gecko/xpcom/ds/nsAtomTable.h

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#ifndef nsAtomTable_h__
#define nsAtomTable_h__

#include "nsIAtom.h"
#include "nsStringBuffer.h"

/**
 * Note that AtomImpl objects are sometimes converted into PermanentAtomImpl
 * objects using placement new and just overwriting the vtable pointer.
 */

class AtomImpl : public nsIAtom {
public:
  AtomImpl(const nsACString& aString);

  // This is currently only used during startup when creating a permanent atom
  // from NS_RegisterStaticAtoms
  AtomImpl(nsStringBuffer* aData, PRUint32 aLength);

protected:
  // This is only intended to be used when a normal atom is turned into a
  // permanent one.
  AtomImpl() {
    // We can't really assert that mString is a valid nsStringBuffer string,
    // so do the best we can do and check for some consistencies.
    NS_ASSERTION((mLength + 1) * sizeof(char) <=
                 nsStringBuffer::FromData(mString)->StorageSize() &&
                 mString[mLength] == 0,
                 "Not initialized atom");
  }

  // We don't need a virtual destructor here because PermanentAtomImpl
  // deletions aren't handled through Release().
  ~AtomImpl();

public:
  NS_DECL_ISUPPORTS
  NS_DECL_NSIATOM

  enum { REFCNT_PERMANENT_SENTINEL = PR_UINT32_MAX };

  virtual PRBool IsPermanent();

  // We can't use the virtual function in the base class destructor.
  PRBool IsPermanentInDestructor() {
    return mRefCnt == REFCNT_PERMANENT_SENTINEL;
  }

  // for |#ifdef NS_BUILD_REFCNT_LOGGING| access to reference count
  nsrefcnt GetRefCount() { return mRefCnt; }

  // The length of the string in the atom.
  PRUint32 mLength;

  // This always points to the data owned by a nsStringBuffer
  char* mString;
};

/**
 * A non-refcounted implementation of nsIAtom.
 */

class PermanentAtomImpl : public AtomImpl {
public:
  PermanentAtomImpl(const nsACString& aString)
    : AtomImpl(aString)
  {}
  PermanentAtomImpl(nsStringBuffer* aData, PRUint32 aLength)
    : AtomImpl(aData, aLength)
  {}
  PermanentAtomImpl()
  {}

  ~PermanentAtomImpl();
  NS_IMETHOD_(nsrefcnt) AddRef();
  NS_IMETHOD_(nsrefcnt) Release();

  virtual PRBool IsPermanent();

  void* operator new(size_t size, AtomImpl* aAtom) CPP_THROW_NEW;
  void* operator new(size_t size) CPP_THROW_NEW
  {
    return ::operator new(size);
  }

};

void NS_PurgeAtomTable();

#endif // nsAtomTable_h__