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/* 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
/**
* 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();
// NOTE: We rely on mRecentlyUsedParserAtoms keeping alive the returned atom,
// but the caller is responsible to take a reference before calling GetAtom
// again.
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;
}
}
#ifdef DEBUG
void SetPermittedLookupEventTarget(nsISerialEventTarget* aEventTarget) {
mPermittedLookupEventTarget = aEventTarget;
}
#endif
private:
RefPtr<nsAtom> mRecentlyUsedParserAtoms[RECENTLY_USED_PARSER_ATOMS_SIZE];
#ifdef DEBUG
nsCOMPtr<nsISerialEventTarget> mPermittedLookupEventTarget;
#endif
};
#endif // nsHtml5AtomTable_h
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