 | ||
|
| ||
| ||
|
| ||
PERCLIEN - Client of Persistent Object Servers |
 |
 Tutorial Home |
 Previous Lesson |
Lesson List |
 Next Lesson |
The PERCLIEN sample completes a sequence of four samples that cover persistent COM objects. The first three samples discuss three COM servers that each house COM objects having a different kind of object persistence. The first sample, PERSERVE, shows how to use the IPersistStream interface to give COPageList COM objects their persistence in a stream of a structured storage compound file. The second sample, PERTEXT, shows how to use the IPersistStreamInit interface is used to give COTextPage COM object their persistence in streams. The IPersistStreamInit::InitNew method is covered in detail. The third sample, PERDRAW, shows how to use the IPersistStorage interface to give CODrawPage COM objects their persistence in substorages of a compound file. The IPersistStorage::HandsOffStorage and IPersistStorage::SaveCompleted methods are covered in detail. This sample, PERCLIEN, integrates the use of the three previous servers into a single COM client application.
The PERCLIEN client uses the components in the PERSERVE, PERTEXT, and PERDRAW to build a document editing application that presents a list of pages to users. The user can add, delete, open, and name the page items in the list. When an item is opened, the content appears in a separate window for editing. The separate edit windows are child windows of PERCLIEN's main window. Two types of pages are supported: text pages and drawing pages.
PERCLIEN provides the graphical user interface for editing the page list as well as for editing the content of the two page types. PERCLIEN's CGuiList C++ object encapsulates the editing of the page list in PERCLIEN's main window. CGuiList controls the server-side COPageList object in PERSERVE. PERCLIEN's CGuiText C++ object encapsulates the editing of text pages in separate child windows. CGuiText controls the server-side COTextPage object in PERTEXT. PERCLIEN's CGuiDraw C++ object encapsulates the editing of drawing pages in separate child windows. CGuiDraw controls the server-side CODrawPage object in PERDRAW.
The separate text page windows of CGuiText provide for the editing of text using the standard Win32 multi-line edit control. The separate drawing page windows of CGuiDraw provide the free-form line drawing functionality that appeared in the STOSERVE and STOCLIEN samples.
The PERCLIEN sample relies on each page's persistent COM object to load and store the page's content. PERCLIEN acquires a pointer to the IPersistStream interface on COPageList to control persistent stream storage of the page list. It acquires a pointer to the IPersistStreamInit interface on COTextPage to control persistent stream storage (with InitNew capability) of a text page. It acquires a pointer to the IPersistStorage interface on CODrawPage to control persistent storage in a substorage (with the HandsOffStorage protocol) of a drawing page.
PERCLIEN controls the use of the compound file and provides the COM objects on the server side with appropriate interface pointers for the storages or streams used to store the data. PERSERVE's COPageList COM object exposes the IPersistStream interface and receives an IStream pointer from PERCLIEN. PERTEXT's COTextPage COM object exposes the IPersistStreamInit interface and receives an IStream pointer by PERCLIEN. PERDRAW's CODrawPage COM object exposes the IPersistStorage interface and receives an IStorage pointer by PERCLIEN. These IStorage and IStream interfaces are not implemented inside PERCLIEN or PERSERVE: They are implemented by the COM libraries. When a pointer to one of these interfaces is obtained, their methods are essentially used as a set of services to operate on areas in a compound file. If you have not used streams (IStream) or storages (IStorage) in structured storage compound files, see the STOSERVE and STOCLIEN samples for coverage of this topic.
PERCLIEN manages its structured storage compound file as a kind of document file where the page list and the pages themselves are stored. PERCLIEN loads and saves its page list, text pages, and drawing pages in the structured storage of this compound file. The compound file has a unique format because of the various streams and storages used. PERCLIEN identifies these compound files as page files with a .PAG file extension.
The connectable-object technology that was shown in the CONSERVE and CONCLIEN samples is used between PERCLIEN and the COM objects in its servers. Thus, PERCLIEN implements custom event sink interfaces for the connectable objects in the servers: IPageListSink, ITextPageSink, and IDrawPageSink.
For functional descriptions and a tutorial code tour of PERCLIEN, see the Code Tour section in PERCLIEN.HTM. For details on the external user operation of PERCLIEN, see both the Usage and Operation sections in PERCLIEN.HTM. To read PERCLIEN.HTM, run TUTORIAL.EXE in the main tutorial directory and click the PERCLIEN lesson in the table of lessons. You can also do same thing by double-clicking the PERCLIEN.HTM file after locating it in the main tutorial directory in Windows Explorer. See also PERSERVE.HTM, PERTEXT.HTM, and PERDRAW.HTM in the main tutorial directory for more details on how these servers work and expose their services to PERCLIEN. The makefile for each of the servers automatically registers that server in the system registry, so you must build the PERSERVE, PERTEXT, and PERDRAW servers before you can run PERCLIEN.
For details on setting up your system to build and test the code samples in this COM Tutorial series, see TUTORIAL.HTM. The supplied MAKEFILE is Microsoft NMAKE-compatible. To create a debug build, issue the NMAKE command at the Command Prompt.
PERCLIEN is an application that you can execute directly from Windows in the normal manner or from the Command Prompt window. PERCLIEN accepts an optional file name parameter on the command line. For example:
PERCLIEN c:\pages\mynotes.pag
Where mynotes.pag is a compound file containing pages of text and drawings previously made by PERCLIEN. If no file name argument is specified, PERCLIEN uses the default file name PERCLIEN.PAG and attempts to open it in the same directory as the executing PERCLIEN.EXE.
The client sample and other related samples must be compiled before you can run the client. For more details on building the samples, see Building the Code Samples.
If you have already built the appropriate samples, PERCLIEN.EXE is the client executable to run for this sample.
The PERCLIEN.EXE application provides the user interface for this sample. It uses the associated but independent PERSERVE.DLL, PERTEXT.DLL, and PERDRAW.DLL in-process servers to demonstrate both client and server use of the persistent objects in these servers. The following summarizes the operation from the standpoint of PERCLIEN.EXE as a COM client of those servers.
The PERCLIEN application's main window client area displays the page list for the currently opened page file. PERCLIEN has a main menu helps the user control the page file and items in the page list. The following menu commands are provided.
