xpcom/ds/nsAtomTable.h

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   2 /* ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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  15  * The Original Code is mozilla.org code.
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  17  * The Initial Developer of the Original Code is
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  19  * Portions created by the Initial Developer are Copyright (C) 1998
  20  * the Initial Developer. All Rights Reserved.
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  36  * ***** END LICENSE BLOCK ***** */
  37
  38 #ifndef nsAtomTable_h__
  39 #define nsAtomTable_h__
  40
  41 #include "nsIAtom.h"
  42
  43 /**
  44  * A threadsafely-refcounted implementation of nsIAtom.  Note that
  45  * AtomImpl objects are sometimes converted into PermanentAtomImpl
  46  * objects using placement new and just overwriting the vtable pointer.
  47  */
  48
  49 class AtomImpl : public nsIAtom {
  50 public:
  51   AtomImpl();
  52
  53 protected:
  54   // We don't need a virtual destructor here because PermanentAtomImpl
  55   // deletions aren't handled through Release().
  56   ~AtomImpl();
  57
  58 public:
  59   NS_DECL_ISUPPORTS
  60   NS_DECL_NSIATOM
  61
  62   enum { REFCNT_PERMANENT_SENTINEL = PR_UINT32_MAX };
  63
  64   virtual PRBool IsPermanent();
  65
  66   // We can't use the virtual function in the base class destructor.
  67   PRBool IsPermanentInDestructor() {
  68     return mRefCnt == REFCNT_PERMANENT_SENTINEL;
  69   }
  70
  71   void* operator new(size_t size, const nsACString& aString) CPP_THROW_NEW;
  72
  73   void operator delete(void* ptr) {
  74     ::operator delete(ptr);
  75   }
  76
  77   // for |#ifdef NS_BUILD_REFCNT_LOGGING| access to reference count
  78   nsrefcnt GetRefCount() { return mRefCnt; }
  79
  80   // The length of the string in the atom.
  81   PRUint32 mLength;
  82
  83   // Actually more; 0 terminated. This slot is reserved for the
  84   // terminating zero.
  85   char mString[1];
  86 };
  87
  88 /**
  89  * A non-refcounted implementation of nsIAtom.
  90  */
  91
  92 class PermanentAtomImpl : public AtomImpl {
  93 public:
  94   PermanentAtomImpl();
  95   ~PermanentAtomImpl();
  96   NS_IMETHOD_(nsrefcnt) AddRef();
  97   NS_IMETHOD_(nsrefcnt) Release();
  98
  99   virtual PRBool IsPermanent();
 100
 101   void* operator new(size_t size, const nsACString& aString) CPP_THROW_NEW {
 102     return AtomImpl::operator new(size, aString);
 103   }
 104   void* operator new(size_t size, AtomImpl* aAtom) CPP_THROW_NEW;
 105
 106 };
 107
 108 void NS_PurgeAtomTable();
 109
 110 #endif // nsAtomTable_h__