uBlock/src/js/pagestore.js

/*******************************************************************************

    uBlock Origin - a browser extension to block requests.
    Copyright (C) 2014-present Raymond Hill

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see {http://www.gnu.org/licenses/}.

    Home: https://github.com/gorhill/uBlock
*/

'use strict';

/*******************************************************************************

A PageRequestStore object is used to store net requests in two ways:

To record distinct net requests
To create a log of net requests

**/

{

// start of private namespace
// >>>>>

/******************************************************************************/

const µb = µBlock;

/******************************************************************************/

const NetFilteringResultCache = class {
    constructor() {
        this.init();
    }

    init() {
        this.blocked = new Map();
        this.results = new Map();
        this.hash = 0;
        this.timer = undefined;
        return this;
    }

    // https://github.com/gorhill/uBlock/issues/3619
    //   Don't collapse redirected resources
    rememberResult(fctxt, result) {
        if ( fctxt.tabId <= 0 ) { return; }
        if ( this.results.size === 0 ) {
            this.pruneAsync();
        }
        const key = `${fctxt.getDocHostname()} ${fctxt.type} ${fctxt.url}`;
        this.results.set(key, {
            result,
            redirectURL: fctxt.redirectURL,
            logData: fctxt.filter,
            tstamp: Date.now()
        });
        if ( result !== 1 || fctxt.redirectURL !== undefined ) { return; }
        const now = Date.now();
        this.blocked.set(key, now);
        this.hash = now;
    }

    rememberBlock(fctxt) {
        if ( fctxt.tabId <= 0 ) { return; }
        if ( this.blocked.size === 0 ) {
            this.pruneAsync();
        }
        if ( fctxt.redirectURL !== undefined ) { return; }
        const now = Date.now();
        this.blocked.set(
            `${fctxt.getDocHostname()} ${fctxt.type} ${fctxt.url}`,
            now
        );
        this.hash = now;
    }

    forgetResult(docHostname, type, url) {
        const key = `${docHostname} ${type} ${url}`;
        this.results.delete(key);
        this.blocked.delete(key);
    }

    empty() {
        this.blocked.clear();
        this.results.clear();
        this.hash = 0;
        if ( this.timer !== undefined ) {
            clearTimeout(this.timer);
            this.timer = undefined;
        }
    }

    prune() {
        const obsolete = Date.now() - this.shelfLife;
        for ( const entry of this.blocked ) {
            if ( entry[1] <= obsolete ) {
                this.results.delete(entry[0]);
                this.blocked.delete(entry[0]);
            }
        }
        for ( const entry of this.results ) {
            if ( entry[1].tstamp <= obsolete ) {
                this.results.delete(entry[0]);
            }
        }
        if ( this.blocked.size !== 0 || this.results.size !== 0 ) {
            this.pruneAsync();
        }
    }

    pruneAsync() {
        if ( this.timer !== undefined ) { return; }
        this.timer = vAPI.setTimeout(
            ( ) => {
                this.timer = undefined;
                this.prune();
            },
            this.shelfLife
        );
    }

    lookupResult(fctxt) {
        return this.results.get(
            fctxt.getDocHostname() + ' ' +
            fctxt.type + ' ' +
            fctxt.url
        );
    }

    lookupAllBlocked(hostname) {
        const result = [];
        for ( const entry of this.blocked ) {
            const pos = entry[0].indexOf(' ');
            if ( entry[0].slice(0, pos) === hostname ) {
                result[result.length] = entry[0].slice(pos + 1);
            }
        }
        return result;
    }

    static factory() {
        return new NetFilteringResultCache();
    }
};

NetFilteringResultCache.prototype.shelfLife = 15000;

/******************************************************************************/

// Frame stores are used solely to associate a URL with a frame id.

