/**************************************************************************/
/*
/* LibLoader.java
/* Copyright (C) 2001 Bjorn Bringert (bjorn@mumblebee.com)
/*
/* 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 2
/* 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, write to the Free Software
/* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
/*
/**************************************************************************/

package com.mumblebee.util;

import java.io.*;
import java.net.URL;

/**
 * Utilities for loading native code from different sources. The main use
 * of this class is to load native code libraries for an application
 * without knowing where the application files reside.
 * Usage example:
 * <pre>
 * import com.mumblebee.util.LibLoader;
 * public class Foo {
 *   static {
 *     String libname = System.mapLibraryName("foo");
 *     LibLoader.load(Foo.class, libname);
 *   }
 * ...
 * </pre>
 *
 * @author Bjorn Bringert
 */
public class LibLoader {

	/** Prevents instantiation. */
	private LibLoader() {}

	/**
	 * Locates and loads a native code library.
	 * @param cls The class relative to which the lookup should be done
	 * @param libname The file name of the library to look for. The following changes
	 * are made to the library file name: if the name starts with
     * "/", it is unchanged; otherwise, the package name och the supplied class
	 * is prepended to the name after converting "." to "/"
	 * @throws UnsatisfiedLinkError If there is an error locating or loading
	 * the library
	 */
	public static void load(Class cls, String libname) {
		try {
			loadNative(cls, libname);
		} catch (IOException ex) {
			throw new UnsatisfiedLinkError(ex.toString());
		}
	}

	/**
	 * Locates and loads a native code library.
 	 * @param cls The class relative to which the lookup should be done
	 * @param libname The file name of the library to look for. The following changes
	 * are made to the library file name: if the name starts with
     * "/", it is unchanged; otherwise, the package name och the supplied class
	 * is prepended to the name after converting "." to "/"
	 * @throws IOException If an I/O problem occurs
	 */
	public static void loadNative(Class cls, String name) throws IOException {
		String libfile = findNative(cls, name);
		if (libfile == null) throw new IOException("native code library " + name + " not found");
		System.load(libfile);
	}

	/**
	 * Loads a native code library.
	 * @param url The url of the library file
	 * @throws IOException If an I/O problem occurs
	 */
	public static void loadNative(URL url) throws IOException {
		System.load(findNative(url));
	}

	/**
	 * Loads a native code library.
	 * @param file The library file
	 * @throws IOException If an I/O problem occurs
	 */
	public static void loadNative(File file) throws IOException {
		System.load(findNative(file));
	}

	/**
	 * Loads a native code library from an input stream.
	 * @param in The stream to load the library from.
	 * @throws IOException If an I/O problem occurs
	 */
	public static void loadNative(InputStream in) throws IOException {
		System.load(findNative(in));
	}

	/**
	 * Locates but does not load a native code library.
 	 * @param cls The class relative to which the lookup should be done
	 * @param libname The file name of the library to look for. The following changes
	 * are made to the library file name: if the name starts with
     * "/", it is unchanged; otherwise, the package name och the supplied class
	 * is prepended to the name after converting "." to "/"
	 * @return An absolute pathname that can be passed to <code>System.load()</code>
	 * @throws IOException If an I/O problem occurs
	 */
	public static String findNative(Class cls, String name) throws IOException {
		URL url = cls.getResource(name);
		if (url == null) return null;
		return findNative(url);
	}

	/**
	 * Gets an absolute pathname for a native code library.
	 * @param url The url of the library file
	 * @return An absolute pathname that can be passed to <code>System.load()</code>
	 * @throws IOException If an I/O problem occurs
	 */
	private static String findNative(URL url) throws IOException {
		if (url.getProtocol().equals("file")) {
			// uses getFile() instead of getPath()
			// since getPath() is not available in JDK1.2.2
			return new File(url.getFile()).getAbsolutePath();
		} else {
			return findNative(url.openStream());
		}
	}

	/**
	 * Gets an absolute pathname for a native code library.
	 * @param file The library file
	 * @return An absolute pathname that can be passed to <code>System.load()</code>
	 * @throws IOException If an I/O problem occurs
	 */
	private static String findNative(File file) throws IOException {
		return file.getAbsolutePath();
	}

	/**
	 * Gets an absolute pathname for a native code library.
	 * @param in The stream to load the library from.
	 * @return An absolute pathname that can be passed to <code>System.load()</code>
	 * @throws IOException If an I/O problem occurs
	 */
	private static String findNative(InputStream in) throws IOException {
		File libfile = File.createTempFile("tmplib", null);
		libfile.deleteOnExit();
		IOUtil.save(in, libfile, true);
		return libfile.getAbsolutePath();
	}

}