--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/com/go/trove/io/PushbackPositionReader.java	Sat Mar 21 11:00:06 2009 +0000
@@ -0,0 +1,190 @@
+/* ====================================================================
+ * Trove - Copyright (c) 1997-2000 Walt Disney Internet Group
+ * ====================================================================
+ * The Tea Software License, Version 1.1
+ *
+ * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. The end-user documentation included with the redistribution,
+ *    if any, must include the following acknowledgment:
+ *       "This product includes software developed by the
+ *        Walt Disney Internet Group (http://opensource.go.com/)."
+ *    Alternately, this acknowledgment may appear in the software itself,
+ *    if and wherever such third-party acknowledgments normally appear.
+ *
+ * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
+ *    not be used to endorse or promote products derived from this
+ *    software without prior written permission. For written
+ *    permission, please contact opensource@dig.com.
+ *
+ * 5. Products derived from this software may not be called "Tea",
+ *    "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
+ *    "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
+ *    written permission of the Walt Disney Internet Group.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED.  IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ * For more information about Tea, please see http://opensource.go.com/.
+ */
+
+package com.go.trove.io;
+
+import java.io.*;
+
+/******************************************************************************
+ * The PushbackPositionReader is a kind of pushback reader that tracks the 
+ * postion in the stream of the next character to be read.
+ * The java.io.PushbackReader allows arbitrary characters
+ * to be pushed back. Since this Reader may need to keep track of how many
+ * characters were scanned from the underlying Reader to actually produce
+ * a character, the unread operation cannot accept any arbitrary character.
+ * 
+ * @author Brian S O'Neill
+ * @version
+ * <!--$$Revision: 1.1 $-->, <!--$$JustDate:--> 12/11/00 <!-- $-->
+ * @see java.io.PushbackReader
+ */
+public class PushbackPositionReader extends PositionReader {
+    /** Maximum pushback allowed. */
+    private int mMaxPushback;
+
+    /** Most recently read characters with escapes already processed. */
+    private int[] mCharacters;
+
+    /** The scan lengths of the most recently read characters. */
+    private int[] mPositions;
+
+    /** The cursor marks the position in the arrays of the last character. */
+    private int mCursor;
+
+    /** Amount of characters currently pushed back. */
+    private int mPushback;
+
+    public PushbackPositionReader(Reader reader) {
+        this(reader, 0);
+    }
+
+    public PushbackPositionReader(Reader reader, int pushback) {
+        super(reader);
+
+        // Two more are required for correct operation
+        pushback += 2;
+
+        mMaxPushback = pushback;
+        mCharacters = new int[pushback];
+        mPositions = new int[pushback];
+        mCursor = 0;
+        mPushback = 0;
+    }
+
+    /**
+     * @return the start position of the last read character.
+     */
+    public int getStartPosition() {
+        int back = mCursor - 2;
+        if (back < 0) back += mMaxPushback;
+
+        return mPositions[back];
+    }
+
+    public int read() throws IOException {
+        int c;
+
+        if (mPushback > 0) {
+            mPushback--;
+
+            mPosition = mPositions[mCursor];
+            c = mCharacters[mCursor++];
+            if (mCursor >= mMaxPushback) mCursor = 0;
+            
+            return c;
+        }
+
+        c = super.read();
+        
+        mPositions[mCursor] = mPosition;
+        mCharacters[mCursor++] = c;
+        if (mCursor >= mMaxPushback) mCursor = 0;
+
+        return c;
+    }
+
+    public int peek() throws IOException {
+        int c = read();
+        unread();
+        return c;
+    }
+
+    /**
+     * Unread the last several characters read.
+     *
+     * <p>Unlike PushbackReader, unread does not allow arbitrary characters to
+     * to be unread. Rather, it functions like an undo operation.
+     *
+     * @param amount Amount of characters to unread.
+     * @see java.io.PushbackReader#unread(int)
+     */
+    public void unread(int amount) throws IOException {
+        for (int i=0; i<amount; i++) {
+            unread();
+        }
+    }
+    
+    /**
+     * Unread the last character read.
+     * 
+     * <p>Unlike PushbackReader, unread does not allow arbitrary characters to
+     * to be unread. Rather, it functions like an undo operation.
+     *
+     * @see java.io.PushbackReader#unread(int)
+     */
+    public void unread() throws IOException {
+        mPushback++;
+
+        if (mPushback > mMaxPushback - 2) {
+            throw new IOException(this.getClass().getName() + 
+                                  ": pushback exceeded " + (mMaxPushback - 2));
+        }
+
+        if ((--mCursor) < 0) mCursor += mMaxPushback;
+
+        if (mCursor > 0) {
+            mPosition = mPositions[mCursor - 1];
+        }
+        else {
+            mPosition = mPositions[mMaxPushback - 1];
+        }
+
+        unreadHook(mCharacters[mCursor]);
+    }
+
+    /**
+     * A hook call from the unread method(s). Every unread character is
+     * passed to this method.
+     */
+    protected void unreadHook(int c) {
+    }
+}