Mercurial > hg > blitz_condensed
diff src/com/go/trove/io/PushbackPositionReader.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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--- /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) { + } +}