1 /*
2  * Licensed to the Apache Software Foundation (ASF) under one or more
3  * contributor license agreements.  See the NOTICE file distributed with
4  * this work for additional information regarding copyright ownership.
5  * The ASF licenses this file to You under the Apache License, Version 2.0
6  * (the "License"); you may not use this file except in compliance with
7  * the License.  You may obtain a copy of the License at
8  *
9  *      http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 package org.apache.commons.io.input;
18 
19 import java.io.Reader;
20 import java.io.Serializable;
21 
22 /**
23  * {@link Reader} implementation that can read from String, StringBuffer,
24  * StringBuilder or CharBuffer.
25  * <p>
26  * <strong>Note:</strong> Supports {@link #mark(int)} and {@link #reset()}.
27  *
28  * @version $Revision: 610516 $ $Date: 2008-01-09 19:05:05 +0000 (Wed, 09 Jan 2008) $
29  * @since Commons IO 1.4
30  */
31 public class CharSequenceReader extends Reader implements Serializable {
32 
33     private final CharSequence charSequence;
34     private int idx;
35     private int mark;
36 
37     /**
38      * Construct a new instance with the specified character sequence.
39      *
40      * @param charSequence The character sequence, may be <code>null</code>
41      */
CharSequenceReader(CharSequence charSequence)42     public CharSequenceReader(CharSequence charSequence) {
43         this.charSequence = (charSequence != null ? charSequence : "");
44     }
45 
46     /**
47      * Close resets the file back to the start and removes any marked position.
48      */
close()49     public void close() {
50         idx = 0;
51         mark = 0;
52     }
53 
54     /**
55      * Mark the current position.
56      *
57      * @param readAheadLimit ignored
58      */
mark(int readAheadLimit)59     public void mark(int readAheadLimit) {
60         mark = idx;
61     }
62 
63     /**
64      * Mark is supported (returns true).
65      *
66      * @return <code>true</code>
67      */
markSupported()68     public boolean markSupported() {
69         return true;
70     }
71 
72     /**
73      * Read a single character.
74      *
75      * @return the next character from the character sequence
76      * or -1 if the end has been reached.
77      */
read()78     public int read() {
79         if (idx >= charSequence.length()) {
80             return -1;
81         } else {
82             return charSequence.charAt(idx++);
83         }
84     }
85 
86     /**
87      * Read the sepcified number of characters into the array.
88      *
89      * @param array The array to store the characters in
90      * @param offset The starting position in the array to store
91      * @param length The maximum number of characters to read
92      * @return The number of characters read or -1 if there are
93      * no more
94      */
read(char[] array, int offset, int length)95     public int read(char[] array, int offset, int length) {
96         if (idx >= charSequence.length()) {
97             return -1;
98         }
99         if (array == null) {
100             throw new NullPointerException("Character array is missing");
101         }
102         if (length < 0 || (offset + length) > array.length) {
103             throw new IndexOutOfBoundsException("Array Size=" + array.length +
104                     ", offset=" + offset + ", length=" + length);
105         }
106         int count = 0;
107         for (int i = 0; i < length; i++) {
108             int c = read();
109             if (c == -1) {
110                 return count;
111             }
112             array[offset + i] = (char)c;
113             count++;
114         }
115         return count;
116     }
117 
118     /**
119      * Reset the reader to the last marked position (or the beginning if
120      * mark has not been called).
121      */
reset()122     public void reset() {
123         idx = mark;
124     }
125 
126     /**
127      * Skip the specified number of characters.
128      *
129      * @param n The number of characters to skip
130      * @return The actual number of characters skipped
131      */
skip(long n)132     public long skip(long n) {
133         if (n < 0) {
134             throw new IllegalArgumentException(
135                     "Number of characters to skip is less than zero: " + n);
136         }
137         if (idx >= charSequence.length()) {
138             return -1;
139         }
140         int dest = (int)Math.min(charSequence.length(), (idx + n));
141         int count = dest - idx;
142         idx = dest;
143         return count;
144     }
145 
146     /**
147      * Return a String representation of the underlying
148      * character sequence.
149      *
150      * @return The contents of the character sequence
151      */
toString()152     public String toString() {
153         return charSequence.toString();
154     }
155 }
156