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/* 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/. */
"use strict";
var EXPORTED_SYMBOLS = ["PlacesPreviews", "PlacesPreviewsHelperService"];
const { XPCOMUtils } = ChromeUtils.import(
);
const { ComponentUtils } = ChromeUtils.import(
);
XPCOMUtils.defineLazyModuleGetters(this, {
});
XPCOMUtils.defineLazyGetter(this, "logConsole", function() {
return console.createInstance({
prefix: "PlacesPreviews",
maxLogLevel: Services.prefs.getBoolPref("places.previews.log", false)
? "Debug"
: "Warn",
});
});
// Toggling Places previews requires a restart, because a database trigger
// filling up tombstones is enabled on the database only when the pref is set
// on startup.
XPCOMUtils.defineLazyGetter(this, "previewsEnabled", function() {
return Services.prefs.getBoolPref("places.previews.enabled", false);
});
// Preview deletions are done in chunks of this size.
const DELETE_CHUNK_SIZE = 50;
// This is the time between deletion chunks.
const DELETE_TIMEOUT_MS = 60000;
// The folder inside the profile folder where to store previews.
const PREVIEWS_DIRECTORY = "places-previews";
// How old a preview file should be before we replace it.
const DAYS_BEFORE_REPLACEMENT = 30;
/**
* This extends Set to only keep the latest 100 entries.
*/
class LimitedSet extends Set {
#limit = 100;
add(key) {
super.add(key);
let oversize = this.size - this.#limit;
if (oversize > 0) {
for (let entry of this) {
if (oversize-- <= 0) {
break;
}
this.delete(entry);
}
}
}
}
/**
* This class handles previews deletion from tombstones in the database.
* Deletion happens in chunks, each chunk runs after DELETE_TIMEOUT_MS, and
* the process is interrupted once there's nothing more to delete.
* Any page removal operations on the Places database will restart the timer.
*/
class DeletionHandler {
#timeoutId = null;
#shutdownProgress = {};
/**
* This can be set by tests to speed up the deletion process, otherwise the
* product should just use the default value.
*/
#timeout = DELETE_TIMEOUT_MS;
get timeout() {
return this.#timeout;
}
set timeout(val) {
if (this.#timeoutId) {
clearTimeout(this.#timeoutId);
this.#timeoutId = null;
}
this.#timeout = val;
this.ensureRunning();
}
constructor() {
// Clear any pending timeouts on shutdown.
PlacesUtils.history.shutdownClient.jsclient.addBlocker(
"PlacesPreviews.jsm::DeletionHandler",
async () => {
this.#shutdownProgress.shuttingDown = true;
clearTimeout(this.#timeoutId);
this.#timeoutId = null;
},
{ fetchState: () => this.#shutdownProgress }
);
}
/**
* This should be invoked everytime we expect there are tombstones to
* handle. If deletion is already pending, this is a no-op.
*/
ensureRunning() {
if (this.#timeoutId || this.#shutdownProgress.shuttingDown) {
return;
}
this.#timeoutId = setTimeout(() => {
this.#timeoutId = null;
ChromeUtils.idleDispatch(() => {
this.#deleteChunk().catch(ex =>
logConsole.error("Error during previews deletion:" + ex)
);
});
}, this.timeout);
}
/**
* Deletes a chunk of previews.
*/
async #deleteChunk() {
if (this.#shutdownProgress.shuttingDown) {
return;
}
// Select tombstones, delete images, then delete tombstones. This order
// ensures that in case of problems we'll try again in the future.
let db = await PlacesUtils.promiseDBConnection();
let count;
let hashes = (
await db.executeCached(
`SELECT hash, (SELECT count(*) FROM moz_previews_tombstones) AS count
FROM moz_previews_tombstones LIMIT ${DELETE_CHUNK_SIZE}`
)
).map(r => {
if (count === undefined) {
count = r.getResultByName("count");
}
return r.getResultByName("hash");
});
if (!count || this.#shutdownProgress.shuttingDown) {
// There's nothing to delete, or it's too late.
