 then begin
cweoEvent := externalEvent;
cweoEventIsExternal := true;
end
else begin
cweoEvent := Windows.CreateEvent(nil, false, false, nil);
cweoEventIsExternal := false;
end;
end; { TOmniContainerWindowsEventObserverImpl.Create }
destructor TOmniContainerWindowsEventObserverImpl.Destroy;
begin
if not cweoEventIsExternal then
DSiCloseHandleAndNull(cweoEvent);
cweoEvent := 0;
inherited;
end; { TOmniContainerWindowsEventObserverImpl.Destroy }
function TOmniContainerWindowsEventObserverImpl.GetEvent: THandle;
begin
Result := cweoEvent;
end; { TOmniContainerWindowsEventObserverImpl.GetEvent }
procedure TOmniContainerWindowsEventObserverImpl.Notify;
begin
Win32Check(SetEvent(GetEvent));
end; { TOmniContainerWindowsEventObserverImpl.Notify }
{ TOmniContainerWindowsMessageObserver }
constructor TOmniContainerWindowsMessageObserverImpl.Create(handle: THandle; aMessage:
cardinal; wParam, lParam: integer);
begin
inherited Create;
cwmoHandle := handle;
cwmoMessage := aMessage;
cwmoWParam := wParam;
cwmoLParam := lParam;
end; { TOmniContainerWindowsMessageObserver.Create }
function TOmniContainerWindowsMessageObserverImpl.GetHandle: THandle;
begin
Result := cwmoHandle;
end; { TOmniContainerWindowsMessageObserverImpl.GetHandle }
procedure TOmniContainerWindowsMessageObserverImpl.Notify;
begin
Win32Check(PostMessage(cwmoHandle, cwmoMessage, cwmoWParam, cwmoLParam));
end; { TOmniContainerWindowsMessageObserver.Notify }
procedure TOmniContainerWindowsMessageObserverImpl.Send(aMessage: cardinal;
wParam, lParam: integer);
begin
Win32Check(PostMessage(cwmoHandle, aMessage, wParam, lParam));
end; { TOmniContainerWindowsMessageObserverImpl.Send }
{ TOmniContainerSubject }
constructor TOmniContainerSubject.Create;
var
interest: TOmniContainerObserverInterest;
begin
inherited Create;
for interest := Low(TOmniContainerObserverInterest) to High(TOmniContainerObserverInterest) do
csObserverLists[interest] := TList.Create;
end; { TOmniContainerSubject.Create }
destructor TOmniContainerSubject.Destroy;
var
interest: TOmniContainerObserverInterest;
begin
for interest := Low(TOmniContainerObserverInterest) to High(TOmniContainerObserverInterest) do begin
csObserverLists[interest].Free;
csObserverLists[interest] := nil;
end;
inherited;
end; { TOmni ContainerSubject.Destroy }
procedure TOmniContainerSubject.Attach(const observer: TOmniContainerObserver;
interest: TOmniContainerObserverInterest);
begin
csListLocks[interest].EnterWriteLock;
try
if csObserverLists[interest].IndexOf(observer) < 0 then
csObserverLists[interest].Add(observer);
finally csListLocks[interest].ExitWriteLock; end;
end; { TOmniContainerSubject.Attach }
procedure TOmniContainerSubject.Detach(const observer: TOmniContainerObserver;
interest: TOmniContainerObserverInterest);
begin
csListLocks[interest].EnterWriteLock;
try
csObserverLists[interest].Remove(observer);
finally csListLocks[interest].ExitWriteLock; end;
end; { TOmniContainerSubject.Detach }
procedure TOmniContainerSubject.Notify(interest: TOmniContainerObserverInterest);
var
iObserver: integer;
list : TList;
begin
{$R-}
csListLocks[interest].EnterReadLock;
try
list := csObserverLists[interest];
for iObserver := 0 to list.Count - 1 do begin
TOmniContainerObserver(list[iObserver]).Notify;
end;
finally csListLocks[interest].ExitReadLock; end;
{$R+}
end; { TOmniContainerSubject.Notify }
procedure TOmniContainerSubject.NotifyOnce(interest: TOmniContainerObserverInterest);
var
iObserver: integer;
list : TList;
observer : TOmniContainerObserver;
begin
{$R-}
csListLocks[interest].EnterReadLock;
try
list := csObserverLists[interest];
for iObserver := 0 to list.Count - 1 do begin
observer := TOmniContainerObserver(list[iObserver]);
if observer.CanNotify then begin
observer.Notify;
observer.Deactivate;
end;
end;
finally csListLocks[interest].ExitReadLock; end;
{$R+}
end; { TOmniContainerSubject.NotifyAndRemove }
procedure TOmniContainerSubject.Rearm(interest: TOmniContainerObserverInterest);
var
iObserver: integer;
list : TList;
begin
{$R-}
csListLocks[interest].EnterReadLock;
try
list := csObserverLists[interest];
for iObserver := 0 to list.Count - 1 do
TOmniContainerObserver(list[iObserver]).Activate;
finally csListLocks[interest].ExitReadLock; end;
{$R+}
end; { TOmniContainerSubject.Rearm }
end.