view java/src/uk/ac/qmul/eecs/ccmi/utils/NativeLibFileWriter.java @ 0:9418ab7b7f3f

Initial import

/*  
 CCmI Editor - A Collaborative Cross-Modal Diagram Editing Tool
  
 Copyright (C) 2011  Queen Mary University of London (http://ccmi.eecs.qmul.ac.uk/)

 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/>.
*/  

package uk.ac.qmul.eecs.ccmi.utils;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

/**
 * This class is used to extract a native library (e.g. .dll file in windows) from within a jar 
 * to the local file system, in order to allow the virtual machine to load it.
 *
 */
public class NativeLibFileWriter {
	
	/**
	 * Creates an instance of the the class linked to a native library file.
	 * @param resource the URL of the native library file. The URL can be obtained by  
	 * @see Class#getResource(String), therefore can be called from a class within a jar file
	 * which needs to access a static library.  
	 */
	public NativeLibFileWriter(URL resource){
		this.resource = resource;
	}

	/**
	 * Writes the file in a directory returned by {@link PreferencesService#get(String, String)}} if defined, or 
	 * the System default temporary directory otherwise. 
	 * The path to the file can be retrieved by @see {@link #getFilePath()} and then passed as argument 
	 * to {@link System#load(String)} 
	 * 
	 * @param prefix a prefix the temporary native library file will have in the temporary directory  
	 */
	public void writeToDisk(String fileName){
		InputStream in = null;
		FileOutputStream out = null;
		File lib = new File(PreferencesService.getInstance().get("dir.libs", System.getProperty("java.io.tmpdir")),fileName);
		if(lib.exists()){ //if dll already exists. no job needs to be done.
			path = lib.getAbsolutePath();
			return;
		}
		try{
			in = resource.openStream();
			out = new FileOutputStream(lib);
			int byteRead;
			byte[] b = new byte[1024];
			while((byteRead = in.read(b)) > 0){
				out.write(b, 0, byteRead);
			}
			path = lib.getAbsolutePath();
		}catch(IOException ioe){
			path = null;
		}finally{
			if(in != null) 
				try{in.close();}catch(IOException ioe){}
			if(out != null) 
				try{out.close();}catch(IOException ioe){}	
		}
		
	}
	
	public String getFilePath(){
		return path;
	}
	
	private URL resource;
	private String path;
}