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+/* Transformer.java --
+ Copyright (C) 2003, 2006 Free Software Foundation, Inc.
+
+This file is a 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 of the License, 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; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
+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.javax.crypto.assembly;
+
+import gnu.javax.crypto.pad.IPad;
+
+import java.io.ByteArrayOutputStream;
+import java.util.Map;
+
+/**
+ * A <code>Transformer</code> is an abstract representation of a two-way
+ * <i>transformation</i> that can be chained together with other instances of
+ * this type. Examples of such transformations in this library are:
+ * {@link Cascade} cipher, {@link gnu.javax.crypto.pad.IPad} algorithm, and a
+ * ZLib-based deflater/inflater algorithm. A special implementation of a
+ * <code>Transformer</code> to close a chain is also provided.
+ * <p>
+ * A <code>Transformer</code> is characterised by the followings:
+ * <ul>
+ * <li>It can be chained to other instances, to form an {@link Assembly}.</li>
+ * <li>When configured in an {@link Assembly}, it can be set to apply its
+ * internal transformation on the input data stream before (pre-processing) or
+ * after (post-processing) passing the input data to the next element in the
+ * chain. Note that the same type <code>Transformer</code> can be used as
+ * either in pre-processing or a post-processing modes.</li>
+ * <li>A special transformer --<code>LoopbackTransformer</code>-- is used
+ * to close the chain.</li>
+ * <li>A useful type of <code>Transformer</code> --one we're interested in--
+ * has internal buffers. The distinction between a casual push (update)
+ * operation and the last one allows to correctly flush any intermediate bytes
+ * that may exist in those buffers.</li>
+ * </ul>
+ * <p>
+ * To allow wiring <code>Transformer</code> instances together, a
+ * <i>minimal-output-size</i> in bytes is necessary. The trivial case of a
+ * value of <code>1</code> for such attribute practically means that no output
+ * buffering, from the previous element, is needed --which is independant of
+ * buffering the input if the <code>Transformer</code> implementation itself
+ * is block-based.
+ *
+ * @see CascadeTransformer
+ * @see PaddingTransformer
+ * @see DeflateTransformer
+ */
+public abstract class Transformer
+{
+ public static final String DIRECTION = "gnu.crypto.assembly.transformer.direction";
+
+ protected Direction wired;
+
+ protected Operation mode;
+
+ protected Transformer tail = null;
+
+ protected ByteArrayOutputStream inBuffer = new ByteArrayOutputStream(2048);
+
+ protected ByteArrayOutputStream outBuffer = new ByteArrayOutputStream(2048);
+
+ /** Trivial protected constructor. */
+ protected Transformer()
+ {
+ super();
+
+ this.wired = null;
+ }
+
+ public static final Transformer getCascadeTransformer(Cascade cascade)
+ {
+ return new CascadeTransformer(cascade);
+ }
+
+ public static final Transformer getPaddingTransformer(IPad padding)
+ {
+ return new PaddingTransformer(padding);
+ }
+
+ public static final Transformer getDeflateTransformer()
+ {
+ return new DeflateTransformer();
+ }
+
+ /**
+ * Sets the operational mode of this <code>Transformer</code>.
+ *
+ * @param mode the processing mode this <code>Transformer</code> is required
+ * to operate in.
+ * @throws IllegalStateException if this instance has already been assigned an
+ * operational mode.
+ */
+ public void setMode(final Operation mode)
+ {
+ if (this.mode != null)
+ throw new IllegalStateException();
+ this.mode = mode;
+ }
+
+ /**
+ * Returns <code>true</code> if this <code>Transformer</code> was wired in
+ * pre-processing mode; <code>false</code> otherwise.
+ *
+ * @return <code>true</code> if this <code>Transformer</code> has been
+ * wired in pre-processing mode; <code>false</code> otherwise.
+ * @throws IllegalStateException if this instance has not yet been assigned an
+ * operational <i>type</i>.
+ */
+ public boolean isPreProcessing()
+ {
+ if (mode == null)
+ throw new IllegalStateException();
+ return (mode == Operation.PRE_PROCESSING);
+ }
+
+ /**
+ * Returns <code>true</code> if this <code>Transformer</code> was wired in
+ * post-processing mode; <code>false</code> otherwise.
+ *
+ * @return <code>true</code> if this <code>Transformer</code> has been
+ * wired in post-processing mode; <code>false</code> otherwise.