Menu Selection: File/New
Displays the Save As dialog box to obtain a name and path for a new page file to create. A default .PAG file extension for these files is assumed. The newly created page file becomes the currently open page file. If changes were made to the existing page file before this menu item was chosen, a separate dialog box asks the user if the current page list (and any other open pages) should be saved into its associated compound file.
Menu Selection: File/Open
Displays the Open dialog box to obtain a name and path for an existing page file to open. A default .PAG file extension for these files is assumed. The newly opened page file becomes the currently open page file. If changes were made to the existing page file before this menu item was chosen, a separate dialog box asks the user if the current page list (and any other open pages) should be saved into its associated compound file.
Menu Selection: File/Save
Saves the current drawing into its associated compound file.
Menu Selection: File/Save As
Displays the Save As dialog box to obtain a name and path for a new page file to create. The currently open page list and pages become the saved content of the new file, and the new file becomes the new associated compound file.
Menu Selection: File/Exit
Exits PERCLIEN. If the current page file was changed then a dialog box will ask the user whether a save should be done.
Menu Selection: Page/Open
Opens the page edit window for the page currently selected in the page list.
Menu Selection: Page/Title
Displays a dialog box so the user can edit the list title for the page currently selected in the page list.
Menu Selection: Page/Delete
Deletes the page currently selected in the page list.
Menu Selection: Page/New Text
Creates an empty text page and opens an edit window for it.
Menu Selection: Page/New Drawing
Creates an empty drawing page and opens an edit window for it.
Menu Selection: Help/PERCLIEN Tutorial
Opens the PERCLIEN.HTM tutorial file in the Web browser.
Menu Selection: Help/PERSERVE Tutorial
Opens the PERSERVE.HTM tutorial file in the Web browser.
Menu Selection: Help/PERTEXT Tutorial
Opens the PERTEXT.HTM tutorial file in the Web browser.
Menu Selection: Help/PERDRAW Tutorial
Opens the PERDRAW.HTM tutorial file in the Web browser.
Menu Selection: Help/Read Source File
Displays the Open dialog box so you can open a source file from this lesson or another one in the Windows Notepad.
Menu Selection: Help/About PERCLIEN
Displays the About dialog box for this application.
The PERCLIEN application's text-page window client area displays the currently opened text page. Users edit a the page in a separate window with its own menu that provides for user control of the text page. The following menu commands are available:
Menu Selection: Text/Save
Saves the current text page to the currently open page file.
Menu Selection: Text/Clear
Clears the current text page to a blank text page.
Menu Selection: Text/Exit
Exits the text page. If the text page was changed, a dialog box prompts the user to save the changes.
Menu Selection: Edit/Undo
Undoes the previous editing action.
Menu Selection: Edit/Select All
Selects all text in the text page.
Menu Selection: Edit/Cut
Cuts the currently selected text from the current text page and stores it on the clipboard for later paste.
Menu Selection: Edit/Copy
Copies the currently selected text from the currrent text page and stores it on the clipboard for later paste.
Menu Selection: Edit/Paste
Pastes the text content on the clipboard into the text page at the current cursor.
Menu Selection: Edit/Delete
Deletes the currently selected text from the current text page. This text is not placed on the clipboard.
Menu Selection: Help/PERCLIEN Tutorial
Opens the PERCLIEN.HTM tutorial file in the Web browser.
Menu Selection: Help/PERTEXT Tutorial
Opens the PERTEXT.HTM tutorial file in the Web browser.
Menu Selection: Help/Read Source &File
Displays the Open dialog box so you can use Windows Notepad to open a source file from this or another sample.
Menu Selection: Help/About PERCLIEN
Displays the About dialog box for this application.
The PERCLIEN application's drawing page window client area displays a currently opened drawing page. Users edit this page is provided in a separate window with its own menu that helps the user control the drawing page. The following menu commands are provided:
Menu Selection: Drawing/Save
Saves the current drawing into the currently open page file.
Menu Selection: Drawing/Clear
Clears the current drawing to a blank drawing page.
Menu Selection: Drawing/Exit
Exits the drawing page. If the drawing page was changed, a dialog box prompts the user to save the file.
Menu Selection: Pen/Color
Displays the Choose Color dialog box to obtain a new pen color for drawing.
Menu Selection: Pen/Thin
Chooses the thin width for drawing. A check mark on this menu choice indicates that thin is the current pen width.
Menu Selection: Pen/Medium
Chooses the medium width for drawing. A check mark on this menu choice indicates that medium is the current pen width.
Menu Selection: Pen/Thick
Chooses the thick width for drawing. A check mark on this menu choice indicates that thick is the current pen width.
Menu Selection: Help/PERCLIEN Tutorial
Opens the PERCLIEN.HTM tutorial file in the Web browser.
Menu Selection: Help/PERDRAW Tutorial
Opens the PERDRAW.HTM tutorial file in the Web browser.
Menu Selection: Help/Read Source &File
Displays the Open dialog box so a user can use Windows Notepad to open a source file from this or another lesson.
Menu Selection: Help/About PERCLIEN
Displays the About dialog box for this application.
Files Description
PERCLIEN.TXT Short description of the sample.
MAKEFILE The generic makefile for building the code sample
application of this tutorial lesson.
PERCLIEN.H The include file for the PERCLIEN application.
Contains
class declarations for main window and dialogs.
PERCLIEN.CPP The main implementation file for PERCLIEN.EXE. Has
WinMain
and CMainWindow implementation and the main menu
dispatching.
PERCLIEN.RC The application's resource definition file.
PERCLIEN.ICO The application's main icon resource.
PERCLIEN.PAG A default page file for the application (with two
pages).
RESDEF.H Resource ID definitions for application menu,
strings, etc.
PENCIL.CUR A pencil image for the drawing page window cursor.
GUILIST.H The class declaration for the CGuiList C++ class.
GUILIST.CPP Implementation file for the CGuiList C++ class. Has
user
interface to handle the main page list display
window.
LISTWIN.H The class declaration for the CListWin C++ class.
LISTWIN.CPP Implementation file for the CListWin C++ class.
Encapsulates the list box control used to show the
page list.
LISTSINK.H The class declaration for the COPageListSink COM
object class.
