uBlock/src/js/cosmetic-filtering.js

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

    µBlock - a browser extension to block requests.
    Copyright (C) 2014 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
*/

/* jshint bitwise: false */
/* global punycode, µBlock */

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

µBlock.cosmeticFilteringEngine = (function(){

'use strict';

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

var µb = µBlock;

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

// Could be replaced with encodeURIComponent/decodeURIComponent,
// which seems faster on Firefox.
var encode = JSON.stringify;
var decode = JSON.parse;

var isBadRegex = function(s) {
    try {
        void new RegExp(s);
    } catch (ex) {
        isBadRegex.message = ex.toString();
        return true;
    }
    return false;
};

/******************************************************************************/
/*
var histogram = function(label, buckets) {
    var h = [],
        bucket;
    for ( var k in buckets ) {
        if ( buckets.hasOwnProperty(k) === false ) {
            continue;
        }
        bucket = buckets[k];
        h.push({
            k: k,
            n: bucket instanceof FilterBucket ? bucket.filters.length : 1
        });
    }

    console.log('Histogram %s', label);

    var total = h.length;
    h.sort(function(a, b) { return b.n - a.n; });

    // Find indices of entries of interest
    var target = 3;
    for ( var i = 0; i < total; i++ ) {
        if ( h[i].n === target ) {
            console.log('\tEntries with only %d filter(s) start at index %s (key = "%s")', target, i, h[i].k);
            target -= 1;
        }
    }

    h = h.slice(0, 50);

    h.forEach(function(v) {
        console.log('\tkey="%s" count=%d', v.k, v.n);
    });
    console.log('\tTotal buckets count: %d', total);
};
*/
/******************************************************************************/

// Pure id- and class-based filters
// Examples:
//   #A9AdsMiddleBoxTop
//   .AD-POST

var FilterPlain = function() {
};

FilterPlain.prototype.retrieve = function(s, out) {
    out.push(s);
};

FilterPlain.prototype.fid = '#';

FilterPlain.prototype.toSelfie = function() {
};

FilterPlain.fromSelfie = function() {
    return filterPlain;
};

var filterPlain = new FilterPlain();

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

// Id- and class-based filters with extra selector stuff following.
// Examples:
//   #center_col > div[style="font-size:14px;margin-right:0;min-height:5px"] ...
//   #adframe:not(frameset)
//   .l-container > #fishtank

var FilterPlainMore = function(s) {
    this.s = s;
};

FilterPlainMore.prototype.retrieve = function(s, out) {
    if ( this.s.lastIndexOf(s, 0) === 0 ) {
        out.push(this.s);
    }
};

FilterPlainMore.prototype.fid = '#+';

FilterPlainMore.prototype.toSelfie = function() {
    return this.s;
};

FilterPlainMore.fromSelfie = function(s) {
    return new FilterPlainMore(s);
};

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

var FilterBucket = function(a, b) {
    this.f = null;
    this.filters = [];
    if ( a !== undefined ) {
        this.filters[0] = a;
        if ( b !== undefined ) {
            this.filters[1] = b;
        }
    }
};

FilterBucket.prototype.add = function(a) {
    this.filters.push(a);
};

FilterBucket.prototype.retrieve = function(s, out) {
    var i = this.filters.length;
    while ( i-- ) {
        this.filters[i].retrieve(s, out);
    }
};

FilterBucket.prototype.fid = '[]';

FilterBucket.prototype.toSelfie = function() {
    return this.filters.length.toString();
};

FilterBucket.fromSelfie = function() {
    return new FilterBucket();
};

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

// Any selector specific to a hostname
// Examples:
//   search.snapdo.com###ABottomD
//   facebook.com##.-cx-PRIVATE-fbAdUnit__root
//   sltrib.com###BLContainer + div[style="height:90px;"]
//   myps3.com.au##.Boxer[style="height: 250px;"]
//   lindaikeji.blogspot.com##a > img[height="600"]
//   japantimes.co.jp##table[align="right"][width="250"]
//   mobilephonetalk.com##[align="center"] > b > a[href^="http://tinyurl.com/"]

var FilterHostname = function(s, hostname) {
    this.s = s;
    this.hostname = hostname;
};

FilterHostname.prototype.retrieve = function(hostname, out) {
    if ( hostname.slice(-this.hostname.length) === this.hostname ) {
        out.push(this.s);
    }
};

FilterHostname.prototype.fid = 'h';

FilterHostname.prototype.toSelfie = function() {
    return encode(this.s) + '\t' + this.hostname;
};

FilterHostname.fromSelfie = function(s) {
    var pos = s.indexOf('\t');
    return new FilterHostname(decode(s.slice(0, pos)), s.slice(pos + 1));
};

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

// Any selector specific to an entity
// Examples:
//   google.*###cnt #center_col > #res > #topstuff > .ts

var FilterEntity = function(s, entity) {
    this.s = s;
    this.entity = entity;
};

