The Tor Browser: layout/base/FramePropertyTable.h@b8a032363ba2 (annotated)

layout/base/FramePropertyTable.h@b8a032363ba2 (annotated)

layout/base/FramePropertyTable.h

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: C++; tab-width: 20; 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 FRAMEPROPERTYTABLE_H_
 #define FRAMEPROPERTYTABLE_H_
 #include "mozilla/MemoryReporting.h"
 #include "nsTArray.h"
 #include "nsTHashtable.h"
 #include "nsHashKeys.h"
 class nsIFrame;
 namespace mozilla {
 struct FramePropertyDescriptor;
 typedef void (*FramePropertyDestructor)(void* aPropertyValue);
 typedef void (*FramePropertyDestructorWithFrame)(nsIFrame* aFrame,
                                                  void* aPropertyValue);
 /**
  * A pointer to a FramePropertyDescriptor serves as a unique property ID.
  * The FramePropertyDescriptor stores metadata about the property.
  * Currently the only metadata is a destructor function. The destructor
  * function is called on property values when they are overwritten or
  * deleted.
  *
  * To use this class, declare a global (i.e., file, class or function-scope
  * static member) FramePropertyDescriptor and pass its address as
  * aProperty in the FramePropertyTable methods.
  */
 struct FramePropertyDescriptor {
   /**
    * mDestructor will be called if it's non-null.
    */
   FramePropertyDestructor          mDestructor;
   /**
    * mDestructorWithFrame will be called if it's non-null and mDestructor
    * is null. WARNING: The frame passed to mDestructorWithFrame may
    * be a dangling frame pointer, if this is being called during
    * presshell teardown. Do not use it except to compare against
    * other frame pointers. No frame will have been allocated with
    * the same address yet.
    */
   FramePropertyDestructorWithFrame mDestructorWithFrame;
   /**
    * mDestructor and mDestructorWithFrame may both be null, in which case
    * no value destruction is a no-op.
    */
 };
 /**
  * The FramePropertyTable is optimized for storing 0 or 1 properties on
  * a given frame. Storing very large numbers of properties on a single
  * frame will not be efficient.
  *
  * Property values are passed as void* but do not actually have to be
  * valid pointers. You can use NS_INT32_TO_PTR/NS_PTR_TO_INT32 to
  * store int32_t values. Null/zero values can be stored and retrieved.
  * Of course, the destructor function (if any) must handle such values
  * correctly.
  */
 class FramePropertyTable {
 public:
   FramePropertyTable() : mLastFrame(nullptr), mLastEntry(nullptr)
   {
   }
   ~FramePropertyTable()
   {
     DeleteAll();
   }
   /**
    * Set a property value on a frame. This requires one hashtable
    * lookup (using the frame as the key) and a linear search through
    * the properties of that frame. Any existing value for the property
    * is destroyed.
    */
   void Set(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
            void* aValue);
   /**
    * Get a property value for a frame. This requires one hashtable
    * lookup (using the frame as the key) and a linear search through
    * the properties of that frame. If the frame has no such property,
    * returns null.
    * @param aFoundResult if non-null, receives a value 'true' iff
    * the frame has a value for the property. This lets callers
    * disambiguate a null result, which can mean 'no such property' or
    * 'property value is null'.
    */
   void* Get(const nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
             bool* aFoundResult = nullptr);
   /**
    * Remove a property value for a frame. This requires one hashtable
    * lookup (using the frame as the key) and a linear search through
    * the properties of that frame. The old property value is returned
    * (and not destroyed). If the frame has no such property,
    * returns null.
    * @param aFoundResult if non-null, receives a value 'true' iff
    * the frame had a value for the property. This lets callers
    * disambiguate a null result, which can mean 'no such property' or
    * 'property value is null'.
    */
   void* Remove(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
                bool* aFoundResult = nullptr);
   /**
    * Remove and destroy a property value for a frame. This requires one
    * hashtable lookup (using the frame as the key) and a linear search
    * through the properties of that frame. If the frame has no such
