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The source code

/*
 * Copyright 2001-2004 The Apache Software Foundation
 *
 * Licensed 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;

/***
 * 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.
 * 

*

* @author Daniel F. Savarese ***/ public final class FromNetASCIIInputStream extends PushbackInputStream { static final boolean _noConversionRequired; static final String _lineSeparator; static final byte[] _lineSeparatorBytes; static { _lineSeparator = System.getProperty("line.separator"); _noConversionRequired = _lineSeparator.equals("\r\n"); _lineSeparatorBytes = _lineSeparator.getBytes(); } private int __length = 0; /*** * 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 final boolean isConversionRequired() { return !_noConversionRequired; } /*** * Creates a FromNetASCIIInputStream instance that wraps an existing * InputStream. ***/ public FromNetASCIIInputStream(InputStream input) { super(input, _lineSeparatorBytes.length + 1); } private int __read() throws IOException { int ch; ch = super.read(); if (ch == '\r') { ch = super.read(); if (ch == '\n') { unread(_lineSeparatorBytes); ch = super.read(); // This is a kluge for read(byte[], ...) to read the right amount --__length; } else { if (ch != -1) unread(ch); return '\r'; } } return ch; } /*** * 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. * @exception IOException If an error occurs while reading the underlying * stream. ***/ public int read() throws IOException { if (_noConversionRequired) return super.read(); return __read(); } /*** * 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. * @exception IOException If an error occurs in reading the underlying * stream. ***/ public int read(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. * @exception IOException If an error occurs while reading the underlying * stream. ***/ public int read(byte buffer[], int offset, int length) throws IOException { int ch, off; if (length < 1) return 0; ch = available(); __length = (length > ch ? ch : length); // If nothing is available, block to read only one character if (__length < 1) __length = 1; if (_noConversionRequired) return super.read(buffer, offset, __length); if ((ch = __read()) == -1) return -1; off = offset; do { buffer[offset++] = (byte)ch; } while (--__length > 0 && (ch = __read()) != -1); return (offset - off); } // PushbackInputStream in JDK 1.1.3 returns the wrong thing /*** * 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. ***/ public int available() throws IOException { return (buf.length - pos) + in.available(); } }

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