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   * 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
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   */
  
  package java.security.cert;
  
  import java.util.Arrays;
  
  import java.security.Provider;
  import java.security.PublicKey;
  import java.security.NoSuchAlgorithmException;
  import java.security.NoSuchProviderException;
  import java.security.InvalidKeyException;
  import java.security.SignatureException;
  
  import sun.security.x509.X509CertImpl;
  
  /**
   * <p>Abstract class for managing a variety of identity certificates.
   * An identity certificate is a binding of a principal to a public key which
   * is vouched for by another principal.  (A principal represents
   * an entity such as an individual user, a group, or a corporation.)
   *<p>
   * This class is an abstraction for certificates that have different
   * formats but important common uses.  For example, different types of
   * certificates, such as X.509 and PGP, share general certificate
   * functionality (like encoding and verifying) and
   * some types of information (like a public key).
   * <p>
   * X.509, PGP, and SDSI certificates can all be implemented by
   * subclassing the Certificate class, even though they contain different
   * sets of information, and they store and retrieve the information in
   * different ways.
   *
   * @see X509Certificate
   * @see CertificateFactory
   *
   * @author Hemma Prafullchandra
   */
  
  public abstract class Certificate implements java.io.Serializable {
  
      private static final long serialVersionUID = -3585440601605666277L;
  
      // the certificate type
      private final String type;
  
      /** Cache the hash code for the certiticate */
      private int hash = -1; // Default to -1
  
      /**
       * Creates a certificate of the specified type.
       *
       * @param type the standard name of the certificate type.
       * See the CertificateFactory section in the <a href=
       * "{@docRoot}/../technotes/guides/security/StandardNames.html#CertificateFactory">
       * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
       * for information about standard certificate types.
       */
      protected Certificate(String type) {
          this.type = type;
      }
  
      /**
       * Returns the type of this certificate.
       *
       * @return the type of this certificate.
       */
      public final String getType() {
          return this.type;
      }
  
      /**
       * Compares this certificate for equality with the specified
       * object. If the {@code other} object is an
       * {@code instanceof} {@code Certificate}, then
       * its encoded form is retrieved and compared with the
       * encoded form of this certificate.
       *
       * @param other the object to test for equality with this certificate.
       * @return true iff the encoded forms of the two certificates
       * match, false otherwise.
       */
      public boolean equals(Object other) {
          if (this == other) {
              return true;
          }
          if (!(other instanceof Certificate)) {
              return false;
          }
          try {
              byte[] thisCert = X509CertImpl.getEncodedInternal(this);
              byte[] otherCert = X509CertImpl.getEncodedInternal((Certificate)other);
  
              return Arrays.equals(thisCert, otherCert);
          } catch (CertificateException e) {
              return false;
          }
      }
  
      /**
       * Returns a hashcode value for this certificate from its
       * encoded form.
       *
       * @return the hashcode value.
       */
      public int hashCode() {
          int h = hash;
          if (h == -1) {
              try {
                  h = Arrays.hashCode(X509CertImpl.getEncodedInternal(this));
              } catch (CertificateException e) {
                  h = 0;
              }
              hash = h;
          }
          return h;
      }
  
      /**
       * Returns the encoded form of this certificate. It is
       * assumed that each certificate type would have only a single
       * form of encoding; for example, X.509 certificates would
       * be encoded as ASN.1 DER.
       *
       * @return the encoded form of this certificate
       *
       * @exception CertificateEncodingException if an encoding error occurs.
       */
      public abstract byte[] getEncoded()
          throws CertificateEncodingException;
  
      /**
       * Verifies that this certificate was signed using the
       * private key that corresponds to the specified public key.
       *
       * @param key the PublicKey used to carry out the verification.
       *
       * @exception NoSuchAlgorithmException on unsupported signature
       * algorithms.
       * @exception InvalidKeyException on incorrect key.
       * @exception NoSuchProviderException if there's no default provider.
       * @exception SignatureException on signature errors.
       * @exception CertificateException on encoding errors.
       */
      public abstract void verify(PublicKey key)
          throws CertificateException, NoSuchAlgorithmException,
          InvalidKeyException, NoSuchProviderException,
          SignatureException;
  