    * property, nothing happens.
    */
   void Delete(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty);
   /**
    * Remove and destroy all property values for a frame. This requires one
    * hashtable lookup (using the frame as the key).
    */
   void DeleteAllFor(nsIFrame* aFrame);
   /**
    * Remove and destroy all property values for all frames.
    */
   void DeleteAll();
   size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
 protected:
   /**
    * Stores a property descriptor/value pair. It can also be used to
    * store an nsTArray of PropertyValues.
    */
   struct PropertyValue {
     PropertyValue() : mProperty(nullptr), mValue(nullptr) {}
     PropertyValue(const FramePropertyDescriptor* aProperty, void* aValue)
       : mProperty(aProperty), mValue(aValue) {}
     bool IsArray() { return !mProperty && mValue; }
     nsTArray<PropertyValue>* ToArray()
     {
       NS_ASSERTION(IsArray(), "Must be array");
       return reinterpret_cast<nsTArray<PropertyValue>*>(&mValue);
     }
     void DestroyValueFor(nsIFrame* aFrame) {
       if (mProperty->mDestructor) {
         mProperty->mDestructor(mValue);
       } else if (mProperty->mDestructorWithFrame) {
         mProperty->mDestructorWithFrame(aFrame, mValue);
       }
     }
     size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) {
       size_t n = 0;
       // We don't need to measure mProperty because it always points to static
       // memory.  As for mValue:  if it's a single value we can't measure it,
       // because the type is opaque;  if it's an array, we measure the array
       // storage, but we can't measure the individual values, again because
       // their types are opaque.
       if (IsArray()) {
         nsTArray<PropertyValue>* array = ToArray();
         n += array->SizeOfExcludingThis(aMallocSizeOf);
       }
       return n;
     }
     const FramePropertyDescriptor* mProperty;
     void* mValue;
   };
   /**
    * Used with an array of PropertyValues to allow lookups that compare
    * only on the FramePropertyDescriptor.
    */
   class PropertyComparator {
   public:
     bool Equals(const PropertyValue& a, const PropertyValue& b) const {
       return a.mProperty == b.mProperty;
     }
     bool Equals(const FramePropertyDescriptor* a, const PropertyValue& b) const {
       return a == b.mProperty;
     }
     bool Equals(const PropertyValue& a, const FramePropertyDescriptor* b) const {
       return a.mProperty == b;
     }
   };
   /**
    * Our hashtable entry. The key is an nsIFrame*, the value is a
    * PropertyValue representing one or more property/value pairs.
    */
   class Entry : public nsPtrHashKey<nsIFrame>
   {
   public:
     Entry(KeyTypePointer aKey) : nsPtrHashKey<nsIFrame>(aKey) {}
     Entry(const Entry &toCopy) :
       nsPtrHashKey<nsIFrame>(toCopy), mProp(toCopy.mProp) {}
     PropertyValue mProp;
   };
   static void DeleteAllForEntry(Entry* aEntry);
   static PLDHashOperator DeleteEnumerator(Entry* aEntry, void* aArg);
   static size_t SizeOfPropertyTableEntryExcludingThis(Entry* aEntry,
                   mozilla::MallocSizeOf aMallocSizeOf, void *);
   nsTHashtable<Entry> mEntries;
   nsIFrame* mLastFrame;
   Entry* mLastEntry;
 };
 /**
  * This class encapsulates the properties of a frame.
  */
 class FrameProperties {
 public:
   FrameProperties(FramePropertyTable* aTable, nsIFrame* aFrame)
     : mTable(aTable), mFrame(aFrame) {}
   FrameProperties(FramePropertyTable* aTable, const nsIFrame* aFrame)
     : mTable(aTable), mFrame(const_cast<nsIFrame*>(aFrame)) {}
   void Set(const FramePropertyDescriptor* aProperty, void* aValue) const
   {
     mTable->Set(mFrame, aProperty, aValue);
   }
   void* Get(const FramePropertyDescriptor* aProperty,
             bool* aFoundResult = nullptr) const
   {
     return mTable->Get(mFrame, aProperty, aFoundResult);
   }
   void* Remove(const FramePropertyDescriptor* aProperty,
                bool* aFoundResult = nullptr) const
   {
     return mTable->Remove(mFrame, aProperty, aFoundResult);
   }
   void Delete(const FramePropertyDescriptor* aProperty)
   {
     mTable->Delete(mFrame, aProperty);
   }
 private:
   FramePropertyTable* mTable;
   nsIFrame* mFrame;
 };
 }
 #endif /* FRAMEPROPERTYTABLE_H_ */

The Tor Browser / annotate

layout/base/FramePropertyTable.h@b8a032363ba2 (annotated)

layout/base/FramePropertyTable.h