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Java > Open Source Codes > gnu > regexp > CharIndexedInputStream


1 /*
2  * gnu/regexp/CharIndexedReader.java
3  * Copyright (C) 1998-2001 Wes Biggs
4  *
5  * This library is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU Lesser General Public License as published
7  * by the Free Software Foundation; either version 2.1 of the License, or
8  * (at your option) any later version.
9  *
10  * This library is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  * GNU Lesser General Public License for more details.
14  *
15  * You should have received a copy of the GNU Lesser General Public License
16  * along with this program; if not, write to the Free Software
17  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
18  */
19
20 package gnu.regexp;
21 import java.io.InputStream JavaDoc;
22 import java.io.BufferedInputStream JavaDoc;
23 import java.io.IOException JavaDoc;
24
25 // TODO: move(x) shouldn't rely on calling next() x times
26
27 class CharIndexedInputStream implements CharIndexed {
28     private static final int BUFFER_INCREMENT = 1024;
29     private static final int UNKNOWN = Integer.MAX_VALUE; // value for end
30
31     private BufferedInputStream JavaDoc br;
32
33     // so that we don't try to reset() right away
34 private int index = -1;
35
36     private int bufsize = BUFFER_INCREMENT;
37
38     private int end = UNKNOWN;
39
40     private char cached = OUT_OF_BOUNDS;
41
42     // Big enough for a \r\n pair
43 // lookBehind[0] = most recent
44 // lookBehind[1] = second most recent
45 private char[] lookBehind = new char[] { OUT_OF_BOUNDS, OUT_OF_BOUNDS };
46     
47     CharIndexedInputStream(InputStream JavaDoc str, int index) {
48     if (str instanceof BufferedInputStream JavaDoc) br = (BufferedInputStream JavaDoc) str;
49     else br = new BufferedInputStream JavaDoc(str,BUFFER_INCREMENT);
50     next();
51     if (index > 0) move(index);
52     }
53     
54     private boolean next() {
55     if (end == 1) return false;
56     end--; // closer to end
57
58     try {
59         if (index != -1) {
60         br.reset();
61         }
62         int i = br.read();
63         br.mark(bufsize);
64         if (i == -1) {
65         end = 1;
66         cached = OUT_OF_BOUNDS;
67         return false;
68         }
69         cached = (char) i;
70         index = 1;
71     } catch (IOException JavaDoc e) {
72         e.printStackTrace();
73         cached = OUT_OF_BOUNDS;
74         return false;
75     }
76     return true;
77     }
78     
79     public char charAt(int index) {
80     if (index == 0) {
81         return cached;
82     } else if (index >= end) {
83         return OUT_OF_BOUNDS;
84     } else if (index == -1) {
85         return lookBehind[0];
86     } else if (index == -2) {
87         return lookBehind[1];
88     } else if (index < -2) {
89         return OUT_OF_BOUNDS;
90     } else if (index >= bufsize) {
91         // Allocate more space in the buffer.
92 try {
93         while (bufsize <= index) bufsize += BUFFER_INCREMENT;
94         br.reset();
95         br.mark(bufsize);
96         br.skip(index-1);
97         } catch (IOException JavaDoc e) { }
98     } else if (this.index != index) {
99         try {
100         br.reset();
101         br.skip(index-1);
102         } catch (IOException JavaDoc e) { }
103     }
104     char ch = OUT_OF_BOUNDS;
105     
106     try {
107         int i = br.read();
108         this.index = index+1; // this.index is index of next pos relative to charAt(0)
109 if (i == -1) {
110         // set flag that next should fail next time?
111 end = index;
112         return ch;
113         }
114         ch = (char) i;
115     } catch (IOException JavaDoc ie) { }
116     
117     return ch;
118     }
119     
120     public boolean move(int index) {
121     // move read position [index] clicks from 'charAt(0)'
122 boolean retval = true;
123     while (retval && (index-- > 0)) retval = next();
124     return retval;
125     }
126     
127     public boolean isValid() {
128     return (cached != OUT_OF_BOUNDS);
129     }
130 }
131
132
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