parser/html/nsHtml5AtomTable.h

   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 "nsAutoPtr.h"
  11 #include "nsIAtom.h"
  12 #include "nsIThread.h"
  13
  14 class nsHtml5Atom;
  15
  16 class nsHtml5AtomEntry : public nsStringHashKey
  17 {
  18   public:
  19     nsHtml5AtomEntry(KeyTypePointer aStr);
  20     nsHtml5AtomEntry(const nsHtml5AtomEntry& aOther);
  21     ~nsHtml5AtomEntry();
  22     inline nsHtml5Atom* GetAtom() {
  23       return mAtom;
  24     }
  25   private:
  26     nsAutoPtr<nsHtml5Atom> mAtom;
  27 };
  28
  29 /**
  30  * nsHtml5AtomTable provides non-locking lookup and creation of atoms for
  31  * nsHtml5Parser or nsHtml5StreamParser.
  32  *
  33  * The hashtable holds dynamically allocated atoms that are private to an
  34  * instance of nsHtml5Parser or nsHtml5StreamParser. (Static atoms are used on
  35  * interned nsHtml5ElementNames and interned nsHtml5AttributeNames. Also, when
  36  * the doctype name is 'html', that identifier needs to be represented as a
  37  * static atom.)
  38  *
  39  * Each instance of nsHtml5Parser has a single instance of nsHtml5AtomTable,
  40  * and each instance of nsHtml5StreamParser has a single instance of
  41  * nsHtml5AtomTable. Dynamic atoms obtained from an nsHtml5AtomTable are valid
  42  * for == comparison with each other or with atoms declared in nsHtml5Atoms
  43  * within the nsHtml5Tokenizer and the nsHtml5TreeBuilder instances owned by
  44  * the same nsHtml5Parser/nsHtml5StreamParser instance that owns the
  45  * nsHtml5AtomTable instance.
  46  *
  47  * Dynamic atoms (atoms whose IsStaticAtom() returns false) obtained from
  48  * nsHtml5AtomTable must be re-obtained from another atom table when there's a
  49  * need to migrate atoms from an nsHtml5Parser to its nsHtml5StreamParser
  50  * (re-obtain from the other nsHtml5AtomTable), from an nsHtml5Parser to its
  51  * owner nsHtml5Parser (re-obtain from the other nsHtml5AtomTable) or from the
  52  * parser to the DOM (re-obtain from the application-wide atom table). To
  53  * re-obtain an atom from another atom table, obtain a string from the atom
  54  * using ToString(nsAString&) and look up an atom in the other table using that
  55  * string.
  56  *
  57  * An instance of nsHtml5AtomTable that belongs to an nsHtml5Parser is only
  58  * accessed from the main thread. An instance of nsHtml5AtomTable that belongs
  59  * to an nsHtml5StreamParser is accessed both from the main thread and from the
  60  * thread that executes the runnables of the nsHtml5StreamParser instance.
  61  * However, the threads never access the nsHtml5AtomTable instance concurrently
  62  * in the nsHtml5StreamParser case.
  63  *
  64  * Methods on the atoms obtained from nsHtml5AtomTable may be called on any
  65  * thread, although they only need to be called on the main thread or on the
  66  * thread working for the nsHtml5StreamParser when nsHtml5AtomTable belongs to
  67  * an nsHtml5StreamParser.
  68  *
  69  * Dynamic atoms obtained from nsHtml5AtomTable are deleted when the
  70  * nsHtml5AtomTable itself is destructed, which happens when the owner
  71  * nsHtml5Parser or nsHtml5StreamParser is destructed.
  72  */
  73 class nsHtml5AtomTable
  74 {
  75   public:
  76     nsHtml5AtomTable();
  77     ~nsHtml5AtomTable();
  78
  79     /**
  80      * Must be called after the constructor before use.
  81      */
  82     inline void Init() {
  83       mTable.Init();
  84     }
  85
  86     /**
  87      * Obtains the atom for the given string in the scope of this atom table.
  88      */
  89     nsIAtom* GetAtom(const nsAString& aKey);
  90
  91     /**
  92      * Empties the table.
  93      */
  94     void Clear() {
  95       mTable.Clear();
  96     }
  97
  98 #ifdef DEBUG
  99     void SetPermittedLookupThread(nsIThread* aThread) {
 100       mPermittedLookupThread = aThread;
 101     }
 102 #endif
 103
 104   private:
 105     nsTHashtable<nsHtml5AtomEntry> mTable;
 106 #ifdef DEBUG
 107     nsCOMPtr<nsIThread>            mPermittedLookupThread;
 108 #endif
 109 };
 110
 111 #endif // nsHtml5AtomTable_h_