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   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   * 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
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  package java.security.cert;
  
  import java.io.InputStream;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.List;
  import java.security.Provider;
  import java.security.NoSuchAlgorithmException;
  import java.security.NoSuchProviderException;
  
  /**
   * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
   * for the {@code CertificateFactory} class.
   * All the abstract methods in this class must be implemented by each
   * cryptographic service provider who wishes to supply the implementation
   * of a certificate factory for a particular certificate type, e.g., X.509.
   *
   * <p>Certificate factories are used to generate certificate, certification path
   * ({@code CertPath}) and certificate revocation list (CRL) objects from
   * their encodings.
   *
   * <p>A certificate factory for X.509 must return certificates that are an
   * instance of {@code java.security.cert.X509Certificate}, and CRLs
   * that are an instance of {@code java.security.cert.X509CRL}.
   *
   * @author Hemma Prafullchandra
   * @author Jan Luehe
   * @author Sean Mullan
   *
   *
   * @see CertificateFactory
   * @see Certificate
   * @see X509Certificate
   * @see CertPath
   * @see CRL
   * @see X509CRL
   *
   * @since 1.2
   */
  
  public abstract class CertificateFactorySpi {
  
      /**
       * Generates a certificate object and initializes it with
       * the data read from the input stream {@code inStream}.
       *
       * <p>In order to take advantage of the specialized certificate format
       * supported by this certificate factory,
       * the returned certificate object can be typecast to the corresponding
       * certificate class. For example, if this certificate
       * factory implements X.509 certificates, the returned certificate object
       * can be typecast to the {@code X509Certificate} class.
       *
       * <p>In the case of a certificate factory for X.509 certificates, the
       * certificate provided in {@code inStream} must be DER-encoded and
       * may be supplied in binary or printable (Base64) encoding. If the
       * certificate is provided in Base64 encoding, it must be bounded at
       * the beginning by -----BEGIN CERTIFICATE-----, and must be bounded at
       * the end by -----END CERTIFICATE-----.
       *
       * <p>Note that if the given input stream does not support
       * {@link InputStream#mark(int) mark} and
       * {@link InputStream#reset() reset}, this method will
       * consume the entire input stream. Otherwise, each call to this
       * method consumes one certificate and the read position of the input stream
       * is positioned to the next available byte after the inherent
       * end-of-certificate marker. If the data in the
       * input stream does not contain an inherent end-of-certificate marker (other
       * than EOF) and there is trailing data after the certificate is parsed, a
       * {@code CertificateException} is thrown.
       *
       * @param inStream an input stream with the certificate data.
       *
       * @return a certificate object initialized with the data
       * from the input stream.
       *
       * @exception CertificateException on parsing errors.
       */
      public abstract Certificate engineGenerateCertificate(InputStream inStream)
          throws CertificateException;
  
      /**
       * Generates a {@code CertPath} object and initializes it with
       * the data read from the {@code InputStream} inStream. The data
       * is assumed to be in the default encoding.
       *
       * <p> This method was added to version 1.4 of the Java 2 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 inStream an {@code InputStream} containing the data
       * @return a {@code CertPath} initialized with the data from the
       *   {@code InputStream}
       * @exception CertificateException if an exception occurs while decoding
       * @exception UnsupportedOperationException if the method is not supported
       * @since 1.4
       */
      public CertPath engineGenerateCertPath(InputStream inStream)
          throws CertificateException
      {
          throw new UnsupportedOperationException();
      }
  
      /**
       * Generates a {@code CertPath} object and initializes it with
       * the data read from the {@code InputStream} inStream. The data
       * is assumed to be in the specified encoding.
       *
       * <p> This method was added to version 1.4 of the Java 2 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 inStream an {@code InputStream} containing the data
       * @param encoding the encoding used for the data
       * @return a {@code CertPath} initialized with the data from the
       *   {@code InputStream}
       * @exception CertificateException if an exception occurs while decoding or
       *   the encoding requested is not supported
       * @exception UnsupportedOperationException if the method is not supported
       * @since 1.4
       */
      public CertPath engineGenerateCertPath(InputStream inStream,
          String encoding) throws CertificateException
      {
          throw new UnsupportedOperationException();
      }
  
      /**
       * Generates a {@code CertPath} object and initializes it with
       * a {@code List} of {@code Certificate}s.
       * <p>
       * The certificates supplied must be of a type supported by the
       * {@code CertificateFactory}. They will be copied out of the supplied
       * {@code List} object.
       *
       * <p> This method was added to version 1.4 of the Java 2 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 certificates a {@code List} of {@code Certificate}s
       * @return a {@code CertPath} initialized with the supplied list of
       *   certificates
       * @exception CertificateException if an exception occurs
       * @exception UnsupportedOperationException if the method is not supported
       * @since 1.4
       */
      public CertPath
          engineGenerateCertPath(List<? extends Certificate> certificates)
          throws CertificateException
      {
          throw new UnsupportedOperationException();
      }
  
