1/*
2 * Copyright (C) 2013 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.io;
18
19import static com.google.common.base.Preconditions.checkArgument;
20import static com.google.common.base.Preconditions.checkNotNull;
21import static com.google.common.base.Preconditions.checkPositionIndexes;
22
23import java.io.IOException;
24import java.io.Reader;
25import java.nio.CharBuffer;
26
27/**
28 * A {@link Reader} that reads the characters in a {@link CharSequence}. Like {@code StringReader},
29 * but works with any {@link CharSequence}.
30 *
31 * @author Colin Decker
32 */
33// TODO(user): make this public? as a type, or a method in CharStreams?
34final class CharSequenceReader extends Reader {
35
36  private CharSequence seq;
37  private int pos;
38  private int mark;
39
40  /**
41   * Creates a new reader wrapping the given character sequence.
42   */
43  public CharSequenceReader(CharSequence seq) {
44    this.seq = checkNotNull(seq);
45  }
46
47  private void checkOpen() throws IOException {
48    if (seq == null) {
49      throw new IOException("reader closed");
50    }
51  }
52
53  private boolean hasRemaining() {
54    return remaining() > 0;
55  }
56
57  private int remaining() {
58    return seq.length() - pos;
59  }
60
61  @Override
62  public synchronized int read(CharBuffer target) throws IOException {
63    checkNotNull(target);
64    checkOpen();
65    if (!hasRemaining()) {
66      return -1;
67    }
68    int charsToRead = Math.min(target.remaining(), remaining());
69    for (int i = 0; i < charsToRead; i++) {
70      target.put(seq.charAt(pos++));
71    }
72    return charsToRead;
73  }
74
75  @Override
76  public synchronized int read() throws IOException {
77    checkOpen();
78    return hasRemaining() ? seq.charAt(pos++) : -1;
79  }
80
81  @Override
82  public synchronized int read(char[] cbuf, int off, int len) throws IOException {
83    checkPositionIndexes(off, off + len, cbuf.length);
84    checkOpen();
85    if (!hasRemaining()) {
86      return -1;
87    }
88    int charsToRead = Math.min(len, remaining());
89    for (int i = 0; i < charsToRead; i++) {
90      cbuf[off + i] = seq.charAt(pos++);
91    }
92    return charsToRead;
93  }
94
95  @Override
96  public synchronized long skip(long n) throws IOException {
97    checkArgument(n >= 0, "n (%s) may not be negative", n);
98    checkOpen();
99    int charsToSkip = (int) Math.min(remaining(), n); // safe because remaining is an int
100    pos += charsToSkip;
101    return charsToSkip;
102  }
103
104  @Override
105  public synchronized boolean ready() throws IOException {
106    checkOpen();
107    return true;
108  }
109
110  @Override
111  public boolean markSupported() {
112    return true;
113  }
114
115  @Override
116  public synchronized void mark(int readAheadLimit) throws IOException {
117    checkArgument(readAheadLimit >= 0, "readAheadLimit (%s) may not be negative", readAheadLimit);
118    checkOpen();
119    mark = pos;
120  }
121
122  @Override
123  public synchronized void reset() throws IOException {
124    checkOpen();
125    pos = mark;
126  }
127
128  @Override
129  public synchronized void close() throws IOException {
130    seq = null;
131  }
132}
133