Mercurial > hg > blitz_stable
comparison 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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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 } |