/*
* 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.annotations.GwtIncompatible;
import com.google.common.base.Preconditions;
import com.google.common.primitives.Ints;
import com.google.common.primitives.Longs;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
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
@GwtIncompatible
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}.
*/
@CanIgnoreReturnValue // to skip a line
@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);
}
@CanIgnoreReturnValue // to skip a byte
@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
*/
@CanIgnoreReturnValue // to skip some bytes
@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
*/
@CanIgnoreReturnValue // to skip some bytes
@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
*/
@CanIgnoreReturnValue // to skip some bytes
@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
*/
@CanIgnoreReturnValue // to skip some bytes
@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
*/
@CanIgnoreReturnValue // to skip some bytes
@Override
public double readDouble() throws IOException {
return Double.longBitsToDouble(readLong());
}
@CanIgnoreReturnValue // to skip a field
@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.
*/
@CanIgnoreReturnValue // to skip some bytes
@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
*/
@CanIgnoreReturnValue // to skip some bytes
@Override
public char readChar() throws IOException {
return (char) readUnsignedShort();
}
@CanIgnoreReturnValue // to skip a byte
@Override
public byte readByte() throws IOException {
return (byte) readUnsignedByte();
}
@CanIgnoreReturnValue // to skip a byte
@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;
}
}