EndianUtils.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.io;
import static org.apache.commons.io.IOUtils.EOF;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* Helps with reading and writing primitive numeric types ({@code short},
* {@code int}, {@code long}, {@code float}, and {@code double}) that are
* encoded in little endian using two's complement or unsigned representations.
* <p>
* Different computer architectures have different conventions for
* byte ordering. In "Little Endian" architectures (e.g. X86),
* the low-order byte is stored in memory at the lowest address, and
* subsequent bytes at higher addresses. In "Big Endian" architectures
* (e.g. Motorola 680X0), the situation is reversed.
* Most methods and classes throughout Java — e.g. {@code DataInputStream} and
* {@code Double.longBitsToDouble()} — assume data is laid out
* in big endian order with the most significant byte first.
* The methods in this class read and write data in little endian order,
* generally by reversing the bytes and then using the
* regular Java methods to convert the swapped bytes to a primitive type.
* </p>
* <p>
* Provenance: Excalibur
* </p>
*
* @see org.apache.commons.io.input.SwappedDataInputStream
*/
public class EndianUtils {
/**
* Reads the next byte from the input stream.
* @param input the stream
* @return the byte
* @throws IOException if the end of file is reached
*/
private static int read(final InputStream input) throws IOException {
final int value = input.read();
if (EOF == value) {
throw new EOFException("Unexpected EOF reached");
}
return value;
}
/**
* Reads a little endian {@code double} value from a byte array at a given offset.
*
* @param data source byte array
* @param offset starting offset in the byte array
* @return the value read
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 8 bytes
*/
public static double readSwappedDouble(final byte[] data, final int offset) {
return Double.longBitsToDouble(readSwappedLong(data, offset));
}
/**
* Reads a little endian {@code double} value from an InputStream.
*
* @param input source InputStream
* @return the value just read
* @throws IOException in case of an I/O problem
*/
public static double readSwappedDouble(final InputStream input) throws IOException {
return Double.longBitsToDouble(readSwappedLong(input));
}
/**
* Reads a little endian {@code float} value from a byte array at a given offset.
*
* @param data source byte array
* @param offset starting offset in the byte array
* @return the value read
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes
*/
public static float readSwappedFloat(final byte[] data, final int offset) {
return Float.intBitsToFloat(readSwappedInteger(data, offset));
}
/**
* Reads a little endian {@code float} value from an InputStream.
*
* @param input source InputStream
* @return the value just read
* @throws IOException in case of an I/O problem
*/
public static float readSwappedFloat(final InputStream input) throws IOException {
return Float.intBitsToFloat(readSwappedInteger(input));
}
/**
* Reads a little endian {@code int} value from a byte array at a given offset.
*
* @param data source byte array
* @param offset starting offset in the byte array
* @return the value read
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes
*/
public static int readSwappedInteger(final byte[] data, final int offset) {
validateByteArrayOffset(data, offset, Integer.SIZE / Byte.SIZE);
return ((data[offset + 0] & 0xff) << 0) +
((data[offset + 1] & 0xff) << 8) +
((data[offset + 2] & 0xff) << 16) +
((data[offset + 3] & 0xff) << 24);
}
/**
* Reads a little endian {@code int} value from an InputStream.
*
* @param input source InputStream
* @return the value just read
* @throws IOException in case of an I/O problem
*/
public static int readSwappedInteger(final InputStream input) throws IOException {
final int value1 = read(input);
final int value2 = read(input);
final int value3 = read(input);
final int value4 = read(input);
return ((value1 & 0xff) << 0) + ((value2 & 0xff) << 8) + ((value3 & 0xff) << 16) + ((value4 & 0xff) << 24);
}
/**
* Reads a little endian {@code long} value from a byte array at a given offset.
*
* @param data source byte array
* @param offset starting offset in the byte array
* @return the value read
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 8 bytes
*/
public static long readSwappedLong(final byte[] data, final int offset) {
validateByteArrayOffset(data, offset, Long.SIZE / Byte.SIZE);
final long low = readSwappedInteger(data, offset);
final long high = readSwappedInteger(data, offset + 4);
return (high << 32) + (0xffffffffL & low);
}
/**
* Reads a little endian {@code long} value from an InputStream.
*
* @param input source InputStream
* @return the value just read
* @throws IOException in case of an I/O problem
*/
public static long readSwappedLong(final InputStream input) throws IOException {
final byte[] bytes = new byte[8];
for (int i = 0; i < 8; i++) {
bytes[i] = (byte) read(input);
}
return readSwappedLong(bytes, 0);
}
/**
* Reads a little endian {@code short} value from a byte array at a given offset.
*
* @param data source byte array
* @param offset starting offset in the byte array
* @return the value read
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 2 bytes
*/
public static short readSwappedShort(final byte[] data, final int offset) {
validateByteArrayOffset(data, offset, Short.SIZE / Byte.SIZE);
return (short) (((data[offset + 0] & 0xff) << 0) + ((data[offset + 1] & 0xff) << 8));
}
/**
* Reads a little endian {@code short} value from an InputStream.
