1 mike  1.2 //%2006////////////////////////////////////////////////////////////////////////
  2           //
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  4           // Company, L.P.; IBM Corp.; The Open Group; Tivoli Systems.
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  6           // IBM Corp.; EMC Corporation, The Open Group.
  7           // Copyright (c) 2004 BMC Software; Hewlett-Packard Development Company, L.P.;
  8           // IBM Corp.; EMC Corporation; VERITAS Software Corporation; The Open Group.
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 10           // EMC Corporation; VERITAS Software Corporation; The Open Group.
 11           // Copyright (c) 2006 Hewlett-Packard Development Company, L.P.; IBM Corp.;
 12           // EMC Corporation; Symantec Corporation; The Open Group.
 13           //
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 22 mike  1.2 // ALL COPIES OR SUBSTANTIAL PORTIONS OF THE SOFTWARE. THE SOFTWARE IS PROVIDED
 23           // "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
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 30           //==============================================================================
 31           //
 32           //%/////////////////////////////////////////////////////////////////////////////
 33           
 34           #ifndef Pegasus_Magic_h
 35           #define Pegasus_Magic_h
 36           
 37           #include <Pegasus/Common/Config.h>
 38           
 39           PEGASUS_NAMESPACE_BEGIN
 40           
 41           /** The Magic class implements a convenient way to use magic numbers in
 42               user-defined classes. Magic numbers help detect use of uninitialized, 
 43 mike  1.2     destructed, or corrupted objects.
 44           
 45               To instrument a class to use magic numbers simply add a class member 
 46               of type Magic<> as shown in thsi example:
 47           
 48           	\code
 49           	class MyClass
 50           	{
 51           	public:
 52           
 53           	    MyClass();
 54           
 55           	    ~MyClass();
 56           
 57           	    void foo();
 58           
 59           	private:
 60           	    Magic<0xC531B144> _magic;
 61           	};
 62           	\endcode
 63           
 64 mike  1.2     Choose whatever number you like for a magic number. The number above was
 65               generated by the Linux uuidgen utility (Windows has a utility with the 
 66               same name).
 67           
 68               To test magic number, add the following expression wherever necessary
 69               (usually as the first line of every member function).
 70           
 71           	\code
 72           	PEGASUS_ASSERT_DEBUG(_magic);
 73           	\endcode
 74           
 75               Here's a typical example:
 76           
 77           	\code
 78           	MyClass::~MyClass()
 79           	{
 80           	    PEGASUS_ASSERT_DEBUG(_magic);
 81           	}
 82           	\endcode
 83           
 84               This tests whether the magic number is 0xC531B144 and asserts if it is
 85 mike  1.2     not.
 86           
 87               Note that using a magic number makes the user-defined class 4 bytes larger
 88               but there is no run-time overhead unless you compile with PEGASUS_DEBUG.
 89               The Magic constructor and destructor are empty without PEGASUS_DEBUG and
 90               are discarded by the compiler.
 91           
 92               CAUTION: You may be tempted to compile out the magic member when
 93               PEGASUS_DEBUG undefined. However, this will causes unpredictable
 94               behavior when debug libraries are mixed with non-debug libraries. The
 95               structure alignment and size will be different and will lead to crashes.
 96               This is only safe if a class is internal to a library.
 97           */
 98           template<Uint32 MAGIC_NUMBER>
 99           class Magic
100           {
101           public:
102           
103               /** Default constructor. Sets the magic number.
104               */
105               Magic() 
106 mike  1.2     {
107           #ifdef PEGASUS_DEBUG
108           	_magic = MAGIC_NUMBER;
109           #endif
110               }
111           
112               /** Destructor. Clears the magic number (with the pattern 0xDDDDDDDD).
113               */
114               ~Magic() 
115               {
116           #ifdef PEGASUS_DEBUG
117           	_magic = 0xDDDDDDDD; 
118           #endif
119               }
120           
121               /** Allows magic number to be used as a boolean expression. This function
122           	tests the magic number and return true if valid.
123               */
124               operator bool() const 
125               { 
126           #ifdef PEGASUS_DEBUG
127 mike  1.2 	return _magic == MAGIC_NUMBER; 
128           #else
129           	return true;
130           #endif
131               }
132           
133           private:
134               Uint32 _magic;
135           };
136           
137           PEGASUS_NAMESPACE_END
138           
139           #endif /* Pegasus_Magic_h */