      /**
       * Returns an iteration of the {@code CertPath} encodings supported
       * by this certificate factory, with the default encoding first. See
       * the CertPath Encodings section in the <a href=
       * "{@docRoot}/../technotes/guides/security/StandardNames.html#CertPathEncodings">
       * Java Cryptography Architecture Standard Algorithm Name Documentation</a>
       * for information about standard encoding names.
       * <p>
       * Attempts to modify the returned {@code Iterator} via its
       * {@code remove} method result in an
       * {@code UnsupportedOperationException}.
       *
       * <p> This method was added to version 1.4 of the Java 2 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}.
       *
       * @return an {@code Iterator} over the names of the supported
       *         {@code CertPath} encodings (as {@code String}s)
       * @exception UnsupportedOperationException if the method is not supported
       * @since 1.4
       */
      public Iterator<String> engineGetCertPathEncodings() {
          throw new UnsupportedOperationException();
      }
  
      /**
       * Returns a (possibly empty) collection view of the certificates read
       * from the given input stream {@code inStream}.
       *
       * <p>In order to take advantage of the specialized certificate format
       * supported by this certificate factory, each element in
       * the returned collection view can be typecast to the corresponding
       * certificate class. For example, if this certificate
       * factory implements X.509 certificates, the elements in the returned
       * collection can be typecast to the {@code X509Certificate} class.
       *
       * <p>In the case of a certificate factory for X.509 certificates,
       * {@code inStream} may contain a single DER-encoded certificate
       * in the formats described for
       * {@link CertificateFactory#generateCertificate(InputStream)
       * generateCertificate}.
       * In addition, {@code inStream} may contain a PKCS#7 certificate
       * chain. This is a PKCS#7 <i>SignedData</i> object, with the only
       * significant field being <i>certificates</i>. In particular, the
       * signature and the contents are ignored. This format allows multiple
       * certificates to be downloaded at once. If no certificates are present,
       * an empty collection is returned.
       *
       * <p>Note that if the given input stream does not support
       * {@link InputStream#mark(int) mark} and
       * {@link InputStream#reset() reset}, this method will
       * consume the entire input stream.
       *
       * @param inStream the input stream with the certificates.
       *
       * @return a (possibly empty) collection view of
       * java.security.cert.Certificate objects
       * initialized with the data from the input stream.
       *
       * @exception CertificateException on parsing errors.
       */
      public abstract Collection<? extends Certificate>
              engineGenerateCertificates(InputStream inStream)
              throws CertificateException;
  
      /**
       * Generates a certificate revocation list (CRL) object and initializes it
       * with the data read from the input stream {@code inStream}.
       *
       * <p>In order to take advantage of the specialized CRL format
       * supported by this certificate factory,
       * the returned CRL object can be typecast to the corresponding
       * CRL class. For example, if this certificate
       * factory implements X.509 CRLs, the returned CRL object
       * can be typecast to the {@code X509CRL} class.
       *
       * <p>Note that if the given input stream does not support
       * {@link InputStream#mark(int) mark} and
       * {@link InputStream#reset() reset}, this method will
       * consume the entire input stream. Otherwise, each call to this
       * method consumes one CRL and the read position of the input stream
       * is positioned to the next available byte after the inherent
       * end-of-CRL marker. If the data in the
       * input stream does not contain an inherent end-of-CRL marker (other
       * than EOF) and there is trailing data after the CRL is parsed, a
       * {@code CRLException} is thrown.
       *
       * @param inStream an input stream with the CRL data.
       *
       * @return a CRL object initialized with the data
       * from the input stream.
       *
       * @exception CRLException on parsing errors.
       */
      public abstract CRL engineGenerateCRL(InputStream inStream)
          throws CRLException;
  
      /**
       * Returns a (possibly empty) collection view of the CRLs read
       * from the given input stream {@code inStream}.
       *
       * <p>In order to take advantage of the specialized CRL format
       * supported by this certificate factory, each element in
       * the returned collection view can be typecast to the corresponding
       * CRL class. For example, if this certificate
       * factory implements X.509 CRLs, the elements in the returned
       * collection can be typecast to the {@code X509CRL} class.
       *
       * <p>In the case of a certificate factory for X.509 CRLs,
       * {@code inStream} may contain a single DER-encoded CRL.
       * In addition, {@code inStream} may contain a PKCS#7 CRL
       * set. This is a PKCS#7 <i>SignedData</i> object, with the only
       * significant field being <i>crls</i>. In particular, the
       * signature and the contents are ignored. This format allows multiple
       * CRLs to be downloaded at once. If no CRLs are present,
       * an empty collection is returned.
       *
       * <p>Note that if the given input stream does not support
       * {@link InputStream#mark(int) mark} and
       * {@link InputStream#reset() reset}, this method will
       * consume the entire input stream.
       *
       * @param inStream the input stream with the CRLs.
       *
       * @return a (possibly empty) collection view of
       * java.security.cert.CRL objects initialized with the data from the input
       * stream.
       *
       * @exception CRLException on parsing errors.
       */
      public abstract Collection<? extends CRL> engineGenerateCRLs
              (InputStream inStream) throws CRLException;
  }
  