The Tor Browser: layout/xul/tree/nsTreeStyleCache.h@7e26c7da4463

     1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

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

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

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

     6 #ifndef nsTreeStyleCache_h__

     7 #define nsTreeStyleCache_h__

     9 #include "mozilla/Attributes.h"

    10 #include "nsHashtable.h"

    11 #include "nsIAtom.h"

    12 #include "nsCOMArray.h"

    13 #include "nsICSSPseudoComparator.h"

    14 #include "nsStyleContext.h"

    16 typedef nsCOMArray<nsIAtom> AtomArray;

    18 class nsDFAState : public nsHashKey

    19 {

    20 public:

    21   uint32_t mStateID;

    23   nsDFAState(uint32_t aID) :mStateID(aID) {}

    25   uint32_t GetStateID() { return mStateID; }

    27   uint32_t HashCode(void) const MOZ_OVERRIDE {

    28     return mStateID;

    29   }

    31   bool Equals(const nsHashKey *aKey) const MOZ_OVERRIDE {

    32     nsDFAState* key = (nsDFAState*)aKey;

    33     return key->mStateID == mStateID;

    34   }

    36   nsHashKey *Clone(void) const MOZ_OVERRIDE {

    37     return new nsDFAState(mStateID);

    38   }

    39 };

    41 class nsTransitionKey : public nsHashKey

    42 {

    43 public:

    44   uint32_t mState;

    45   nsCOMPtr<nsIAtom> mInputSymbol;

    47   nsTransitionKey(uint32_t aState, nsIAtom* aSymbol) :mState(aState), mInputSymbol(aSymbol) {}

    49   uint32_t HashCode(void) const MOZ_OVERRIDE {

    50     // Make a 32-bit integer that combines the low-order 16 bits of the state and the input symbol.

    51     int32_t hb = mState << 16;

    52     int32_t lb = (NS_PTR_TO_INT32(mInputSymbol.get()) << 16) >> 16;

    53     return hb+lb;

    54   }

    56   bool Equals(const nsHashKey *aKey) const MOZ_OVERRIDE {

    57     nsTransitionKey* key = (nsTransitionKey*)aKey;

    58     return key->mState == mState && key->mInputSymbol == mInputSymbol;

    59   }

    61   nsHashKey *Clone(void) const MOZ_OVERRIDE {

    62     return new nsTransitionKey(mState, mInputSymbol);

    63   }

    64 };

    66 class nsTreeStyleCache

    67 {

    68 public:

    69   nsTreeStyleCache() :mTransitionTable(nullptr), mCache(nullptr), mNextState(0) {}

    70   ~nsTreeStyleCache() { Clear(); }

    72   void Clear() { delete mTransitionTable; mTransitionTable = nullptr; delete mCache; mCache = nullptr; mNextState = 0; }

    74   nsStyleContext* GetStyleContext(nsICSSPseudoComparator* aComparator,

    75                                   nsPresContext* aPresContext,

    76                                   nsIContent* aContent,

    77                                   nsStyleContext* aContext,

    78                                   nsIAtom* aPseudoElement,

    79                                   const AtomArray & aInputWord);

    81   static bool DeleteDFAState(nsHashKey *aKey, void *aData, void *closure);

    83   static bool ReleaseStyleContext(nsHashKey *aKey, void *aData, void *closure);

    85 protected:

    86   // A transition table for a deterministic finite automaton.  The DFA

    87   // takes as its input a single pseudoelement and an ordered set of properties.

    88   // It transitions on an input word that is the concatenation of the pseudoelement supplied

    89   // with the properties in the array.

    90   //

    91   // It transitions from state to state by looking up entries in the transition table (which is

    92   // a mapping from (S,i)->S', where S is the current state, i is the next

    93   // property in the input word, and S' is the state to transition to.

    94   //

    95   // If S' is not found, it is constructed and entered into the hashtable

    96   // under the key (S,i).

    97   //

    98   // Once the entire word has been consumed, the final state is used

    99   // to reference the cache table to locate the style context.

   100   nsObjectHashtable* mTransitionTable;

   102   // The cache of all active style contexts.  This is a hash from

   103   // a final state in the DFA, Sf, to the resultant style context.

   104   nsObjectHashtable* mCache;

   106   // An integer counter that is used when we need to make new states in the

   107   // DFA.

   108   uint32_t mNextState;

   109 };

   111 #endif // nsTreeStyleCache_h__

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