Update #0 - First Release

sources/main/java/com/google/common/io/LittleEndianDataInputStream.java

@@ -0,0 +1,230 @@
+/*
+ * 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 java.io.DataInput;
+import java.io.DataInputStream;
+import java.io.EOFException;
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import com.google.common.annotations.Beta;
+import com.google.common.base.Preconditions;
+import com.google.common.primitives.Ints;
+import com.google.common.primitives.Longs;
+
+/**
+ * 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;
+	}
+
+}