content: /*
   * Tencent is pleased to support the open source community by making Angel available.
   *
   * Copyright (C) 2017-2018 THL A29 Limited, a Tencent company. All rights reserved.
   *
   * 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
   *
   * https://opensource.org/licenses/Apache-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 com.tencent.angel.utils;
  
  import java.io.*;
  
  /**
   * A simple library class which helps with loading dynamic libraries stored in the JAR archive.
   * These libraries usualy contain implementation of some methods in native code (using JNI - Java
   * Native Interface).
   */
  public class NativeUtils {
  
    /**
     * Private constructor - this class will never be instanced
     */
    private NativeUtils() {
    }
  
    /**
     * Loads library from current JAR archive
     * <p>
     * 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 {@see File#createTempFile(java.lang.String, *java.lang.String)}).
     */
    public static void loadLibraryFromJar(String path) throws IOException {
  
      if (!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;
  
      // Split filename to prexif and suffix (extension)
      String prefix = "";
      String suffix = null;
      if (filename != null) {
        parts = filename.split("\\.", 2);
        prefix = parts[0];
        suffix = (parts.length > 1) ? "." + parts[parts.length - 1] : null; // Thanks, davs! :-)
      }
  
      // Check if the filename is okay
      if (filename == null || prefix.length() < 3) {
        throw new IllegalArgumentException("The filename has to be at least 3 characters long.");
      }
  
      // Prepare temporary file
      File temp = File.createTempFile(prefix, suffix);
      temp.deleteOnExit();
      System.out.println("Temp file for native so file is " + temp.getAbsolutePath());
  
      if (!temp.exists()) {
        throw new FileNotFoundException("File " + temp.getAbsolutePath() + " does not exist.");
      }
  
      // Prepare buffer for data copying
      byte[] buffer = new byte[1024];
      int readBytes;
  
      // Open and check input stream
      InputStream is = NativeUtils.class.getResourceAsStream(path);
      if (is == null) {
        throw new FileNotFoundException("File " + path + " was not found inside JAR.");
      }
  
      // Open output stream and copy data between source file in JAR and the temporary file
      OutputStream os = new FileOutputStream(temp);
      try {
        while ((readBytes = is.read(buffer)) != -1) {
          os.write(buffer, 0, readBytes);
        }
      } finally {
        // If read/write fails, close streams safely before throwing an exception
        os.close();
        is.close();
      }
  
      // Finally, load the library
      System.load(temp.getAbsolutePath());
    }
  }
  