/*
* 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;
}
}