Native.java

package net.jpountz.util;

/*
 * Copyright 2020 Adrien Grand and the lz4-java contributors.
 *
 * 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.
 */

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.FilenameFilter;

/** <b>FOR INTERNAL USE ONLY</b> */
public enum Native {
  ;

  private enum OS {
    WINDOWS("windows", "dll"), LINUX("linux", "so"), MAC("darwin", "dylib"), SOLARIS("solaris", "so");
    public final String name, libExtension;

    private OS(String name, String libExtension) {
      this.name = name;
      this.libExtension = libExtension;
    }
  }

  private static String arch() {
    return System.getProperty("os.arch");
  }

  private static OS os() {
    String osName = System.getProperty("os.name");
    if (osName.contains("Linux")) {
      return OS.LINUX;
    } else if (osName.contains("Mac")) {
      return OS.MAC;
    } else if (osName.contains("Windows")) {
      return OS.WINDOWS;
    } else if (osName.contains("Solaris") || osName.contains("SunOS")) {
      return OS.SOLARIS;
    } else {
      throw new UnsupportedOperationException("Unsupported operating system: "
        + osName);
    }
  }

  private static String resourceName() {
    OS os = os();
    String packagePrefix = Native.class.getPackage().getName().replace('.', '/');

    return "/" + packagePrefix + "/" + os.name + "/" + arch() + "/liblz4-java." + os.libExtension;
  }

  private static boolean loaded = false;

  public static synchronized boolean isLoaded() {
    return loaded;
  }

  /** Temporary libraries older than this are considered stale and removed by {@link #cleanupOldTempLibs()}. */
  private static final long TEMP_LIB_MAX_AGE_MILLIS = 60 * 60 * 1000L;

  private static void cleanupOldTempLibs() {
    cleanupOldTempLibs(new File(System.getProperty("java.io.tmpdir")).getAbsoluteFile(), System.currentTimeMillis());
  }

  static void cleanupOldTempLibs(File dir, long now) {
    // This also matches .lck files left behind by older versions.
    File[] tempLibFiles = dir.listFiles(new FilenameFilter() {
      private final String searchPattern = "liblz4-java-";

      @Override
      public boolean accept(File dir, String name) {
        return name.startsWith(searchPattern);
      }
    });

    if (tempLibFiles != null) {
      for (File tempLibFile : tempLibFiles) {
        // Libraries that are currently being extracted or loaded by another process are fresh.
        if (now - tempLibFile.lastModified() > TEMP_LIB_MAX_AGE_MILLIS) {
          try {
            tempLibFile.delete();
          } catch (SecurityException e) {
            System.err.println("Failed to delete old temp lib: " + e.getMessage());
          }
        }
      }
    }
  }

  public static synchronized void load() {
    if (loaded) {
      return;
    }

    cleanupOldTempLibs();

    // Try to load lz4-java (liblz4-java.so on Linux) from the java.library.path.
    try {
      System.loadLibrary("lz4-java");
      loaded = true;
      return;
    } catch (UnsatisfiedLinkError ex) {
      // Doesn't exist, so proceed to loading bundled library.
    }

    String resourceName = resourceName();
    InputStream is = Native.class.getResourceAsStream(resourceName);
    if (is == null) {
      throw new UnsupportedOperationException("Unsupported OS/arch, cannot find " + resourceName + ". Please try building from source.");
    }
    File tempLib = null;
    try {
      // createTempFile exclusively creates a new file with a random name, so we never write to
      // (or follow a symlink planted as) a file created by someone else.
      tempLib = File.createTempFile("liblz4-java-", "." + os().libExtension);
      // copy to tempLib
      try (FileOutputStream out = new FileOutputStream(tempLib)) {
        byte[] buf = new byte[4096];
        while (true) {
          int read = is.read(buf);
          if (read == -1) {
            break;
          }
          out.write(buf, 0, read);
        }
      }
      System.load(tempLib.getAbsolutePath());
      loaded = true;
    } catch (IOException e) {
      throw new ExceptionInInitializerError(new IOException("Cannot unpack liblz4-java: " + e, e));
    } finally {
      try {
        is.close();
      } catch (IOException ignored) {
      }
      if (!loaded) {
        if (tempLib != null) {
          // Best effort, so that the original error is not masked. Leftovers are removed by cleanupOldTempLibs.
          tempLib.delete();
        }
      } else {
        final String keepEnv = System.getenv("LZ4JAVA_KEEP_TEMP_JNI_LIB");
        final String keepProp = System.getProperty("lz4java.jnilib.temp.keep");
        if ((keepEnv == null || !keepEnv.equals("true")) &&
            (keepProp == null || !keepProp.equals("true")))
          tempLib.deleteOnExit();
      }
    }
  }
}