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250 lines
8.3 KiB
C++
250 lines
8.3 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef FRAMEPROPERTYTABLE_H_
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#define FRAMEPROPERTYTABLE_H_
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#include "nsTArray.h"
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#include "nsTHashtable.h"
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#include "nsHashKeys.h"
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class nsIFrame;
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namespace mozilla {
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struct FramePropertyDescriptor;
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typedef void (*FramePropertyDestructor)(void* aPropertyValue);
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typedef void (*FramePropertyDestructorWithFrame)(nsIFrame* aFrame,
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void* aPropertyValue);
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/**
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* A pointer to a FramePropertyDescriptor serves as a unique property ID.
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* The FramePropertyDescriptor stores metadata about the property.
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* Currently the only metadata is a destructor function. The destructor
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* function is called on property values when they are overwritten or
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* deleted.
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*
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* To use this class, declare a global (i.e., file, class or function-scope
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* static member) FramePropertyDescriptor and pass its address as
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* aProperty in the FramePropertyTable methods.
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*/
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struct FramePropertyDescriptor {
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/**
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* mDestructor will be called if it's non-null.
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*/
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FramePropertyDestructor mDestructor;
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/**
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* mDestructorWithFrame will be called if it's non-null and mDestructor
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* is null. WARNING: The frame passed to mDestructorWithFrame may
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* be a dangling frame pointer, if this is being called during
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* presshell teardown. Do not use it except to compare against
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* other frame pointers. No frame will have been allocated with
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* the same address yet.
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*/
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FramePropertyDestructorWithFrame mDestructorWithFrame;
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/**
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* mDestructor and mDestructorWithFrame may both be null, in which case
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* no value destruction is a no-op.
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*/
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};
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/**
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* The FramePropertyTable is optimized for storing 0 or 1 properties on
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* a given frame. Storing very large numbers of properties on a single
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* frame will not be efficient.
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*
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* Property values are passed as void* but do not actually have to be
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* valid pointers. You can use NS_INT32_TO_PTR/NS_PTR_TO_INT32 to
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* store int32_t values. Null/zero values can be stored and retrieved.
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* Of course, the destructor function (if any) must handle such values
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* correctly.
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*/
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class FramePropertyTable {
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public:
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FramePropertyTable() : mLastFrame(nullptr), mLastEntry(nullptr)
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{
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mEntries.Init();
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}
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~FramePropertyTable()
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{
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DeleteAll();
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}
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/**
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* Set a property value on a frame. This requires one hashtable
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* lookup (using the frame as the key) and a linear search through
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* the properties of that frame. Any existing value for the property
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* is destroyed.
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*/
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void Set(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
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void* aValue);
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/**
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* Get a property value for a frame. This requires one hashtable
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* lookup (using the frame as the key) and a linear search through
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* the properties of that frame. If the frame has no such property,
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* returns null.
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* @param aFoundResult if non-null, receives a value 'true' iff
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* the frame has a value for the property. This lets callers
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* disambiguate a null result, which can mean 'no such property' or
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* 'property value is null'.
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*/
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void* Get(const nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
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bool* aFoundResult = nullptr);
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/**
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* Remove a property value for a frame. This requires one hashtable
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* lookup (using the frame as the key) and a linear search through
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* the properties of that frame. The old property value is returned
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* (and not destroyed). If the frame has no such property,
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* returns null.
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* @param aFoundResult if non-null, receives a value 'true' iff
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* the frame had a value for the property. This lets callers
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* disambiguate a null result, which can mean 'no such property' or
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* 'property value is null'.
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*/
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void* Remove(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty,
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bool* aFoundResult = nullptr);
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/**
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* Remove and destroy a property value for a frame. This requires one
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* hashtable lookup (using the frame as the key) and a linear search
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* through the properties of that frame. If the frame has no such
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* property, nothing happens.
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*/
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void Delete(nsIFrame* aFrame, const FramePropertyDescriptor* aProperty);
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/**
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* Remove and destroy all property values for a frame. This requires one
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* hashtable lookup (using the frame as the key).
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*/
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void DeleteAllFor(nsIFrame* aFrame);
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/**
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* Remove and destroy all property values for all frames.
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*/
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void DeleteAll();
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size_t SizeOfExcludingThis(nsMallocSizeOfFun aMallocSizeOf) const;
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protected:
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/**
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* Stores a property descriptor/value pair. It can also be used to
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* store an nsTArray of PropertyValues.