// To mitigate memory churning
const frameStoreJunkyard = [];
const frameStoreJunkyardMax = 50;

const FrameStore = class {
    constructor(frameURL) {
        this.init(frameURL);
    }

    init(frameURL) {
        this.t0 = Date.now();
        this.exceptCname = undefined;
        this.clickToLoad = false;
        this.rawURL = frameURL;
        if ( frameURL !== undefined ) {
            this.hostname = vAPI.hostnameFromURI(frameURL);
            this.domain =
                vAPI.domainFromHostname(this.hostname) || this.hostname;
        }
        return this;
    }

    dispose() {
        this.exceptCname = undefined;
        this.rawURL = this.hostname = this.domain = '';
        if ( frameStoreJunkyard.length < frameStoreJunkyardMax ) {
            frameStoreJunkyard.push(this);
        }
        return null;
    }

    static factory(frameURL) {
        const entry = frameStoreJunkyard.pop();
        if ( entry === undefined ) {
            return new FrameStore(frameURL);
        }
        return entry.init(frameURL);
    }
};

/******************************************************************************/

// To mitigate memory churning
const pageStoreJunkyard = [];
const pageStoreJunkyardMax = 10;

const PageStore = class {
    constructor(tabId, context) {
        this.extraData = new Map();
        this.journal = [];
        this.journalTimer = null;
        this.journalLastCommitted = this.journalLastUncommitted = undefined;
        this.journalLastUncommittedURL = undefined;
        this.netFilteringCache = NetFilteringResultCache.factory();
        this.init(tabId, context);
    }

    static factory(tabId, context) {
        let entry = pageStoreJunkyard.pop();
        if ( entry === undefined ) {
            entry = new PageStore(tabId, context);
        } else {
            entry.init(tabId, context);
        }
        return entry;
    }

    // https://github.com/gorhill/uBlock/issues/3201
    //   The context is used to determine whether we report behavior change
    //   to the logger.

    init(tabId, context) {
        const tabContext = µb.tabContextManager.mustLookup(tabId);
        this.tabId = tabId;

        // If we are navigating from-to same site, remember whether large
        // media elements were temporarily allowed.
        if (
            typeof this.allowLargeMediaElementsUntil !== 'number' ||
            tabContext.rootHostname !== this.tabHostname
        ) {
            this.allowLargeMediaElementsUntil = Date.now();
        }

        this.tabHostname = tabContext.rootHostname;
        this.title = tabContext.rawURL;
        this.rawURL = tabContext.rawURL;
        this.hostnameToCountMap = new Map();
        this.contentLastModified = 0;
        this.logData = undefined;
        this.perLoadBlockedRequestCount = 0;
        this.perLoadAllowedRequestCount = 0;
        this.remoteFontCount = 0;
        this.popupBlockedCount = 0;
        this.largeMediaCount = 0;
        this.largeMediaTimer = null;
        this.internalRedirectionCount = 0;
        this.allowLargeMediaElementsRegex = undefined;
        this.extraData.clear();

        this.frameAddCount = 0;
        this.frames = new Map();
        this.setFrameURL(0, tabContext.rawURL);

        // The current filtering context is cloned because:
        // - We may be called with or without the current context having been
        //   initialized.
        // - If it has been initialized, we do not want to change the state
        //   of the current context.
        const fctxt = µb.logger.enabled
            ? µb.filteringContext
                .duplicate()
                .fromTabId(tabId)
                .setURL(tabContext.rawURL)
            : undefined;

        // https://github.com/uBlockOrigin/uBlock-issues/issues/314
        const masterSwitch = tabContext.getNetFilteringSwitch();

        this.noCosmeticFiltering = µb.sessionSwitches.evaluateZ(
            'no-cosmetic-filtering',
            tabContext.rootHostname
        ) === true;
        if (
            masterSwitch &&
            this.noCosmeticFiltering &&
            µb.logger.enabled &&
            context === 'tabCommitted'
        ) {
            fctxt.setRealm('cosmetic')
                 .setType('dom')
                 .setFilter(µb.sessionSwitches.toLogData())
                 .toLogger();
        }

        return this;
    }

    reuse(context) {
        // When force refreshing a page, the page store data needs to be reset.

        // If the hostname changes, we can't merely just update the context.
        const tabContext = µb.tabContextManager.mustLookup(this.tabId);
        if ( tabContext.rootHostname !== this.tabHostname ) {
            context = '';
        }

        // If URL changes without a page reload (more and more common), then
        // we need to keep all that we collected for reuse. In particular,
        // not doing so was causing a problem in `videos.foxnews.com`:
        // clicking a video thumbnail would not work, because the frame
        // hierarchy structure was flushed from memory, while not really being
        //  flushed on the page.
        if ( context === 'tabUpdated' ) {
            // As part of https://github.com/chrisaljoudi/uBlock/issues/405
            // URL changed, force a re-evaluation of filtering switch
            this.rawURL = tabContext.rawURL;
            this.setFrameURL(0, this.rawURL);
            return this;
        }