+ * @throws IllegalStateException if this instance has not yet been assigned an
+ * operational <i>type</i>.
+ */
+ public boolean isPostProcessing()
+ {
+ return ! isPreProcessing();
+ }
+
+ /**
+ * Initialises the <code>Transformer</code> for operation with specific
+ * characteristics.
+ *
+ * @param attributes a set of name-value pairs that describes the desired
+ * future behaviour of this instance.
+ * @throws IllegalStateException if the instance is already initialised.
+ */
+ public void init(Map attributes) throws TransformerException
+ {
+ if (wired != null)
+ throw new IllegalStateException();
+ Direction flow = (Direction) attributes.get(DIRECTION);
+ if (flow == null)
+ flow = Direction.FORWARD;
+ wired = flow;
+ inBuffer.reset();
+ outBuffer.reset();
+ tail.init(attributes); // initialise tail first
+ initDelegate(attributes); // initialise this instance
+ }
+
+ /**
+ * Returns the block-size of this <code>Transformer</code>. A value of
+ * <code>1</code> indicates that this instance is block-agnostic.
+ *
+ * @return the current minimal required block size.
+ */
+ public int currentBlockSize()
+ {
+ if (wired == null)
+ throw new IllegalStateException();
+ return delegateBlockSize();
+ }
+
+ /**
+ * Resets the <code>Transformer</code> for re-initialisation and use with
+ * other characteristics. This method always succeeds.
+ */
+ public void reset()
+ {
+ resetDelegate();
+ wired = null;
+ inBuffer.reset();
+ outBuffer.reset();
+ tail.reset(); // reset tail last
+ }
+
+ /**
+ * Convenience method that calls the method with same name and three
+ * arguments, using a byte array of length <code>1</code> whose contents are
+ * the designated byte.
+ *
+ * @param b the byte to process.
+ * @return the result of transformation.
+ * @throws IllegalStateException if the instance is not initialised.
+ * @throws TransformerException if a transformation-related exception occurs
+ * during the operation.
+ * @see #update(byte[], int, int)
+ */
+ public byte[] update(byte b) throws TransformerException
+ {
+ return update(new byte[] { b }, 0, 1);
+ }
+
+ /**
+ * Convenience method that calls the same method with three arguments. All
+ * bytes in <code>in</code>, starting from index position <code>0</code>
+ * are considered.
+ *
+ * @param in the input data bytes.
+ * @return the result of transformation.
+ * @throws IllegalStateException if the instance is not initialised.
+ * @throws TransformerException if a transformation-related exception occurs
+ * during the operation.
+ * @see #update(byte[], int, int)
+ */
+ public byte[] update(byte[] in) throws TransformerException
+ {
+ return update(in, 0, in.length);
+ }
+
+ /**
+ * Processes a designated number of bytes from a given byte array.
+ *
+ * @param in the input data bytes.
+ * @param offset index of <code>in</code> from which to start considering
+ * data.
+ * @param length the count of bytes to process.
+ * @return the result of transformation.
+ * @throws IllegalStateException if the instance is not initialised.
+ * @throws TransformerException if a transformation-related exception occurs
+ * during the operation.
+ */
+ public byte[] update(byte[] in, int offset, int length)
+ throws TransformerException
+ {
+ if (wired == null)
+ throw new IllegalStateException();
+ byte[] result = (wired == Direction.FORWARD ? forwardUpdate(in, offset, length)
+ : inverseUpdate(in, offset, length));
+ return result;
+ }
+
+ /**
+ * Convenience method that calls the same method with three arguments. A
+ * zero-long byte array is used.
+ *
+ * @return the result of transformation.
+ * @throws IllegalStateException if the instance is not initialised.
+ * @throws TransformerException if a transformation-related exception occurs
+ * during the operation.
+ * @see #lastUpdate(byte[], int, int)
+ */
+ public byte[] lastUpdate() throws TransformerException
+ {
+ byte[] result = (wired == Direction.FORWARD ? lastForwardUpdate()
+ : lastInverseUpdate());
+ if (inBuffer.size() != 0) // we still have some buffered bytes
+ throw new TransformerException("lastUpdate(): input buffer not empty");
+ return result;
+ }
+
+ /**
+ * Convenience method that calls the method with same name and three
+ * arguments, using a byte array of length <code>1</code> whose contents are
+ * the designated byte.
