75 lines
2.8 KiB
C++
75 lines
2.8 KiB
C++
//------------------------------------------------------------------------------
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// File: Cache.h
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//
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// Desc: DirectShow base classes - efines a non-MFC generic cache class.
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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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/* This class implements a simple cache. A cache object is instantiated
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with the number of items it is to hold. An item is a pointer to an
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object derived from CBaseObject (helps reduce memory leaks). The cache
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can then have objects added to it and removed from it. The cache size
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is fixed at construction time and may therefore run out or be flooded.
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If it runs out it returns a NULL pointer, if it fills up it also returns
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a NULL pointer instead of a pointer to the object just inserted */
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/* Making these classes inherit from CBaseObject does nothing for their
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functionality but it allows us to check there are no memory leaks */
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/* WARNING Be very careful when using this class, what it lets you do is
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store and retrieve objects so that you can minimise object creation
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which in turns improves efficiency. However the object you store is
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exactly the same as the object you get back which means that it short
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circuits the constructor initialisation phase. This means any class
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variables the object has (eg pointers) are highly likely to be invalid.
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Therefore ensure you reinitialise the object before using it again */
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#ifndef __CACHE__
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#define __CACHE__
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class CCache : CBaseObject {
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/* Make copy constructor and assignment operator inaccessible */
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CCache(const CCache &refCache);
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CCache &operator=(const CCache &refCache);
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private:
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/* These are initialised in the constructor. The first variable points to
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an array of pointers, each of which points to a CBaseObject derived
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object. The m_iCacheSize is the static fixed size for the cache and the
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m_iUsed defines the number of places filled with objects at any time.
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We fill the array of pointers from the start (ie m_ppObjects[0] first)
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and then only add and remove objects from the end position, so in this
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respect the array of object pointers should be treated as a stack */
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CBaseObject **m_ppObjects;
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const INT m_iCacheSize;
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INT m_iUsed;
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public:
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CCache(__in_opt LPCTSTR pName,INT iItems);
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virtual ~CCache();
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/* Add an item to the cache */
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CBaseObject *AddToCache(__in CBaseObject *pObject);
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/* Remove an item from the cache */
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CBaseObject *RemoveFromCache();
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/* Delete all the objects held in the cache */
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void RemoveAll(void);
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/* Return the cache size which is set during construction */
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INT GetCacheSize(void) const {return m_iCacheSize;};
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};
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#endif /* __CACHE__ */
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