FilterEntity.prototype.retrieve = function(entity, out) {
    if ( entity.slice(-this.entity.length) === this.entity ) {
        out.push(this.s);
    }
};

FilterEntity.prototype.fid = 'e';

FilterEntity.prototype.toSelfie = function() {
    return encode(this.s) + '\t' + this.entity;
};

FilterEntity.fromSelfie = function(s) {
    var pos = s.indexOf('\t');
    return new FilterEntity(decode(s.slice(0, pos)), s.slice(pos + 1));
};

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

var FilterParser = function() {
    this.prefix =  this.suffix = this.style = '';
    this.unhide = 0;
    this.hostnames = [];
    this.invalid = false;
    this.cosmetic = true;
    this.reParser = /^([^#]*?)(##|#@#)(.+)$/;
    this.reScriptContains = /^script:contains\(.+?\)$/;
};

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

FilterParser.prototype.reset = function() {
    this.prefix = this.suffix = this.style = '';
    this.unhide = 0;
    this.hostnames.length = 0;
    this.invalid = false;
    this.cosmetic = true;
    return this;
};

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

FilterParser.prototype.parse = function(raw) {
    // important!
    this.reset();

    var matches = this.reParser.exec(raw);
    if ( matches === null || matches.length !== 4 ) {
        this.cosmetic = false;
        return this;
    }
    this.prefix = matches[1].trim();
    this.unhide = matches[2].charAt(1) === '@' ? 1 : 0;
    this.suffix = matches[3].trim();

    // Cosmetic filters with explicit style properties can apply only:
    // - to specific cosmetic filters (those which apply to a specific site)
    // - to block cosmetic filters (not exception cosmetic filters)
    if ( this.suffix.slice(-1) === '}' ) {
        // Not supported for now: this code will ensure some backward
        // compatibility for when cosmetic filters with explicit style
        // properties start to be in use.
        this.invalid = true;
        return this;
    }

    // 2014-05-23:
    // https://github.com/gorhill/httpswitchboard/issues/260
    // Any sequence of `#` longer than one means the line is not a valid
    // cosmetic filter.
    if ( this.suffix.indexOf('##') !== -1 ) {
        this.cosmetic = false;
        return this;
    }

    // Normalize high-medium selectors: `href` is assumed to imply `a` tag. We
    // need to do this here in order to correctly avoid duplicates. The test
    // is designed to minimize overhead -- this is a low occurrence filter.
    if ( this.suffix.charAt(1) === '[' && this.suffix.slice(2, 9) === 'href^="' ) {
        this.suffix = this.suffix.slice(1);
    }

    if ( this.prefix !== '' ) {
        this.hostnames = this.prefix.split(/\s*,\s*/);
    }

    // Script tag filters: pre-process them so that can be used with minimal
    // overhead in the content script.
    // Examples:
    //   focus.de##script:contains(/uabInject/)
    //   focus.de##script:contains(uabInject)

    // Inline script tag filter?
    if (
        this.suffix.charAt(0) !== 's' ||
        this.reScriptContains.test(this.suffix) === false )
    {
        return this;
    }

    // Currently supported only as non-generic selector. Also, exception
    // script tag filter makes no sense, ignore.
    if ( this.hostnames.length === 0 || this.unhide === 1 ) {
        this.invalid = true;
        return this;
    }

    var suffix = this.suffix;
    this.suffix = 'script//:';

    // Plain string-based?
    if ( suffix.charAt(16) !== '/' || suffix.slice(-2) !== '/)' ) {
        this.suffix += suffix.slice(16, -1).replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
        return this;
    }

    // Regex-based
    this.suffix += suffix.slice(17, -2).replace(/\\/g, '\\');

    // Valid regex?
    if ( isBadRegex(this.suffix) ) {
        console.error(
            "uBlock Origin> discarding bad regular expression-based cosmetic filter '%s': '%s'",
            raw,
            isBadRegex.message
        );
        this.invalid = true;
        return this;
    }

    return this;
};

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

var SelectorCacheEntry = function() {
    this.reset();
};

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

SelectorCacheEntry.junkyard = [];

SelectorCacheEntry.factory = function() {
    var entry = SelectorCacheEntry.junkyard.pop();
    if ( entry ) {
        return entry.reset();
    }
    return new SelectorCacheEntry();
};

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

SelectorCacheEntry.prototype.netLowWaterMark = 20;
SelectorCacheEntry.prototype.netHighWaterMark = 30;

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

SelectorCacheEntry.prototype.reset = function() {
    this.cosmetic = {};
    this.net = {};
    this.netCount = 0;
    this.lastAccessTime = Date.now();
    return this;
};

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

SelectorCacheEntry.prototype.dispose = function() {
    this.cosmetic = this.net = null;
    if ( SelectorCacheEntry.junkyard.length < 25 ) {
        SelectorCacheEntry.junkyard.push(this);
    }
};