return;
}
let deleted = [];
for (let hash of hashes) {
let filePath = PlacesPreviews.getPathForHash(hash);
try {
await IOUtils.remove(filePath);
PlacesPreviews.onDelete(filePath);
deleted.push(hash);
} catch (ex) {
if (DOMException.isInstance(ex) && ex.name == "NotFoundError") {
deleted.push(hash);
} else {
logConsole.error("Unable to delete file: " + filePath);
}
}
if (this.#shutdownProgress.shuttingDown) {
return;
}
}
// Delete hashes from tombstones.
let params = deleted.reduce((p, c, i) => {
p["hash" + i] = c;
return p;
}, {});
await PlacesUtils.withConnectionWrapper(
"PlacesPreviews.jsm::ExpirePreviews",
async db => {
await db.execute(
`DELETE FROM moz_previews_tombstones WHERE hash in
(${Object.keys(params)
.map(p => `:${p}`)
.join(",")})`,
params
);
}
);
if (count > DELETE_CHUNK_SIZE) {
this.ensureRunning();
}
}
}
/**
* Handles previews for Places urls.
* Previews are stored in WebP format, using MD5 hash of the page url in hex
* format. All the previews are saved into a "places-previews" folder under
* the roaming profile folder.
*/
const PlacesPreviews = new (class extends EventEmitter {
#placesObserver = null;
#deletionHandler = null;
// This is used as a cache to avoid fetching the same preview multiple
// times in a short timeframe.
#recentlyUpdatedPreviews = new LimitedSet();
fileExtension = ".webp";
fileContentType = "image/webp";
constructor() {
super();
// Observe page removals and delete previews when necessary.
this.#placesObserver = new PlacesWeakCallbackWrapper(
this.handlePlacesEvents.bind(this)
);
PlacesObservers.addListener(
["history-cleared", "page-removed"],
this.#placesObserver
);
// Start deletion in case it was interruped during the previous session,
// it will end once there's nothing more to delete.
this.#deletionHandler = new DeletionHandler();
this.#deletionHandler.ensureRunning();
}
handlePlacesEvents(events) {
for (const event of events) {
if (
event.type == "history-cleared" ||
(event.type == "page-removed" && event.isRemovedFromStore)
) {
this.#deletionHandler.ensureRunning();
return;
}
}
}
/**
* Whether the feature is enabled. Use this instead of directly checking
* the pref, since it requires a restart.
*/
get enabled() {
return previewsEnabled;
}
/**
* Returns the path to the previews folder.
* @returns {string} The path to the previews folder.
*/
getPath() {
return PathUtils.join(
Services.dirsvc.get("ProfD", Ci.nsIFile).path,
PREVIEWS_DIRECTORY
);
}
/**
* Returns the file path of the preview for the given url.
* This doesn't guarantee the file exists.
* @param {string} url Address of the page.
* @returns {string} File path of the preview for the given url.
*/
getPathForUrl(url) {
return PathUtils.join(
this.getPath(),
PlacesUtils.md5(url, { format: "hex" }) + this.fileExtension
);
}
/**
* Returns the file path of the preview having the given hash.
* @param {string} hash md5 hash in hex format.
* @returns {string } File path of the preview having the given hash.
*/
getPathForHash(hash) {
return PathUtils.join(this.getPath(), hash + this.fileExtension);
}
/**
* Returns the moz-page-thumb: url to show the preview for the given url.
* @param {string} url Address of the page.
* @returns {string} Preview url for the given page url.
*/
getPageThumbURL(url) {
return (
"moz-page-thumb://" +
"places-previews" +
"/?url=" +
encodeURIComponent(url) +
"&revision=" +
PageThumbsStorage.getRevision(url)
);
}
/**
* Updates the preview for the given page url. The update happens in
* background, using a windowless browser with very conservative privacy
* settings. Due to this, it may not look exactly like the page that the user
* is normally facing when logged in. See BackgroundPageThumbs.jsm for
* additional details.
* Unless `forceUpdate` is set, the preview is not updated if:
* - It was already fetched recently
* - The stored preview is younger than DAYS_BEFORE_REPLACEMENT
* The previem image is encoded using WebP.
* @param {string} url The address of the page.
* @param {boolean} [forceUpdate] Whether to update the preview regardless.
* @returns {boolean} Whether a preview is available and ready.
