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 static org.apache.commons.io.IOUtils.EOF;
20
21 import java.io.FilterReader;
22 import java.io.IOException;
23 import java.io.Reader;
24 import java.util.function.IntPredicate;
25
26 /**
27 * A filter reader that filters out characters where subclasses decide which characters to filter out.
28 */
29 public abstract class AbstractCharacterFilterReader extends FilterReader {
30
31 /**
32 * Skips nothing.
33 *
34 * @since 2.9.0
35 */
36 protected static final IntPredicate SKIP_NONE = ch -> false;
37
38 private final IntPredicate skip;
39
40 /**
41 * Constructs a new reader.
42 *
43 * @param reader the reader to filter
44 */
45 protected AbstractCharacterFilterReader(final Reader reader) {
46 this(reader, SKIP_NONE);
47 }
48
49 /**
50 * Constructs a new reader.
51 *
52 * @param reader the reader to filter.
53 * @param skip Skip test.
54 * @since 2.9.0
55 */
56 protected AbstractCharacterFilterReader(final Reader reader, final IntPredicate skip) {
57 super(reader);
58 this.skip = skip == null ? SKIP_NONE : skip;
59 }
60
61 /**
62 * Returns true if the given character should be filtered out, false to keep the character.
63 *
64 * @param ch the character to test.
65 * @return true if the given character should be filtered out, false to keep the character.
66 */
67 protected boolean filter(final int ch) {
68 return skip.test(ch);
69 }
70
71 @Override
72 public int read() throws IOException {
73 int ch;
74 do {
75 ch = in.read();
76 } while (ch != EOF && filter(ch));
77 return ch;
78 }
79
80 @Override
81 public int read(final char[] cbuf, final int off, final int len) throws IOException {
82 final int read = super.read(cbuf, off, len);
83 if (read == EOF) {
84 return EOF;
85 }
86 int pos = off - 1;
87 for (int readPos = off; readPos < off + read; readPos++) {
88 if (filter(cbuf[readPos])) {
89 continue;
90 }
91 pos++;
92 if (pos < readPos) {
93 cbuf[pos] = cbuf[readPos];
94 }
95 }
96 return pos - off + 1;
97 }
98 }