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

SelectorCacheEntry.prototype.addCosmetic = function(selectors) {
    var dict = this.cosmetic;
    var i = selectors.length || 0;
    while ( i-- ) {
        dict[selectors[i]] = true;
    }
};

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

SelectorCacheEntry.prototype.addNet = function(selectors) {
    if ( typeof selectors === 'string' ) {
        this.addNetOne(selectors, Date.now());
    } else {
        this.addNetMany(selectors, Date.now());
    }
    // Net request-derived selectors: I limit the number of cached selectors,
    // as I expect cases where the blocked net-requests are never the
    // exact same URL.
    if ( this.netCount < this.netHighWaterMark ) {
        return;
    }
    var dict = this.net;
    var keys = Object.keys(dict).sort(function(a, b) {
        return dict[b] - dict[a];
    }).slice(this.netLowWaterMark);
    var i = keys.length;
    while ( i-- ) {
        delete dict[keys[i]];
    }
};

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

SelectorCacheEntry.prototype.addNetOne = function(selector, now) {
    var dict = this.net;
    if ( dict[selector] === undefined ) {
        this.netCount += 1;
    }
    dict[selector] = now;
};

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

SelectorCacheEntry.prototype.addNetMany = function(selectors, now) {
    var dict = this.net;
    var i = selectors.length || 0;
    var selector;
    while ( i-- ) {
        selector = selectors[i];
        if ( dict[selector] === undefined ) {
            this.netCount += 1;
        }
        dict[selector] = now;
    }
};

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

SelectorCacheEntry.prototype.add = function(selectors, type) {
    this.lastAccessTime = Date.now();
    if ( type === 'cosmetic' ) {
        this.addCosmetic(selectors);
    } else {
        this.addNet(selectors);
    }
};

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

// https://github.com/chrisaljoudi/uBlock/issues/420
SelectorCacheEntry.prototype.remove = function(type) {
    this.lastAccessTime = Date.now();
    if ( type === undefined || type === 'cosmetic' ) {
        this.cosmetic = {};
    }
    if ( type === undefined || type === 'net' ) {
        this.net = {};
        this.netCount = 0;
    }
};

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

SelectorCacheEntry.prototype.retrieve = function(type, out) {
    this.lastAccessTime = Date.now();
    var dict = type === 'cosmetic' ? this.cosmetic : this.net;
    for ( var selector in dict ) {
        if ( dict.hasOwnProperty(selector) ) {
            out.push(selector);
        }
    }
};

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

// Two Unicode characters:
// T0HHHHHHH HHHHHHHHH
// |       |         |
// |       |         |
// |       |         |
// |       |         +-- bit 8-0 of FNV
// |       |
// |       +-- bit 15-9 of FNV
// |
// +-- filter type (0=hide 1=unhide)
//

var makeHash = function(unhide, token, mask) {
    // Ref: Given a URL, returns a unique 4-character long hash string
    // Based on: FNV32a
    // http://www.isthe.com/chongo/tech/comp/fnv/index.html#FNV-reference-source
    // The rest is custom, suited for µBlock.
    var i1 = token.length;
    var i2 = i1 >> 1;
    var i4 = i1 >> 2;
    var i8 = i1 >> 3;
    var hval = (0x811c9dc5 ^ token.charCodeAt(0)) >>> 0;
        hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
        hval >>>= 0;
        hval ^= token.charCodeAt(i8);
        hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
        hval >>>= 0;
        hval ^= token.charCodeAt(i4);
        hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
        hval >>>= 0;
        hval ^= token.charCodeAt(i4+i8);
        hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
        hval >>>= 0;
        hval ^= token.charCodeAt(i2);
        hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
        hval >>>= 0;
        hval ^= token.charCodeAt(i2+i8);
        hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
        hval >>>= 0;
        hval ^= token.charCodeAt(i2+i4);
        hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
        hval >>>= 0;
        hval ^= token.charCodeAt(i1-1);
        hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
        hval >>>= 0;
        hval &= mask;
        if ( unhide !== 0 ) {
            hval |= 0x20000;
        }
    return hval.toString(36);
};

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

// Cosmetic filter family tree:
//
// Generic
//    Low generic simple: class or id only
//    Low generic complex: class or id + extra stuff after
//    High generic:
//       High-low generic: [alt="..."],[title="..."]
//       High-medium generic: [href^="..."]
//       High-high generic: everything else
// Specific
//    Specfic hostname
//    Specific entity
// Generic filters can only be enforced once the main document is loaded.
// Specific filers can be enforced before the main document is loaded.

var FilterContainer = function() {
    this.domainHashMask = (1 << 10) - 1; // 10 bits
    this.type0NoDomainHash = 'type0NoDomain';
    this.type1NoDomainHash = 'type1NoDomain';
    this.parser = new FilterParser();
    this.selectorCachePruneDelay = 5 * 60 * 1000; // 5 minutes
    this.selectorCacheAgeMax = 20 * 60 * 1000; // 20 minutes
    this.selectorCacheCountMin = 10;
    this.selectorCacheTimer = null;
    this.reHasUnicode = /[^\x00-\x7F]/;
    this.punycode = punycode;
    this.reset();
};

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

// Reset all, thus reducing to a minimum memory footprint of the context.