LISTSINK.CPP Implementation file for the COPageListSink COM object
class.
Connectable object notifications of page list events
are
handled by COPageListSink.
PAGEFILE.H The class declaration for the CPageFile C++ class.
PAGEFILE.CPP Implementation file for the CPageFile C++ class.
Encapsulates operations on the .PAG page list
compound file.
GUITEXT.H The class declaration for the CGuiText C++ class.
GUITEXT.CPP Implementaton file for the CGuiText C++ class. Has
the
user interface for the separate editing of text
pages.
TEXTWIN.H The class declaration for the CTextWin C++ class.
TEXTWIN.CPP Implementation file for the CTextWin C++ class.
Encapsulates
the text edit control used to edit text page.s
TEXTSINK.H The class declaration for the COTextPageSink COM
object class.
TEXTSINK.CPP Implementation file for the COTextPageSink COM object
class.
Connectable object notifications of text edit events
are
handled by COTextPageSink.
GUIDRAW.H The class declaration for the CGuiDraw C++ class.
GUIDRAW.CPP Implementation file for the CGuiDraw C++ class. Has
the
user interface for the separate drawing in draw
pages.
DRAWSINK.H The class declaration for the CODrawPageSink COM
object class.
DRAWSINK.CPP Implementation file for the CODrawPageSink COM object
class.
Connectable object notifications of drawing-related
events
are handled by COTextPageSink.
PERCLIEN uses many of the utility classes and services provided by APPUTIL. For more details on APPUTIL, study the APPUTIL library source code in the common APPUTIL directory and APPUTIL.HTM in the main tutorial directory.
This sample focuses mainly on the client's use of the persistence features that are exposed by the persistent objects in the servers. Most of the infrastructure that makes PERCLIEN an application is a straightforward reuse of technology studied in previous samples and is not covered in this lesson. For example, the drawing functionality provided in CGuiDraw windows is very similar to the "scribble" functionality used in the STOCLIEN sample. Other COM-based infastructure is present in PERCLIEN but is not covered. For example, the connectable object sinks in PERCLIEN are very similar to the sink mechanisms studied in several previous samples.
The major topics covered in this code tour are:
The CGuiList, CGuiText, and CGuiDraw C++ classes all encapsulate the GUI behavior of PERCLIEN. As in previous client samples, PERCLIEN uses a CMainWindow that derives from APPUTIL's CVirWindow abstract class. PERCLIEN's CMainWindow::InitInstance method creates the CGuiList object. This object in turn creates the main application window and attempts to load a default page file. Such a load process will be covered in detail below. With a page file loaded, a page list is displayed to the user as the content of a standard Win32 listbox control. This control is encapsulated in the CListWin C++ object (coded in LISTWIN.H and LISTWIN.CPP). The displayed list shows the page number, page type, and title of all the pages in the page file.
With a page list entry selected, the user can open the corresponding page, which calls CGuiList::PageOpen (in GUILIST.CPP). Using the page number of the page to be opened, PageOpen calls IPageList::Get (implemented by the COPageList object in the PERSERVE server) to obtain the page type, title, and data name of the page. The obtained title is used in the page list display. The page type determines whether CGuiText or CGuiDraw is used to create the window for the new page. Both CGuiText and CGuiDraw are C++ classes derived from APPUTIL's CVirWindow abstract class to facilitate greatly their treatment as separate child windows of PERCLIEN's main window.
Both text page and drawing page windows have their own menus. See PERCLIEN.RC for the resource definitions of the menus for the list, text, and drawing windows. The menu commands are handled by respective DoCommand methods: for the main list window see CMainWindow::DoCommand in PERCLIEN.CPP; for the text window see CGuiText::DoCommand in GUITEXT.CPP; and for the drawing window see CGuiDraw::DoCommand in GUIDRAW.CPP.
Every page has a unique internal data name (for example, Text0001 or Drawing0002) and a counter ensures this uniqueness of data names within the page file. The data name is assigned when the page is first created. It is stored persistently in the page list entry for each page. The data name is also used as the name for the stream or storage located elsewhere in the same compound file in which the page's object data is stored. The page type determines whether a stream or storage branch is used to contain the object's data. For the page list itself, an IStream interface is used by COPageList's implementation of IPersistStream. For a text page, an IStream interface is used by COTextPage's implementation of IPersistStreamInit. For a drawing page, an IStorage interface is used by CODrawPage's implementation of IPersistStorage.
If the page being opened is a text page, then CGuiList::PageOpen creates a new CGuiText C++ object and calls CGuiText::OpenWin (in GUITEXT.CPP) to create a separate text page window that has its own menu. After the window is successfully created as a child window of PERCLIEN's main window, OpenWin calls CGuiText::Load to restore the object's data from its persistent storage. We will cover this load of a text page in more detail below.
If the page being opened is a drawing page, then CGuiList::PageOpen creates a new CGuiDraw C++ object and calls CGuiDraw::OpenWin (in GUIDRAW.CPP) to create a separate drawing page window. This window has its own menu. After the window is successfully created as a child window of PERCLIEN's main window, OpenWin calls CGuiDraw::Load to restore the object's data from its persistent storage. This load of a drawing page is covered in more detail below.
CGuiList uses the persistence features of the COPageList object in the PERSERVE.DLL server. It does this in CGuiList::New, CGuiList::Load, CGuiList::Save, and CGuiList::SaveAs. These methods rely on an additional level of encapsulation in the CPageFile C++ object. For example, CGuiList::Load calls CPageFile::Load to load the page list. CPageFile is the heart of PERCLIEN's management of the persistence of the page list. The CPageFile object is first created in CGuiList::Init just after CGuiList is created. We will tour CPageFile and see how it uses COPageList's implementation of IPersistStream. The following is CPageFile::New from PAGEFILE.CPP:
HRESULT CPageFile::New(
TCHAR* pszFileName,
IStorage** ppIStorage,
IPageList** ppIPageList)
{
HRESULT hr = E_POINTER;
BOOL bNewFile = (NULL != pszFileName);
TCHAR* pszFile;
IStorage* pIStorage;
IStream* pIStream;
IPersistStream* pIPersistStream;
IPageList* pIPageList;
ULARGE_INTEGER uliMaxSize;
if (NULL != ppIStorage && NULL != ppIPageList)
{
// Zero the output pointers in case of errror.
