DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Mercurial (5350524bb654)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557
// 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/.

this.EXPORTED_SYMBOLS = ["Prefetcher"];

const Ci = Components.interfaces;
const Cu = Components.utils;

Cu.import("resource://gre/modules/XPCOMUtils.jsm");
Cu.import("resource://gre/modules/Services.jsm");

XPCOMUtils.defineLazyModuleGetter(this, "Preferences",
                                  "resource://gre/modules/Preferences.jsm");

// Rules are defined at the bottom of this file.
var PrefetcherRules = {};

/*
 * When events that trigger in the content process are forwarded to
 * add-ons in the chrome process, we expect the add-ons to send a lot
 * of CPOWs to query content nodes while processing the events. To
 * speed this up, the prefetching system anticipates which properties
 * will be read and reads them ahead of time. The prefetched
 * properties are passed to the chrome process along with each
 * event. A typical scenario might work like this:
 *
 * 1. "load" event fires in content
 * 2. Content process prefetches:
 *      event.target.defaultView = <win 1>
 *      <win 1>.location = <location obj>
 *      event.target.getElementsByTagName("form") = [<elt 1>, <elt 2>]
 *      <elt 1>.id = "login-form"
 *      <elt 2>.id = "subscribe-form"
 * 3. Content process forwards "load" event to add-on along with
 *    prefetched data
 * 4. Add-on reads:
 *      event.target.defaultView (already prefetched)
 *      event.target.getElementsByTagName("form") (already prefetched)
 *      <elt 1>.id (already prefetched)
 *      <elt 1>.className (not prefetched; CPOW must be sent)
 *
 * The amount of data to prefetch is determined based on the add-on ID
 * and the event type. The specific data to select is determined using
 * a set of Datalog-like rules (http://en.wikipedia.org/wiki/Datalog).
 *
 * Rules operate on a series of "tables" like in a database. Each
 * table contains a set of content-process objects. When an event
 * handler runs, it seeds some initial tables with objects of
 * interest. For example, the Event table might start out containing
 * the event that fired.
 *
 * Objects are added to tables using a set of rules of the form "if X
 * is in table A, then add F(X) to table B", where F(X) is typically a
 * property access or a method call. The most common functions F are:
 *
 * PropertyOp(destTable, sourceTable, property):
 *   For each object X in sourceTable, add X.property to destTable.
 * MethodOp(destTable, sourceTable, method, args):
 *   For each object X in sourceTable, add X.method(args) to destTable.
 * CollectionOp(destTable, sourceTable):
 *   For each object X in sourceTable, add X[i] to destTable for
 *   all i from 0 to X.length - 1.
 *
 * To generate the prefetching in the example above, the following
 * rules would work:
 *
 * 1. PropertyOp("EventTarget", "Event", "target")
 * 2. PropertyOp("Window", "EventTarget", "defaultView")
 * 3. MethodOp("FormCollection", "EventTarget", "getElementsByTagName", "form")
 * 4. CollectionOp("Form", "FormCollection")
 * 5. PropertyOp(null, "Form", "id")
 *
 * Rules are written at the bottom of this file.
 *
 * When a rule runs, it will usually generate some cache entries that
 * will be passed to the chrome process. For example, when PropertyOp
 * prefetches obj.prop and gets the value X, it caches the value of
 * obj and X. When the chrome process receives this data, it creates a
 * two-level map [obj -> [prop -> X]]. When the add-on accesses a
 * property on obj, the add-on shim code consults this map to see if
 * the property has already been cached.
 */

const PREF_PREFETCHING_ENABLED = "extensions.interposition.prefetching";

function isPrimitive(v) {
  if (!v)
    return true;
  let type = typeof(v);
  return type !== "object" && type !== "function";
}

function objAddr(obj)
{
/*
  if (!isPrimitive(obj)) {
    return String(obj) + "[" + Cu.getJSTestingFunctions().objectAddress(obj) + "]";
  }
  return String(obj);
*/
}

function log(/* ...args*/)
{
/*
  for (let arg of args) {
    dump(arg);
    dump(" ");
  }
  dump("\n");
*/
}

function logPrefetch(/* kind, value1, component, value2*/)
{
/*
  log("prefetching", kind, objAddr(value1) + "." + component, "=", objAddr(value2));
*/
}