FilterContainer.prototype.reset = function() {
    this.parser.reset();
    this.µburi = µb.URI;
    this.frozen = false;
    this.acceptedCount = 0;
    this.duplicateCount = 0;
    this.duplicateBuster = {};

    this.selectorCache = {};
    this.selectorCacheCount = 0;

    // permanent
    // [class], [id]
    this.lowGenericHide = {};

    // [alt="..."], [title="..."]
    this.highLowGenericHide = {};
    this.highLowGenericHideCount = 0;

    // a[href^="http..."]
    this.highMediumGenericHide = {};
    this.highMediumGenericHideCount = 0;

    // everything else
    this.highHighGenericHideArray = [];
    this.highHighGenericHide = '';
    this.highHighGenericHideCount = 0;

    // generic exception filters
    this.genericDonthide = [];

    // hostname, entity-based filters
    this.hostnameFilters = {};
    this.entityFilters = {};
    this.scriptTagFilters = {};
    this.scriptTagFilterCount = 0;
};

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

// https://github.com/chrisaljoudi/uBlock/issues/1004
// Detect and report invalid CSS selectors.

FilterContainer.prototype.isValidSelector = (function() {
    var div = document.createElement('div');

    // Not all browsers support `Element.matches`:
    // http://caniuse.com/#feat=matchesselector
    if ( typeof div.matches !== 'function' ) {
        return function() {
            return true;
        };
    }

    return function(s) {
        try {
            // https://github.com/gorhill/uBlock/issues/693
            div.matches(s + ',\n#foo');
            return true;
        } catch (e) {
        }
        if ( s.lastIndexOf('script//:', 0) === 0 ) {
            return true;
        }
        console.error('uBlock> invalid cosmetic filter:', s);
        return false;
    };
})();

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

FilterContainer.prototype.compile = function(s, out) {
    var parsed = this.parser.parse(s);
    if ( parsed.cosmetic === false ) {
        return false;
    }
    if ( parsed.invalid ) {
        return true;
    }

    var hostnames = parsed.hostnames;
    var i = hostnames.length;
    if ( i === 0 ) {
        this.compileGenericSelector(parsed, out);
        return true;
    }

    // For hostname- or entity-based filters, class- or id-based selectors are
    // still the most common, and can easily be tested using a plain regex.
    if (
        this.reClassOrIdSelector.test(parsed.suffix) === false &&
        this.isValidSelector(parsed.suffix) === false
    ) {
        return true;
    }

    // https://github.com/chrisaljoudi/uBlock/issues/151
    // Negated hostname means the filter applies to all non-negated hostnames
    // of same filter OR globally if there is no non-negated hostnames.
    var applyGlobally = true;
    var hostname;
    while ( i-- ) {
        hostname = hostnames[i];
        if ( hostname.charAt(0) !== '~' ) {
            applyGlobally = false;
        }
        if ( hostname.slice(-2) === '.*' ) {
            this.compileEntitySelector(hostname, parsed, out);
        } else {
            this.compileHostnameSelector(hostname, parsed, out);
        }
    }
    if ( applyGlobally ) {
        this.compileGenericSelector(parsed, out);
    }

    return true;
};

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

FilterContainer.prototype.compileGenericSelector = function(parsed, out) {
    var selector = parsed.suffix;

    // https://github.com/chrisaljoudi/uBlock/issues/497
    // All generic exception filters are put in the same bucket: they are
    // expected to be very rare.
    if ( parsed.unhide ) {
        if ( this.isValidSelector(selector) ) {
            out.push('c\vg1\v' + selector);
        }
        return;
    }

    var type = selector.charAt(0);
    var matches;

    if ( type === '#' || type === '.' ) {
        matches = this.rePlainSelector.exec(selector);
        if ( matches === null ) {
            return;
        }
        // Single-CSS rule: no need to test for whether the selector
        // is valid, the regex took care of this. Most generic selector falls
        // into that category.
        if ( matches[0] === selector ) {
            out.push(
                'c\vlg\v' +
                 matches[0]
            );
            return;
        }
        // Many-CSS rules
        if ( this.isValidSelector(selector) ) {
            out.push(
                'c\vlg+\v' +
                 matches[0] + '\v' +
                selector
            );
        }
        return;
    }

    // ["title"] and ["alt"] will go in high-low generic bin.
    if ( this.reHighLow.test(selector) ) {
        if ( this.isValidSelector(selector) ) {
            out.push('c\vhlg0\v' + selector);
        }
        return;
    }