*ppIStorage = NULL;
*ppIPageList = NULL;
// If NULL file name passed then use current file name.
pszFile = bNewFile ? pszFileName : m_szCurFileName;
// Use COM service to create a new compound file.
hr = StgCreateDocfile(
pszFile,
STGM_CREATE | STGM_DIRECT | STGM_READWRITE
| STGM_SHARE_EXCLUSIVE,
0,
&pIStorage);
if (SUCCEEDED(hr))
{
// We have created a new compound file. Now store the CLSID
of
// COPageList.
hr = WriteClassStg(pIStorage, m_CidPageList);
if (SUCCEEDED(hr))
{
// Now Create the single 'PageList' stream under the root
storage.
hr = pIStorage->CreateStream(
PAGELIST_USTR,
STGM_CREATE | STGM_WRITE | STGM_DIRECT |
STGM_SHARE_EXCLUSIVE,
0,
0,
&pIStream);
if (SUCCEEDED(hr))
{
// Now use the Class ID to create a COPageList object.
Initially
// ask for the IPageList interface.
hr = CoCreateInstance(
m_CidPageList,
NULL,
CLSCTX_INPROC_SERVER,
IID_IPageList ,
(PPVOID)&pIPageList);
if (SUCCEEDED(hr))
{
// Clear the content of the Page List.
pIPageList->Clear();
// Now obtain the IPersistStream interface on the new
// COPageList object. At this point the client assumes
that
// PageList COM objects support the IPersistStream
interface.
hr = pIPageList->QueryInterface(
IID_IPersistStream,
(PPVOID)&pIPersistStream);
if (SUCCEEDED(hr))
{
// And as expected by this client, COPageList
supports
// the IPersistStream interface. Now use this
interface
// to ask the COPageList object to save an empty
Page List.
// First ask the COPageList object how much space
the
// maximum save would consume and then pre-allocate
that
// space in the stream.
hr =
pIPersistStream->GetSizeMax(&uliMaxSize);
if (SUCCEEDED(hr))
{
hr = pIStream->SetSize(uliMaxSize);
if (SUCCEEDED(hr))
{
// Now save the new Page List into the
// pre-allocated space.
hr = pIPersistStream->Save(pIStream, TRUE);
}
}
// Done with IPersistStream for now so release it.
pIPersistStream->Release();
}
// Done with the stream for now so release it.
pIStream->Release();
}
}
}
}
if (SUCCEEDED(hr))
{
// COPageList is fully created and the page list is
// loaded. Assign a copy of COPageList's IPageList
// interface for use by the caller.
*ppIPageList = pIPageList;
// For performance, keep the Page List 'Document' file
// open (ie, don't release IStorage here) and give the
// caller a copy of the IStorage Pointer.
*ppIStorage = pIStorage;
// The page list was loaded and we have a current compound
// file name. Copy it for later use in saves and loads.
if (bNewFile)
lstrcpy(m_szCurFileName, pszFileName);
}
}
return (hr);
}
The name of the compound file to create is passed to New as the first parameter. StgCreateDocfile expects a Unicode string. When PERCLIEN is compiled for ANSI strings (the UNICODE macro is not defined--which is the default in the makefile), this call actually reduces to a call to an internal APPUTIL function, A_StgCreateDocfile. This function performs the proper conversion of the ANSI pszFile parameter to a Unicode version before calling StgCreateDocfile. For more details, see APPUTIL.H and STOSERVE.HTM.
The New method also receives the addresses of two output pointer variables. When New is done, it assigns an IStorage interface pointer for the root storage of the newly created compound file. New also assigns a pointer to an IPageList interface on the persistent COPageList object that is created to manage the page list data.
The COM standard StgCreateDocfile service function is called to create the compound file in which the page list data will be saved. WriteClassStg stores the CLSID under the root storage for the page list component, making the page list component the main handler of data in .PAG compound files. With a successfully created root storage, a PageList stream is created to hold the persistent object data for COPageList objects. With this stream created, an instance of COPageList is created on the server side by calling CoCreateInstance. The initial interface requested is the native IPageList interface. The COPageList object obtained from the PERSERVE server now saves an empty copy of its persistent object data into the newly created compound file. QueryInterface is called to obtain the IPersistStream interface on COPageList. IPersistStream::GetSize is called to obtain the largest size that the maximum save would consume. IPersistStream::SetSize is then used to reserve that space in the stream. To complete the new persistent COPageList, IPersistStream::Save is called to save an initial copy of the object's persistent data. Since there is no page list yet, no list array is saved, but this does save an initial set of page list properties. Some data must be saved to blank file space even for an "empty" page list. When all this is done successfully, the caller is given a copy of the pointer to the file's root storage and a copy of the pointer to the IPageList interface on the new COPageList object.
If a page list compound file already exists then CPageFile::Load is called to open the root storage of the file, create the COPageList COM object, and load COPageList's persistent data from the storage. The following is CPageFile::Load from PAGEFILE.CPP:
HRESULT CPageFile::Load(
TCHAR* pszFileName,
IStorage** ppIStorage,
IPageList** ppIPageList)
{
HRESULT hr = E_POINTER;
BOOL bNewFile = (NULL != pszFileName);
TCHAR* pszFile;
IStorage* pIStorage;
IStream* pIStream;
IPersistStream* pIPersistStream;
IPageList* pIPageList;
ULARGE_INTEGER uliMaxSize;
if (NULL != ppIStorage && NULL != ppIPageList)
{
// Zero the output pointers in case of errror.
