001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * https://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package org.apache.commons.net.io; 019 020import java.io.FilterOutputStream; 021import java.io.IOException; 022import java.io.OutputStream; 023 024/** 025 * This class wraps an output stream, replacing all occurrences of <CR><LF> (carriage return followed by a linefeed), which is the NETASCII standard 026 * for representing a newline, with the local line separator representation. You would use this class to implement ASCII file transfers requiring conversion 027 * from NETASCII. 028 * <p> 029 * Because of the translation process, a call to {@code flush()} will not flush the last byte written if that byte was a carriage return. A call to 030 * {@link #close close()}, however, will flush the carriage return. 031 * </p> 032 */ 033public final class FromNetASCIIOutputStream extends FilterOutputStream { 034 private boolean lastWasCR; 035 036 /** 037 * Creates a FromNetASCIIOutputStream instance that wraps an existing OutputStream. 038 * 039 * @param output The OutputStream to wrap. 040 */ 041 public FromNetASCIIOutputStream(final OutputStream output) { 042 super(output); 043 } 044 045 /** 046 * Closes the stream, writing all pending data. 047 * 048 * @throws IOException If an error occurs while closing the stream. 049 */ 050 @Override 051 public synchronized void close() throws IOException { 052 if (FromNetASCIIInputStream.NO_CONVERSION_REQUIRED) { 053 super.close(); 054 return; 055 } 056 if (lastWasCR) { 057 out.write('\r'); 058 } 059 super.close(); 060 } 061 062 /** 063 * Writes a byte array to the stream. 064 * 065 * @param buffer The byte array to write. 066 * @throws IOException If an error occurs while writing to the underlying stream. 067 */ 068 @Override 069 public synchronized void write(final byte buffer[]) throws IOException { 070 write(buffer, 0, buffer.length); 071 } 072 073 /** 074 * Writes a number of bytes from a byte array to the stream starting from a given offset. 075 * 076 * @param buffer The byte array to write. 077 * @param offset The offset into the array at which to start copying data. 078 * @param length The number of bytes to write. 079 * @throws IOException If an error occurs while writing to the underlying stream. 080 */ 081 @Override 082 public synchronized void write(final byte buffer[], int offset, int length) throws IOException { 083 if (FromNetASCIIInputStream.NO_CONVERSION_REQUIRED) { 084 // FilterOutputStream method is very slow. 085 // super.write(buffer, offset, length); 086 out.write(buffer, offset, length); 087 return; 088 } 089 while (length-- > 0) { 090 writeInt(buffer[offset++]); 091 } 092 } 093 094 /** 095 * Writes a byte to the stream. Note that a call to this method might not actually write a byte to the underlying stream until a subsequent character is 096 * written, from which it can be determined if a NETASCII line separator was encountered. This is transparent to the programmer and is only mentioned for 097 * completeness. 098 * 099 * @param ch The byte to write. 100 * @throws IOException If an error occurs while writing to the underlying stream. 101 */ 102 @Override 103 public synchronized void write(final int ch) throws IOException { 104 if (FromNetASCIIInputStream.NO_CONVERSION_REQUIRED) { 105 out.write(ch); 106 return; 107 } 108 writeInt(ch); 109 } 110 111 private void writeInt(final int ch) throws IOException { 112 switch (ch) { 113 case '\r': 114 lastWasCR = true; 115 // Don't write anything. We need to see if next one is linefeed 116 break; 117 case '\n': 118 if (lastWasCR) { 119 out.write(FromNetASCIIInputStream.LINE_SEPARATOR_BYTES); 120 lastWasCR = false; 121 break; 122 } 123 out.write('\n'); 124 break; 125 default: 126 if (lastWasCR) { 127 out.write('\r'); 128 lastWasCR = false; 129 } 130 out.write(ch); 131 break; 132 } 133 } 134}