Initial revision

From-SVN: r102074

libjava/classpath/gnu/java/nio/charset/UTF_16Decoder.java

@@ -0,0 +1,152 @@
+/* UTF_16Decoder.java -- 
+   Copyright (C) 2002 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., 51 Franklin Street, 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.java.nio.charset;
+
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.Charset;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CoderResult;
+
+/**
+ * Decoder for UTF-16, UTF-15LE, and UTF-16BE.
+ *
+ * @author Jesse Rosenstock
+ */
+final class UTF_16Decoder extends CharsetDecoder
+{
+  // byte orders
+  static final int BIG_ENDIAN = 0;
+  static final int LITTLE_ENDIAN = 1;
+  static final int UNKNOWN_ENDIAN = 2;
+
+  private static final char BYTE_ORDER_MARK = 0xFEFF;
+  private static final char REVERSED_BYTE_ORDER_MARK = 0xFFFE;
+
+  private final int originalByteOrder;
+  private int byteOrder;
+
+  UTF_16Decoder (Charset cs, int byteOrder)
+  {
+    super (cs, 0.5f, 1.0f);
+    this.originalByteOrder = byteOrder;
+    this.byteOrder = byteOrder;
+  }
+
+  protected CoderResult decodeLoop (ByteBuffer in, CharBuffer out)
+  {
+    // TODO: Optimize this in the case in.hasArray() / out.hasArray()
+
+    int inPos = in.position ();
+    try
+      {
+        while (in.remaining () >= 2)
+          {
+            byte b1 = in.get ();
+            byte b2 = in.get ();
+
+            // handle byte order mark
+            if (byteOrder == UNKNOWN_ENDIAN)
+              {
+                char c = (char) (((b1 & 0xFF) << 8) | (b2 & 0xFF));
+                if (c == BYTE_ORDER_MARK)
+                  {
+                    byteOrder = BIG_ENDIAN;
+                    inPos += 2;
+                    continue;
+                  }
+                else if (c == REVERSED_BYTE_ORDER_MARK)
+                  {
+                    byteOrder = LITTLE_ENDIAN;
+                    inPos += 2;
+                    continue;
+                  }
+                else
+                  {
+                    // assume big endian, do not consume bytes,
+                    // continue with normal processing
+                    byteOrder = BIG_ENDIAN;
+                  }
+              }
+
+	    // FIXME: Change so you only do a single comparison here.
+            char c = byteOrder == BIG_ENDIAN ? (char) ((b1 << 8) | b2)
+                                             : (char) ((b2 << 8) | b1);
+
+            if (0xD800 <= c && c <= 0xDFFF)
+              {
+                // c is a surrogate
+                
+                // make sure c is a high surrogate
+                if (c > 0xDBFF)
+                  return CoderResult.malformedForLength (2);
+                if (in.remaining () < 2)
+                  return CoderResult.UNDERFLOW;
+                byte b3 = in.get ();
+                byte b4 = in.get ();
+                char d = byteOrder == BIG_ENDIAN ? (char) ((b3 << 8) | b4)
+                                                 : (char) ((b4 << 8) | b3);
+                // make sure d is a low surrogate
+                if (d < 0xDC00 || d > 0xDFFF)
+                  return CoderResult.malformedForLength (2);
+                out.put (c);
+                out.put (d);
+                inPos += 4;
+              }
+            else
+              {
+                if (!out.hasRemaining ())
+                  return CoderResult.UNDERFLOW;
+                out.put (c);
+                inPos += 2;
+              }
+          }
+
+        return CoderResult.UNDERFLOW;
+      }
+    finally
+      {
+        in.position (inPos);
+      }
+  }
+
+  protected void implReset ()
+  {
+    byteOrder = originalByteOrder;
+  }
+}