/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef nsHtml5AtomTable_h

#define nsHtml5AtomTable_h

#include "nsHashKeys.h"

#include "nsTHashtable.h"

#include "nsAtom.h"

#include "nsISerialEventTarget.h"

#define RECENTLY_USED_PARSER_ATOMS_SIZE 31

class nsHtml5AtomEntry : public nsStringHashKey

{

public:

  explicit nsHtml5AtomEntry(KeyTypePointer aStr);

  nsHtml5AtomEntry(nsHtml5AtomEntry&& aOther);

  ~nsHtml5AtomEntry();

  inline nsAtom* GetAtom() { return mAtom; }

private:

  nsDynamicAtom* mAtom;

};

/**

 * nsHtml5AtomTable provides non-locking lookup and creation of atoms for

 * nsHtml5Parser or nsHtml5StreamParser.

 *

 * The hashtable holds dynamically allocated atoms that are private to an

 * instance of nsHtml5Parser or nsHtml5StreamParser. (Static atoms are used on

 * interned nsHtml5ElementNames and interned nsHtml5AttributeNames. Also, when

 * the doctype name is 'html', that identifier needs to be represented as a

 * static atom.)

 *

 * Each instance of nsHtml5Parser has a single instance of nsHtml5AtomTable,

 * and each instance of nsHtml5StreamParser has a single instance of

 * nsHtml5AtomTable. Dynamic atoms obtained from an nsHtml5AtomTable are valid

 * for == comparison with each other or with atoms declared in nsHtml5Atoms

 * within the nsHtml5Tokenizer and the nsHtml5TreeBuilder instances owned by

 * the same nsHtml5Parser/nsHtml5StreamParser instance that owns the

 * nsHtml5AtomTable instance.

 *

 * Dynamic atoms (atoms whose IsStatic() returns false) obtained from

 * nsHtml5AtomTable must be re-obtained from another atom table when there's a

 * need to migrate atoms from an nsHtml5Parser to its nsHtml5StreamParser

 * (re-obtain from the other nsHtml5AtomTable), from an nsHtml5Parser to its

 * owner nsHtml5Parser (re-obtain from the other nsHtml5AtomTable) or from the

 * parser to the DOM (re-obtain from the application-wide atom table). To

 * re-obtain an atom from another atom table, obtain a string from the atom

 * using ToString(nsAString&) and look up an atom in the other table using that

 * string.

 *

 * An instance of nsHtml5AtomTable that belongs to an nsHtml5Parser is only

 * accessed from the main thread. An instance of nsHtml5AtomTable that belongs

 * to an nsHtml5StreamParser is accessed both from the main thread and from the

 * thread that executes the runnables of the nsHtml5StreamParser instance.

 * However, the threads never access the nsHtml5AtomTable instance concurrently

 * in the nsHtml5StreamParser case.

 *

 * Methods on the atoms obtained from nsHtml5AtomTable may be called on any

 * thread, although they only need to be called on the main thread or on the

 * thread working for the nsHtml5StreamParser when nsHtml5AtomTable belongs to

 * an nsHtml5StreamParser.

 *

 * Dynamic atoms obtained from nsHtml5AtomTable are deleted when the

 * nsHtml5AtomTable itself is destructed, which happens when the owner

 * nsHtml5Parser or nsHtml5StreamParser is destructed.

 */

class nsHtml5AtomTable

{

public:

  nsHtml5AtomTable();

  ~nsHtml5AtomTable();

  /**

   * Obtains the atom for the given string in the scope of this atom table.

   */

  nsAtom* GetAtom(const nsAString& aKey);

  /**

   * Empties the table.

   */

  void Clear()

  {

    for (uint32_t i = 0; i < RECENTLY_USED_PARSER_ATOMS_SIZE; ++i) {

      mRecentlyUsedParserAtoms[i] = nullptr;

    }

    mTable.Clear();

  }

#ifdef DEBUG

  void SetPermittedLookupEventTarget(nsISerialEventTarget* aEventTarget)

  {

    mPermittedLookupEventTarget = aEventTarget;

  }

#endif

private:

  nsTHashtable<nsHtml5AtomEntry> mTable;

  nsAtom* mRecentlyUsedParserAtoms[RECENTLY_USED_PARSER_ATOMS_SIZE];

#ifdef DEBUG

  nsCOMPtr<nsISerialEventTarget> mPermittedLookupEventTarget;

#endif

};

#endif // nsHtml5AtomTable_h