gecko-dev/dom/base/nsPropertyTable.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */

/**
 * nsPropertyTable allows a set of arbitrary key/value pairs to be stored
 * for any number of nodes, in a global hashtable rather than on the nodes
 * themselves.  Nodes can be any type of object; the hashtable keys are
 * nsAtom pointers, and the values are void pointers.
 */

#ifndef nsPropertyTable_h_
#define nsPropertyTable_h_

#include "mozilla/MemoryReporting.h"
#include "nscore.h"

class nsAtom;

using NSPropertyFunc = void (*)(void* aObject, nsAtom* aPropertyName,
                                void* aPropertyValue, void* aData);

/**
 * Callback type for property destructors.  |aObject| is the object
 * the property is being removed for, |aPropertyName| is the property
 * being removed, |aPropertyValue| is the value of the property, and |aData|
 * is the opaque destructor data that was passed to SetProperty().
 **/
using NSPropertyDtorFunc = NSPropertyFunc;
class nsINode;
class nsIFrame;

class nsPropertyOwner {
 public:
  nsPropertyOwner(const nsPropertyOwner& aOther) = default;

  // These are the types of objects that can own properties. No object should
  // inherit more then one of these classes.
  // To add support for more types just add to this list.
  MOZ_IMPLICIT nsPropertyOwner(const nsINode* aObject) : mObject(aObject) {}
  MOZ_IMPLICIT nsPropertyOwner(const nsIFrame* aObject) : mObject(aObject) {}

  operator const void*() { return mObject; }
  const void* get() { return mObject; }

 private:
  const void* mObject;
};

class nsPropertyTable {
 public:
  /**
   * Get the value of the property |aPropertyName| for node |aObject|.
   * |aResult|, if supplied, is filled in with a return status code.
   **/
  void* GetProperty(const nsPropertyOwner& aObject, const nsAtom* aPropertyName,
                    nsresult* aResult = nullptr) {
    return GetPropertyInternal(aObject, aPropertyName, false, aResult);
  }

  /**
   * Set the value of the property |aPropertyName| to
   * |aPropertyValue| for node |aObject|.  |aDtor| is a destructor for the
   * property value to be called if the property is removed.  It can be null
   * if no destructor is required.  |aDtorData| is an optional pointer to an
   * opaque context to be passed to the property destructor.  Note that the
   * destructor is global for each property name regardless of node; it is an
   * error to set a given property with a different destructor than was used
   * before (this will return NS_ERROR_INVALID_ARG). If |aTransfer| is true
   * the property will be transfered to the new table when the property table
   * for |aObject| changes (currently the tables for nodes are owned by their
   * ownerDocument, so if the ownerDocument for a node changes, its property
   * table changes too). If |aTransfer| is false the property will just be
   * deleted instead.
   */
  nsresult SetProperty(const nsPropertyOwner& aObject, nsAtom* aPropertyName,
                       void* aPropertyValue, NSPropertyDtorFunc aDtor,
                       void* aDtorData, bool aTransfer = false) {
    return SetPropertyInternal(aObject, aPropertyName, aPropertyValue, aDtor,
                               aDtorData, aTransfer);
  }

  /**
   * Remove the property |aPropertyName| in the global category for object
   * |aObject|. The property's destructor function will be called.
   */
  nsresult RemoveProperty(nsPropertyOwner aObject, const nsAtom* aPropertyName);

  /**
   * Remove the property |aPropertyName| in the global category for object
   * |aObject|, but do not call the property's destructor function.  The
   * property value is returned.
   */
  void* TakeProperty(const nsPropertyOwner& aObject,
                     const nsAtom* aPropertyName, nsresult* aStatus = nullptr) {
    return GetPropertyInternal(aObject, aPropertyName, true, aStatus);
  }

  /**
   * Removes all of the properties for object |aObject|, calling the destructor
   * function for each property.
   */
  void RemoveAllPropertiesFor(nsPropertyOwner aObject);

  /**
   * Transfers all properties for object |aObject| that were set with the
   * |aTransfer| argument as true to |aTable|. Removes the other properties for
   * object |aObject|, calling the destructor function for each property.
   * If transfering a property fails, this deletes all the properties for object
   * |aObject|.
   */
  nsresult TransferOrRemoveAllPropertiesFor(nsPropertyOwner aObject,
                                            nsPropertyTable& aOtherTable);

  /**
   * Enumerate the properties for object |aObject|.
   * For every property |aCallback| will be called with as arguments |aObject|,
   * the property name, the property value and |aData|.
   */
  void Enumerate(nsPropertyOwner aObject, NSPropertyFunc aCallback,
                 void* aData);

  /**
   * Enumerate all the properties.
   * For every property |aCallback| will be called with arguments the owner,
   * the property name, the property value and |aData|.
   */
  void EnumerateAll(NSPropertyFunc aCallback, void* aData);

  /**
   * Removes all of the properties for all objects in the property table,
   * calling the destructor function for each property.
   */
  void RemoveAllProperties();

  nsPropertyTable() : mPropertyList(nullptr) {}
  ~nsPropertyTable() { RemoveAllProperties(); }

  /**
   * Function useable as destructor function for property data that is
   * XPCOM objects. The function will call NS_IF_RELASE on the value
   * to destroy it.
   */
  static void SupportsDtorFunc(void* aObject, nsAtom* aPropertyName,
                               void* aPropertyValue, void* aData);

  class PropertyList;

  size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;

 private:
  void DestroyPropertyList();
  PropertyList* GetPropertyListFor(const nsAtom* aPropertyName) const;
  void* GetPropertyInternal(nsPropertyOwner aObject,
                            const nsAtom* aPropertyName, bool aRemove,
                            nsresult* aStatus);
  nsresult SetPropertyInternal(nsPropertyOwner aObject, nsAtom* aPropertyName,
                               void* aPropertyValue, NSPropertyDtorFunc aDtor,
                               void* aDtorData, bool aTransfer);

  PropertyList* mPropertyList;
};
#endif