115 lines
4 KiB
C
115 lines
4 KiB
C
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//------------------------------------------------------------------------------
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// File: PStream.h
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//
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// Desc: DirectShow base classes - defines a class for persistent properties
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// of filters.
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//
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// Copyright (c) 1992-2001 Microsoft Corporation. All rights reserved.
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//------------------------------------------------------------------------------
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#ifndef __PSTREAM__
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#define __PSTREAM__
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// Base class for persistent properties of filters
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// (i.e. filter properties in saved graphs)
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// The simplest way to use this is:
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// 1. Arrange for your filter to inherit this class
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// 2. Implement in your class WriteToStream and ReadFromStream
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// These will override the "do nothing" functions here.
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// 3. Change your NonDelegatingQueryInterface to handle IPersistStream
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// 4. Implement SizeMax to return the number of bytes of data you save.
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// If you save UNICODE data, don't forget a char is 2 bytes.
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// 5. Whenever your data changes, call SetDirty()
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//
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// At some point you may decide to alter, or extend the format of your data.
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// At that point you will wish that you had a version number in all the old
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// saved graphs, so that you can tell, when you read them, whether they
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// represent the old or new form. To assist you in this, this class
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// writes and reads a version number.
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// When it writes, it calls GetSoftwareVersion() to enquire what version
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// of the software we have at the moment. (In effect this is a version number
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// of the data layout in the file). It writes this as the first thing in the data.
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// If you want to change the version, implement (override) GetSoftwareVersion().
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// It reads this from the file into mPS_dwFileVersion before calling ReadFromStream,
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// so in ReadFromStream you can check mPS_dwFileVersion to see if you are reading
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// an old version file.
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// Normally you should accept files whose version is no newer than the software
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// version that's reading them.
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// CPersistStream
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//
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// Implements IPersistStream.
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// See 'OLE Programmers Reference (Vol 1):Structured Storage Overview' for
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// more implementation information.
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class CPersistStream : public IPersistStream {
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private:
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// Internal state:
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protected:
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DWORD mPS_dwFileVersion; // version number of file (being read)
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BOOL mPS_fDirty;
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public:
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// IPersistStream methods
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STDMETHODIMP IsDirty()
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{return (mPS_fDirty ? S_OK : S_FALSE);} // note FALSE means clean
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STDMETHODIMP Load(LPSTREAM pStm);
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STDMETHODIMP Save(LPSTREAM pStm, BOOL fClearDirty);
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STDMETHODIMP GetSizeMax(ULARGE_INTEGER * pcbSize)
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// Allow 24 bytes for version.
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{ pcbSize->QuadPart = 12*sizeof(WCHAR)+SizeMax(); return NOERROR; }
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// implementation
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CPersistStream(IUnknown *punk, HRESULT *phr);
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~CPersistStream();
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HRESULT SetDirty(BOOL fDirty)
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{ mPS_fDirty = fDirty; return NOERROR;}
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// override to reveal IPersist & IPersistStream
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// STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void **ppv);
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// --- IPersist ---
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// You must override this to provide your own class id
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STDMETHODIMP GetClassID(CLSID *pClsid) PURE;
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// overrideable if you want
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// file version number. Override it if you ever change format
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virtual DWORD GetSoftwareVersion(void) { return 0; }
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//=========================================================================
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// OVERRIDE THESE to read and write your data
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// OVERRIDE THESE to read and write your data
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// OVERRIDE THESE to read and write your data
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virtual int SizeMax() {return 0;}
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virtual HRESULT WriteToStream(IStream *pStream);
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virtual HRESULT ReadFromStream(IStream *pStream);
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//=========================================================================
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private:
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};
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// --- Useful helpers ---
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// Writes an int to an IStream as UNICODE.
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STDAPI WriteInt(IStream *pIStream, int n);
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// inverse of WriteInt
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STDAPI_(int) ReadInt(IStream *pIStream, HRESULT &hr);
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#endif // __PSTREAM__
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