*ppIStorage = NULL;
*ppIPageList = NULL;
// If NULL file name passed then use current file name.
pszFile = bNewFile ? pszFileName : m_szCurFileName;
// Use COM service to check if the file is out there and is
actually
// a valid compound file.
hr = StgIsStorageFile(pszFile);
if (SUCCEEDED(hr))
{
// We have a compound file. Use COM service to open the
compound file
// and obtain a IStorage interface.
hr = StgOpenStorage(
pszFile,
NULL,
STGM_DIRECT | STGM_READWRITE | STGM_SHARE_EXCLUSIVE,
NULL,
0,
&pIStorage);
if (SUCCEEDED(hr))
{
// We have an IStorage. Now get the ClassID of the COM
Server
// that handles Page Files.
hr = ReadClassStg(pIStorage, &m_CidPageList);
if (SUCCEEDED(hr))
{
// We have a ClassID for a server. Now Open the single
'PageList'
// stream under the root storage.
hr = pIStorage->OpenStream(
PAGELIST_USTR,
0,
STGM_READ | STGM_DIRECT | STGM_SHARE_EXCLUSIVE,
0,
&pIStream);
if (SUCCEEDED(hr))
{
// Now use the previously obtained Class ID to create
a
// COPageList object. Initially ask for IPageList
interface.
hr = CoCreateInstance(
m_CidPageList,
NULL,
CLSCTX_INPROC_SERVER,
IID_IPageList ,
(PPVOID)&pIPageList);
if (SUCCEEDED(hr))
{
// We have a new COPageList object. Now obtain the
// IPersistStream interface on it. The client
assumes at
// this point that PageList COM objects support only
the
// IPersistStream interface for their persistence.
hr = pIPageList->QueryInterface(
IID_IPersistStream,
(PPVOID)&pIPersistStream);
if (SUCCEEDED(hr))
{
// And as expected by this client, COPageList
supports
// the IPersistStream interface. Now use this
interface
// to ask the COPageList object to load the Page
List.
hr = pIPersistStream->Load(pIStream);
// Done with IPersistStream for now so release it.
pIPersistStream->Release();
}
else
pIPageList->Release();
}
// Done with the stream for now so release it.
pIStream->Release();
}
}
}
}
else
{
// If there was no existing compound file use COM services
to
// create a new compound file.
hr = StgCreateDocfile(
pszFile,
STGM_CREATE | STGM_DIRECT | STGM_READWRITE
| STGM_SHARE_EXCLUSIVE,
0,
&pIStorage);
if (SUCCEEDED(hr))
{
// We have created a new compound file. Now store the
CLSID of
// COPageList.
hr = WriteClassStg(pIStorage, m_CidPageList);
if (SUCCEEDED(hr))
{
// Now Create the single 'PageList' stream under the
root storage.
hr = pIStorage->CreateStream(
PAGELIST_USTR,
STGM_CREATE | STGM_WRITE | STGM_DIRECT |
STGM_SHARE_EXCLUSIVE,
0,
0,
&pIStream);
if (SUCCEEDED(hr))
{
// Now use the Class ID to create a COPageList object.
Initially
// ask for the IPageList interface.
hr = CoCreateInstance(
m_CidPageList,
NULL,
CLSCTX_INPROC_SERVER,
IID_IPageList ,
(PPVOID)&pIPageList);
if (SUCCEEDED(hr))
{
// We have a new COPageList object. Now obtain the
// IPersistStream interface on it. The client
assumes at
// this point that PageList COM objects support only
the
// IPersistStream interface for their persistence.
hr = pIPageList->QueryInterface(
IID_IPersistStream,
(PPVOID)&pIPersistStream);
if (SUCCEEDED(hr))
{
// And as expected by this client, COPageList
supports
// the IPersistStream interface. Now use this
interface
// to ask the COPageList object to save an empty
Page List.
// First ask the COPageList object how much space
the
// next save would consume and then pre-allocate
that
// space in the stream.
hr =
pIPersistStream->GetSizeMax(&uliMaxSize);
if (SUCCEEDED(hr))
{
hr = pIStream->SetSize(uliMaxSize);
if (SUCCEEDED(hr))
{
// Now save the new Page List into the
// pre-allocated space.
hr = pIPersistStream->Save(pIStream, TRUE);
}
}
// Done with IPersistStream for now so release it.
pIPersistStream->Release();
}
// Done with the stream for now so release it.
pIStream->Release();
}
}
}
}
}
if (SUCCEEDED(hr))
{
// COPageList is fully created and the page list is
// loaded. Assign a copy of COPageList's IPageList
// interface for use by the caller.
*ppIPageList = pIPageList;
// For performance, keep the Page List 'Document' file
// open (ie, don't release IStorage here) and give the
// caller a copy of the IStorage Pointer.
*ppIStorage = pIStorage;
// The page list was loaded and we have a current compound
// file name. Copy it for later use in saves and loads.
if (bNewFile)
lstrcpy(m_szCurFileName, pszFileName);
}
}
return (hr);
}
CPageFile::Load does double duty, either creating a new compound file or opening and loading an existing one. The file path name is passed and the StgIsStorageFile is called to determine if the file exists and is a valid compound file. If the file does not exist or is not a valid compound file, Load creates a new file in the same manner as in the New method above. If the file does exist, the StgOpenStorage function opens the compound file and obtain an IStorage interface pointer to the root storage in the file. All the stored elements of a previously saved page list is assumed present in the root storage branch. ReadClassStg is called to obtain the CLSID to use in creating the persistent COPageList object. The PageList stream is opened with the standard IStorage::OpenStream method. CoCreateInstance is called to create the persistent COPageList object. With COPageList created, the IPageList interface is used to QueryInterface for a pointer to the IPersistStream interface. Using the IPersistStream interface on the COPageList object, IPersistStream::Load directs the object to load its persistent object data from the stream.
CPageFile::Save is called in PERCLIEN to save the currently active COPageList persistent object. The following is CPageFile::Save from PAGEFILE.CPP:
HRESULT CPageFile::Save(
IStorage* pIStorage,
IPageList* pIPageList)
{
HRESULT hr = E_POINTER;
IStream* pIStream;
IPersistStream* pIPersistStream;
if (NULL != pIStorage && NULL != pIPageList)
{
// Obtain the IPersistStream interface on the COPageList
// COM object.
hr = pIPageList->QueryInterface(
IID_IPersistStream,
(PPVOID)&pIPersistStream);
if (SUCCEEDED(hr))
{
// Save if the data is dirty (ie, doesn't match file data).
if (S_FALSE != pIPersistStream->IsDirty())
{
// Use the existing IStorage to Open the single 'PageList'
stream
// under the root storage.
hr = pIStorage->OpenStream(
PAGELIST_USTR,
0,
STGM_WRITE | STGM_DIRECT | STGM_SHARE_EXCLUSIVE,
0,
&pIStream);
if (SUCCEEDED(hr))
{
// Ask the persistent object to save itself in the
stream
// and clear the PageList dirty bit.