      /**
       * Verifies that this certificate was signed using the
       * private key that corresponds to the specified public key.
       * This method uses the signature verification engine
       * supplied by the specified provider.
       *
       * @param key the PublicKey used to carry out the verification.
       * @param sigProvider the name of the signature provider.
       *
       * @exception NoSuchAlgorithmException on unsupported signature
       * algorithms.
       * @exception InvalidKeyException on incorrect key.
       * @exception NoSuchProviderException on incorrect provider.
       * @exception SignatureException on signature errors.
       * @exception CertificateException on encoding errors.
       */
      public abstract void verify(PublicKey key, String sigProvider)
          throws CertificateException, NoSuchAlgorithmException,
          InvalidKeyException, NoSuchProviderException,
          SignatureException;
  
      /**
       * Verifies that this certificate was signed using the
       * private key that corresponds to the specified public key.
       * This method uses the signature verification engine
       * supplied by the specified provider. Note that the specified
       * Provider object does not have to be registered in the provider list.
       *
       * <p> This method was added to version 1.8 of the Java Platform
       * Standard Edition. In order to maintain backwards compatibility with
       * existing service providers, this method cannot be {@code abstract}
       * and by default throws an {@code UnsupportedOperationException}.
       *
       * @param key the PublicKey used to carry out the verification.
       * @param sigProvider the signature provider.
       *
       * @exception NoSuchAlgorithmException on unsupported signature
       * algorithms.
       * @exception InvalidKeyException on incorrect key.
       * @exception SignatureException on signature errors.
       * @exception CertificateException on encoding errors.
       * @exception UnsupportedOperationException if the method is not supported
       * @since 1.8
       */
      public void verify(PublicKey key, Provider sigProvider)
          throws CertificateException, NoSuchAlgorithmException,
          InvalidKeyException, SignatureException {
          throw new UnsupportedOperationException();
      }
  
      /**
       * Returns a string representation of this certificate.
       *
       * @return a string representation of this certificate.
       */
      public abstract String toString();
  
      /**
       * Gets the public key from this certificate.
       *
       * @return the public key.
       */
      public abstract PublicKey getPublicKey();
  
      /**
       * Alternate Certificate class for serialization.
       * @since 1.3
       */
      protected static class CertificateRep implements java.io.Serializable {
  
          private static final long serialVersionUID = -8563758940495660020L;
  
          private String type;
          private byte[] data;
  
          /**
           * Construct the alternate Certificate class with the Certificate
           * type and Certificate encoding bytes.
           *
           * <p>
           *
           * @param type the standard name of the Certificate type. <p>
           *
           * @param data the Certificate data.
           */
          protected CertificateRep(String type, byte[] data) {
              this.type = type;
              this.data = data;
          }
  
          /**
           * Resolve the Certificate Object.
           *
           * <p>
           *
           * @return the resolved Certificate Object
           *
           * @throws java.io.ObjectStreamException if the Certificate
           *      could not be resolved
           */
          protected Object readResolve() throws java.io.ObjectStreamException {
              try {
                  CertificateFactory cf = CertificateFactory.getInstance(type);
                  return cf.generateCertificate
                          (new java.io.ByteArrayInputStream(data));
              } catch (CertificateException e) {
                  throw new java.io.NotSerializableException
                                  ("java.security.cert.Certificate: " +
                                  type +
                                  ": " +
                                  e.getMessage());
              }
          }
      }
  
      /**
       * Replace the Certificate to be serialized.
       *
       * @return the alternate Certificate object to be serialized
       *
       * @throws java.io.ObjectStreamException if a new object representing
       * this Certificate could not be created
       * @since 1.3
       */
      protected Object writeReplace() throws java.io.ObjectStreamException {
          try {
              return new CertificateRep(type, getEncoded());
          } catch (CertificateException e) {
              throw new java.io.NotSerializableException
                                  ("java.security.cert.Certificate: " +
                                  type +
                                  ": " +
                                  e.getMessage());
          }
      }
  }
  