001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.io; 016 017import com.google.common.annotations.Beta; 018import com.google.common.annotations.GwtIncompatible; 019import com.google.common.base.Preconditions; 020import com.google.common.primitives.Longs; 021import java.io.DataOutput; 022import java.io.DataOutputStream; 023import java.io.FilterOutputStream; 024import java.io.IOException; 025import java.io.OutputStream; 026 027/** 028 * An implementation of {@link DataOutput} that uses little-endian byte ordering for writing {@code 029 * char}, {@code short}, {@code int}, {@code float}, {@code double}, and {@code long} values. 030 * 031 * <p><b>Note:</b> This class intentionally violates the specification of its supertype {@code 032 * DataOutput}, which explicitly requires big-endian byte order. 033 * 034 * @author Chris Nokleberg 035 * @author Keith Bottner 036 * @since 8.0 037 */ 038@Beta 039@GwtIncompatible 040public final class LittleEndianDataOutputStream extends FilterOutputStream implements DataOutput { 041 042 /** 043 * Creates a {@code LittleEndianDataOutputStream} that wraps the given stream. 044 * 045 * @param out the stream to delegate to 046 */ 047 public LittleEndianDataOutputStream(OutputStream out) { 048 super(new DataOutputStream(Preconditions.checkNotNull(out))); 049 } 050 051 @Override 052 public void write(byte[] b, int off, int len) throws IOException { 053 // Override slow FilterOutputStream impl 054 out.write(b, off, len); 055 } 056 057 @Override 058 public void writeBoolean(boolean v) throws IOException { 059 ((DataOutputStream) out).writeBoolean(v); 060 } 061 062 @Override 063 public void writeByte(int v) throws IOException { 064 ((DataOutputStream) out).writeByte(v); 065 } 066 067 /** 068 * @deprecated The semantics of {@code writeBytes(String s)} are considered dangerous. Please use 069 * {@link #writeUTF(String s)}, {@link #writeChars(String s)} or another write method instead. 070 */ 071 @Deprecated 072 @Override 073 public void writeBytes(String s) throws IOException { 074 ((DataOutputStream) out).writeBytes(s); 075 } 076 077 /** 078 * Writes a char as specified by {@link DataOutputStream#writeChar(int)}, except using 079 * little-endian byte order. 080 * 081 * @throws IOException if an I/O error occurs 082 */ 083 @Override 084 public void writeChar(int v) throws IOException { 085 writeShort(v); 086 } 087 088 /** 089 * Writes a {@code String} as specified by {@link DataOutputStream#writeChars(String)}, except 090 * each character is written using little-endian byte order. 091 * 092 * @throws IOException if an I/O error occurs 093 */ 094 @Override 095 public void writeChars(String s) throws IOException { 096 for (int i = 0; i < s.length(); i++) { 097 writeChar(s.charAt(i)); 098 } 099 } 100 101 /** 102 * Writes a {@code double} as specified by {@link DataOutputStream#writeDouble(double)}, except 103 * using little-endian byte order. 104 * 105 * @throws IOException if an I/O error occurs 106 */ 107 @Override 108 public void writeDouble(double v) throws IOException { 109 writeLong(Double.doubleToLongBits(v)); 110 } 111 112 /** 113 * Writes a {@code float} as specified by {@link DataOutputStream#writeFloat(float)}, except using 114 * little-endian byte order. 115 * 116 * @throws IOException if an I/O error occurs 117 */ 118 @Override 119 public void writeFloat(float v) throws IOException { 120 writeInt(Float.floatToIntBits(v)); 121 } 122 123 /** 124 * Writes an {@code int} as specified by {@link DataOutputStream#writeInt(int)}, except using 125 * little-endian byte order. 126 * 127 * @throws IOException if an I/O error occurs 128 */ 129 @Override 130 public void writeInt(int v) throws IOException { 131 out.write(0xFF & v); 132 out.write(0xFF & (v >> 8)); 133 out.write(0xFF & (v >> 16)); 134 out.write(0xFF & (v >> 24)); 135 } 136 137 /** 138 * Writes a {@code long} as specified by {@link DataOutputStream#writeLong(long)}, except using 139 * little-endian byte order. 140 * 141 * @throws IOException if an I/O error occurs 142 */ 143 @Override 144 public void writeLong(long v) throws IOException { 145 byte[] bytes = Longs.toByteArray(Long.reverseBytes(v)); 146 write(bytes, 0, bytes.length); 147 } 148 149 /** 150 * Writes a {@code short} as specified by {@link DataOutputStream#writeShort(int)}, except using 151 * little-endian byte order. 152 * 153 * @throws IOException if an I/O error occurs 154 */ 155 @Override 156 public void writeShort(int v) throws IOException { 157 out.write(0xFF & v); 158 out.write(0xFF & (v >> 8)); 159 } 160 161 @Override 162 public void writeUTF(String str) throws IOException { 163 ((DataOutputStream) out).writeUTF(str); 164 } 165 166 // Overriding close() because FilterOutputStream's close() method pre-JDK8 has bad behavior: 167 // it silently ignores any exception thrown by flush(). Instead, just close the delegate stream. 168 // It should flush itself if necessary. 169 @Override 170 public void close() throws IOException { 171 out.close(); 172 } 173}