/*
 * All the Op classes (representing Datalog rules) have the same interface:
 *   outputTable: Table that objects generated by the rule are added to.
 *     Note that this can be null.
 *   inputTable: Table that the rule draws objects from.
 *   addObject(database, obj): Called when an object is added to inputTable.
 *     This code should take care of adding objects to outputTable.
 *     Data to be cached should be stored by calling database.cache.
 *   makeCacheEntry(item, cache):
 *     Called by the chrome process to create the two-level map of
 *     prefetched objects. |item| holds the cached data
 *     generated by the content process. |cache| is the map to be
 *     generated.
 */

function PropertyOp(outputTable, inputTable, prop)
{
  this.outputTable = outputTable;
  this.inputTable = inputTable;
  this.prop = prop;
}

PropertyOp.prototype.addObject = function(database, obj)
{
  let has = false, propValue;
  try {
    if (this.prop in obj) {
      has = true;
      propValue = obj[this.prop];
    }
  } catch (e) {
    // Don't cache anything if an exception is thrown.
    return;
  }

  logPrefetch("prop", obj, this.prop, propValue);
  database.cache(this.index, obj, has, propValue);
  if (has && !isPrimitive(propValue) && this.outputTable) {
    database.add(this.outputTable, propValue);
  }
}

PropertyOp.prototype.makeCacheEntry = function(item, cache)
{
  let [, obj, , propValue] = item;

  let desc = { configurable: false, enumerable: true, writable: false, value: propValue };

  if (!cache.has(obj)) {
    cache.set(obj, new Map());
  }
  let propMap = cache.get(obj);
  propMap.set(this.prop, desc);
}

function MethodOp(outputTable, inputTable, method, ...args)
{
  this.outputTable = outputTable;
  this.inputTable = inputTable;
  this.method = method;
  this.args = args;
}

MethodOp.prototype.addObject = function(database, obj)
{
  let result;
  try {
    result = obj[this.method].apply(obj, this.args);
  } catch (e) {
    // Don't cache anything if an exception is thrown.
    return;
  }

  logPrefetch("method", obj, this.method + "(" + this.args + ")", result);
  database.cache(this.index, obj, result);
  if (!isPrimitive(result) && this.outputTable) {
    database.add(this.outputTable, result);
  }
}

MethodOp.prototype.makeCacheEntry = function(item, cache)
{
  let [, obj, result] = item;

  if (!cache.has(obj)) {
    cache.set(obj, new Map());
  }
  let propMap = cache.get(obj);
  let fallback = propMap.get(this.method);

  let method = this.method;
  let selfArgs = this.args;
  let methodImpl = function(...args) {
    if (args.length == selfArgs.length && args.every((v, i) => v === selfArgs[i])) {
      return result;
    }

    if (fallback) {
      return fallback.value(...args);
    }
    return obj[method](...args);
  };

  let desc = { configurable: false, enumerable: true, writable: false, value: methodImpl };
  propMap.set(this.method, desc);
}

function CollectionOp(outputTable, inputTable)
{
  this.outputTable = outputTable;
  this.inputTable = inputTable;
}

CollectionOp.prototype.addObject = function(database, obj)
{
  let elements = [];
  try {
    let len = obj.length;
    for (let i = 0; i < len; i++) {
      logPrefetch("index", obj, i, obj[i]);
      elements.push(obj[i]);
    }
  } catch (e) {
    // Don't cache anything if an exception is thrown.
    return;
  }

  database.cache(this.index, obj, ...elements);
  for (let i = 0; i < elements.length; i++) {
    if (!isPrimitive(elements[i]) && this.outputTable) {
      database.add(this.outputTable, elements[i]);
    }
  }
}

CollectionOp.prototype.makeCacheEntry = function(item, cache)
{
  let [, obj, ...elements] = item;

  if (!cache.has(obj)) {
    cache.set(obj, new Map());
  }
  let propMap = cache.get(obj);

  let lenDesc = { configurable: false, enumerable: true, writable: false, value: elements.length };
  propMap.set("length", lenDesc);

  for (let i = 0; i < elements.length; i++) {
    let desc = { configurable: false, enumerable: true, writable: false, value: elements[i] };
    propMap.set(i, desc);
  }
}

function CopyOp(outputTable, inputTable)
{
  this.outputTable = outputTable;
  this.inputTable = inputTable;
}

CopyOp.prototype.addObject = function(database, obj)
{
  database.add(this.outputTable, obj);
}

function Database(trigger, addons)
{
  // Create a map of rules that apply to this specific trigger and set
  // of add-ons. The rules are indexed based on their inputTable.
  this.rules = new Map();
  for (let addon of addons) {
    let addonRules = PrefetcherRules[addon] || {};
    let triggerRules = addonRules[trigger] || [];
    for (let rule of triggerRules) {
      let inTable = rule.inputTable;
      if (!this.rules.has(inTable)) {
        this.rules.set(inTable, new Set());
      }
      let set = this.rules.get(inTable);
      set.add(rule);
    }
  }

