gistfile1.js

/**
 * Rough FileAppender implementation for log4javascript 1.4.
 *
 * Copyright 2013 Tim Down.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

(function() {
    function BrowserFileAppender(fileName) {
        fileName = fileName || "log4javascript.log";
        var appender = this;

        // Use HTML5 file API if available
        window.requestFileSystem = window.requestFileSystem || window.webkitRequestFileSystem;
        if (window.requestFileSystem && window.Blob) {
            appender.writeMessageToFile = (function() {
                var queuedMessages = [];

                var errorHandler = function(err) {
                    var msg = '';

                    switch (err.code) {
                        case FileError.QUOTA_EXCEEDED_ERR:
                            msg = "QUOTA_EXCEEDED_ERR";
                            break;
                        case FileError.NOT_FOUND_ERR:
                            msg = "NOT_FOUND_ERR";
                            break;
                        case FileError.SECURITY_ERR:
                            msg = "SECURITY_ERR";
                            break;
                        case FileError.INVALID_MODIFICATION_ERR:
                            msg = "INVALID_MODIFICATION_ERR";
                            break;
                        case FileError.INVALID_STATE_ERR:
                            msg = "INVALID_STATE_ERR";
                            break;
                        default:
                            msg = "Unknown Error";
                            break;
                    }

                    if (window.console && window.console.error) {
                        console.error("An error occurred: " + msg, arguments);
                    }
                };

                var appendQueuedMessages;
                var writing = false;

                window.requestFileSystem(
                    window.TEMPORARY,
                    5 * 1024 * 1024,
                    function(fs) {
                        if (window.console && window.console.log) {
                            console.log("File system object initialized!");
                        }

                        fs.root.getFile(fileName, {create: true}, function(fileEntry) {
                            appendQueuedMessages = function() {
                                writing = true;
                                fileEntry.createWriter(function(fileWriter) {
                                    fileWriter.seek(fileWriter.length);
                                    var blob = new Blob(queuedMessages, {type: 'text/plain'});
                                    fileWriter.write(blob);
                                    queuedMessages.length = 0;
                                    writing = false;
                                }, errorHandler);
                            };
                        }, errorHandler);
                    },
                    errorHandler
                );

                return function(msg) {
                    queuedMessages.push(msg);
                    if (appendQueuedMessages && !writing) {
                        appendQueuedMessages();
                    }
                };
            })();
        }

        // Next strategy: ActiveX, as used in IE.
        else if (typeof window.ActiveXObject != "undefined") {
            appender.writeMessageToFile = (function() {
                var fso;
                var queuedMessages = [];
                var timer;
                var writeMessageToFile = null;

                try {
                    fso = new ActiveXObject("Scripting.FileSystemObject");

                    var appendQueuedMessages = function() {
                        timer = null;

                        // Try opening existing file and create it first if it does not exist
                        try {
                            var file = fso.OpenTextFile(fileName, 8, true);
                            file.Write( queuedMessages.join("") );
                            file.close();
                            queuedMessages.length = 0;
                        } catch (e) {
                            // Prevent further attempts to write to this file
                            appender.writeMessageToFile = null;
                        }
                    };

                    writeMessageToFile = function(msg) {
                        queuedMessages.push(msg);
                        if (timer) {
                            window.clearTimeout(timer);
                        }
                        timer = window.setTimeout(appendQueuedMessages, 200);
                    };
                } catch(e) {
                }

                return writeMessageToFile;
            })();
        }
    }

    BrowserFileAppender.prototype = new log4javascript.Appender();

    BrowserFileAppender.prototype.layout = new log4javascript.PatternLayout("%d{yyyy-MM-dd HH:mm:ss} %-5p - %m{1}%n");

    BrowserFileAppender.prototype.append = function(loggingEvent) {
        if (this.writeMessageToFile) {
            this.writeMessageToFile( this.getLayout().formatWithException(loggingEvent) );
        }
    };

    BrowserFileAppender.prototype.toString = function() {
        return "BrowserFileAppender";
    };

    log4javascript.BrowserFileAppender = BrowserFileAppender;
})();