    // [href^="..."] will go in high-medium generic bin.
    matches = this.reHighMedium.exec(selector);
    if ( matches && matches.length === 2 ) {
        if ( this.isValidSelector(selector) ) {
            out.push(
                'c\vhmg0\v' +
                matches[1] + '\v' +
                selector
            );
        }
        return;
    }

    // All else
    if ( this.isValidSelector(selector) ) {
        out.push('c\vhhg0\v' + selector);
    }
};

FilterContainer.prototype.reClassOrIdSelector = /^[#.][\w-]+$/;
FilterContainer.prototype.rePlainSelector = /^[#.][\w-]+/;
FilterContainer.prototype.reHighLow = /^[a-z]*\[(?:alt|title)="[^"]+"\]$/;
FilterContainer.prototype.reHighMedium = /^\[href\^="https?:\/\/([^"]{8})[^"]*"\]$/;

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

FilterContainer.prototype.compileHostnameSelector = function(hostname, parsed, out) {
    // https://github.com/chrisaljoudi/uBlock/issues/145
    var unhide = parsed.unhide;
    if ( hostname.charAt(0) === '~' ) {
        hostname = hostname.slice(1);
        unhide ^= 1;
    }

    // punycode if needed
    if ( this.reHasUnicode.test(hostname) ) {
        //console.debug('µBlock.cosmeticFilteringEngine/FilterContainer.compileHostnameSelector> punycoding:', hostname);
        hostname = this.punycode.toASCII(hostname);
    }

    // https://github.com/chrisaljoudi/uBlock/issues/188
    // If not a real domain as per PSL, assign a synthetic one
    var hash;
    var domain = this.µburi.domainFromHostname(hostname);
    if ( domain === '' ) {
        hash = unhide === 0 ? this.type0NoDomainHash : this.type1NoDomainHash;
    } else {
        hash = makeHash(unhide, domain, this.domainHashMask);
    }
    out.push(
        'c\v' +
        'h\v' +
        hash + '\v' +
        hostname + '\v' +
        parsed.suffix
    );
};

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

FilterContainer.prototype.compileEntitySelector = function(hostname, parsed, out) {
    var entity = hostname.slice(0, -2);
    out.push(
        'c\v' +
        'e\v' +
        entity + '\v' +
        parsed.suffix
    );
};

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

FilterContainer.prototype.fromCompiledContent = function(text, lineBeg, skip) {
    if ( skip ) {
        return this.skipCompiledContent(text, lineBeg);
    }

    var lineEnd;
    var textEnd = text.length;
    var line, fields, filter, key, bucket;

    while ( lineBeg < textEnd ) {
        if ( text.charAt(lineBeg) !== 'c' ) {
            return lineBeg;
        }
        lineEnd = text.indexOf('\n', lineBeg);
        if ( lineEnd === -1 ) {
            lineEnd = textEnd;
        }
        line = text.slice(lineBeg + 2, lineEnd);
        lineBeg = lineEnd + 1;


        this.acceptedCount += 1;
        if ( this.duplicateBuster.hasOwnProperty(line) ) {
            this.duplicateCount += 1;
            continue;
        }
        this.duplicateBuster[line] = true;

        fields = line.split('\v');

        // h	ir	twitter.com	.promoted-tweet
        if ( fields[0] === 'h' ) {
            // Special filter: script tags. Not a real CSS selector.
            if ( fields[3].lastIndexOf('script//:', 0) === 0 ) {
                this.createScriptTagFilter(fields[2], fields[3].slice(9));
                continue;
            }
            filter = new FilterHostname(fields[3], fields[2]);
            bucket = this.hostnameFilters[fields[1]];
            if ( bucket === undefined ) {
                this.hostnameFilters[fields[1]] = filter;
            } else if ( bucket instanceof FilterBucket ) {
                bucket.add(filter);
            } else {
                this.hostnameFilters[fields[1]] = new FilterBucket(bucket, filter);
            }
            continue;
        }

        // lg	105	.largeAd
        // lg+	2jx	.Mpopup + #Mad > #MadZone
        if ( fields[0] === 'lg' || fields[0] === 'lg+' ) {
            filter = fields[0] === 'lg' ?
                        filterPlain :
                        new FilterPlainMore(fields[2]);
            bucket = this.lowGenericHide[fields[1]];
            if ( bucket === undefined ) {
                this.lowGenericHide[fields[1]] = filter;
            } else if ( bucket instanceof FilterBucket ) {
                bucket.add(filter);
            } else {
                this.lowGenericHide[fields[1]] = new FilterBucket(bucket, filter);
            }
            continue;
        }

