uBlock/src/js/logger.js

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

    uBlock - a browser extension to block requests.
    Copyright (C) 2015 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
*/

/* global µBlock */

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

µBlock.logger = (function() {

'use strict';

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

var LogEntry = function(args) {
    this.init(args);
};

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

LogEntry.prototype.init = function(args) {
    this.tstamp = Date.now();
    this.tab = args[0] || '';
    this.cat = args[1] || '';
    this.d0 = args[2];
    this.d1 = args[3];
    this.d2 = args[4];
    this.d3 = args[5];
    this.d4 = args[6];
};

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

var LogBuffer = function() {
    this.lastReadTime = 0;
    this.size = 50;
    this.buffer = new Array(this.size);
    this.readPtr = 0;
    this.writePtr = 0;
};

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

LogBuffer.prototype.clearBuffer = function(beg, end) {
    for ( var i = beg; i < end; i++ ) {
        this.buffer[i] = null;
    }
};

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

LogBuffer.prototype.writeOne = function(args) {
    // Reusing log entry = less memory churning
    var entry = this.buffer[this.writePtr];
    if ( entry instanceof LogEntry === false ) {
        this.buffer[this.writePtr] = new LogEntry(args);
    } else {
        entry.init(args);
    }
    this.writePtr += 1;
    if ( this.writePtr === this.size ) {
        this.writePtr = 0;
    }
    // Grow the buffer between 1.5x-2x the current size
    if ( this.writePtr === this.readPtr ) {
        var toMove = this.buffer.slice(0, this.writePtr);
        // https://github.com/gorhill/uBlock/issues/391
        // "The slice() method returns a shallow copy of a portion of an
        // "array into a new array object."
        // "shallow" => since we reuse entries, we need to remove the copied
        // entries to prevent single instance of LogEntry being used in
        // more than one slot.
        this.clearBuffer(0, this.writePtr);
        var minSize = Math.ceil(this.size * 1.5);
        this.size += toMove.length;
        if ( this.size < minSize ) {
            this.buffer = this.buffer.concat(toMove, new Array(minSize - this.size));
            this.writePtr = this.size;
        } else {
            this.buffer = this.buffer.concat(toMove);
            this.writePtr = 0;
        }
        this.size = this.buffer.length;
    }
};

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

LogBuffer.prototype.readAll = function() {
    var out;
    if ( this.readPtr < this.writePtr ) {
        out = this.buffer.slice(this.readPtr, this.writePtr);
    } else if ( this.writePtr < this.readPtr ) {
        out = this.buffer.slice(this.readPtr).concat(this.buffer.slice(0, this.writePtr));
    } else {
        out = [];
    }
    this.readPtr = this.writePtr;
    this.lastReadTime = Date.now();
    return out;
};

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

// Tab id to log buffer instances
var logBuffer = null;

// After 60 seconds without being read, a buffer will be considered unused, and
// thus removed from memory.
var logBufferObsoleteAfter = 60 * 1000;

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

var janitor = function() {
    if (
        logBuffer !== null &&
        logBuffer.lastReadTime < (Date.now() - logBufferObsoleteAfter)
    ) {
        api.writeOne = writeOneNoop;
        logBuffer = null;
    }
    if ( logBuffer !== null ) {
        vAPI.setTimeout(janitor, logBufferObsoleteAfter);
    }
};

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

var writeOneNoop = function() {
};

var writeOne = function() {
    logBuffer.writeOne(arguments);
};

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

var readAll = function() {
    if ( logBuffer === null ) {
        api.writeOne = writeOne;
        logBuffer = new LogBuffer();
        vAPI.setTimeout(janitor, logBufferObsoleteAfter);
    }
    return logBuffer.readAll();
};

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

var isEnabled = function() {
    return logBuffer !== null;
};

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

var api = {
    writeOne: writeOneNoop,
    readAll: readAll,
    isEnabled: isEnabled
};

return api;

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

})();

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