  // this.tables maps table names to sets of objects contained in them.
  this.tables = new Map();

  // todo is a worklist of items added to tables that have not had
  // rules run on them yet.
  this.todo = [];

  // Cached data to be sent to the chrome process.
  this.cached = [];
}

Database.prototype = {
  // Add an object to a table.
  add: function(table, obj) {
    if (!this.tables.has(table)) {
      this.tables.set(table, new Set());
    }
    let tableSet = this.tables.get(table);
    if (tableSet.has(obj)) {
      return;
    }
    tableSet.add(obj);

    this.todo.push([table, obj]);
  },

  cache: function(...args) {
    this.cached.push(args);
  },

  // Run a fixed-point iteration that adds objects to table based on
  // this.rules until there are no more objects to add.
  process: function() {
    while (this.todo.length) {
      let [table, obj] = this.todo.pop();
      let rules = this.rules.get(table);
      if (!rules) {
        continue;
      }
      for (let rule of rules) {
        rule.addObject(this, obj);
      }
    }
  },
};

var Prefetcher = {
  init: function() {
    // Give an index to each rule and store it in this.ruleMap based
    // on the index. The index is used to serialize and deserialize
    // data from content to chrome.
    let counter = 0;
    this.ruleMap = new Map();
    for (let addon in PrefetcherRules) {
      for (let trigger in PrefetcherRules[addon]) {
        for (let rule of PrefetcherRules[addon][trigger]) {
          rule.index = counter++;
          this.ruleMap.set(rule.index, rule);
        }
      }
    }

    this.prefetchingEnabled = Preferences.get(PREF_PREFETCHING_ENABLED, false);
    Services.prefs.addObserver(PREF_PREFETCHING_ENABLED, this, false);
    Services.obs.addObserver(this, "xpcom-shutdown", false);
  },

  observe: function(subject, topic, data) {
    if (topic == "xpcom-shutdown") {
      Services.prefs.removeObserver(PREF_PREFETCHING_ENABLED, this);
      Services.obs.removeObserver(this, "xpcom-shutdown");
    } else if (topic == PREF_PREFETCHING_ENABLED) {
      this.prefetchingEnabled = Preferences.get(PREF_PREFETCHING_ENABLED, false);
    }
  },

  // Called when an event occurs in the content process. The event is
  // described by the trigger string. |addons| is a list of addons
  // that have listeners installed for the event. |args| is
  // event-specific data (such as the event object).
  prefetch: function(trigger, addons, args) {
    if (!this.prefetchingEnabled) {
      return [[], []];
    }

    let db = new Database(trigger, addons);
    for (let table in args) {
      log("root", table, "=", objAddr(args[table]));
      db.add(table, args[table]);
    }

    // Prefetch objects and add them to tables.
    db.process();

    // Data passed to sendAsyncMessage must be split into a JSON
    // portion and a CPOW portion. This code splits apart db.cached
    // into these two pieces. Any object in db.cache is added to an
    // array of CPOWs and replaced with {cpow: <index in array>}.
    let cpowIndexes = new Map();
    let prefetched = [];
    let cpows = [];
    for (let item of db.cached) {
      item = item.map((elt) => {
        if (!isPrimitive(elt)) {
          if (!cpowIndexes.has(elt)) {
            let index = cpows.length;
            cpows.push(elt);
            cpowIndexes.set(elt, index);
          }
          return {cpow: cpowIndexes.get(elt)};
        }
        return elt;
      });

      prefetched.push(item);
    }

    return [prefetched, cpows];
  },

  cache: null,

  // Generate a two-level mapping based on cached data received from
  // the content process.
  generateCache: function(prefetched, cpows) {
    let cache = new Map();
    for (let item of prefetched) {
      // Replace anything of the form {cpow: <index>} with the actual
      // object in |cpows|.
      item = item.map((elt) => {
        if (!isPrimitive(elt)) {
          return cpows[elt.cpow];
        }
        return elt;
      });

      let index = item[0];
      let op = this.ruleMap.get(index);
      op.makeCacheEntry(item, cache);
    }
    return cache;
  },

  // Run |func|, using the prefetched data in |prefetched| and |cpows|
  // as a cache.
  withPrefetching: function(prefetched, cpows, func) {
    if (!this.prefetchingEnabled) {
      return func();
    }

    this.cache = this.generateCache(prefetched, cpows);

    try {
      log("Prefetching on");
      return func();
    } finally {
      // After we return from this event handler, the content process
      // is free to continue executing, so we invalidate our cache.
      log("Prefetching off");
      this.cache = null;
    }
  },