        // entity	selector
        if ( fields[0] === 'e' ) {
            // Special filter: script tags. Not a real CSS selector.
            if ( fields[2].lastIndexOf('script//:', 0) === 0 ) {
                this.createScriptTagFilter(fields[1], fields[2].slice(9));
                continue;
            }
            bucket = this.entityFilters[fields[1]];
            if ( bucket === undefined ) {
                this.entityFilters[fields[1]] = [fields[2]];
            } else {
                bucket.push(fields[2]);
            }
            continue;
        }

        if ( fields[0] === 'hlg0' ) {
            this.highLowGenericHide[fields[1]] = true;
            this.highLowGenericHideCount += 1;
            continue;
        }

        if ( fields[0] === 'hmg0' ) {
            key = fields[1];
            bucket = this.highMediumGenericHide[key];
            if ( bucket === undefined ) {
                this.highMediumGenericHide[key] = fields[2];
            } else if ( Array.isArray(bucket) ) {
                bucket.push(fields[2]);
            } else {
                this.highMediumGenericHide[key] = [bucket, fields[2]];
            }
            this.highMediumGenericHideCount += 1;
            continue;
        }

        if ( fields[0] === 'hhg0' ) {
            this.highHighGenericHideArray.push(fields[1]);
            this.highHighGenericHideCount += 1;
            continue;
        }

        // https://github.com/chrisaljoudi/uBlock/issues/497
        // Generic exception filters: expected to be a rare occurrence.
        if ( fields[0] === 'g1' ) {
            this.genericDonthide.push(fields[1]);
        }
    }
    return textEnd;
};

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

FilterContainer.prototype.skipCompiledContent = function(text, lineBeg) {
    var lineEnd;
    var textEnd = text.length;

    while ( lineBeg < textEnd ) {
        if ( text.charAt(lineBeg) !== 'c' ) {
            return lineBeg;
        }
        lineEnd = text.indexOf('\n', lineBeg);
        if ( lineEnd === -1 ) {
            lineEnd = textEnd;
        }
        lineBeg = lineEnd + 1;
    }
    return textEnd;
};

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

FilterContainer.prototype.createScriptTagFilter = function(hostname, s) {
    if ( this.scriptTagFilters.hasOwnProperty(hostname) ) {
        this.scriptTagFilters[hostname] += '|' + s;
    } else {
        this.scriptTagFilters[hostname] = s;
    }
    this.scriptTagFilterCount += 1;
};

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

FilterContainer.prototype.retrieveScriptTagRegex = function(domain, hostname) {
    if ( this.scriptTagFilterCount === 0 ) {
        return;
    }
    var out = [], hn = hostname, pos;
    for (;;) {
        if ( this.scriptTagFilters.hasOwnProperty(hn) ) {
            out.push(this.scriptTagFilters[hn]);
        }
        if ( hn === domain ) {
            break;
        }
        pos = hn.indexOf('.');
        if ( pos === -1 ) {
            break;
        }
        hn = hn.slice(pos + 1);
    }
    pos = domain.indexOf('.');
    if ( pos !== -1 ) {
        hn = domain.slice(0, pos);
        if ( this.scriptTagFilters.hasOwnProperty(hn) ) {
            out.push(this.scriptTagFilters[hn]);
        }
    }
    if ( out.length !== 0 ) {
        return out.join('|');
    }
};

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

FilterContainer.prototype.freeze = function() {
    this.duplicateBuster = {};

    if ( this.highHighGenericHide !== '' ) {
        this.highHighGenericHideArray.unshift(this.highHighGenericHide);
    }
    this.highHighGenericHide = this.highHighGenericHideArray.join(',\n');
    this.highHighGenericHideArray = [];

    this.parser.reset();
    this.frozen = true;
};

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

FilterContainer.prototype.toSelfie = function() {
    var selfieFromDict = function(dict) {
        var selfie = [];
        var bucket, ff, n, i, f;
        for ( var k in dict ) {
            if ( dict.hasOwnProperty(k) === false ) {
                continue;
            }
            // We need to encode the key because there could be a `\n`
            // character in it, which would trip the code at parse time.
            selfie.push('k\t' + encode(k));
            bucket = dict[k];
            selfie.push(bucket.fid + '\t' + bucket.toSelfie());
            if ( bucket.fid !== '[]' ) {
                continue;
            }
            ff = bucket.filters;
            n = ff.length;
            for ( i = 0; i < n; i++ ) {
                f = ff[i];
                selfie.push(f.fid + '\t' + f.toSelfie());
            }
        }
        return selfie.join('\n');
    };

    return {
        acceptedCount: this.acceptedCount,
        duplicateCount: this.duplicateCount,
        hostnameSpecificFilters: selfieFromDict(this.hostnameFilters),
        entitySpecificFilters: this.entityFilters,
        lowGenericHide: selfieFromDict(this.lowGenericHide),
        highLowGenericHide: this.highLowGenericHide,
        highLowGenericHideCount: this.highLowGenericHideCount,
        highMediumGenericHide: this.highMediumGenericHide,
        highMediumGenericHideCount: this.highMediumGenericHideCount,
        highHighGenericHide: this.highHighGenericHide,
        highHighGenericHideCount: this.highHighGenericHideCount,
        genericDonthide: this.genericDonthide,
        scriptTagFilters: this.scriptTagFilters,
        scriptTagFilterCount: this.scriptTagFilterCount
    };
};