        // A new page is completely reloaded from scratch, reset all.
        if ( this.largeMediaTimer !== null ) {
            clearTimeout(this.largeMediaTimer);
            this.largeMediaTimer = null;
        }
        this.disposeFrameStores();
        this.init(this.tabId, context);
        return this;
    }

    dispose() {
        this.tabHostname = '';
        this.title = '';
        this.rawURL = '';
        this.hostnameToCountMap = null;
        this.netFilteringCache.empty();
        this.allowLargeMediaElementsUntil = Date.now();
        this.allowLargeMediaElementsRegex = undefined;
        if ( this.largeMediaTimer !== null ) {
            clearTimeout(this.largeMediaTimer);
            this.largeMediaTimer = null;
        }
        this.disposeFrameStores();
        if ( this.journalTimer !== null ) {
            clearTimeout(this.journalTimer);
            this.journalTimer = null;
        }
        this.journal = [];
        this.journalLastUncommittedURL = undefined;
        if ( pageStoreJunkyard.length < pageStoreJunkyardMax ) {
            pageStoreJunkyard.push(this);
        }
        return null;
    }

    disposeFrameStores() {
        for ( const frameStore of this.frames.values() ) {
            frameStore.dispose();
        }
        this.frames.clear();
    }

    getFrameStore(frameId) {
        return this.frames.get(frameId) || null;
    }

    setFrameURL(frameId, frameURL) {
        let frameStore = this.frames.get(frameId);
        if ( frameStore !== undefined ) {
            frameStore.init(frameURL);
        } else {
            frameStore = FrameStore.factory(frameURL);
            this.frames.set(frameId, frameStore);
            this.frameAddCount += 1;
            if ( (this.frameAddCount & 0b111111) === 0 ) {
                this.pruneFrames();
            }
        }
        return frameStore;
    }

    // There is no event to tell us a specific subframe has been removed from
    // the main document. The code below will remove subframes which are no
    // longer present in the root document. Removing obsolete subframes is
    // not a critical task, so this is executed just once on a while, to avoid
    // bloated dictionary of subframes.
    // A TTL is used to avoid race conditions when new iframes are added
    // through the webRequest API but still not yet visible through the
    // webNavigation API.
    async pruneFrames() {
        let entries;
        try {
            entries = await webext.webNavigation.getAllFrames({
                tabId: this.tabId
            });
        } catch(ex) {
        }
        if ( Array.isArray(entries) === false ) { return; }
        const toKeep = new Set();
        for ( const { frameId } of entries ) {
            toKeep.add(frameId);
        }
        const obsolete = Date.now() - 60000;
        for ( const [ frameId, { t0 } ] of this.frames ) {
            if ( toKeep.has(frameId) || t0 >= obsolete ) { continue; }
            this.frames.delete(frameId);
        }
    }

    getNetFilteringSwitch() {
        return µb.tabContextManager
                 .mustLookup(this.tabId)
                 .getNetFilteringSwitch();
    }

    getSpecificCosmeticFilteringSwitch() {
        return this.noCosmeticFiltering !== true;
    }

    toggleNetFilteringSwitch(url, scope, state) {
        µb.toggleNetFilteringSwitch(url, scope, state);
        this.netFilteringCache.empty();
    }

    injectLargeMediaElementScriptlet() {
        vAPI.tabs.executeScript(this.tabId, {
            file: '/js/scriptlets/load-large-media-interactive.js',
            allFrames: true,
            runAt: 'document_idle',
        });
        µb.contextMenu.update(this.tabId);
    }

    temporarilyAllowLargeMediaElements(state) {
        this.largeMediaCount = 0;
        µb.contextMenu.update(this.tabId);
        if ( state ) {
            this.allowLargeMediaElementsUntil = 0;
            this.allowLargeMediaElementsRegex = undefined;
        } else {
            this.allowLargeMediaElementsUntil = Date.now();
        }
        µb.scriptlets.injectDeep(this.tabId, 'load-large-media-all');
    }