*
* @param input source InputStream
* @return the value just read
* @throws IOException in case of an I/O problem
*/
public static short readSwappedShort(final InputStream input) throws IOException {
return (short) (((read(input) & 0xff) << 0) + ((read(input) & 0xff) << 8));
}
/**
* Reads a little endian unsigned integer (32-bit) value from a byte array at a given
* offset.
*
* @param data source byte array
* @param offset starting offset in the byte array
* @return the value read
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes
*/
public static long readSwappedUnsignedInteger(final byte[] data, final int offset) {
validateByteArrayOffset(data, offset, Integer.SIZE / Byte.SIZE);
final long low = ((data[offset + 0] & 0xff) << 0) +
((data[offset + 1] & 0xff) << 8) +
((data[offset + 2] & 0xff) << 16);
final long high = data[offset + 3] & 0xff;
return (high << 24) + (0xffffffffL & low);
}
/**
* Reads a little endian unsigned integer (32-bit) from an InputStream.
*
* @param input source InputStream
* @return the value just read
* @throws IOException in case of an I/O problem
*/
public static long readSwappedUnsignedInteger(final InputStream input) throws IOException {
final int value1 = read(input);
final int value2 = read(input);
final int value3 = read(input);
final int value4 = read(input);
final long low = ((value1 & 0xff) << 0) + ((value2 & 0xff) << 8) + ((value3 & 0xff) << 16);
final long high = value4 & 0xff;
return (high << 24) + (0xffffffffL & low);
}
/**
* Reads an unsigned short (16-bit) value from a byte array in little endian order at a given
* offset.
*
* @param data source byte array
* @param offset starting offset in the byte array
* @return the value read
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 2 bytes
*/
public static int readSwappedUnsignedShort(final byte[] data, final int offset) {
validateByteArrayOffset(data, offset, Short.SIZE / Byte.SIZE);
return ((data[offset + 0] & 0xff) << 0) + ((data[offset + 1] & 0xff) << 8);
}
/**
* Reads an unsigned short (16-bit) from an InputStream in little endian order.
*
* @param input source InputStream
* @return the value just read
* @throws IOException in case of an I/O problem
*/
public static int readSwappedUnsignedShort(final InputStream input) throws IOException {
final int value1 = read(input);
final int value2 = read(input);
return ((value1 & 0xff) << 0) + ((value2 & 0xff) << 8);
}
/**
* Converts a {@code double} value from big endian to little endian
* and vice versa. That is, it converts the {@code double} to bytes,
* reverses the bytes, and then reinterprets those bytes as a new {@code double}.
* This can be useful if you have a number that was read from the
* underlying source in the wrong endianness.
*
* @param value value to convert
* @return the converted value
*/
public static double swapDouble(final double value) {
return Double.longBitsToDouble(swapLong(Double.doubleToLongBits(value)));
}
/**
* Converts a {@code float} value from big endian to little endian and vice versa.
*
* @param value value to convert
* @return the converted value
*/
public static float swapFloat(final float value) {
return Float.intBitsToFloat(swapInteger(Float.floatToIntBits(value)));
}
/**
* Converts an {@code int} value from big endian to little endian and vice versa.
*
* @param value value to convert
* @return the converted value
*/
public static int swapInteger(final int value) {
return
((value >> 0 & 0xff) << 24) +
((value >> 8 & 0xff) << 16) +
((value >> 16 & 0xff) << 8) +
((value >> 24 & 0xff) << 0);
}
/**
* Converts a {@code long} value from big endian to little endian and vice versa.
*
* @param value value to convert
* @return the converted value
*/
public static long swapLong(final long value) {
return
((value >> 0 & 0xff) << 56) +
((value >> 8 & 0xff) << 48) +
((value >> 16 & 0xff) << 40) +
((value >> 24 & 0xff) << 32) +
((value >> 32 & 0xff) << 24) +
((value >> 40 & 0xff) << 16) +
((value >> 48 & 0xff) << 8) +
((value >> 56 & 0xff) << 0);
}
/**
* Converts a {@code short} value from big endian to little endian and vice versa.
*
* @param value value to convert
* @return the converted value
*/
public static short swapShort(final short value) {
return (short) (((value >> 0 & 0xff) << 8) +
((value >> 8 & 0xff) << 0));
}
/**
* Validates if the provided byte array has enough data.
*
* @param data the input byte array
* @param offset the input offset
* @param byteNeeded the needed number of bytes
* @throws IllegalArgumentException if the byte array does not have enough data
*/
private static void validateByteArrayOffset(final byte[] data, final int offset, final int byteNeeded) {
if (data.length < offset + byteNeeded) {
throw new IllegalArgumentException("Data only has " + data.length + "bytes, needed " + (offset + byteNeeded) + "bytes.");
}
}
/**
* Writes the 8 bytes of a {@code double} to a byte array at a given offset in little endian order.