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

FilterContainer.prototype.fromSelfie = function(selfie) {
    var factories = {
        '[]': FilterBucket,
         '#': FilterPlain,
        '#+': FilterPlainMore,
         'h': FilterHostname,
         'e': FilterEntity
    };

    var dictFromSelfie = function(selfie) {
        var dict = {};
        var dictKey;
        var bucket = null;
        var rawText = selfie;
        var rawEnd = rawText.length;
        var lineBeg = 0, lineEnd;
        var line, pos, what, factory;
        while ( lineBeg < rawEnd ) {
            lineEnd = rawText.indexOf('\n', lineBeg);
            if ( lineEnd < 0 ) {
                lineEnd = rawEnd;
            }
            line = rawText.slice(lineBeg, lineEnd);
            lineBeg = lineEnd + 1;
            pos = line.indexOf('\t');
            what = line.slice(0, pos);
            if ( what === 'k' ) {
                dictKey = decode(line.slice(pos + 1));
                bucket = null;
                continue;
            }
            factory = factories[what];
            if ( bucket === null ) {
                bucket = dict[dictKey] = factory.fromSelfie(line.slice(pos + 1));
                continue;
            }
            // When token key is reused, it can't be anything
            // else than FilterBucket
            bucket.add(factory.fromSelfie(line.slice(pos + 1)));
        }
        return dict;
    };

    this.acceptedCount = selfie.acceptedCount;
    this.duplicateCount = selfie.duplicateCount;
    this.hostnameFilters = dictFromSelfie(selfie.hostnameSpecificFilters);
    this.entityFilters = selfie.entitySpecificFilters;
    this.lowGenericHide = dictFromSelfie(selfie.lowGenericHide);
    this.highLowGenericHide = selfie.highLowGenericHide;
    this.highLowGenericHideCount = selfie.highLowGenericHideCount;
    this.highMediumGenericHide = selfie.highMediumGenericHide;
    this.highMediumGenericHideCount = selfie.highMediumGenericHideCount;
    this.highHighGenericHide = selfie.highHighGenericHide;
    this.highHighGenericHideCount = selfie.highHighGenericHideCount;
    this.genericDonthide = selfie.genericDonthide;
    this.scriptTagFilters = selfie.scriptTagFilters;
    this.scriptTagFilterCount = selfie.scriptTagFilterCount;
    this.frozen = true;
};

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

FilterContainer.prototype.triggerSelectorCachePruner = function() {
    if ( this.selectorCacheTimer !== null ) {
        return;
    }
    if ( this.selectorCacheCount <= this.selectorCacheCountMin ) {
        return;
    }
    // Of interest: http://fitzgeraldnick.com/weblog/40/
    // http://googlecode.blogspot.ca/2009/07/gmail-for-mobile-html5-series-using.html
    this.selectorCacheTimer = vAPI.setTimeout(
        this.pruneSelectorCacheAsync.bind(this),
        this.selectorCachePruneDelay
    );
};

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

FilterContainer.prototype.addToSelectorCache = function(details) {
    var hostname = details.hostname;
    if ( typeof hostname !== 'string' || hostname === '' ) {
        return;
    }
    var selectors = details.selectors;
    if ( !selectors ) {
        return;
    }
    var entry = this.selectorCache[hostname];
    if ( entry === undefined ) {
        entry = this.selectorCache[hostname] = SelectorCacheEntry.factory();
        this.selectorCacheCount += 1;
        this.triggerSelectorCachePruner();
    }
    entry.add(selectors, details.type);
};

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

FilterContainer.prototype.removeFromSelectorCache = function(targetHostname, type) {
    for ( var hostname in this.selectorCache ) {
        if ( this.selectorCache.hasOwnProperty(hostname) === false ) {
            continue;
        }
        if ( targetHostname !== '*' ) {
            if ( hostname.slice(0 - targetHostname.length) !== targetHostname ) {
                continue;
            }
            if ( hostname.length !== targetHostname.length &&
                 hostname.charAt(0 - targetHostname.length - 1) !== '.' ) {
                continue;
            }
        }
        this.selectorCache[hostname].remove(type);
    }
};

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

FilterContainer.prototype.retrieveFromSelectorCache = function(hostname, type, out) {
    var entry = this.selectorCache[hostname];
    if ( entry === undefined ) {
        return;
    }
    entry.retrieve(type, out);
};

