Java tutorial
/* * Copyright (C) 2007 The Guava Authors * * 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 com.google.common.io; import com.google.common.annotations.Beta; import com.google.common.base.Preconditions; import com.google.common.primitives.Ints; import com.google.common.primitives.Longs; import java.io.DataInput; import java.io.DataInputStream; import java.io.EOFException; import java.io.FilterInputStream; import java.io.IOException; import java.io.InputStream; /** * An implementation of {@link DataInput} that uses little-endian byte ordering * for reading {@code short}, {@code int}, {@code float}, {@code double}, and * {@code long} values. * <p> * <b>Note:</b> This class intentionally violates the specification of its * supertype {@code DataInput}, which explicitly requires big-endian byte order. * * @author Chris Nokleberg * @author Keith Bottner * @since 8.0 */ @Beta public final class LittleEndianDataInputStream extends FilterInputStream implements DataInput { /** * Creates a {@code LittleEndianDataInputStream} that wraps the given stream. * * @param in the stream to delegate to */ public LittleEndianDataInputStream(InputStream in) { super(Preconditions.checkNotNull(in)); } /** * This method will throw an {@link UnsupportedOperationException}. */ @Override public String readLine() { throw new UnsupportedOperationException("readLine is not supported"); } @Override public void readFully(byte[] b) throws IOException { ByteStreams.readFully(this, b); } @Override public void readFully(byte[] b, int off, int len) throws IOException { ByteStreams.readFully(this, b, off, len); } @Override public int skipBytes(int n) throws IOException { return (int) in.skip(n); } @Override public int readUnsignedByte() throws IOException { int b1 = in.read(); if (0 > b1) { throw new EOFException(); } return b1; } /** * Reads an unsigned {@code short} as specified by * {@link DataInputStream#readUnsignedShort()}, except using little-endian * byte order. * * @return the next two bytes of the input stream, interpreted as an * unsigned 16-bit integer in little-endian byte order * @throws IOException if an I/O error occurs */ @Override public int readUnsignedShort() throws IOException { byte b1 = readAndCheckByte(); byte b2 = readAndCheckByte(); return Ints.fromBytes((byte) 0, (byte) 0, b2, b1); } /** * Reads an integer as specified by {@link DataInputStream#readInt()}, except * using little-endian byte order. * * @return the next four bytes of the input stream, interpreted as an * {@code int} in little-endian byte order * @throws IOException if an I/O error occurs */ @Override public int readInt() throws IOException { byte b1 = readAndCheckByte(); byte b2 = readAndCheckByte(); byte b3 = readAndCheckByte(); byte b4 = readAndCheckByte(); return Ints.fromBytes(b4, b3, b2, b1); } /** * Reads a {@code long} as specified by {@link DataInputStream#readLong()}, * except using little-endian byte order. * * @return the next eight bytes of the input stream, interpreted as a * {@code long} in little-endian byte order * @throws IOException if an I/O error occurs */ @Override public long readLong() throws IOException { byte b1 = readAndCheckByte(); byte b2 = readAndCheckByte(); byte b3 = readAndCheckByte(); byte b4 = readAndCheckByte(); byte b5 = readAndCheckByte(); byte b6 = readAndCheckByte(); byte b7 = readAndCheckByte(); byte b8 = readAndCheckByte(); return Longs.fromBytes(b8, b7, b6, b5, b4, b3, b2, b1); } /** * Reads a {@code float} as specified by {@link DataInputStream#readFloat()}, * except using little-endian byte order. * * @return the next four bytes of the input stream, interpreted as a * {@code float} in little-endian byte order * @throws IOException if an I/O error occurs */ @Override public float readFloat() throws IOException { return Float.intBitsToFloat(readInt()); } /** * Reads a {@code double} as specified by * {@link DataInputStream#readDouble()}, except using little-endian byte * order. * * @return the next eight bytes of the input stream, interpreted as a * {@code double} in little-endian byte order * @throws IOException if an I/O error occurs */ @Override public double readDouble() throws IOException { return Double.longBitsToDouble(readLong()); } @Override public String readUTF() throws IOException { return new DataInputStream(in).readUTF(); } /** * Reads a {@code short} as specified by {@link DataInputStream#readShort()}, * except using little-endian byte order. * * @return the next two bytes of the input stream, interpreted as a * {@code short} in little-endian byte order. * @throws IOException if an I/O error occurs. */ @Override public short readShort() throws IOException { return (short) readUnsignedShort(); } /** * Reads a char as specified by {@link DataInputStream#readChar()}, except * using little-endian byte order. * * @return the next two bytes of the input stream, interpreted as a * {@code char} in little-endian byte order * @throws IOException if an I/O error occurs */ @Override public char readChar() throws IOException { return (char) readUnsignedShort(); } @Override public byte readByte() throws IOException { return (byte) readUnsignedByte(); } @Override public boolean readBoolean() throws IOException { return readUnsignedByte() != 0; } /** * Reads a byte from the input stream checking that the end of file (EOF) * has not been encountered. * * @return byte read from input * @throws IOException if an error is encountered while reading * @throws EOFException if the end of file (EOF) is encountered. */ private byte readAndCheckByte() throws IOException, EOFException { int b1 = in.read(); if (-1 == b1) { throw new EOFException(); } return (byte) b1; } }