/*
 * Copyright (C) 2007 The Android Open Source 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 com.github.shadowsocks;

import java.io.FileDescriptor;

/**
 * Utility methods for creating and managing a subprocess.
 * <p/>
 * Note: The native methods access a package-private java.io.FileDescriptor
 * field to get and set the raw Linux file descriptor. This might break if the
 * implementation of java.io.FileDescriptor is changed.
 */

public class Exec {
  static {
    java.lang.System.loadLibrary("exec");
  }

  /** Close a given file descriptor. */
  public static native void close(FileDescriptor fd);

  /**
   * Create a subprocess. Differs from java.lang.ProcessBuilder in that a pty
   * is used to communicate with the subprocess.
   * <p/>
   * Callers are responsible for calling Exec.close() on the returned file
   * descriptor.
   *
   * @param rdt Whether redirect stdout and stderr
   * @param cmd The command to execute.
   * @param args An array of arguments to the command.
   * @param envVars An array of strings of the form "VAR=value" to be added to the
   * environment of the process.
   * @param scripts The scripts to execute.
   * @param processId A one-element array to which the process ID of the started
   * process will be written.
   * @return File descriptor
   */
  public static native FileDescriptor createSubprocess(int rdt, String cmd, String[] args,
      String[] envVars, String scripts, int[] processId);

  /** Send SIGHUP to a process group. */
  public static native void hangupProcessGroup(int processId);

  /**
   * Causes the calling thread to wait for the process associated with the
   * receiver to finish executing.
   *
   * @return The exit value of the Process being waited on
   */
  public static native int waitFor(int processId);
}