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comparison src/com/go/trove/io/PushbackPositionReader.java @ 0:3dc0c5604566

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Initial checkin of blitz 2.0 fcs - no installer yet.
author Dan Creswell <dan.creswell@gmail.com>
date Sat, 21 Mar 2009 11:00:06 +0000
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1 /* ====================================================================
2 * Trove - Copyright (c) 1997-2000 Walt Disney Internet Group
3 * ====================================================================
4 * The Tea Software License, Version 1.1
5 *
6 * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in
17 * the documentation and/or other materials provided with the
18 * distribution.
19 *
20 * 3. The end-user documentation included with the redistribution,
21 * if any, must include the following acknowledgment:
22 * "This product includes software developed by the
23 * Walt Disney Internet Group (http://opensource.go.com/)."
24 * Alternately, this acknowledgment may appear in the software itself,
25 * if and wherever such third-party acknowledgments normally appear.
26 *
27 * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
28 * not be used to endorse or promote products derived from this
29 * software without prior written permission. For written
30 * permission, please contact opensource@dig.com.
31 *
32 * 5. Products derived from this software may not be called "Tea",
33 * "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
34 * "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
35 * written permission of the Walt Disney Internet Group.
36 *
37 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40 * DISCLAIMED. IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
41 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
42 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
43 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
44 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
45 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
46 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
47 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
48 * ====================================================================
49 *
50 * For more information about Tea, please see http://opensource.go.com/.
51 */
52
53 package com.go.trove.io;
54
55 import java.io.*;
56
57 /******************************************************************************
58 * The PushbackPositionReader is a kind of pushback reader that tracks the
59 * postion in the stream of the next character to be read.
60 * The java.io.PushbackReader allows arbitrary characters
61 * to be pushed back. Since this Reader may need to keep track of how many
62 * characters were scanned from the underlying Reader to actually produce
63 * a character, the unread operation cannot accept any arbitrary character.
64 *
65 * @author Brian S O'Neill
66 * @version
67 * <!--$$Revision: 1.1 $-->, <!--$$JustDate:--> 12/11/00 <!-- $-->
68 * @see java.io.PushbackReader
69 */
70 public class PushbackPositionReader extends PositionReader {
71 /** Maximum pushback allowed. */
72 private int mMaxPushback;
73
74 /** Most recently read characters with escapes already processed. */
75 private int[] mCharacters;
76
77 /** The scan lengths of the most recently read characters. */
78 private int[] mPositions;
79
80 /** The cursor marks the position in the arrays of the last character. */
81 private int mCursor;
82
83 /** Amount of characters currently pushed back. */
84 private int mPushback;
85
86 public PushbackPositionReader(Reader reader) {
87 this(reader, 0);
88 }
89
90 public PushbackPositionReader(Reader reader, int pushback) {
91 super(reader);
92
93 // Two more are required for correct operation
94 pushback += 2;
95
96 mMaxPushback = pushback;
97 mCharacters = new int[pushback];
98 mPositions = new int[pushback];
99 mCursor = 0;
100 mPushback = 0;
101 }
102
103 /**
104 * @return the start position of the last read character.
105 */
106 public int getStartPosition() {
107 int back = mCursor - 2;
108 if (back < 0) back += mMaxPushback;
109
110 return mPositions[back];
111 }
112
113 public int read() throws IOException {
114 int c;
115
116 if (mPushback > 0) {
117 mPushback--;
118
119 mPosition = mPositions[mCursor];
120 c = mCharacters[mCursor++];
121 if (mCursor >= mMaxPushback) mCursor = 0;
122
123 return c;
124 }
125
126 c = super.read();
127
128 mPositions[mCursor] = mPosition;
129 mCharacters[mCursor++] = c;
130 if (mCursor >= mMaxPushback) mCursor = 0;
131
132 return c;
133 }
134
135 public int peek() throws IOException {
136 int c = read();
137 unread();
138 return c;
139 }
140
141 /**
142 * Unread the last several characters read.
143 *
144 * <p>Unlike PushbackReader, unread does not allow arbitrary characters to
145 * to be unread. Rather, it functions like an undo operation.
146 *
147 * @param amount Amount of characters to unread.
148 * @see java.io.PushbackReader#unread(int)
149 */
150 public void unread(int amount) throws IOException {
151 for (int i=0; i<amount; i++) {
152 unread();
153 }
154 }
155
156 /**
157 * Unread the last character read.
158 *
159 * <p>Unlike PushbackReader, unread does not allow arbitrary characters to
160 * to be unread. Rather, it functions like an undo operation.
161 *
162 * @see java.io.PushbackReader#unread(int)
163 */
164 public void unread() throws IOException {
165 mPushback++;
166
167 if (mPushback > mMaxPushback - 2) {
168 throw new IOException(this.getClass().getName() +
169 ": pushback exceeded " + (mMaxPushback - 2));
170 }
171
172 if ((--mCursor) < 0) mCursor += mMaxPushback;
173
174 if (mCursor > 0) {
175 mPosition = mPositions[mCursor - 1];
176 }
177 else {
178 mPosition = mPositions[mMaxPushback - 1];
179 }
180
181 unreadHook(mCharacters[mCursor]);
182 }
183
184 /**
185 * A hook call from the unread method(s). Every unread character is
186 * passed to this method.
187 */
188 protected void unreadHook(int c) {
189 }
190 }