content: /*
   * Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package openjdk.tools.javac.processing;
  
  import java.io.BufferedReader;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.net.MalformedURLException;
  import java.net.URL;
  
  /**
   * Utility class to determine if a service can be found on the
   * path that might be used to create a class loader.
   *
   * <p><b>This is NOT part of any supported API.
   * If you write code that depends on this, you do so at your own risk.
   * This code and its internal interfaces are subject to change or
   * deletion without notice.</b>
   *
   */
  // based on sun.misc.Service
  class ServiceProxy {
      static class ServiceConfigurationError extends Error {
          static final long serialVersionUID = 7732091036771098303L;
  
          ServiceConfigurationError(String msg) {
              super(msg);
          }
      }
  
      private static final String prefix = "META-INF/services/";
  
      private static void fail(Class<?> service, String msg)
              throws ServiceConfigurationError {
          throw new ServiceConfigurationError(service.getName() + ": " + msg);
      }
  
      private static void fail(Class<?> service, URL u, int line, String msg)
              throws ServiceConfigurationError {
          fail(service, u + ":" + line + ": " + msg);
      }
  
      /**
       * Parse the content of the given URL as a provider-configuration file.
       *
       * @param  service
       *         The service class for which providers are being sought;
       *         used to construct error detail strings
       *
       * @param  u
       *         The URL naming the configuration file to be parsed
       *
       * @return true if the name of a service is found
       *
       * @throws ServiceConfigurationError
       *         If an I/O error occurs while reading from the given URL, or
       *         if a configuration-file format error is detected
       */
      private static boolean parse(Class<?> service, URL u) throws ServiceConfigurationError {
          InputStream in = null;
          BufferedReader r = null;
          try {
              in = u.openStream();
              r = new BufferedReader(new InputStreamReader(in, "utf-8"));
              int lc = 1;
              String ln;
              while ((ln = r.readLine()) != null) {
                  int ci = ln.indexOf('#');
                  if (ci >= 0) ln = ln.substring(0, ci);
                  ln = ln.trim();
                  int n = ln.length();
                  if (n != 0) {
                      if ((ln.indexOf(' ') >= 0) || (ln.indexOf('\t') >= 0))
                          fail(service, u, lc, "Illegal configuration-file syntax");
                      int cp = ln.codePointAt(0);
                      if (!Character.isJavaIdentifierStart(cp))
                          fail(service, u, lc, "Illegal provider-class name: " + ln);
                      for (int i = Character.charCount(cp); i < n; i += Character.charCount(cp)) {
                          cp = ln.codePointAt(i);
                          if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))
                              fail(service, u, lc, "Illegal provider-class name: " + ln);
                      }
                      return true;
                  }
              }
          } catch (FileNotFoundException x) {
              return false;
          } catch (IOException x) {
              fail(service, ": " + x);
          } finally {
              try {
                  if (r != null) r.close();
              } catch (IOException y) {
                  fail(service, ": " + y);
              }
              try {
                  if (in != null) in.close();
              } catch (IOException y) {
                  fail(service, ": " + y);
              }
          }
          return false;
      }
  
      /**
       * Return true if a description for at least one service is found in the
       * service configuration files in the given URLs.
       */
      public static boolean hasService(Class<?> service, URL[] urls)
              throws ServiceConfigurationError {
          for (URL url: urls) {
              try {
                  String fullName = prefix + service.getName();
                  URL u = new URL(url, fullName);
                  boolean found = parse(service, u);
                  if (found)
                      return true;
              } catch (MalformedURLException e) {
                  // should not happen; ignore it if it does
              }
          }
          return false;
      }
  }
  