*
* @param data target byte array
* @param offset starting offset in the byte array
* @param value value to write
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 8 bytes
*/
public static void writeSwappedDouble(final byte[] data, final int offset, final double value) {
writeSwappedLong(data, offset, Double.doubleToLongBits(value));
}
/**
* Writes the 8 bytes of a {@code double} to an output stream in little endian order.
*
* @param output target OutputStream
* @param value value to write
* @throws IOException in case of an I/O problem
*/
public static void writeSwappedDouble(final OutputStream output, final double value) throws IOException {
writeSwappedLong(output, Double.doubleToLongBits(value));
}
/**
* Writes the 4 bytes of a {@code float} to a byte array at a given offset in little endian order.
*
* @param data target byte array
* @param offset starting offset in the byte array
* @param value value to write
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes
*/
public static void writeSwappedFloat(final byte[] data, final int offset, final float value) {
writeSwappedInteger(data, offset, Float.floatToIntBits(value));
}
/**
* Writes the 4 bytes of a {@code float} to an output stream in little endian order.
*
* @param output target OutputStream
* @param value value to write
* @throws IOException in case of an I/O problem
*/
public static void writeSwappedFloat(final OutputStream output, final float value) throws IOException {
writeSwappedInteger(output, Float.floatToIntBits(value));
}
/**
* Writes the 4 bytes of an {@code int} to a byte array at a given offset in little endian order.
*
* @param data target byte array
* @param offset starting offset in the byte array
* @param value value to write
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 4 bytes
*/
public static void writeSwappedInteger(final byte[] data, final int offset, final int value) {
validateByteArrayOffset(data, offset, Integer.SIZE / Byte.SIZE);
data[offset + 0] = (byte) (value >> 0 & 0xff);
data[offset + 1] = (byte) (value >> 8 & 0xff);
data[offset + 2] = (byte) (value >> 16 & 0xff);
data[offset + 3] = (byte) (value >> 24 & 0xff);
}
/**
* Writes the 4 bytes of an {@code int} to an output stream in little endian order.
*
* @param output target OutputStream
* @param value value to write
* @throws IOException in case of an I/O problem
*/
public static void writeSwappedInteger(final OutputStream output, final int value) throws IOException {
output.write((byte) (value >> 0 & 0xff));
output.write((byte) (value >> 8 & 0xff));
output.write((byte) (value >> 16 & 0xff));
output.write((byte) (value >> 24 & 0xff));
}
/**
* Writes the 8 bytes of a {@code long} to a byte array at a given offset in little endian order.
*
* @param data target byte array
* @param offset starting offset in the byte array
* @param value value to write
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 8 bytes
*/
public static void writeSwappedLong(final byte[] data, final int offset, final long value) {
validateByteArrayOffset(data, offset, Long.SIZE / Byte.SIZE);
data[offset + 0] = (byte) (value >> 0 & 0xff);
data[offset + 1] = (byte) (value >> 8 & 0xff);
data[offset + 2] = (byte) (value >> 16 & 0xff);
data[offset + 3] = (byte) (value >> 24 & 0xff);
data[offset + 4] = (byte) (value >> 32 & 0xff);
data[offset + 5] = (byte) (value >> 40 & 0xff);
data[offset + 6] = (byte) (value >> 48 & 0xff);
data[offset + 7] = (byte) (value >> 56 & 0xff);
}
/**
* Writes the 8 bytes of a {@code long} to an output stream in little endian order.
*
* @param output target OutputStream
* @param value value to write
* @throws IOException in case of an I/O problem
*/
public static void writeSwappedLong(final OutputStream output, final long value) throws IOException {
output.write((byte) (value >> 0 & 0xff));
output.write((byte) (value >> 8 & 0xff));
output.write((byte) (value >> 16 & 0xff));
output.write((byte) (value >> 24 & 0xff));
output.write((byte) (value >> 32 & 0xff));
output.write((byte) (value >> 40 & 0xff));
output.write((byte) (value >> 48 & 0xff));
output.write((byte) (value >> 56 & 0xff));
}
/**
* Writes the 2 bytes of a {@code short} to a byte array at a given offset in little endian order.
*
* @param data target byte array
* @param offset starting offset in the byte array
* @param value value to write
* @throws IllegalArgumentException if the part of the byte array starting at offset does not have at least 2 bytes
*/
public static void writeSwappedShort(final byte[] data, final int offset, final short value) {
validateByteArrayOffset(data, offset, Short.SIZE / Byte.SIZE);
data[offset + 0] = (byte) (value >> 0 & 0xff);
data[offset + 1] = (byte) (value >> 8 & 0xff);
}
/**
* Writes the 2 bytes of a {@code short} to an output stream using little endian encoding.
*
* @param output target OutputStream
* @param value value to write
* @throws IOException in case of an I/O problem
*/
public static void writeSwappedShort(final OutputStream output, final short value) throws IOException {
output.write((byte) (value >> 0 & 0xff));
output.write((byte) (value >> 8 & 0xff));
}
/**
* Instances should NOT be constructed in standard programming.
*
* @deprecated TODO Make private in 3.0.
*/
@Deprecated
public EndianUtils() {
// empty
}
}