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
18 package org.apache.commons.net.io;
19
20 import java.io.FilterInputStream;
21 import java.io.IOException;
22 import java.io.InputStream;
23
24 import org.apache.commons.net.util.NetConstants;
25
26 /**
27 * This class wraps an input stream, replacing all singly occurring <LF> (linefeed) characters with <CR><LF> (carriage return followed by
28 * linefeed), which is the NETASCII standard for representing a newline. You would use this class to implement ASCII file transfers requiring conversion to
29 * NETASCII.
30 */
31
32 public final class ToNetASCIIInputStream extends FilterInputStream {
33 private static final int NOTHING_SPECIAL = 0;
34 private static final int LAST_WAS_CR = 1;
35 private static final int LAST_WAS_NL = 2;
36 private int status;
37
38 /**
39 * Creates a ToNetASCIIInputStream instance that wraps an existing InputStream.
40 *
41 * @param input The InputStream to wrap.
42 */
43 public ToNetASCIIInputStream(final InputStream input) {
44 super(input);
45 status = NOTHING_SPECIAL;
46 }
47
48 @Override
49 public int available() throws IOException {
50 final int result;
51
52 result = in.available();
53
54 if (status == LAST_WAS_NL) {
55 return result + 1;
56 }
57
58 return result;
59 }
60
61 /** Returns false. Mark is not supported. */
62 @Override
63 public boolean markSupported() {
64 return false;
65 }
66
67 /**
68 * Reads and returns the next byte in the stream. If the end of the message has been reached, returns -1.
69 *
70 * @return The next character in the stream. Returns -1 if the end of the stream has been reached.
71 * @throws IOException If an error occurs while reading the underlying stream.
72 */
73 @Override
74 public int read() throws IOException {
75 final int ch;
76
77 if (status == LAST_WAS_NL) {
78 status = NOTHING_SPECIAL;
79 return '\n';
80 }
81
82 ch = in.read();
83
84 switch (ch) {
85 case '\r':
86 status = LAST_WAS_CR;
87 return '\r';
88 case '\n':
89 if (status != LAST_WAS_CR) {
90 status = LAST_WAS_NL;
91 return '\r';
92 }
93 //$FALL-THROUGH$
94 default:
95 status = NOTHING_SPECIAL;
96 return ch;
97 }
98 // statement not reached
99 // return ch;
100 }
101
102 /**
103 * Reads the next number of bytes from the stream into an array and returns the number of bytes read. Returns -1 if the end of the stream has been reached.
104 *
105 * @param buffer The byte array in which to store the data.
106 * @return The number of bytes read. Returns -1 if the end of the message has been reached.
107 * @throws IOException If an error occurs in reading the underlying stream.
108 */
109 @Override
110 public int read(final byte[] buffer) throws IOException {
111 return read(buffer, 0, buffer.length);
112 }
113
114 /**
115 * Reads the next number of bytes from the stream into an array and returns the number of bytes read. Returns -1 if the end of the message has been reached.
116 * The characters are stored in the array starting from the given offset and up to the length specified.
117 *
118 * @param buffer The byte array in which to store the data.
119 * @param offset The offset into the array at which to start storing data.
120 * @param length The number of bytes to read.
121 * @return The number of bytes read. Returns -1 if the end of the stream has been reached.
122 * @throws IOException If an error occurs while reading the underlying stream.
123 */
124 @Override
125 public int read(final byte[] buffer, int offset, int length) throws IOException {
126 int ch;
127 final int off;
128
129 if (length < 1) {
130 return 0;
131 }
132
133 ch = available();
134
135 if (length > ch) {
136 length = ch;
137 }
138
139 // If nothing is available, block to read only one character
140 if (length < 1) {
141 length = 1;
142 }
143
144 if ((ch = read()) == NetConstants.EOS) {
145 return NetConstants.EOS;
146 }
147
148 off = offset;
149
150 do {
151 buffer[offset++] = (byte) ch;
152 } while (--length > 0 && (ch = read()) != NetConstants.EOS);
153
154 return offset - off;
155 }
156 }