1 /* This Source Code Form is subject to the terms of the Mozilla Public 2 * License, v. 2.0. If a copy of the MPL was not distributed with this 3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 4 5 #ifndef nsHtml5AtomTable_h 6 #define nsHtml5AtomTable_h 7 8 #include "nsHashKeys.h" 9 #include "nsTHashtable.h" 10 #include "nsAtom.h" 11 #include "nsISerialEventTarget.h" 12 13 #define RECENTLY_USED_PARSER_ATOMS_SIZE 31 14 15 /** 16 * nsHtml5AtomTable provides non-locking lookup and creation of atoms for 17 * nsHtml5Parser or nsHtml5StreamParser. 18 * 19 * The hashtable holds dynamically allocated atoms that are private to an 20 * instance of nsHtml5Parser or nsHtml5StreamParser. (Static atoms are used on 21 * interned nsHtml5ElementNames and interned nsHtml5AttributeNames. Also, when 22 * the doctype name is 'html', that identifier needs to be represented as a 23 * static atom.) 24 * 25 * Each instance of nsHtml5Parser has a single instance of nsHtml5AtomTable, 26 * and each instance of nsHtml5StreamParser has a single instance of 27 * nsHtml5AtomTable. Dynamic atoms obtained from an nsHtml5AtomTable are valid 28 * for == comparison with each other or with atoms declared in nsHtml5Atoms 29 * within the nsHtml5Tokenizer and the nsHtml5TreeBuilder instances owned by 30 * the same nsHtml5Parser/nsHtml5StreamParser instance that owns the 31 * nsHtml5AtomTable instance. 32 * 33 * Dynamic atoms (atoms whose IsStatic() returns false) obtained from 34 * nsHtml5AtomTable must be re-obtained from another atom table when there's a 35 * need to migrate atoms from an nsHtml5Parser to its nsHtml5StreamParser 36 * (re-obtain from the other nsHtml5AtomTable), from an nsHtml5Parser to its 37 * owner nsHtml5Parser (re-obtain from the other nsHtml5AtomTable) or from the 38 * parser to the DOM (re-obtain from the application-wide atom table). To 39 * re-obtain an atom from another atom table, obtain a string from the atom 40 * using ToString(nsAString&) and look up an atom in the other table using that 41 * string. 42 * 43 * An instance of nsHtml5AtomTable that belongs to an nsHtml5Parser is only 44 * accessed from the main thread. An instance of nsHtml5AtomTable that belongs 45 * to an nsHtml5StreamParser is accessed both from the main thread and from the 46 * thread that executes the runnables of the nsHtml5StreamParser instance. 47 * However, the threads never access the nsHtml5AtomTable instance concurrently 48 * in the nsHtml5StreamParser case. 49 * 50 * Methods on the atoms obtained from nsHtml5AtomTable may be called on any 51 * thread, although they only need to be called on the main thread or on the 52 * thread working for the nsHtml5StreamParser when nsHtml5AtomTable belongs to 53 * an nsHtml5StreamParser. 54 * 55 * Dynamic atoms obtained from nsHtml5AtomTable are deleted when the 56 * nsHtml5AtomTable itself is destructed, which happens when the owner 57 * nsHtml5Parser or nsHtml5StreamParser is destructed. 58 */ 59 class nsHtml5AtomTable { 60 public: 61 nsHtml5AtomTable(); 62 ~nsHtml5AtomTable(); 63 64 // NOTE: We rely on mRecentlyUsedParserAtoms keeping alive the returned atom, 65 // but the caller is responsible to take a reference before calling GetAtom 66 // again. 67 nsAtom* GetAtom(const nsAString& aKey); 68 69 /** 70 * Empties the table. 71 */ Clear()72 void Clear() { 73 for (uint32_t i = 0; i < RECENTLY_USED_PARSER_ATOMS_SIZE; ++i) { 74 mRecentlyUsedParserAtoms[i] = nullptr; 75 } 76 } 77 78 #ifdef DEBUG SetPermittedLookupEventTarget(nsISerialEventTarget * aEventTarget)79 void SetPermittedLookupEventTarget(nsISerialEventTarget* aEventTarget) { 80 mPermittedLookupEventTarget = aEventTarget; 81 } 82 #endif 83 84 private: 85 RefPtr<nsAtom> mRecentlyUsedParserAtoms[RECENTLY_USED_PARSER_ATOMS_SIZE]; 86 #ifdef DEBUG 87 nsCOMPtr<nsISerialEventTarget> mPermittedLookupEventTarget; 88 #endif 89 }; 90 91 #endif // nsHtml5AtomTable_h 92