FromNetASCIIInputStream.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.net.io;
import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import java.nio.charset.StandardCharsets;
import org.apache.commons.net.util.NetConstants;
/**
* This class wraps an input stream, replacing all occurrences of <CR><LF> (carriage return followed by a linefeed), which is the NETASCII standard
* for representing a newline, with the local line separator representation. You would use this class to implement ASCII file transfers requiring conversion
* from NETASCII.
*/
public final class FromNetASCIIInputStream extends PushbackInputStream {
static final boolean _noConversionRequired;
static final String _lineSeparator;
static final byte[] _lineSeparatorBytes;
static {
_lineSeparator = System.lineSeparator();
_noConversionRequired = _lineSeparator.equals("\r\n");
_lineSeparatorBytes = _lineSeparator.getBytes(StandardCharsets.US_ASCII);
}
/**
* 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
* whether or not you need to instantiate a FromNetASCIIInputStream object.
*
* @return True if the NETASCII line separator differs from the local system line separator, false if they are the same.
*/
public static boolean isConversionRequired() {
return !_noConversionRequired;
}
private int length;
/**
* Creates a FromNetASCIIInputStream instance that wraps an existing InputStream.
*
* @param input the stream to wrap
*/
public FromNetASCIIInputStream(final InputStream input) {
super(input, _lineSeparatorBytes.length + 1);
}
// PushbackInputStream in JDK 1.1.3 returns the wrong thing
// TODO - can we delete this override now?
/**
* 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
* bytes. In other words, you really should not rely on the value returned by this method if you are trying to avoid blocking.
*/
@Override
public int available() throws IOException {
if (in == null) {
throw new IOException("Stream closed");
}
return buf.length - pos + in.available();
}
/**
* 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
* multiple reads from the underlying input stream in order to convert NETASCII line separators to the local line separator format. This is transparent to
* the programmer and is only mentioned for completeness.
*
* @return The next character in the stream. Returns -1 if the end of the stream has been reached.
* @throws IOException If an error occurs while reading the underlying stream.
*/
@Override
public int read() throws IOException {
if (_noConversionRequired) {
return super.read();
}
return readInt();
}
/**
* 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.
*
* @param buffer The byte array in which to store the data.
* @return The number of bytes read. Returns -1 if the end of the message has been reached.
* @throws IOException If an error occurs in reading the underlying stream.
*/
@Override
public int read(final byte buffer[]) throws IOException {
return read(buffer, 0, buffer.length);
}
/**
* 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.
* The characters are stored in the array starting from the given offset and up to the length specified.
*
* @param buffer The byte array in which to store the data.
* @param offset The offset into the array at which to start storing data.
* @param length The number of bytes to read.
* @return The number of bytes read. Returns -1 if the end of the stream has been reached.
* @throws IOException If an error occurs while reading the underlying stream.
*/
@Override
public int read(final byte buffer[], int offset, final int length) throws IOException {
if (_noConversionRequired) {
return super.read(buffer, offset, length);
}
if (length < 1) {
return 0;
}
int ch;
final int off;
ch = available();
this.length = Math.min(length, ch);
// If nothing is available, block to read only one character
if (this.length < 1) {
this.length = 1;
}
if ((ch = readInt()) == -1) {
return NetConstants.EOS;
}
off = offset;
do {
buffer[offset++] = (byte) ch;
} while (--this.length > 0 && (ch = readInt()) != -1);
return offset - off;
}
private int readInt() throws IOException {
int ch;
ch = super.read();
if (ch == '\r') {
ch = super.read();
if (ch != '\n') {
if (ch != -1) {
unread(ch);
}
return '\r';
}
unread(_lineSeparatorBytes);
ch = super.read();
// This is a kluge for read(byte[], ...) to read the right amount
--length;
}
return ch;
}
}