    // https://github.com/gorhill/uBlock/issues/2053
    //   There is no way around using journaling to ensure we deal properly with
    //   potentially out of order navigation events vs. network request events.
    journalAddRequest(hostname, result) {
        if ( hostname === '' ) { return; }
        this.journal.push(
            hostname,
            result === 1 ? 0x00000001 : 0x00010000
        );
        if ( this.journalTimer === null ) {
            this.journalTimer = vAPI.setTimeout(
                ( ) => { this.journalProcess(true); },
                µb.hiddenSettings.requestJournalProcessPeriod
            );
        }
    }

    journalAddRootFrame(type, url) {
        if ( type === 'committed' ) {
            this.journalLastCommitted = this.journal.length;
            if (
                this.journalLastUncommitted !== undefined &&
                this.journalLastUncommitted < this.journalLastCommitted &&
                this.journalLastUncommittedURL === url
            ) {
                this.journalLastCommitted = this.journalLastUncommitted;
                this.journalLastUncommitted = undefined;
            }
        } else if ( type === 'uncommitted' ) {
            this.journalLastUncommitted = this.journal.length;
            this.journalLastUncommittedURL = url;
        }
        if ( this.journalTimer !== null ) {
            clearTimeout(this.journalTimer);
        }
        this.journalTimer = vAPI.setTimeout(
            ( ) => { this.journalProcess(true); },
            µb.hiddenSettings.requestJournalProcessPeriod
        );
    }

    journalProcess(fromTimer) {
        if ( !fromTimer ) {
            clearTimeout(this.journalTimer);
        }
        this.journalTimer = null;

        const journal = this.journal;
        const now = Date.now();
        let aggregateCounts = 0;
        let pivot = this.journalLastCommitted || 0;

        // Everything after pivot originates from current page.
        for ( let i = pivot; i < journal.length; i += 2 ) {
            const hostname = journal[i];
            let hostnameCounts = this.hostnameToCountMap.get(hostname);
            if ( hostnameCounts === undefined ) {
                hostnameCounts = 0;
                this.contentLastModified = now;
            }
            let count = journal[i+1];
            this.hostnameToCountMap.set(hostname, hostnameCounts + count);
            aggregateCounts += count;
        }
        this.perLoadBlockedRequestCount += aggregateCounts & 0xFFFF;
        this.perLoadAllowedRequestCount += aggregateCounts >>> 16 & 0xFFFF;
        this.journalLastCommitted = undefined;

        // https://github.com/chrisaljoudi/uBlock/issues/905#issuecomment-76543649
        //   No point updating the badge if it's not being displayed.
        if ( (aggregateCounts & 0xFFFF) && µb.userSettings.showIconBadge ) {
            µb.updateToolbarIcon(this.tabId, 0x02);
        }

        // Everything before pivot does not originate from current page -- we
        // still need to bump global blocked/allowed counts.
        for ( let i = 0; i < pivot; i += 2 ) {
            aggregateCounts += journal[i+1];
        }
        if ( aggregateCounts !== 0 ) {
            µb.localSettings.blockedRequestCount +=
                aggregateCounts & 0xFFFF;
            µb.localSettings.allowedRequestCount +=
                aggregateCounts >>> 16 & 0xFFFF;
            µb.localSettingsLastModified = now;
        }
        journal.length = 0;
    }

    filterRequest(fctxt) {
        fctxt.filter = undefined;

        if ( this.getNetFilteringSwitch(fctxt) === false ) {
            return 0;
        }

        if (
            fctxt.itype === fctxt.CSP_REPORT &&
            this.filterCSPReport(fctxt) === 1
        ) {
            return 1;
        }

        if (
            (fctxt.itype & fctxt.FONT_ANY) !== 0 &&
            this.filterFont(fctxt) === 1 )
        {
            return 1;
        }

        if (
            fctxt.itype === fctxt.SCRIPT &&
            this.filterScripting(fctxt, true) === 1
        ) {
            return 1;
        }

        const cacheableResult = this.cacheableResults.has(fctxt.itype);

        if ( cacheableResult ) {
            const entry = this.netFilteringCache.lookupResult(fctxt);
            if ( entry !== undefined ) {
                fctxt.redirectURL = entry.redirectURL;
                fctxt.filter = entry.logData;
                return entry.result;
            }
        }

        const requestType = fctxt.type;
        const loggerEnabled = µb.logger.enabled;

        // Dynamic URL filtering.
        let result = µb.sessionURLFiltering.evaluateZ(
            fctxt.getTabHostname(),
            fctxt.url,
            requestType
        );
        if ( result !== 0 && loggerEnabled ) {
            fctxt.filter = µb.sessionURLFiltering.toLogData();
        }

