tor-browser

TabStateCache.sys.mjs (4852B)

---

/* 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/. */

/**
* A cache for tabs data.
*
* This cache implements a weak map from tabs (as XUL elements)
* to tab data (as objects).
*
* Note that we should never cache private data, as:
* - that data is used very seldom by SessionStore;
* - caching private data in addition to public data is memory consuming.
*/
export var TabStateCache = Object.freeze({
 /**
  * Retrieves cached data for a given |tab| or associated |browser|.
  *
  * @param permanentKey (object)
  *        The tab or browser to retrieve cached data for.
  * @return (object)
  *         The cached data stored for the given |tab|
  *         or associated |browser|.
  */
 get(permanentKey) {
   return TabStateCacheInternal.get(permanentKey);
 },

 /**
  * Updates cached data for a given |tab| or associated |browser|.
  *
  * @param permanentKey (object)
  *        The tab or browser belonging to the given tab data.
  * @param newData (object)
  *        The new data to be stored for the given |tab|
  *        or associated |browser|.
  */
 update(permanentKey, newData) {
   TabStateCacheInternal.update(permanentKey, newData);
 },
});

var TabStateCacheInternal = {
 _data: new WeakMap(),

 /**
  * Retrieves cached data for a given |tab| or associated |browser|.
  *
  * @param permanentKey (object)
  *        The tab or browser to retrieve cached data for.
  * @return (object)
  *         The cached data stored for the given |tab|
  *         or associated |browser|.
  */
 get(permanentKey) {
   return this._data.get(permanentKey);
 },

 /**
  * Helper function used by update (see below). For message size
  * optimization sometimes we don't update the whole session storage
  * only the values that have been changed.
  *
  * @param data (object)
  *        The cached data where we want to update the changes.
  * @param change (object)
  *        The actual changed values per domain.
  */
 updatePartialStorageChange(data, change) {
   if (!data.storage) {
     data.storage = {};
   }

   let storage = data.storage;
   for (let domain of Object.keys(change)) {
     if (!change[domain]) {
       // We were sent null in place of the change object, which means
       // we should delete session storage entirely for this domain.
       delete storage[domain];
     } else {
       for (let key of Object.keys(change[domain])) {
         let value = change[domain][key];
         if (value === null) {
           if (storage[domain] && storage[domain][key]) {
             delete storage[domain][key];
           }
         } else {
           if (!storage[domain]) {
             storage[domain] = {};
           }
           storage[domain][key] = value;
         }
       }
     }
   }
 },

 /**
  * Helper function used by update (see below). For message size
  * optimization sometimes we don't update the whole browser history
  * only the current index and the tail of the history from a certain
  * index (specified by change.fromIdx)
  *
  * @param data (object)
  *        The cached data where we want to update the changes.
  * @param change (object)
  *        Object containing the tail of the history array, and
  *        some additional metadata.
  */
 updatePartialHistoryChange(data, change) {
   const kLastIndex = Number.MAX_SAFE_INTEGER - 1;

   if (!data.history) {
     data.history = { entries: [] };
   }

   let history = data.history;
   for (let key of Object.keys(change)) {
     if (key == "entries") {
       if (change.fromIdx != kLastIndex) {
         let start = change.fromIdx + 1;
         history.entries.splice(start, Infinity, ...change.entries);
       }
     } else if (key != "fromIdx") {
       history[key] = change[key];
     }
   }
 },

 /**
  * Updates cached data for a given |tab| or associated |browser|.
  *
  * @param permanentKey (object)
  *        The tab or browser belonging to the given tab data.
  * @param newData (object)
  *        The new data to be stored for the given permanent key.
  */
 update(permanentKey, newData) {
   let data = this._data.get(permanentKey) || {};

   for (let key of Object.keys(newData)) {
     if (key == "storagechange") {
       this.updatePartialStorageChange(data, newData.storagechange);
       continue;
     }

     if (key == "historychange") {
       this.updatePartialHistoryChange(data, newData.historychange);
       continue;
     }

     let value = newData[key];
     if (value === null) {
       delete data[key];
     } else {
       data[key] = value;
     }
   }

   this._data.set(permanentKey, data);
 },
};