hr = pIPersistStream->Save(pIStream, TRUE);
// Done with the stream for now so release it.
pIStream->Release();
}
}
// Done with IPersistStream for now so release it.
pIPersistStream->Release();
}
}
return (hr);
}
A pointer to the IStorage interface for the root storage of the currently open page list compound file is passed as well as a pointer to the IPageList interface for the persistent COPageList object. QueryInterface is called on IPageList to obtain a pointer to COPageList's IPersistStream interface. IPersistStream::IsDirty then asks the object if it needs to be saved. ("Dirty" here means that the object data in RAM does not match the data stored on file.) If the object does not need to be saved then Save releases IPersistStream and returns without saving. If the object does need saving then the IStorage interface is used to open the PageList stream. Note that CPageFile holds interface pointers for the storage and COPageList but does not retain any stream interface pointers. CPageFile freshly opens the stream as needed and closes it when done. With the PageList stream open, IPersistStream::Save is called on the COPageList persistent object to direct it to save its object data.
You have seen how PERCLIEN uses the IPersistStream interface on the persistent COPageList object to load and save the page list. This section describes how PERCLIEN uses the IPersistStreamInit interface on the persistent COTextPage object to load and save text pages. The following is CGuiText::Load from GUITEXT.CPP:
HRESULT CGuiText::Load(void)
{
HRESULT hr = E_FAIL;
IStream* pIStream;
IPersistStreamInit* pIPersistStreamInit;
// Can't do anything without a root storage.
if (NULL != m_pIStorage_Root)
{
// Use the root IStorage to open the existing stream for
// this particular Text Page. Load the data for the text page
from
// the stream. This load internally uses the
IPersistStreamInit
// features in a COTextPage object that is created and
reconstituted
// from persistent storage.
// Open the single stream named by m_wszDataName. It is under
// the root storage.
hr = m_pIStorage_Root->OpenStream(
m_wszDataName,
0,
STGM_READWRITE | STGM_DIRECT | STGM_SHARE_EXCLUSIVE,
0,
&pIStream);
if (SUCCEEDED(hr))
{
// Read the ClassID for the class of Component Objects that
can deal
// with Text Page data.
hr = ReadClassStm(pIStream, &m_CidTextPage);
if (SUCCEEDED(hr))
{
// Now use the obtained Class ID to create a COTextPage
// object. Initially ask for the ITextPage interface.
hr = CoCreateInstance(
m_CidTextPage,
NULL,
CLSCTX_INPROC_SERVER,
IID_ITextPage,
(PPVOID)&m_pITextPage);
if (SUCCEEDED(hr))
{
// We have a new COTextPage object. Now obtain the
// IPersistStreamInit interface on it. At this point in
the
// client we are assuming that COTextPage uses only the
// IPersistStreamInit interface for its persistence.
hr = m_pITextPage->QueryInterface(
IID_IPersistStreamInit,
(PPVOID)&pIPersistStreamInit);
if (SUCCEEDED(hr))
{
// And as expected by this client, COTextPage exposes
// the IPersistStreamInit interface. Now use this
interface
// to ask the COTextPage object to load the Text Page
data.
hr = pIPersistStreamInit->Load(pIStream);
// Done with IPersistStreamInit for now so release it.
pIPersistStreamInit->Release();
}
}
}
// Done with the interface held on the stream.
pIStream->Release();
}
else
{
// If there was no existing Stream then create a new one.
hr = m_pIStorage_Root->CreateStream(
m_wszDataName,
STGM_CREATE | STGM_READWRITE | STGM_DIRECT |
STGM_SHARE_EXCLUSIVE,
0,
0,
&pIStream);
if (SUCCEEDED(hr))
{
// Write the ClassID of the COTextPage component object
class.
hr = WriteClassStm(pIStream, m_CidTextPage);
if (SUCCEEDED(hr))
{
// Now use the Class ID to create a COTextPage
// object. Initially ask for the ITextPage interface.
hr = CoCreateInstance(
m_CidTextPage,
NULL,
CLSCTX_INPROC_SERVER,
IID_ITextPage,
(PPVOID)&m_pITextPage);
if (SUCCEEDED(hr))
{
// We have a new COTextPage object. Now obtain the
// IPersistStreamInit interface on it. At this point
in the
// client we are assuming that COTextPage uses only
the
// IPersistStreamInit interface for its persistence.
hr = m_pITextPage->QueryInterface(
IID_IPersistStreamInit,
(PPVOID)&pIPersistStreamInit);
if (SUCCEEDED(hr))
{
// And as expected by this client, COTextPage
supports
// the IPersistStreamInit interface. Now use this
interface
// to ask the COTextPage object to initialize a new
empty
// text page. Then save it into the stream.
hr = pIPersistStreamInit->InitNew();
if (SUCCEEDED(hr))
hr = pIPersistStreamInit->Save(pIStream, TRUE);
// Done with IPersistStreamInit for now so release
it.
pIPersistStreamInit->Release();
}
}
}
// Done with the interface held on the stream.
pIStream->Release();
if (FAILED(hr))
m_pIStorage_Root->DestroyElement(m_wszDataName);
}
}
}
return hr;
}
Like CPageFile::Load discussed in the preceding section, CGuiText::Load does double duty by either creating a new stream for the text page or opening and loading an existing one. If the text page stream is present it opens and loads from that stream. If the stream is not present, the stream is created and an empty text page is written into the stream. Load assumes the compound file is already opened and that CGuiText::m_pIStorage_Root has the IStorage interface for the file's root storage. Load also assumes that when CGuiText was initialized it was given the data name of the stream where the text page data is stored. This name is kept in CGuiText::m_wszDataName. This name is used to open or create the stream for the text page.
IStorage::OpenStream is called and if the stream exists, the COM ReadClassStm function is called to obtain the CLSID for the server object that can handle text page data. This CLSID is then used in a call to the COM CoCreateInstance function to create the COTextPage COM object in the PERTEXT server. A pointer to the ITextPage interface is initially requested. QueryInterface is also called to obtain a pointer to the IPersistStreamInit interface on the new COTextPage object. IPersistStreamInit::Load is then directs COTextPage to load its persistent object data from the opened stream.