        // Dynamic hostname/type filtering.
        if ( result === 0 && µb.userSettings.advancedUserEnabled ) {
            result = µb.sessionFirewall.evaluateCellZY(
                fctxt.getTabHostname(),
                fctxt.getHostname(),
                requestType
            );
            if ( result !== 0 && result !== 3 && loggerEnabled ) {
                fctxt.filter = µb.sessionFirewall.toLogData();
            }
        }

        // Static filtering has lowest precedence.
        const snfe = µb.staticNetFilteringEngine;
        if ( result === 0 || result === 3 ) {
            result = snfe.matchString(fctxt);
            if ( result !== 0 ) {
                if ( loggerEnabled ) {
                    fctxt.filter = snfe.toLogData();
                }
                // https://github.com/uBlockOrigin/uBlock-issues/issues/943
                //   Blanket-except blocked aliased canonical hostnames?
                if (
                    result === 1 &&
                    fctxt.aliasURL !== undefined &&
                    snfe.isBlockImportant() === false &&
                    this.shouldExceptCname(fctxt)
                ) {
                    return 2;
                }
            }
        }

        // Click-to-load?
        // When frameId is not -1, the resource is always sub_frame.
        if ( result === 1 && fctxt.frameId !== -1 ) {
            const frameStore = this.getFrameStore(fctxt.frameId);
            if ( frameStore !== null && frameStore.clickToLoad ) {
                result = 2;
                if ( loggerEnabled ) {
                    fctxt.pushFilter({
                        result,
                        source: 'network',
                        raw: 'click-to-load',
                    });
                }
            }
        }

        // Modifier(s)?
        // A modifier is an action which transform the original network request.
        // https://github.com/gorhill/uBlock/issues/949
        //   Redirect blocked request?
        // https://github.com/uBlockOrigin/uBlock-issues/issues/760
        //   Redirect non-blocked request?
        if ( (fctxt.itype & fctxt.INLINE_ANY) === 0 ) {
            if ( result === 1 ) {
                if ( µb.hiddenSettings.ignoreRedirectFilters !== true ) {
                    const redirectURL = µb.redirectEngine.toURL(fctxt);
                    if ( redirectURL !== undefined ) {
                        fctxt.redirectURL = redirectURL;
                        this.internalRedirectionCount += 1;
                        fctxt.pushFilter({
                            source: 'redirect',
                            raw: µb.redirectEngine.resourceNameRegister
                        });
                    }
                }
            } else if ( snfe.hasQuery(fctxt) ) {
                const directives = snfe.filterQuery(fctxt);
                if ( directives !== undefined && loggerEnabled ) {
                    fctxt.pushFilters(directives.map(a => a.logData()));
                }
            }
        }

        if ( cacheableResult ) {
            this.netFilteringCache.rememberResult(fctxt, result);
        } else if ( result === 1 && this.collapsibleResources.has(fctxt.itype) ) {
            this.netFilteringCache.rememberBlock(fctxt);
        }

        return result;
    }

    filterCSPReport(fctxt) {
        if (
            µb.sessionSwitches.evaluateZ(
                'no-csp-reports',
                fctxt.getHostname()
            )
        ) {
            if ( µb.logger.enabled ) {
                fctxt.filter = µb.sessionSwitches.toLogData();
            }
            return 1;
        }
        return 0;
    }

    filterFont(fctxt) {
        if ( fctxt.itype === fctxt.FONT ) {
            this.remoteFontCount += 1;
        }
        if (
            µb.sessionSwitches.evaluateZ(
                'no-remote-fonts',
                fctxt.getTabHostname()
            ) !== false
        ) {
            if ( µb.logger.enabled ) {
                fctxt.filter = µb.sessionSwitches.toLogData();
            }
            return 1;
        }
        return 0;
    }

    filterScripting(fctxt, netFiltering) {
        fctxt.filter = undefined;
        if ( netFiltering === undefined ) {
            netFiltering = this.getNetFilteringSwitch(fctxt);
        }
        if (
            netFiltering === false ||
            µb.sessionSwitches.evaluateZ(
                'no-scripting',
                fctxt.getTabHostname()
            ) === false
        ) {
            return 0;
        }
        if ( µb.logger.enabled ) {
            fctxt.filter = µb.sessionSwitches.toLogData();
        }
        return 1;
    }

