1 /*
   2  * Copyright (c) 2020, Red Hat Inc.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.internal.platform;
  27 
  28 import java.io.BufferedReader;
  29 import java.io.IOException;
  30 import java.nio.file.Files;
  31 import java.nio.file.Path;
  32 import java.nio.file.Paths;
  33 import java.security.AccessController;
  34 import java.security.PrivilegedActionException;
  35 import java.security.PrivilegedExceptionAction;
  36 import java.util.List;
  37 import java.util.stream.Stream;
  38 
  39 public final class CgroupUtil {
  40 
  41     public static Stream<String> readFilePrivileged(Path path) throws IOException {
  42         try {
  43             PrivilegedExceptionAction<Stream<String>> pea = () -> Files.lines(path);
  44             return AccessController.doPrivileged(pea);
  45         } catch (PrivilegedActionException e) {
  46             unwrapIOExceptionAndRethrow(e);
  47             throw new InternalError(e.getCause());
  48         }
  49     }
  50 
  51     static void unwrapIOExceptionAndRethrow(PrivilegedActionException pae) throws IOException {
  52         Throwable x = pae.getCause();
  53         if (x instanceof IOException)
  54             throw (IOException) x;
  55         if (x instanceof RuntimeException)
  56             throw (RuntimeException) x;
  57         if (x instanceof Error)
  58             throw (Error) x;
  59     }
  60 
  61     static String readStringValue(CgroupSubsystemController controller, String param) throws IOException {
  62         PrivilegedExceptionAction<BufferedReader> pea = () ->
  63                 Files.newBufferedReader(Paths.get(controller.path(), param));
  64         try (BufferedReader bufferedReader =
  65                      AccessController.doPrivileged(pea)) {
  66             String line = bufferedReader.readLine();
  67             return line;
  68         } catch (PrivilegedActionException e) {
  69             unwrapIOExceptionAndRethrow(e);
  70             throw new InternalError(e.getCause());
  71         }
  72     }
  73 
  74     static List<String> readAllLinesPrivileged(Path path) throws IOException {
  75         try {
  76             PrivilegedExceptionAction<List<String>> pea = () -> Files.readAllLines(path);
  77             return AccessController.doPrivileged(pea);
  78         } catch (PrivilegedActionException e) {
  79             unwrapIOExceptionAndRethrow(e);
  80             throw new InternalError(e.getCause());
  81         }
  82     }
  83 }