*/
async update(url, { forceUpdate = false } = {}) {
if (!this.enabled) {
return false;
}
let filePath = this.getPathForUrl(url);
if (!forceUpdate) {
if (this.#recentlyUpdatedPreviews.has(filePath)) {
logConsole.debug("Skipping update because recently updated");
return true;
}
try {
let fileInfo = await IOUtils.stat(filePath);
if (
fileInfo.lastModified >
Date.now() - DAYS_BEFORE_REPLACEMENT * 86400000
) {
// File is recent enough.
this.#recentlyUpdatedPreviews.add(filePath);
logConsole.debug("Skipping update because file is recent");
return true;
}
} catch (ex) {
// If the file doesn't exist, we always update it.
if (!DOMException.isInstance(ex) || ex.name != "NotFoundError") {
logConsole.error("Error while trying to stat() preview" + ex);
return false;
}
}
}
let buffer = await new Promise(resolve => {
let observer = (subject, topic, errorUrl) => {
if (errorUrl == url) {
resolve(null);
}
};
Services.obs.addObserver(observer, "page-thumbnail:error");
BackgroundPageThumbs.capture(url, {
dontStore: true,
contentType: this.fileContentType,
onDone: (url, reason, handle) => {
Services.obs.removeObserver(observer, "page-thumbnail:error");
resolve(handle?.data);
},
});
});
if (!buffer) {
logConsole.error("Unable to fetch preview: " + url);
return false;
}
try {
await IOUtils.makeDirectory(this.getPath(), { ignoreExisting: true });
await IOUtils.write(filePath, new Uint8Array(buffer), {
tmpPath: filePath + ".tmp",
});
} catch (ex) {
logConsole.error(logConsole.error("Unable to create preview: " + ex));
return false;
}
this.#recentlyUpdatedPreviews.add(filePath);
return true;
}
/**
* Removes orphan previews that are not tracked by Places.
* Orphaning should normally not happen, but unexpected manipulation (e.g. the
* user touching the profile folder, or third party applications) could cause
* it.
* This method is slow, because it has to go through all the Places stored
* pages, thus it's suggested to only run it as periodic maintenance.
* @returns {boolean} Whether orphans deletion ran.
*/
async deleteOrphans() {
if (!this.enabled) {
return false;
}
// From the previews directory, get all the files whose name matches our
// format. Avoid any other filenames, also for safety reasons, since we are
// injecting them into SQL.
let files = await IOUtils.getChildren(this.getPath());
let hashes = files
.map(f => PathUtils.filename(f))
.filter(n => /^[a-f0-9]{32}\.webp$/)
.map(n => n.substring(0, n.lastIndexOf(".")));
await PlacesUtils.withConnectionWrapper(
"PlacesPreviews.jsm::deleteOrphans",
async db => {
await db.execute(
`
WITH files(hash) AS (
VALUES ${hashes.map(h => `('${h}')`).join(", ")}
)
INSERT OR IGNORE INTO moz_previews_tombstones
SELECT hash FROM files
EXCEPT
SELECT md5hex(url) FROM moz_places
`
);
}
);
this.#deletionHandler.ensureRunning();
return true;
}
/**
* This is invoked by #deletionHandler every time a preview file is removed.
* @param {string} filePath The path of the deleted file.
*/
onDelete(filePath) {
this.#recentlyUpdatedPreviews.delete(filePath);
this.emit("places-preview-deleted", filePath);
}
/**
* Used by tests to change the deletion timeout between chunks.
* @param {integer} timeout New timeout in milliseconds.
*/
testSetDeletionTimeout(timeout) {
if (timeout === null) {
this.#deletionHandler.timeout = DELETE_TIMEOUT_MS;
} else {
this.#deletionHandler.timeout = timeout;
}
}
})();
/**
* Used to exposes nsIPlacesPreviewsHelperService to the moz-page-thumb protocol
* cpp implementation.
*/
function PlacesPreviewsHelperService() {}
PlacesPreviewsHelperService.prototype = {
classID: Components.ID("{bd0a4d3b-ff26-4d4d-9a62-a513e1c1bf92}"),
QueryInterface: ChromeUtils.generateQI(["nsIPlacesPreviewsHelperService"]),
_xpcom_factory: ComponentUtils.generateSingletonFactory(
PlacesPreviewsHelperService
),
getFilePathForURL(url) {
return PlacesPreviews.getPathForUrl(url);
},
};