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*/
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struct PropertyValue {
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PropertyValue() : mProperty(nullptr), mValue(nullptr) {}
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PropertyValue(const FramePropertyDescriptor* aProperty, void* aValue)
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: mProperty(aProperty), mValue(aValue) {}
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bool IsArray() { return !mProperty && mValue; }
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nsTArray<PropertyValue>* ToArray()
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{
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NS_ASSERTION(IsArray(), "Must be array");
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return reinterpret_cast<nsTArray<PropertyValue>*>(&mValue);
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}
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void DestroyValueFor(nsIFrame* aFrame) {
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if (mProperty->mDestructor) {
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mProperty->mDestructor(mValue);
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} else if (mProperty->mDestructorWithFrame) {
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mProperty->mDestructorWithFrame(aFrame, mValue);
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}
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}
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size_t SizeOfExcludingThis(nsMallocSizeOfFun aMallocSizeOf) {
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size_t n = 0;
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// We don't need to measure mProperty because it always points to static
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// memory. As for mValue: if it's a single value we can't measure it,
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// because the type is opaque; if it's an array, we measure the array
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// storage, but we can't measure the individual values, again because
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// their types are opaque.
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if (IsArray()) {
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nsTArray<PropertyValue>* array = ToArray();
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n += array->SizeOfExcludingThis(aMallocSizeOf);
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}
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return n;
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}
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const FramePropertyDescriptor* mProperty;
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void* mValue;
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};
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/**
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* Used with an array of PropertyValues to allow lookups that compare
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* only on the FramePropertyDescriptor.
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*/
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class PropertyComparator {
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public:
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bool Equals(const PropertyValue& a, const PropertyValue& b) const {
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return a.mProperty == b.mProperty;
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}
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bool Equals(const FramePropertyDescriptor* a, const PropertyValue& b) const {
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return a == b.mProperty;
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}
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bool Equals(const PropertyValue& a, const FramePropertyDescriptor* b) const {
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return a.mProperty == b;
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}
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};
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/**
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* Our hashtable entry. The key is an nsIFrame*, the value is a
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* PropertyValue representing one or more property/value pairs.
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*/
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class Entry : public nsPtrHashKey<nsIFrame>
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{
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public:
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Entry(KeyTypePointer aKey) : nsPtrHashKey<nsIFrame>(aKey) {}
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Entry(const Entry &toCopy) :
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nsPtrHashKey<nsIFrame>(toCopy), mProp(toCopy.mProp) {}
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PropertyValue mProp;
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};
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static void DeleteAllForEntry(Entry* aEntry);
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static PLDHashOperator DeleteEnumerator(Entry* aEntry, void* aArg);
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static size_t SizeOfPropertyTableEntryExcludingThis(Entry* aEntry,
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nsMallocSizeOfFun aMallocSizeOf, void *);
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nsTHashtable<Entry> mEntries;
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nsIFrame* mLastFrame;
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Entry* mLastEntry;
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};
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/**
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* This class encapsulates the properties of a frame.
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*/
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class FrameProperties {
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public:
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FrameProperties(FramePropertyTable* aTable, nsIFrame* aFrame)
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: mTable(aTable), mFrame(aFrame) {}
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FrameProperties(FramePropertyTable* aTable, const nsIFrame* aFrame)
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: mTable(aTable), mFrame(const_cast<nsIFrame*>(aFrame)) {}
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void Set(const FramePropertyDescriptor* aProperty, void* aValue) const
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{
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mTable->Set(mFrame, aProperty, aValue);
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}
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void* Get(const FramePropertyDescriptor* aProperty,
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bool* aFoundResult = nullptr) const
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{
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return mTable->Get(mFrame, aProperty, aFoundResult);
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}
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void* Remove(const FramePropertyDescriptor* aProperty,
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bool* aFoundResult = nullptr) const
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{
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return mTable->Remove(mFrame, aProperty, aFoundResult);
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}
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void Delete(const FramePropertyDescriptor* aProperty)
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{
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mTable->Delete(mFrame, aProperty);
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}
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private:
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FramePropertyTable* mTable;
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nsIFrame* mFrame;
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};
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}
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#endif /* FRAMEPROPERTYTABLE_H_ */
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