If IStorage::OpenStream indicates that there is no existing stream with the name in m_wszDataName, then IStorage::CreateStream creates a new stream of this name. Because this is a new stream, the WriteClassStm COM function is called to store the CLSID for the class of components that can handle text page data. The COM CoCreateInstance function is called to create the COTextPage object in the PERTEXT server. A pointer to the ITextPage interface is initially requested. QueryInterface is also called to obtain a pointer to the IPersistStreamInit interface on the new COTextPage. Because this is an entirely new instance of COTextPage the IPersistStreamInit::InitNew method is called to initialize the new instance in RAM. With the new instance created, IPersistStreamInit::Save is finally used to save an empty text page into the stream. In contrast to the IPersistStream implementation used for page lists (described above), the InitNew method in IPersistStreamInit adds convenient provisions for initializing the new instance of COTextPage.
CGuiText::Save is called in PERCLIEN to save a currently active COTextPage persistent object. The following is CGuiText::Save from GUITEXT.CPP.
HRESULT CGuiText::Save(void)
{
HRESULT hr = E_FAIL;
HCURSOR hCurWait = LoadCursor(NULL, IDC_WAIT);
HCURSOR hCurPrev;
INT iTextLength;
WCHAR* pwszText;
LARGE_INTEGER liSeek;
IStream* pIStream;
IPersistStreamInit* pIPersistStreamInit;
if (NULL != m_pIStorage_Root && NULL != m_pITextPage)
{
// Change cursor to the hour glass.
hCurPrev = SetCursor(hCurWait);
// Open the single stream named by m_wszDataName. It is under
// the root storage.
hr = m_pIStorage_Root->OpenStream(
m_wszDataName,
0,
STGM_READWRITE | STGM_DIRECT | STGM_SHARE_EXCLUSIVE,
0,
&pIStream);
if (SUCCEEDED(hr))
{
// First ask the edit control how long its text data is.
hr = m_pTextWin->GetLength(&iTextLength);
if (SUCCEEDED(hr))
{
// Allocate some temporary space for the text.
pwszText = new WCHAR[iTextLength+4];
if (NULL != pwszText)
{
// Zero the text string.
memset(pwszText, 0, (iTextLength+2) * sizeof(WCHAR));
// Get the text from the the edit control.
hr = m_pTextWin->GetText(pwszText);
if (SUCCEEDED(hr))
{
// Put the text into the COTextPage object.
hr = m_pITextPage->PutText(pwszText, iTextLength);
if (SUCCEEDED(hr))
{
// Clear the TextWin changed flag.
m_bChanged = FALSE;
// Tell the COTextPage object to save itself
// (via its IPersistStreamInit interface).
hr = m_pITextPage->QueryInterface(
IID_IPersistStreamInit,
(PPVOID)&pIPersistStreamInit);
if (SUCCEEDED(hr))
{
// Recue Stream to start of page text data.
LISet32(liSeek, sizeof(CLSID));
hr = pIStream->Seek(liSeek, STREAM_SEEK_SET,
NULL);
if (SUCCEEDED(hr))
hr = pIPersistStreamInit->Save(pIStream,
TRUE);
// Done with IPersistStreamInit for now so release
it.
pIPersistStreamInit->Release();
}
}
}
// Delete the temporary text buffer.
delete [] pwszText;
}
else
hr = E_OUTOFMEMORY;
}
// Done with the interface held on the stream.
pIStream->Release();
}
// Set Cursor back to what it was.
SetCursor(hCurPrev);
}
return hr;
}
The stream whose name is kept in CGuiText::m_wszDataName is freshly opened and is released at the end. The streams for text pages are not kept open but are opened and closed as needed by CGuiText. With the existing stream open, CGuiText::Save works with the multi-line edit control to obtain a copy of the text of the current text page. The edit control is encapsulated in the CTextWin C++ object. A pointer to this object is kept in CGuiText::m_pTextWin. The text is obtained from CTextWin and ITextPage::PutText is called to put the text into the COTextPage object. COTextPage now has the text in RAM. QueryInterface is called to obtain a pointer to the IPersistStreamInit interface on the COTextPage object. IStream::Seek is called to reset the seek pointer of the stream to its start. Finally, IPersistStreamInit::Save is called to direct the COTextPage object to save its persistent object data to the stream.
This lesson has now explained how PERCLIEN uses the IPersistStream interface on the persistent COPageList object to load and save the page list, and how PERCLIEN uses the IPersistStreamInit interface on the persistent COTextPage object to load and save text pages. This section describes how PERCLIEN uses the IPersistStorage interface on the persistent CODrawPage object to load and save drawing pages. The following is CGuiDraw::Load from GUIDRAW.CPP:
HRESULT CGuiDraw::Load(void)
{
HRESULT hr = E_FAIL;
IPersistStorage* pIPersistStorage;
// Can't do anything without a root storage.
if (NULL != m_pIStorage_Root)
{
// Use the root IStorage to open the nested substorage for
this
// particular DrawPage. Load the drawing data from the
substorage.
// This load internally uses the IPersistStorage features in a
// created CODrawPage object to reconstitute the object from
// persistent storage. CODrawPage handles its own persistence
that
// is client-controlled via its exposed IPersistStorage
interface.
// Open the single storage named by m_wszDataName. It is under
// the root storage. The client here is in charge of the
underlying
// storage that the client asks CODrawPage to use.
hr = m_pIStorage_Root->OpenStorage(
m_wszDataName,
NULL,
STGM_READWRITE | STGM_DIRECT | STGM_SHARE_EXCLUSIVE,
NULL,
0,
&m_pIStorage_Page);
if (SUCCEEDED(hr))
{
// If the storage already exists, read the ClassID for the
class of
// component objects that can deal with DrawPage data.
hr = ReadClassStg(m_pIStorage_Page, &m_CidDrawPage);
if (SUCCEEDED(hr))
{
// Now use the obtained Class ID to create a CODrawPage
// object. Initially ask for the IDrawPage interface.
hr = CoCreateInstance(
m_CidDrawPage,
NULL,
CLSCTX_INPROC_SERVER,
IID_IDrawPage,
(PPVOID)&m_pIDrawPage);
if (SUCCEEDED(hr))
{
// We have a new CODrawPage object. Now obtain the
// IPersistStorage interface on it. At this point in the
// client we are assuming that CODrawPage objects use
only
// the IPersistStorage interface for their persistence.
