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Java > Open Source Codes > gnu > text > QueueReader


1 package gnu.text;
2 import java.io.*;
3
4 /** An InPort that reads from a queue.
5   * The method append can be used to write chars to the end of the queue.
6   * @author Per Bothner <bothner@cygnus.com>
7   */
8
9 public class QueueReader extends Reader
10 {
11   char[] buffer;
12   int readAheadLimit;
13   int mark; // Mark position.
14 int pos; // Read position.
15 int limit; // Write position.
16 boolean EOFseen;
17
18   public QueueReader ()
19   {
20   }
21
22   public boolean markSupported () { return true; }
23
24   public synchronized void mark(int readAheadLimit)
25   {
26     this.readAheadLimit = readAheadLimit;
27     mark = pos;
28   }
29
30   public synchronized void reset ()
31   {
32     if (readAheadLimit > 0)
33       pos = mark;
34   }
35
36   void resize (int len)
37   {
38     int cur_size = limit - pos;
39     if (readAheadLimit > 0 && pos - mark <= readAheadLimit)
40       cur_size = limit - mark;
41     else
42       mark = pos;
43     char[] new_buffer = (buffer.length < cur_size + len
44              ? new char[2 * cur_size + len]
45              : buffer);
46     System.arraycopy(buffer, mark, new_buffer, 0, cur_size);
47     buffer = new_buffer;
48     pos -= mark;
49     mark = 0;
50     limit = cur_size;
51   }
52
53   public void append (String JavaDoc str)
54   {
55     append (str.toCharArray());
56   }
57
58   public void append(char[] chars)
59   {
60     append(chars, 0, chars.length);
61   }
62
63   public synchronized void append(char[] chars, int off, int len)
64   {
65     if (buffer == null)
66       buffer = new char[100+len];
67     else if (buffer.length < limit + len)
68       resize(len);
69     System.arraycopy(chars, off, buffer, limit, len);
70     limit += len;
71     notifyAll();
72   }
73
74   public synchronized void append(char ch)
75   {
76     if (buffer == null)
77       buffer = new char[100];
78     else if (buffer.length <= limit)
79       resize(1);
80     buffer[limit++] = ch;
81     notifyAll();
82   }
83
84   /** For the writer to signal that there is no more data to append. */
85   public synchronized void appendEOF ()
86   {
87     EOFseen = true;
88   }
89
90   public synchronized boolean ready ()
91   {
92     return pos < limit || EOFseen;
93   }
94
95   public synchronized int read ()
96   {
97     while (pos >= limit)
98       {
99     if (EOFseen)
100       return -1;
101     try
102       {
103         wait();
104       }
105     catch (java.lang.InterruptedException JavaDoc ex)
106       {
107       }
108       }
109     char ch = buffer[pos++];
110     return ch;
111   }
112
113   public synchronized int read (char[] cbuf, int off, int len)
114   {
115     if (len == 0)
116       return 0;
117     while (pos >= limit)
118       {
119     if (EOFseen)
120       return -1;
121     try
122       {
123         wait();
124       }
125     catch (java.lang.InterruptedException JavaDoc ex)
126       {
127       }
128       }
129     int avail = limit - pos;
130     if (len > avail)
131       len = avail;
132     System.arraycopy (buffer, pos, cbuf, off, len);
133     pos += len;
134     return len;
135   }
136
137   public synchronized void close ()
138   {
139     pos = 0;
140     limit = 0;
141     mark = 0;
142     EOFseen = true;
143     buffer = null;
144   }
145 }
146
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