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Java > Open Source Codes > com > go > trove > io > PositionReader


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52
53 package com.go.trove.io;
54
55 import java.io.*;
56
57 /******************************************************************************
58  * The PositionReader tracks the postion in the stream of the next character
59  * to be read. PositionReaders chain together such that the position is
60  * read from the earliest PositionReader in the chain.
61  *
62  * <p>Position readers automatically close the underlying input stream when
63  * the end of file is reached. Ordinary input streams don't do this.
64  *
65  * @author Brian S O'Neill
66  * @version
67  * <!--$$Revision:--> 15 <!-- $-->, <!--$$JustDate:--> 12/11/00 <!-- $-->
68  */
69 public class PositionReader extends FilterReader {
70     /** Is non-null when this PositionReader is chained to another. */
71     protected PositionReader mPosReader;
72
73     protected int mPosition = 0;
74
75     private boolean mClosed = false;
76
77     public PositionReader(Reader reader) {
78         super(reader);
79         if (reader instanceof PositionReader) {
80             mPosReader = (PositionReader)reader;
81         }
82     }
83
84     /**
85      * @return the position of the next character to be read.
86      */
87     public int getNextPosition() {
88         return mPosition;
89     }
90
91     public int read() throws IOException {
92         try {
93             int c;
94             if ((c = in.read()) != -1) {
95                 if (mPosReader == null) {
96                     mPosition++;
97                 }
98                 else {
99                     mPosition = mPosReader.getNextPosition();
100                 }
101             }
102             else {
103                 close();
104             }
105             
106             return c;
107         }
108         catch (IOException e) {
109             if (mClosed) {
110                 return -1;
111             }
112             else {
113                 throw e;
114             }
115         }
116     }
117
118     public int read(char[] buf, int off, int length) throws IOException {
119         int i = 0;
120         while (i < length) {
121             int c;
122             if ((c = read()) == -1) {
123                 return (i == 0)? -1 : i;
124             }
125             buf[i++ + off] = (char)c;
126         }
127
128         return i;
129     }
130
131     public void close() throws IOException {
132         mClosed = true;
133         super.close();
134     }
135 }
136
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