import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

layout/xul/tree/nsTreeStyleCache.h

@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 nsTreeStyleCache_h__
+#define nsTreeStyleCache_h__
+
+#include "mozilla/Attributes.h"
+#include "nsAutoPtr.h"
+#include "nsIAtom.h"
+#include "nsCOMArray.h"
+#include "nsICSSPseudoComparator.h"
+#include "nsRefPtrHashtable.h"
+#include "nsStyleContext.h"
+
+typedef nsCOMArray<nsIAtom> AtomArray;
+
+class nsTreeStyleCache
+{
+public:
+  nsTreeStyleCache()
+    : mNextState(0)
+  {
+  }
+
+  ~nsTreeStyleCache()
+  {
+    Clear();
+  }
+
+  void Clear()
+  {
+    mTransitionTable = nullptr;
+    mCache = nullptr;
+    mNextState = 0;
+  }
+
+  nsStyleContext* GetStyleContext(nsICSSPseudoComparator* aComparator,
+                                  nsPresContext* aPresContext,
+                                  nsIContent* aContent,
+                                  nsStyleContext* aContext,
+                                  nsIAtom* aPseudoElement,
+                                  const AtomArray & aInputWord);
+
+protected:
+  typedef uint32_t DFAState;
+
+  class Transition final
+  {
+  public:
+    Transition(DFAState aState, nsIAtom* aSymbol);
+    bool operator==(const Transition& aOther) const;
+    uint32_t Hash() const;
+
+  private:
+    DFAState mState;
+    nsCOMPtr<nsIAtom> mInputSymbol;
+  };
+
+  typedef nsDataHashtable<nsGenericHashKey<Transition>, DFAState> TransitionTable;
+
+  // A transition table for a deterministic finite automaton.  The DFA
+  // takes as its input a single pseudoelement and an ordered set of properties.
+  // It transitions on an input word that is the concatenation of the pseudoelement supplied
+  // with the properties in the array.
+  //
+  // It transitions from state to state by looking up entries in the transition table (which is
+  // a mapping from (S,i)->S', where S is the current state, i is the next
+  // property in the input word, and S' is the state to transition to.
+  //
+  // If S' is not found, it is constructed and entered into the hashtable
+  // under the key (S,i).
+  //
+  // Once the entire word has been consumed, the final state is used
+  // to reference the cache table to locate the style context.
+  nsAutoPtr<TransitionTable> mTransitionTable;
+
+  // The cache of all active style contexts.  This is a hash from
+  // a final state in the DFA, Sf, to the resultant style context.
+  typedef nsRefPtrHashtable<nsUint32HashKey, nsStyleContext> StyleContextCache;
+  nsAutoPtr<StyleContextCache> mCache;
+
+  // An integer counter that is used when we need to make new states in the
+  // DFA.
+  DFAState mNextState;
+};
+
+#endif // nsTreeStyleCache_h__