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sigar-loader
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/* =========================================================================================
 * Copyright © 2013-2014 the kamon project 
 *
 * 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.
 * =========================================================================================
 */

package kamon.sigar;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Field;
import java.util.Vector;
import java.util.logging.Logger;

import org.hyperic.sigar.Sigar;
import org.hyperic.sigar.SigarLoader;

/**
 * Sigar native library extractor and loader.
 *
 * To provision sigar native library at the given folder location:
 *
 *  * SigarProvisioner.provision(new File(location));
 * 
 */
public class SigarProvisioner {

	/** Provisioner logger. */
	private static final Logger logger = Logger
			.getLogger(SigarProvisioner.class.getName());

	/**
	 * Location of native libraries.
	 *
	 * 	 * when stored in loader.jar:     /${LIB_DIR}/libsigar-xxx.so
	 * after default load/extract:    ${user.dir}/${LIB_DIR}/libsigar-xxx.so
	 * 
	 */
	public static final String LIB_DIR = "native";

	/** Environment variable which provides sigar extract location. */
	public static final String ENVIRONMENT_VARIABLE = "KAMON_SIGAR_FOLDER";

	/** System property which provides sigar extract location. */
	public static final String SYSTEM_PROPERTY = "kamon.sigar.folder";

	/** Hard coded value which provides sigar extract location. */
	public static final String DEFAULT_LOCATION = System
			.getProperty("user.dir") + File.separator + LIB_DIR;

	/**
	 * Discover sigar library extract location. 

	 * Priority 1) user provided command line agent options. 

	 * Priority 2) user provided o/s environment variable. 

	 * Priority 3) user provided java system property. 

	 * Priority 4) hard coded location in ${user.dir}/native. 

	 *
	 * @param options
	 *            Command line agent options.
	 * @return Discovered sigar library extract location.
	 */
	public static String discoverLocation(final String options) {

		/** Priority 1) user provided agent command line options. */
		if (options != null) {
			final String[] optionArray = options.split(",");
			for (final String option : optionArray) {
				if (option.startsWith(SYSTEM_PROPERTY) && option.contains("=")) {
					logger.info("Using location provided by options.");
					return option.substring(option.indexOf("=") + 1);
				}
			}
		}

		/** Priority 2) user provided o/s environment variable. */
		final String variable = System.getenv(ENVIRONMENT_VARIABLE);
		if (variable != null) {
			logger.info("Using location provided by environment variable.");
			return variable;
		}

		/** Priority 3) user provided java system property. */
		final String property = System.getProperty(SYSTEM_PROPERTY);
		if (property != null) {
			logger.info("Using location provided by system property.");
			return property;
		}

		/** Priority 4) hard coded location. */
		logger.info("Using location provided by hard coded value.");
		return DEFAULT_LOCATION;

	}

	/**
	 * Verify if sigar native library is loaded and operational.
	 *
	 * @return true, if is native library loaded.
	 */
    public static synchronized boolean isNativeLoaded() {
        try {
            return isSigarAlreadyLoaded();
        } catch (final Throwable e) {
            try {
                final Sigar sigar = new Sigar();
                sigar.getPid();
                sigar.close();
                return true;
            } catch (final Throwable ex) {
                return false;
            }
        }
    }

	/**
	 * Extract and load native sigar library in the default folder.
	 *
	 * @throws Exception
	 *             The provisioning failure exception.
	 */
	public static void provision() throws Exception {
		provision(new File(discoverLocation(null)));
	}

	/**
	 * Extract and load native sigar library in the provided folder.
	 *
	 * @param folder
	 *            Library extraction folder.
	 * @throws Exception
	 *             The provisioning failure exception.
	 */
	public static synchronized void provision(final File folder)
			throws Exception {

		if (isNativeLoaded()) {
			logger.warning("Sigar library is already provisioned.");
			return;
		}

		if (!folder.exists()) {
			folder.mkdirs();
		}

		final SigarLoader sigarLoader = new SigarLoader(Sigar.class);

		/** Library name for given architecture. */
		final String libraryName = sigarLoader.getLibraryName();

		/** Library location embedded in the jar class path. */
		final String sourcePath = "/" + LIB_DIR + "/" + libraryName;

		/** Absolute path to the extracted library the on file system. */
		final File targetPath = new File(folder, libraryName).getAbsoluteFile();

		/** Extract library form the jar to the local file system. */
		final InputStream sourceStream = SigarProvisioner.class
				.getResourceAsStream(sourcePath);
		final OutputStream targetStream = new FileOutputStream(targetPath);
		transfer(sourceStream, targetStream);
		sourceStream.close();
		targetStream.close();

		/** Load library via absolute path. */
		final String libraryPath = targetPath.getAbsolutePath();
		System.load(libraryPath);

		/** Tell sigar loader that the library is already loaded. */
		System.setProperty("org.hyperic.sigar.path", "-");
		sigarLoader.load();

		logger.info("Sigar library provisioned: " + libraryPath);

	}

	/** The Constant EOF. */
	static final int EOF = -1;

	/** The Constant SIZE. */
	static final int SIZE = 64 * 1024;

	/**
	 * Perform stream copy.
	 *
	 * @param input
	 *            The input stream.
	 * @param output
	 *            The output stream.
	 * @throws Exception
	 *             The stream copy failure exception.
	 */
	public static void transfer(final InputStream input,
			final OutputStream output) throws Exception {
		final byte[] data = new byte[SIZE];
		while (true) {
			final int count = input.read(data, 0, SIZE);
			if (count == EOF) {
				break;
			}
			output.write(data, 0, count);
		}
	}

    /**
     * Check silently if sigar was loaded in order to avoid the SigarException: no libsigar-*.
     *
     * @return true, if Sigar native library is present in the ClassLoader otherwise false.
     * @throws IllegalAccessException
     * @throws NoSuchFieldException
     */
	private static boolean isSigarAlreadyLoaded() throws Exception {
        final String libraryName = new SigarLoader(Sigar.class).getLibraryName();
        final Field loadedLibraryNames = ClassLoader.class.getDeclaredField("loadedLibraryNames");
		loadedLibraryNames.setAccessible(true);
        final Vector libraries = (Vector) loadedLibraryNames.get(SigarProvisioner.class.getClassLoader());

        for (String library: libraries) {
            if(library.contains(libraryName)) return true;
        }
        return false;
    }

}