+ *
+ * @param b the byte to process.
+ * @return the result of transformation.
+ * @throws IllegalStateException if the instance is not initialised.
+ * @throws TransformerException if a transformation-related exception occurs
+ * during the operation.
+ * @see #lastUpdate(byte[], int, int)
+ */
+ public byte[] lastUpdate(byte b) throws TransformerException
+ {
+ return lastUpdate(new byte[] { b }, 0, 1);
+ }
+
+ /**
+ * Convenience method that calls the same method with three arguments. All
+ * bytes in <code>in</code>, starting from index position <code>0</code>
+ * are considered.
+ *
+ * @param in the input data bytes.
+ * @return the result of transformation.
+ * @throws IllegalStateException if the instance is not initialised.
+ * @throws TransformerException if a transformation-related exception occurs
+ * during the operation.
+ * @see #lastUpdate(byte[], int, int)
+ */
+ public byte[] lastUpdate(byte[] in) throws TransformerException
+ {
+ return lastUpdate(in, 0, in.length);
+ }
+
+ /**
+ * Processes a designated number of bytes from a given byte array and signals,
+ * at the same time, that this is the last <i>push</i> operation on this
+ * <code>Transformer</code>.
+ *
+ * @param in the input data bytes.
+ * @param offset index of <code>in</code> from which to start considering
+ * data.
+ * @param length the count of bytes to process.
+ * @return the result of transformation.
+ * @throws IllegalStateException if the instance is not initialised.
+ * @throws TransformerException if a transformation-related exception occurs
+ * during the operation.
+ */
+ public byte[] lastUpdate(byte[] in, int offset, int length)
+ throws TransformerException
+ {
+ byte[] result = update(in, offset, length);
+ byte[] rest = lastUpdate();
+ if (rest.length > 0)
+ {
+ byte[] newResult = new byte[result.length + rest.length];
+ System.arraycopy(result, 0, newResult, 0, result.length);
+ System.arraycopy(rest, 0, newResult, result.length, rest.length);
+ result = newResult;
+ }
+ return result;
+ }
+
+ private byte[] forwardUpdate(byte[] in, int off, int len)
+ throws TransformerException
+ {
+ return (isPreProcessing() ? preTransform(in, off, len)
+ : postTransform(in, off, len));
+ }
+
+ private byte[] inverseUpdate(byte[] in, int off, int len)
+ throws TransformerException
+ {
+ return (isPreProcessing() ? postTransform(in, off, len)
+ : preTransform(in, off, len));
+ }
+
+ private byte[] preTransform(byte[] in, int off, int len)
+ throws TransformerException
+ {
+ byte[] result = updateDelegate(in, off, len);
+ result = tail.update(result);
+ return result;
+ }
+
+ private byte[] postTransform(byte[] in, int off, int len)
+ throws TransformerException
+ {
+ byte[] result = tail.update(in, off, len);
+ result = updateDelegate(result, 0, result.length);
+ return result;
+ }
+
+ private byte[] lastForwardUpdate() throws TransformerException
+ {
+ return (isPreProcessing() ? preLastTransform() : postLastTransform());
+ }
+
+ private byte[] lastInverseUpdate() throws TransformerException
+ {
+ return (isPreProcessing() ? postLastTransform() : preLastTransform());
+ }
+
+ private byte[] preLastTransform() throws TransformerException
+ {
+ byte[] result = lastUpdateDelegate();
+ result = tail.lastUpdate(result);
+ return result;
+ }
+
+ private byte[] postLastTransform() throws TransformerException
+ {
+ byte[] result = tail.lastUpdate();
+ result = updateDelegate(result, 0, result.length);
+ byte[] rest = lastUpdateDelegate();
+ if (rest.length > 0)
+ {
+ byte[] newResult = new byte[result.length + rest.length];
+ System.arraycopy(result, 0, newResult, 0, result.length);
+ System.arraycopy(rest, 0, newResult, result.length, rest.length);
+ result = newResult;
+ }
+ return result;
+ }
+
+ abstract void initDelegate(Map attributes) throws TransformerException;
+
+ abstract int delegateBlockSize();
+
+ abstract void resetDelegate();
+
+ abstract byte[] updateDelegate(byte[] in, int off, int len)
+ throws TransformerException;
+
+ abstract byte[] lastUpdateDelegate() throws TransformerException;
+}