codemp/dist/java/src/mp/code/NativeUtils.java

/*
 * Class NativeUtils is published under the The MIT License:
 *
 * Copyright (c) 2012 Adam Heinrich <adam@adamh.cz>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package mp.code;

import java.io.*;
import java.nio.file.FileSystemNotFoundException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.ProviderNotFoundException;
import java.nio.file.StandardCopyOption;
import java.util.Objects;

/**
 * A simple library class which helps with loading dynamic libraries stored in the
 * JAR archive. These libraries usually contain implementation of some methods in
 * native code (using JNI - Java Native Interface).
 * @see <a href="http://adamheinrich.com/blog/2012/how-to-load-native-jni-library-from-jar">http://adamheinrich.com/blog/2012/how-to-load-native-jni-library-from-jar</a>
 * @see <a href="https://github.com/adamheinrich/native-utils">https://github.com/adamheinrich/native-utils</a>
 */
class NativeUtils {

	/**
	 * The minimum length a prefix for a file has to have according to {@link File#createTempFile(String, String)}}.
	 */
	private static final int MIN_PREFIX_LENGTH = 3;

	/**
	 * Prefix of the temporary folder where the native is stored.
	 */
	public static final String NATIVE_FOLDER_PATH_PREFIX = "nativeutils";

	/**
	 * Temporary directory which will contain the DLLs.
	 */
	private static File temporaryDir;

	/**
	 * Private constructor - this class will never be instanced
	 */
	private NativeUtils() {}

	/**
	 * Loads library from current JAR archive.
	 * The file from JAR is copied into system temporary directory and then loaded. The temporary file is deleted after
	 * exiting.
	 * Method uses String as filename because the pathname is "abstract", not system-dependent.
	 * @param path The path of file inside JAR as absolute path (beginning with '/'), e.g. /package/File.ext
	 * @throws IOException If temporary file creation or read/write operation fails
	 * @throws IllegalArgumentException If source file (param path) does not exist
	 * @throws IllegalArgumentException If the path is not absolute or if the filename is shorter than three characters
	 * (restriction of {@link File#createTempFile(java.lang.String, java.lang.String)}).
	 * @throws FileNotFoundException If the file could not be found inside the JAR.
	 */
	@SuppressWarnings("ResultOfMethodCallIgnored")
	private static void loadLibraryFromJar(String path) throws IOException {
		if(null == path || !path.startsWith("/")) {
			throw new IllegalArgumentException("The path has to be absolute (start with '/').");
		}

		// Obtain filename from path
		String[] parts = path.split("/");
		String filename = (parts.length > 1) ? parts[parts.length - 1] : null;

		// Check if the filename is okay
		if(filename == null || filename.length() < MIN_PREFIX_LENGTH) {
			throw new IllegalArgumentException("The filename has to be at least 3 characters long.");
		}

		// Prepare temporary file
		if(temporaryDir == null) {
			temporaryDir = createTempDirectory();
			temporaryDir.deleteOnExit();
		}

		File temp = new File(temporaryDir, filename);

		try(InputStream is = NativeUtils.class.getResourceAsStream(path)) {
			Files.copy(Objects.requireNonNull(is), temp.toPath(), StandardCopyOption.REPLACE_EXISTING);
		} catch (IOException e) {
			temp.delete();
			throw e;
		} catch (NullPointerException e) {
			temp.delete();
			throw new FileNotFoundException("File " + path + " was not found inside JAR.");
		}

		try {
			System.load(temp.getAbsolutePath());
		} finally {
			if(isPosixCompliant()) {
				// Assume POSIX compliant file system, can be deleted after loading
				temp.delete();
			} else {
				// Assume non-POSIX, and don't delete until last file descriptor closed
				temp.deleteOnExit();
			}
		}
	}

	private static boolean isPosixCompliant() {
		try {
			return FileSystems.getDefault()
				.supportedFileAttributeViews()
				.contains("posix");
		} catch (FileSystemNotFoundException | ProviderNotFoundException | SecurityException e) {
			return false;
		}
	}

	private static File createTempDirectory() throws IOException {
		String tempDir = System.getProperty("java.io.tmpdir");
		File generatedDir = new File(tempDir, NativeUtils.NATIVE_FOLDER_PATH_PREFIX + System.nanoTime());

		if(!generatedDir.mkdir())
			throw new IOException("Failed to create temp directory " + generatedDir.getName());

		return generatedDir;
	}

	private static boolean loaded = false;
	static synchronized void loadLibraryIfNeeded() {
		if(loaded) return;
		try {
			String os = System.getProperty("os.name").toLowerCase();

			String filename;
			if(os.startsWith("windows")) {
				filename = "/natives/codemp.dll";
			} else if(os.startsWith("mac")) {
				filename = "/natives/libcodemp.dylib";;
			} else filename = "/natives/libcodemp.so";
			loadLibraryFromJar(filename);

			loaded = true;
		} catch(IOException e) {
			throw new RuntimeException(e);
		}
	}
}