hr = m_pIDrawPage->QueryInterface(
IID_IPersistStorage,
(PPVOID)&pIPersistStorage);
if (SUCCEEDED(hr))
{
// And as expected by this client, CODrawPage exposes
// the IPersistStorage interface. Now use this
interface
// to ask the CODrawPage object to load the drawing
data.
hr = pIPersistStorage->Load(m_pIStorage_Page);
// Done with IPersistStorage for now so release it.
pIPersistStorage->Release();
}
}
}
}
else
{
// If there was no existing page substorage then create a
new one.
hr = m_pIStorage_Root->CreateStorage(
m_wszDataName,
STGM_CREATE | STGM_READWRITE | STGM_DIRECT |
STGM_SHARE_EXCLUSIVE,
0,
0,
&m_pIStorage_Page);
if (SUCCEEDED(hr))
{
// Write the ClassID of the CODrawPage component object
class.
hr = WriteClassStg(m_pIStorage_Page, m_CidDrawPage);
if (SUCCEEDED(hr))
{
// Now use the Class ID to create a CODrawPage
// object. Initially ask for the IDrawPage interface.
hr = CoCreateInstance(
m_CidDrawPage,
NULL,
CLSCTX_INPROC_SERVER,
IID_IDrawPage,
(PPVOID)&m_pIDrawPage);
if (SUCCEEDED(hr))
{
// We have a new CODrawPage object. Now obtain the
// IPersistStorage interface on it. At this point in
the
// client we are assuming that CODrawPage objects use
only
// the IPersistStorage interface for their
persistence.
hr = m_pIDrawPage->QueryInterface(
IID_IPersistStorage,
(PPVOID)&pIPersistStorage);
if (SUCCEEDED(hr))
{
// And as expected by this client, CODrawPage
supports
// the IPersistStorage interface. Now use this
interface
// to ask the CODrawPage object to initialize a new
empty
// drawing page and save it into the substorage.
hr = pIPersistStorage->InitNew(m_pIStorage_Page);
// Done with IPersistStorage for now so release it.
pIPersistStorage->Release();
}
}
}
if (FAILED(hr))
m_pIStorage_Page->DestroyElement(m_wszDataName);
}
}
}
return hr;
}
Like the other load methods above, CGuiDraw::Load does double duty. It either creates a new storage for the drawing page or it opens and loads an existing one. If the drawing page storage is present, it opens and loads from that storage branch. If the storage is not present, the storage is created and an empty drawing page is written into the storage. Load assumes the compound file is already opened and that CGuiDraw::m_pIStorage_Root has the IStorage interface for the file's root storage. Load also assumes that when CGuiDraw was initialized it was given the data name of the storage where the drawing page data is stored. This name is kept in CGuiDraw::m_wszDataName. This name is used to open or create the storage for the drawing page.
IStorage::OpenStorage is called and if the storage exists, the COM ReadClassStg function obtains the CLSID for the server object that can handle drawing page data. This CLSID is then used in a call to the COM CoCreateInstance function to create the CODrawPage COM object in the PERDRAW server. A pointer to the IDrawPage interface is initially requested. QueryInterface is also called to obtain a pointer to the IPersistStorage interface on the new CODrawPage. IPersistStorage::Load is then used to direct CODrawPage to load its persistent object data from the opened storage.
If IStorage::OpenStorage indicates that there is no existing storage with the name in m_wszDataName, then a new storage of this name is created. IStorage::CreateStorage is called to perform the creation. Because this is a new sub-storage, the WriteClassStg COM function is called to store the CLSID for the class of components that can handle drawing page data. The COM CoCreateInstance function is called to create the CODrawPage object in the PERDRAW server. A pointer to the IDrawPage interface is initially requested. QueryInterface is also called to obtain a pointer to the IPersistStorage interface on the new CODrawPage. Since this is an entirely new instance of CODrawPage the IPersistStorage::InitNew is called to initialize the new CODrawPage persistent object. InitNew initializes CODrawPage's object data in RAM and also saves this empty drawing to the storage.
CGuiDraw::Save is called in PERCLIEN to save a currently active CODrawPage persistent object. The followin is CGuiDraw::Save from GUIDRAW.CPP:
HRESULT CGuiDraw::Save(
void)
{
HRESULT hr = E_FAIL;
HCURSOR hCurWait = LoadCursor(NULL, IDC_WAIT);
HCURSOR hCurPrev;
IPersistStorage* pIPersistStorage;
if (NULL != m_pIStorage_Page && NULL != m_pIDrawPage)
{
// Change cursor to the hour glass.
hCurPrev = SetCursor(hCurWait);
// Tell the CODrawPage object to save itself
// (via its IPersistStorage interface).
hr = m_pIDrawPage->QueryInterface(
IID_IPersistStorage,
(PPVOID)&pIPersistStorage);
if (SUCCEEDED(hr))
{
// Perform the save with fSameAsLoad==TRUE.
hr = pIPersistStorage->Save(m_pIStorage_Page, TRUE);
if (SUCCEEDED(hr))
{
// This is the general save by the client. In the case of
// this application the client does not need to do any
other
// intermediate save or write operations to the compound
file
// prior to informing the server that client save
operations
// are completed.
hr = pIPersistStorage->SaveCompleted(NULL);
}
// Done with IPersistStorage for now so release it.
pIPersistStorage->Release();
}
// Set Cursor back to what it was.
SetCursor(hCurPrev);
}
return hr;
}
The CGuiDraw object uses the copy of the IDrawPage interface pointer it keeps in member m_pIDrawPage to QueryInterface for a pointer to the IPersistStorage interface on the CODrawPage object. IPersistStorage::Save is called to direct CODrawPage to save its persistent object data to the already opened storage (m_pIStorage_Page). Finally, IPersistStorage::SaveCompleted is called to complete the save operation. Other intervening save or write actions could be performed between the Save and the SaveCompleted but are not needed in this application.
Did you find this material useful? Gripes? Compliments? Suggestions for other articles? Write us!
© 1999 Microsoft Corporation. All rights reserved. Terms of use.
Back to top