多进程共享内存的MemoryStream

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具体用处呢,有很多,比如多进程浏览器共享Cookie啦,多个进程传送点数据啦.

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共享内存封装. 封装成了MemoryStream的形式. 用法如下:   var     ms : TShareMemStream;   ms := TShareMemStream.Create('Global\test', FILE_MAP_ALL_ACCESS, 4096);   if (ms.Memory <> nil)(*and(ms.AlreadyExists)*) then   //如果创建失败Memory指针是空指针   //AlreadyExists表示已经存在了,也就是之前被别人(也许是别的进程)创建过了.   begin     //获取锁,多个进程线程访问安全访问     if ms.GetLock(INFINITE) then     begin       ms.read(...);       ms.write(...);       //释放锁       ms.ReleaseLock();     end;   end;   ms.free;

 

共享类原文件如下：

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unit ShareMemoryStream;    interface    uses   SysUtils, Classes, Syncobjs,   Windows;    type   TShareMemStream = class(TCustomMemoryStream)   private     FFile: THandle;     FSize: Int64;     FEvent: TEvent;     FAlreadyExists: Boolean;   protected     property Event: TEvent read FEvent;   public     constructor Create(const ShareName: string;       ACCESS: DWORD = FILE_MAP_ALL_ACCESS; ASize: Int64 = 16 * 1024 * 1024);     destructor Destroy; override;        function Write(const Buffer; Count: Integer): Longint; override;        function GetLock(ATimeOut: DWORD = INFINITE): Boolean;     procedure ReleaseLock();        property AlreadyExists: Boolean read FAlreadyExists;   end;    implementation    procedure InitSecAttr(var sa: TSecurityAttributes; var sd: TSecurityDescriptor); begin   sa.nLength := sizeOf(sa);   sa.lpSecurityDescriptor := @sd;   sa.bInheritHandle := false;   InitializeSecurityDescriptor(@sd, SECURITY_DESCRIPTOR_REVISION);   SetSecurityDescriptorDacl(@sd, true, nil, false); end;    { TShareMem }    constructor TShareMemStream.Create(const ShareName: string; ACCESS: DWORD;   ASize: Int64); var   sa: TSecurityAttributes;   sd: TSecurityDescriptor;   lprotect: DWORD;   e: Integer; begin   FEvent := TEvent.Create(nil, false, true, ShareName +     '_TShareMemStream_Event');   FSize := ASize;   InitSecAttr(sa, sd);      ACCESS := ACCESS and (not SECTION_MAP_EXECUTE);      if (ACCESS and FILE_MAP_WRITE) = FILE_MAP_WRITE then     lprotect := PAGE_READWRITE   else if (ACCESS and FILE_MAP_READ) = FILE_MAP_READ then     lprotect := PAGE_READONLY;      FFile := CreateFileMapping(INVALID_HANDLE_VALUE, @sa, lprotect,     Int64Rec(FSize).Hi, Int64Rec(FSize).Lo, PChar(ShareName));   e := GetLastError;   if FFile = 0 then     Exit;   FAlreadyExists := e = ERROR_ALREADY_EXISTS;   SetPointer(MapViewOfFile(FFile, ACCESS, 0, 0, Int64Rec(FSize).Lo),     Int64Rec(FSize).Lo); end;    destructor TShareMemStream.Destroy; begin   if Memory <> nil then   begin     UnmapViewOfFile(Memory);     SetPointer(nil, 0);     Position := 0;   end;   if FFile <> 0 then   begin     CloseHandle(FFile);     FFile := 0;   end;   FEvent.Free;   inherited Destroy; end;    function TShareMemStream.GetLock(ATimeOut: DWORD): Boolean; var   wr : TWaitResult; begin   wr := FEvent.WaitFor(ATimeOut);   Result := wr = wrSignaled; end;    procedure TShareMemStream.ReleaseLock; begin   FEvent.SetEvent; end;    function TShareMemStream.Write(const Buffer; Count: Integer): Longint; begin   Result := 0;   if (Size - Position) >= Count then   begin     System.Move(Buffer, PByte(Memory)[Position], Count);     Position := Position + Count;     Result := Count;   end; end;    end.