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

FilterContainer.prototype.pruneSelectorCacheAsync = function() {
    this.selectorCacheTimer = null;
    if ( this.selectorCacheCount <= this.selectorCacheCountMin ) {
        return;
    }
    var cache = this.selectorCache;
    // Sorted from most-recently-used to least-recently-used, because
    //   we loop beginning at the end below.
    // We can't avoid sorting because we have to keep a minimum number of
    //   entries, and these entries should always be the most-recently-used.
    var hostnames = Object.keys(cache)
        .sort(function(a, b) { return cache[b].lastAccessTime - cache[a].lastAccessTime; })
        .slice(this.selectorCacheCountMin);
    var obsolete = Date.now() - this.selectorCacheAgeMax;
    var hostname, entry;
    var i = hostnames.length;
    while ( i-- ) {
        hostname = hostnames[i];
        entry = cache[hostname];
        if ( entry.lastAccessTime > obsolete ) {
            break;
        }
        // console.debug('pruneSelectorCacheAsync: flushing "%s"', hostname);
        entry.dispose();
        delete cache[hostname];
        this.selectorCacheCount -= 1;
    }
    this.triggerSelectorCachePruner();
};

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

FilterContainer.prototype.retrieveGenericSelectors = function(request) {
    if ( this.acceptedCount === 0 ) {
        return;
    }
    if ( !request.selectors ) {
        return;
    }

    //quickProfiler.start('FilterContainer.retrieve()');

    var r = {
        hide: []
    };

    if ( request.firstSurvey ) {
        r.highGenerics = {
            hideLow: this.highLowGenericHide,
            hideLowCount: this.highLowGenericHideCount,
            hideMedium: this.highMediumGenericHide,
            hideMediumCount: this.highMediumGenericHideCount,
            hideHigh: this.highHighGenericHide,
            hideHighCount: this.highHighGenericHideCount
        };
        // https://github.com/chrisaljoudi/uBlock/issues/497
        r.donthide = this.genericDonthide;
    }

    var hideSelectors = r.hide;
    var selector, bucket;
    var selectors = request.selectors;
    var i = selectors.length;
    while ( i-- ) {
        if (
            (selector = selectors[i]) &&
            (bucket = this.lowGenericHide[selector])
        ) {
            bucket.retrieve(selector, hideSelectors);
        }
    }

    //quickProfiler.stop();

    //console.log(
    //    'µBlock> abp-hide-filters.js: %d selectors in => %d selectors out',
    //    request.selectors.length,
    //    r.hide.length + r.donthide.length
    //);

    return r;
};

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

FilterContainer.prototype.retrieveDomainSelectors = function(request) {
    if ( !request.locationURL ) {
        return;
    }

    //quickProfiler.start('FilterContainer.retrieve()');

    var hostname = this.µburi.hostnameFromURI(request.locationURL);
    var domain = this.µburi.domainFromHostname(hostname) || hostname;
    var pos = domain.indexOf('.');

    // https://github.com/chrisaljoudi/uBlock/issues/587
    // r.ready will tell the content script the cosmetic filtering engine is
    // up and ready.

    var r = {
        ready: this.frozen,
        domain: domain,
        entity: pos === -1 ? domain : domain.slice(0, pos - domain.length),
        skipCosmeticFiltering: this.acceptedCount === 0,
        cosmeticHide: [],
        cosmeticDonthide: [],
        netHide: [],
        netCollapse: µb.userSettings.collapseBlocked
    };

    var hash, bucket;
    hash = makeHash(0, domain, this.domainHashMask);
    if ( (bucket = this.hostnameFilters[hash]) ) {
        bucket.retrieve(hostname, r.cosmeticHide);
    }
    // https://github.com/chrisaljoudi/uBlock/issues/188
    // Special bucket for those filters without a valid domain name as per PSL
    if ( (bucket = this.hostnameFilters[this.type0NoDomainHash]) ) {
        bucket.retrieve(hostname, r.cosmeticHide);
    }

    // entity filter buckets are always plain js array
    if ( (bucket = this.entityFilters[r.entity]) ) {
        r.cosmeticHide = r.cosmeticHide.concat(bucket);
    }
    // No entity exceptions as of now

    hash = makeHash(1, domain, this.domainHashMask);
    if ( (bucket = this.hostnameFilters[hash]) ) {
        bucket.retrieve(hostname, r.cosmeticDonthide);
    }

    // https://github.com/chrisaljoudi/uBlock/issues/188
    // Special bucket for those filters without a valid domain name as per PSL
    if ( (bucket = this.hostnameFilters[this.type1NoDomainHash]) ) {
        bucket.retrieve(hostname, r.cosmeticDonthide);
    }

    this.retrieveFromSelectorCache(hostname, 'cosmetic', r.cosmeticHide);
    this.retrieveFromSelectorCache(hostname, 'net', r.netHide);

    //quickProfiler.stop();

    //console.log(
    //    'µBlock> abp-hide-filters.js: "%s" => %d selectors out',
    //    request.locationURL,
    //    r.cosmeticHide.length + r.cosmeticDonthide.length
    //);

    return r;
};

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

FilterContainer.prototype.getFilterCount = function() {
    return this.acceptedCount - this.duplicateCount;
};

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

return new FilterContainer();

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

})();

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