Moved from java/security/Engine.java

1 files changed, 237 insertions, 0 deletions

diff --git a/gnu/java/security/Engine.java b/gnu/java/security/Engine.java
new file mode 100644
index 000000000..9f6568cdd
--- /dev/null
+++ b/gnu/java/security/Engine.java
@@ -0,0 +1,237 @@
+/* Engine -- generic getInstance method.
+   Copyright (C) 2003  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+02111-1307 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+package gnu.java.security;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+
+import java.security.NoSuchAlgorithmException;
+import java.security.Provider;
+
+/**
+ * Generic implementation of the getInstance methods in the various
+ * engine classes in java.security.
+ * <p>
+ * These classes ({@link java.security.Signature} for example) can be
+ * thought of as the "chrome, upholstery, and steering wheel", and the SPI
+ * (service provider interface, e.g. {@link java.security.SignatureSpi})
+ * classes can be thought of as the "engine" -- providing the actual
+ * functionality of whatever cryptographic algorithm the instance
+ * represents.
+ *
+ * @see Provider
+ * @author Casey Marshall 
+ */
+public final class Engine
+{
+
+  // Constants.
+  // ------------------------------------------------------------------------
+
+  /** Prefix for aliases. */
+  private static final String ALG_ALIAS = "Alg.Alias.";
+
+  /** Maximum number of aliases to try. */
+  private static final int MAX_ALIASES = 5;
+
+  /** Argument list for no-argument constructors. */
+  private static final Object[] NO_ARGS = new Object[0];
+
+  // Constructor.
+  // ------------------------------------------------------------------------
+
+  /** This class cannot be instantiated. */
+  private Engine() { }
+
+  // Class method.
+  // ------------------------------------------------------------------------
+
+  /**
+   * Get the implementation for <i>algorithm</i> for service
+   * <i>service</i> from <i>provider</i>. The service is e.g.
+   * "Signature", and the algorithm "DSA".
+   *
+   * @param service   The service name.
+   * @param algorithm The name of the algorithm to get.
+   * @param provider  The provider to get the implementation from.
+   * @return The engine class for the specified algorithm; the object
+   *         returned is typically a subclass of the SPI class for that
+   *         service, but callers should check that this is so.
+   * @throws NoSuchAlgorithmException If the implementation cannot be
+   *         found or cannot be instantiated.
+   * @throws InvocationTargetException If the SPI class's constructor
+   *         throws an exception.
+   * @throws IllegalArgumentException If any of the three arguments are null.
+   */
+  public static Object getInstance(String service, String algorithm,
+                                   Provider provider)
+    throws InvocationTargetException, NoSuchAlgorithmException
+  {
+    return getInstance(service, algorithm, provider, NO_ARGS);
+  }
+
+  /**
+   * Get the implementation for <i>algorithm</i> for service
+   * <i>service</i> from <i>provider</i>, passing <i>initArgs</i> to the
+   * SPI class's constructor (which cannot be null; pass a zero-length
+   * array if the SPI takes no arguments). The service is e.g.
+   * "Signature", and the algorithm "DSA".
+   *
+   * @param service   The service name.
+   * @param algorithm The name of the algorithm to get.
+   * @param provider  The provider to get the implementation from.
+   * @param initArgs  The arguments to pass to the SPI class's
+   *        constructor (cannot be null).
+   * @return The engine class for the specified algorithm; the object
+   *         returned is typically a subclass of the SPI class for that
+   *         service, but callers should check that this is so.
+   * @throws NoSuchAlgorithmException If the implementation cannot be
+   *         found or cannot be instantiated.
+   * @throws InvocationTargetException If the SPI class's constructor
+   *         throws an exception.
+   * @throws IllegalArgumentException If any of the four arguments are null.
+   */
+  public static Object getInstance(String service, String algorithm,
+                                   Provider provider, Object[] initArgs)
+    throws InvocationTargetException, NoSuchAlgorithmException
+  {
+    if (service == null || algorithm == null
+        || provider == null || initArgs == null)
+      throw new IllegalArgumentException();
+
+    // If there is no property "service.algorithm"
+    if (provider.getProperty(service + "." + algorithm) == null)
+      {
+        // Iterate through aliases, until we find the class name or resolve
+        // too many aliases.
+        String alias = null;
+        int count = 0;
+        while ((alias = provider.getProperty(
+                ALG_ALIAS + service + "." + algorithm)) != null)
+          {
+            if (algorithm.equals(alias))  // Refers to itself!
+              break;
+            algorithm = alias;
+            if (count++ > MAX_ALIASES)
+              throw new NoSuchAlgorithmException("too many aliases");
+          }
+        if (provider.getProperty(service + "." + algorithm) == null)
+          throw new NoSuchAlgorithmException(algorithm);
+      }
+
+    // Find and instantiate the implementation.
+    Class clazz = null;
+    ClassLoader loader = provider.getClass().getClassLoader();
+    Constructor constructor = null;
+    String error = algorithm;
+
+    try
+      {
+        if (loader != null)
+          clazz = loader.loadClass(provider.getProperty(service+"."+algorithm));
+        else
+          clazz = Class.forName(provider.getProperty(service+"."+algorithm));
+        constructor = getCompatibleConstructor(clazz, initArgs);
+        return constructor.newInstance(initArgs);
+      }
+    catch (ClassNotFoundException cnfe)
+      {
+        error = "class not found: " + algorithm;
+      }
+    catch (IllegalAccessException iae)
+      {
+        error = "illegal access: " + iae.getMessage();
+      }
+    catch (InstantiationException ie)
+      {
+        error = "instantiation exception: " + ie.getMessage();
+      }
+    catch (ExceptionInInitializerError eiie)
+      {
+        error = "exception in initializer: " + eiie.getMessage();
+      }
+    catch (SecurityException se)
+      {
+        error = "security exception: " + se.getMessage();
+      }
+    catch (NoSuchMethodException nsme)
+      {
+        error = "no appropriate constructor found";
+      }
+
+    throw new NoSuchAlgorithmException(error);
+  }
+
+  // Own methods.
+  // ------------------------------------------------------------------------
+
+  /**
+   * Find a constructor in the given class that can take the specified
+   * argument list, allowing any of which to be null.
+   *
+   * @param clazz    The class from which to get the constructor.
+   * @param initArgs The argument list to be passed to the constructor.
+   * @return The constructor.
+   * @throws NoSuchMethodException If no constructor of the given class
+   *         can take the specified argument array.
+   */
+  private static Constructor getCompatibleConstructor(Class clazz,
+                                                      Object[] initArgs)
+    throws NoSuchMethodException
+  {
+    Constructor[] c = clazz.getConstructors();
+    outer:for (int i = 0; i < c.length; i++)
+      {
+        Class[] argTypes = c[i].getParameterTypes();
+        if (argTypes.length != initArgs.length)
+          continue;
+        for (int j = 0; j < argTypes.length; j++)
+          {
+            if (initArgs[j] != null &&
+                !argTypes[j].isAssignableFrom(initArgs[j].getClass()))
+              continue outer;
+          }
+        // If we reach this point, we know this constructor (c[i]) has
+        // the same number of parameters as the target parameter list,
+        // and all our parameters are either (1) null, or (2) assignable
+        // to the target parameter type.
+        return c[i];
+      }
+    throw new NoSuchMethodException();
+  }
+}