Continuous HTML5 FileWriter to prevent unexpected behavior happen when asynchronous call

continuous_file_writer.js

/*
 * Copyright (C) 2011 Wolfgang Koller
 * 
 * This file is part of GOFG Sports Computer - http://www.gofg.at/.
 * 
 * GOFG Sports Computer 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.
 * 
 * GOFG Sports Computer 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 GOFG Sports Computer.  If not, see <http://www.gnu.org/licenses/>.
 */

function ContinuousFileWriter( p_fileEntry ) {
  // Define the member variables
	var m_writeStack = new Array();
	var m_fileEntry = p_fileEntry;
	var m_fileWriter = null;
	
	// Define our member functions
	this.writeLine = writeLine;
	this.write = write;
	this._checkWrite = _checkWrite;
	this._write = _write;
	this._fileWriter = _fileWriter;
	this._fileError = _fileError;

	// Create a writer for the file-entry
	m_fileEntry.createWriter( _fileWriter );
	
	function writeLine( p_lineText ) {
		write( p_lineText + "\n" );
	}
	
	function write( p_text ) {
		m_writeStack.push( p_text );
		
		_checkWrite();
	}

	function _checkWrite() {
//		console.log( "Checking write: " + m_fileWriter + " / " + m_fileWriter.readyState );
		
		if( m_fileWriter != null && m_fileWriter.readyState != FileWriter.WRITING ) _write();
	}
	
	function _write() {
		if( m_writeStack.length <= 0 ) return;
//		console.log( "Writing..." );
		
		m_fileWriter.write( m_writeStack.shift() );
	}
	
	// Callback once the writer is ready
	function _fileWriter( p_fileWriter ) {
//		console.log( "CFW: FileWriter ready" );
		
		m_fileWriter = p_fileWriter;
		m_fileWriter.onerror = _fileError;
		m_fileWriter.onwriteend = _checkWrite;
		
		// Check for writing immediately
		_checkWrite();
	}
	
	// Called whenever an error occurs
	function _fileError( p_fileError ) {
		console.log( "Error while handling file-writing: " + p_fileError.code );
	}
}