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 * https://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.IOException;
21 import java.io.InputStream;
22 import java.io.PushbackInputStream;
23 import java.nio.charset.StandardCharsets;
24
25 import org.apache.commons.net.util.NetConstants;
26
27 /**
28 * This class wraps an input stream, replacing all occurrences of <CR><LF> (carriage return followed by a linefeed), which is the NETASCII standard
29 * for representing a newline, with the local line separator representation. You would use this class to implement ASCII file transfers requiring conversion
30 * from NETASCII.
31 */
32 public final class FromNetASCIIInputStream extends PushbackInputStream {
33
34 static final boolean NO_CONVERSION_REQUIRED = System.lineSeparator().equals("\r\n");
35 static final byte[] LINE_SEPARATOR_BYTES = System.lineSeparator().getBytes(StandardCharsets.US_ASCII);
36
37 /**
38 * Returns true if the NetASCII line separator differs from the system line separator, false if they are the same. This method is useful to determine
39 * whether or not you need to instantiate a FromNetASCIIInputStream object.
40 *
41 * @return True if the NETASCII line separator differs from the local system line separator, false if they are the same.
42 */
43 public static boolean isConversionRequired() {
44 return !NO_CONVERSION_REQUIRED;
45 }
46
47 private int length;
48
49 /**
50 * Creates a FromNetASCIIInputStream instance that wraps an existing InputStream.
51 *
52 * @param input the stream to wrap
53 */
54 public FromNetASCIIInputStream(final InputStream input) {
55 super(input, LINE_SEPARATOR_BYTES.length + 1);
56 }
57
58 // PushbackInputStream in JDK 1.1.3 returns the wrong thing
59 // TODO - can we delete this override now?
60 /**
61 * Returns the number of bytes that can be read without blocking EXCEPT when newline conversions have to be made somewhere within the available block of
62 * bytes. In other words, you really should not rely on the value returned by this method if you are trying to avoid blocking.
63 */
64 @Override
65 public int available() throws IOException {
66 if (in == null) {
67 throw new IOException("Stream closed");
68 }
69 return buf.length - pos + in.available();
70 }
71
72 /**
73 * Reads and returns the next byte in the stream. If the end of the message has been reached, returns -1. Note that a call to this method may result in
74 * multiple reads from the underlying input stream in order to convert NETASCII line separators to the local line separator format. This is transparent to
75 * the programmer and is only mentioned for completeness.
76 *
77 * @return The next character in the stream. Returns -1 if the end of the stream has been reached.
78 * @throws IOException If an error occurs while reading the underlying stream.
79 */
80 @Override
81 public int read() throws IOException {
82 if (NO_CONVERSION_REQUIRED) {
83 return super.read();
84 }
85 return readInt();
86 }
87
88 /**
89 * 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.
90 *
91 * @param buffer The byte array in which to store the data.
92 * @return The number of bytes read. Returns -1 if the end of the message has been reached.
93 * @throws IOException If an error occurs in reading the underlying stream.
94 */
95 @Override
96 public int read(final byte buffer[]) throws IOException {
97 return read(buffer, 0, buffer.length);
98 }
99
100 /**
101 * 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.
102 * The characters are stored in the array starting from the given offset and up to the length specified.
103 *
104 * @param buffer The byte array in which to store the data.
105 * @param offset The offset into the array at which to start storing data.
106 * @param length The number of bytes to read.
107 * @return The number of bytes read. Returns -1 if the end of the stream has been reached.
108 * @throws IOException If an error occurs while reading the underlying stream.
109 */
110 @Override
111 public int read(final byte buffer[], int offset, final int length) throws IOException {
112 if (NO_CONVERSION_REQUIRED) {
113 return super.read(buffer, offset, length);
114 }
115 if (length < 1) {
116 return 0;
117 }
118 int ch;
119 final int off;
120 ch = available();
121 this.length = Math.min(length, ch);
122 // If nothing is available, block to read only one character
123 if (this.length < 1) {
124 this.length = 1;
125 }
126 if ((ch = readInt()) == -1) {
127 return NetConstants.EOS;
128 }
129 off = offset;
130 do {
131 buffer[offset++] = (byte) ch;
132 } while (--this.length > 0 && (ch = readInt()) != -1);
133 return offset - off;
134 }
135
136 private int readInt() throws IOException {
137 int ch;
138 ch = super.read();
139 if (ch == '\r') {
140 ch = super.read();
141 if (ch != '\n') {
142 if (ch != -1) {
143 unread(ch);
144 }
145 return '\r';
146 }
147 unread(LINE_SEPARATOR_BYTES);
148 ch = super.read();
149 // This is a kluge for read(byte[], ...) to read the right amount
150 --length;
151 }
152 return ch;
153 }
154
155 }