  // Called by shim code in the chrome process to check if target.prop
  // is cached.
  lookupInCache: function(addon, target, prop) {
    if (!this.cache || !Cu.isCrossProcessWrapper(target)) {
      return null;
    }

    let propMap = this.cache.get(target);
    if (!propMap) {
      return null;
    }

    return propMap.get(prop);
  },
};

var AdblockId = "{d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}";
var AdblockRules = {
  "ContentPolicy.shouldLoad": [
    new MethodOp("Node", "InitNode", "QueryInterface", Ci.nsISupports),
    new PropertyOp("Document", "Node", "ownerDocument"),
    new PropertyOp("Window", "Node", "defaultView"),
    new PropertyOp("Window", "Document", "defaultView"),
    new PropertyOp("TopWindow", "Window", "top"),
    new PropertyOp("WindowLocation", "Window", "location"),
    new PropertyOp(null, "WindowLocation", "href"),
    new PropertyOp("Window", "Window", "parent"),
    new PropertyOp(null, "Window", "name"),
    new PropertyOp("Document", "Window", "document"),
    new PropertyOp("TopDocumentElement", "Document", "documentElement"),
    new MethodOp(null, "TopDocumentElement", "getAttribute", "data-adblockkey"),
  ]
};
PrefetcherRules[AdblockId] = AdblockRules;

var LastpassId = "support@lastpass.com";
var LastpassRules = {
  "EventTarget.handleEvent": [
    new PropertyOp("EventTarget", "Event", "target"),
    new PropertyOp("EventOriginalTarget", "Event", "originalTarget"),
    new PropertyOp("Window", "EventOriginalTarget", "defaultView"),

    new CopyOp("Frame", "Window"),
    new PropertyOp("FrameCollection", "Window", "frames"),
    new CollectionOp("Frame", "FrameCollection"),
    new PropertyOp("FrameCollection", "Frame", "frames"),
    new PropertyOp("FrameDocument", "Frame", "document"),
    new PropertyOp(null, "Frame", "window"),
    new PropertyOp(null, "FrameDocument", "defaultView"),

    new PropertyOp("FrameDocumentLocation", "FrameDocument", "location"),
    new PropertyOp(null, "FrameDocumentLocation", "href"),
    new PropertyOp("FrameLocation", "Frame", "location"),
    new PropertyOp(null, "FrameLocation", "href"),

    new MethodOp("FormCollection", "FrameDocument", "getElementsByTagName", "form"),
    new MethodOp("FormCollection", "FrameDocument", "getElementsByTagName", "FORM"),
    new CollectionOp("Form", "FormCollection"),
    new PropertyOp("FormElementCollection", "Form", "elements"),
    new CollectionOp("FormElement", "FormElementCollection"),
    new PropertyOp("Style", "Form", "style"),

    new PropertyOp(null, "FormElement", "type"),
    new PropertyOp(null, "FormElement", "name"),
    new PropertyOp(null, "FormElement", "value"),
    new PropertyOp(null, "FormElement", "tagName"),
    new PropertyOp(null, "FormElement", "id"),
    new PropertyOp("Style", "FormElement", "style"),

    new PropertyOp(null, "Style", "visibility"),

    new MethodOp("MetaElementsCollection", "EventOriginalTarget", "getElementsByTagName", "meta"),
    new CollectionOp("MetaElement", "MetaElementsCollection"),
    new PropertyOp(null, "MetaElement", "httpEquiv"),

    new MethodOp("InputElementCollection", "FrameDocument", "getElementsByTagName", "input"),
    new MethodOp("InputElementCollection", "FrameDocument", "getElementsByTagName", "INPUT"),
    new CollectionOp("InputElement", "InputElementCollection"),
    new PropertyOp(null, "InputElement", "type"),
    new PropertyOp(null, "InputElement", "name"),
    new PropertyOp(null, "InputElement", "tagName"),
    new PropertyOp(null, "InputElement", "form"),

    new PropertyOp("BodyElement", "FrameDocument", "body"),
    new PropertyOp("BodyInnerText", "BodyElement", "innerText"),

    new PropertyOp("DocumentFormCollection", "FrameDocument", "forms"),
    new CollectionOp("DocumentForm", "DocumentFormCollection"),
  ]
};
PrefetcherRules[LastpassId] = LastpassRules;