    // The caller is responsible to check whether filtering is enabled or not.
    filterLargeMediaElement(fctxt, size) {
        fctxt.filter = undefined;

        if ( this.allowLargeMediaElementsUntil === 0 ) {
            return 0;
        }
        // Disregard large media elements previously allowed: for example, to
        // seek inside a previously allowed audio/video.
        if (
            this.allowLargeMediaElementsRegex instanceof RegExp &&
            this.allowLargeMediaElementsRegex.test(fctxt.url)
        ) {
            return 0;
        }
        if ( Date.now() < this.allowLargeMediaElementsUntil ) {
            const sources = this.allowLargeMediaElementsRegex instanceof RegExp
                ? [ this.allowLargeMediaElementsRegex.source ]
                : [];
            sources.push('^' + µb.escapeRegex(fctxt.url));
            this.allowLargeMediaElementsRegex = new RegExp(sources.join('|'));
            return 0;
        }
        if (
            µb.sessionSwitches.evaluateZ(
                'no-large-media',
                fctxt.getTabHostname()
            ) !== true
        ) {
            this.allowLargeMediaElementsUntil = 0;
            return 0;
        }
        if ( (size >>> 10) < µb.userSettings.largeMediaSize ) {
            return 0;
        }

        this.largeMediaCount += 1;
        if ( this.largeMediaTimer === null ) {
            this.largeMediaTimer = vAPI.setTimeout(( ) => {
                this.largeMediaTimer = null;
                this.injectLargeMediaElementScriptlet();
            }, 500);
        }

        if ( µb.logger.enabled ) {
            fctxt.filter = µb.sessionSwitches.toLogData();
        }

        return 1;
    }

    clickToLoad(frameId, frameURL) {
        let frameStore = this.getFrameStore(frameId);
        if ( frameStore === null ) {
            frameStore = this.setFrameURL(frameId, frameURL);
        }
        this.netFilteringCache.forgetResult(
            this.tabHostname,
            'sub_frame',
            frameURL
        );
        frameStore.clickToLoad = true;
    }

    shouldExceptCname(fctxt) {
        let exceptCname;
        let frameStore;
        if ( fctxt.docId !== undefined ) {
            frameStore = this.getFrameStore(fctxt.docId);
            if ( frameStore instanceof Object ) {
                exceptCname = frameStore.exceptCname;
            }
        }
        if ( exceptCname === undefined ) {
            const result = µb.staticNetFilteringEngine.matchStringReverse(
                'cname',
                frameStore instanceof Object
                    ? frameStore.rawURL
                    : fctxt.getDocOrigin()
            );
            if ( result === 2 ) {
                exceptCname = µb.logger.enabled
                    ? µb.staticNetFilteringEngine.toLogData()
                    : true;
            } else {
                exceptCname = false;
            }
            if ( frameStore instanceof Object ) {
                frameStore.exceptCname = exceptCname;
            }
        }
        if ( exceptCname === false ) { return false; }
        if ( exceptCname instanceof Object ) {
            fctxt.pushFilter(exceptCname);
        }
        return true;
    }

    getBlockedResources(request, response) {
        const normalURL = µb.normalizePageURL(this.tabId, request.frameURL);
        const resources = request.resources;
        const fctxt = µb.filteringContext;
        fctxt.fromTabId(this.tabId)
             .setDocOriginFromURL(normalURL);
        // Force some resources to go through the filtering engine in order to
        // populate the blocked-resources cache. This is required because for
        // some resources it's not possible to detect whether they were blocked
        // content script-side (i.e. `iframes` -- unlike `img`).
        if ( Array.isArray(resources) && resources.length !== 0 ) {
            for ( const resource of resources ) {
                this.filterRequest(
                    fctxt.setType(resource.type).setURL(resource.url)
                );
            }
        }
        if ( this.netFilteringCache.hash === response.hash ) { return; }
        response.hash = this.netFilteringCache.hash;
        response.blockedResources =
            this.netFilteringCache.lookupAllBlocked(fctxt.getDocHostname());
    }
};

PageStore.prototype.cacheableResults = new Set([
    µb.FilteringContext.SUB_FRAME,
]);

PageStore.prototype.collapsibleResources = new Set([
    µb.FilteringContext.IMAGE,
    µb.FilteringContext.MEDIA,
    µb.FilteringContext.OBJECT,
    µb.FilteringContext.SUB_FRAME,
]);

µb.PageStore = PageStore;

/******************************************************************************/

// <<<<<
// end of private namespace

}