xpcom/ds/nsAtomTable.h

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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 #include "nsStringBuffer.h"
  43
  44 /**
  45  * Note that 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(const nsAString& aString);
  52
  53   // This is currently only used during startup when creating a permanent atom
  54   // from NS_RegisterStaticAtoms
  55   AtomImpl(nsStringBuffer* aData, PRUint32 aLength);
  56
  57 protected:
  58   // This is only intended to be used when a normal atom is turned into a
  59   // permanent one.
  60   AtomImpl() {
  61     // We can't really assert that mString is a valid nsStringBuffer string,
  62     // so do the best we can do and check for some consistencies.
  63     NS_ASSERTION((mLength + 1) * sizeof(PRUnichar) <=
  64                  nsStringBuffer::FromData(mString)->StorageSize() &&
  65                  mString[mLength] == 0,
  66                  "Not initialized atom");
  67   }
  68
  69   // We don't need a virtual destructor here because PermanentAtomImpl
  70   // deletions aren't handled through Release().
  71   ~AtomImpl();
  72
  73 public:
  74   NS_DECL_ISUPPORTS
  75   NS_DECL_NSIATOM
  76
  77   enum { REFCNT_PERMANENT_SENTINEL = PR_UINT32_MAX };
  78
  79   virtual PRBool IsPermanent();
  80
  81   // We can't use the virtual function in the base class destructor.
  82   PRBool IsPermanentInDestructor() {
  83     return mRefCnt == REFCNT_PERMANENT_SENTINEL;
  84   }
  85
  86   // for |#ifdef NS_BUILD_REFCNT_LOGGING| access to reference count
  87   nsrefcnt GetRefCount() { return mRefCnt; }
  88 };
  89
  90 /**
  91  * A non-refcounted implementation of nsIAtom.
  92  */
  93
  94 class PermanentAtomImpl : public AtomImpl {
  95 public:
  96   PermanentAtomImpl(const nsAString& aString)
  97     : AtomImpl(aString)
  98   {}
  99   PermanentAtomImpl(nsStringBuffer* aData, PRUint32 aLength)
 100     : AtomImpl(aData, aLength)
 101   {}
 102   PermanentAtomImpl()
 103   {}
 104
 105   ~PermanentAtomImpl();
 106   NS_IMETHOD_(nsrefcnt) AddRef();
 107   NS_IMETHOD_(nsrefcnt) Release();
 108
 109   virtual PRBool IsPermanent();
 110
 111   void* operator new(size_t size, AtomImpl* aAtom) CPP_THROW_NEW;
 112   void* operator new(size_t size) CPP_THROW_NEW
 113   {
 114     return ::operator new(size);
 115   }
 116
 117 };
 118
 119 void NS_PurgeAtomTable();
 120
 121 #endif // nsAtomTable_h__