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com.hfg xml, html, svg, and bioinformatics utility library
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package com.hfg.units;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.ServiceConfigurationError;
import java.util.logging.Level;
import java.util.logging.LogManager;
import java.util.logging.Logger;

//------------------------------------------------------------------------------
/**
 Because we have static class instances extending Unit we
 can't use ServiceLocator directly. This is a variant of ServiceLocator that
 just calls Class.forName() on the extending classes so that their values will
 be populated for subsequent calls to values().
 * @author J. Alex Taylor, hairyfatguy.com
 */
//------------------------------------------------------------------------------
// com.hfg Library
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
// J. Alex Taylor, President, Founder, CEO, COO, CFO, OOPS hairyfatguy.com
// [email protected]
//------------------------------------------------------------------------------
// TODO: extract base functionality from this and the ProteinPropertyServiceLoader

class UnitServiceLoader
{
   private static Logger sLogger;

   static
   {
      String loggerName = UnitServiceLoader.class.getPackage().getName();

      LogManager logManager = LogManager.getLogManager();

      // This method call finds the logger, but won't create one if it doesn't exist.
      sLogger = logManager.getLogger(loggerName);
      if (null == sLogger)
      {
         // Create the new logger. We won't be overwriting settings specified elsewhere.
         sLogger = Logger.getLogger(loggerName);
         sLogger.setLevel(Level.WARNING);
         sLogger.setUseParentHandlers(true);
      }
   }

   //---------------------------------------------------------------------------
   public void load()
         throws Exception
   {
      getLogger().log(Level.FINE, "Loading ProteinProperty values...");
      String fullName = "META-INF/services/" + Unit.class.getName();
      Enumeration configs = getClass().getClassLoader().getResources(fullName);
      while (configs.hasMoreElements())
      {
         Iterator classnames = parse(configs.nextElement());
         while (classnames.hasNext())
         {
            try
            {
               String classname = classnames.next();
               getLogger().log(Level.FINE, "Initializing " + classname + "...");
               Class clazz = Class.forName(classname);
               getLogger().fine(clazz.getSimpleName() + " initialized ***************************************");
            }
            catch (Exception e)
            {
               e.printStackTrace();
            }
         }
      }
   }

   //---------------------------------------------------------------------------
   public static Logger getLogger()
   {
      return sLogger;
   }

   //---------------------------------------------------------------------------
   private Iterator parse(URL u)
         throws ServiceConfigurationError
   {
      InputStream in = null;
      BufferedReader r = null;
      ArrayList names = new ArrayList<>();
      try
      {
         in = u.openStream();
         r = new BufferedReader(new InputStreamReader(in, "utf-8"));
         int lc = 1;
         while ((lc = parseLine(r, lc, names)) >= 0);
      }
      catch (IOException x)
      {
         throw new RuntimeException("Error reading configuration file", x);
      }
      finally
      {
         try
         {
            if (r != null) r.close();
            if (in != null) in.close();
         }
         catch (IOException y)
         {
            throw new RuntimeException("Error closing configuration file", y);
         }
      }
      return names.iterator();
   }

   //---------------------------------------------------------------------------
   private int parseLine(BufferedReader r, int lc, List names)
         throws IOException, ServiceConfigurationError
   {
      String ln = r.readLine();
      if (ln == null)
      {
         return -1;
      }
      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))
            throw new RuntimeException("Illegal configuration-file syntax");
         int cp = ln.codePointAt(0);
         if (!Character.isJavaIdentifierStart(cp))
            throw new RuntimeException("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 != '.'))
               throw new RuntimeException("Illegal provider-class name: " + ln);
         }
         if (!names.contains(ln))
            names.add(ln);
      }
      return lc + 1;
   }
}