ChannelReader: Fixed comments.

2005-02-23  Robert Schuster  <thebohemian@gmx.net>

	* gnu/java/nio/ChannelReader: Fixed comments.

2005-02-23  Robert Schuster  <thebohemian@gmx.net>

	* java/nio/channels/Channels: Added FIXMEs about
	stub method implementation.
	(newReader): Implemented.
	* gnu/java/nio/ChannelReader: New class.

From-SVN: r95444

1 files changed, 211 insertions, 0 deletions

diff --git a/libjava/gnu/java/nio/ChannelReader.java b/libjava/gnu/java/nio/ChannelReader.java
new file mode 100644
index 0000000..11e66a7
--- /dev/null
+++ b/libjava/gnu/java/nio/ChannelReader.java
@@ -0,0 +1,211 @@
+/* ChannelReader.java -- 
+ Copyright (C) 2005 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.nio;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.channels.ReadableByteChannel;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CoderResult;
+import java.nio.charset.CodingErrorAction;
+
+/**
+ * A Reader implementation that works using a ReadableByteChannel and a
+ * CharsetDecoder.
+ * 
+ * <p>
+ * This is a bridge between NIO <-> IO character decoding.
+ * </p>
+ * 
+ * @author Robert Schuster
+ */
+public class ChannelReader extends Reader
+{
+
+  private static final int DEFAULT_BUFFER_CAP = 8192;
+
+  private ReadableByteChannel channel;
+
+  private CharsetDecoder decoder;
+
+  private ByteBuffer byteBuffer;
+
+  private CharBuffer charBuffer;
+
+  public ChannelReader(ReadableByteChannel channel, CharsetDecoder decoder,
+                       int minBufferCap)
+  {
+    this.channel = channel;
+    this.decoder = decoder;
+
+    // JDK reports errors, so we do the same.
+    decoder.onMalformedInput(CodingErrorAction.REPORT);
+    decoder.onUnmappableCharacter(CodingErrorAction.REPORT);
+    decoder.reset();
+
+    int size = (minBufferCap == -1) ? DEFAULT_BUFFER_CAP : minBufferCap;
+
+    // Allocates the buffers and prepares them for reading, because that is the
+    // first operation being done on them.
+    byteBuffer = ByteBuffer.allocate(size);
+    byteBuffer.flip();
+    charBuffer = CharBuffer.allocate((int) (size * decoder.averageCharsPerByte()));
+  }
+
+  public int read(char[] buf, int offset, int count) throws IOException
+  {
+    // I declared channel being null meaning that the reader is closed.
+    if (!channel.isOpen())
+      throw new IOException("Reader was already closed.");
+
+    // I declared decoder being null meaning that there is no more data to read
+    // and convert.
+    if (decoder == null)
+      return -1;
+
+    // Stores the amount of character being read. It -1 so that if no conversion
+    // occured the caller will see this as an 'end of file'.
+    int sum = -1;
+
+    // Copies any characters which may be left from the last invocation into the
+    // destination array.
+    if (charBuffer.remaining() > 0)
+      {
+        sum = Math.min(count, charBuffer.remaining());
+        charBuffer.get(buf, offset, sum);
+
+        // Updates the control variables according to the latest copy operation.
+        offset += sum;
+        count -= sum;
+      }
+
+    // Copies the character which have not been put in the destination array to
+    // the beginning. If data is actually copied count will be 0. If no data is
+    // copied count is >0 and we can now convert some more characters.
+    charBuffer.compact();
+
+    int converted = 0;
+    boolean last = false;
+
+    while (count != 0)
+      {
+        // Tries to convert some bytes (Which will intentionally fail in the
+        // first place because we have not read any bytes yet.)
+        CoderResult result = decoder.decode(byteBuffer, charBuffer, last);
+        if (result.isMalformed() || result.isUnmappable())
+          {
+            // JDK throws exception when bytes are malformed for sure.
+            // FIXME: Unsure what happens when a character is simply
+            // unmappable.
+            result.throwException();
+          }
+
+        // Marks that we should end this loop regardless whether the caller
+        // wants more chars or not, when this was the last conversion.
+        if (last)
+          {
+            decoder = null;
+          }
+        else if (result.isUnderflow())
+          {
+            // We need more bytes to do the conversion.
+
+            // Copies the not yet converted bytes to the beginning making it
+            // being able to receive more bytes.
+            byteBuffer.compact();
+
+            // Reads in another bunch of bytes for being converted.
+            if (channel.read(byteBuffer) == -1)
+              {
+                // If there is no more data available in the channel we mark
+                // that state for the final character conversion run which is
+                // done in the next loop iteration.
+                last = true;
+              }
+
+            // Prepares the byteBuffer for the next character conversion run.
+            byteBuffer.flip();
+          }
+
+        // Prepares the charBuffer for being drained.
+        charBuffer.flip();
+
+        converted = Math.min(count, charBuffer.remaining());
+        charBuffer.get(buf, offset, converted);
+
+        // Copies characters which have not yet being copied into the char-Array
+        // to the beginning making it possible to read them later (If data is
+        // really copied here, then the caller has received enough characters so
+        // far.).
+        charBuffer.compact();
+
+        // Updates the control variables according to the latest copy operation.
+        offset += converted;
+        count -= converted;
+
+        // Updates the amount of transferred characters.
+        sum += converted;
+
+        if (decoder == null)
+          {
+            break;
+          }
+
+        // Now that more characters have been transfered we let the loop decide
+        // what to do next.
+      }
+
+    // Makes the charBuffer ready for reading on the next invocation.
+    charBuffer.flip();
+
+    return sum;
+  }
+
+  public void close() throws IOException
+  {
+    channel.close();
+
+    // Makes sure all intermediate data is released by the decoder.
+    if (decoder != null)
+      decoder.reset();
+  }
+
+}