de.schlichtherle.util.zip.LittleEndian Maven / Gradle / Ivy
/*
* Copyright (C) 2007-2010 Schlichtherle IT Services
*
* 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 de.schlichtherle.util.zip;
/**
* Provides static utility methods for reading and writing integer values in
* little endian format from or to byte arrays.
*
* This class is safe for multithreading.
*
* @author Christian Schlichtherle
* @version $Id$
* @since TrueZIP 6.7
*/
final class LittleEndian {
/** This class cannot get instantiated. */
private LittleEndian() {
}
/**
* Reads a signed short integer value from the byte array
* {@code buf} at the offset {@code off}
* as two bytes, low byte first.
*
* @param buf The byte array to read the signed short integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the signed short integer value is read from.
* @return The signed short integer value read from the byte array.
*/
public static short readShort(final byte[] buf, final int off) {
return (short) ((buf[off + 1] << 8) | (buf[off] & 0xff));
}
/**
* Reads an unsigned short integer value from the byte array
* {@code buf} at the offset {@code off}
* as two bytes, low byte first.
* Note that it is not necessary to check the return value with
* {@link UShort#check}.
*
* @param buf The byte array to read the unsigned short integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the unsigned short integer value is read from.
* @return The unsigned short integer value read from the byte array.
* Java does not provide {@code unsigned short} as a primitive
* type, hence an {@code int} is returned which's two most
* significant bytes are zero.
*/
public static int readUShort(final byte[] buf, final int off) {
return ((buf[off + 1] & 0xff) << 8) | (buf[off] & 0xff);
}
/**
* Reads a signed integer value from the byte array
* {@code buf} at the offset {@code off}
* as four bytes, low byte first.
*
* @param buf The byte array to read the signed integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the signed integer value is read from.
* @return The signed integer value read from the byte array.
*/
public static int readInt(final byte[] buf, int off) {
off += 3;
int i = buf[off--]; // expands sign
i <<= 8;
i |= buf[off--] & 0xff;
i <<= 8;
i |= buf[off--] & 0xff;
i <<= 8;
i |= buf[off] & 0xff;
return i;
}
/**
* Reads an unsigned integer value from the byte array
* {@code buf} at the offset {@code off}
* as four bytes, low byte first.
* Note that it is not necessary to check the return value with
* {@link UInt#check}.
*
* @param buf The byte array to read the unsigned integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the unsigned integer value is read from.
* @return The unsigned integer value read from the byte array.
* Java does not provide {@code unsigned int} as a primitive
* type, hence a {@code long} is returned which's four most
* significant bytes are zero.
*/
public static long readUInt(final byte[] buf, int off) {
return readInt(buf, off) & UInt.MAX_VALUE;
}
/**
* Reads a (signed) long integer value from the byte array
* {@code buf} at the offset {@code off}
* as eight bytes, low byte first.
*
* @param buf The byte array to read the signed long integer value from.
* @param off The zero based offset in the byte array where the first byte
* of the (signed) long integer value is read from.
* @return The (signed) long integer value read from the byte array.
*/
public static long readLong(final byte[] buf, int off) {
off += 7;
long l = buf[off--]; // expands sign
l <<= 8;
l |= buf[off--] & 0xffL;
l <<= 8;
l |= buf[off--] & 0xffL;
l <<= 8;
l |= buf[off--] & 0xffL;
l <<= 8;
l |= buf[off--] & 0xffL;
l <<= 8;
l |= buf[off--] & 0xffL;
l <<= 8;
l |= buf[off--] & 0xffL;
l <<= 8;
l |= buf[off] & 0xffL;
return l;
}
/**
* Writes the integer value {@code s} to the byte array
* {@code buf} at the zero based offset {@code off}
* as two bytes, low byte first.
* The most significant two bytes of the integer value are ignored.
*
* @param s The short integer value to be written.
* @param buf The byte array to write the short integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the short integer value is written to.
*/
public static void writeShort(int s, final byte[] buf, final int off) {
buf[off] = (byte) s;
s >>= 8;
buf[off + 1] = (byte) s;
}
/**
* Writes the integer value {@code i} to the byte array
* {@code buf} at the zero based offset {@code off}
* as four bytes, low byte first.
*
* @param i The integer value to be written.
* @param buf The byte array to write the integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the integer value is written to.
*/
public static void writeInt(int i, final byte[] buf, final int off) {
buf[off] = (byte) i;
i >>= 8;
buf[off + 1] = (byte) i;
i >>= 8;
buf[off + 2] = (byte) i;
i >>= 8;
buf[off + 3] = (byte) i;
}
/**
* Writes the long integer value {@code l} to the byte array
* {@code buf} at the zero based offset {@code off}
* as eight bytes, low byte first.
*
* @param l The long integer value to be written.
* @param buf The byte array to write the long integer value to.
* @param off The zero based offset in the byte array where the first byte
* of the long integer value is written to.
*/
public static void writeLong(long l, final byte[] buf, final int off) {
buf[off] = (byte) l;
l >>= 8;
buf[off + 1] = (byte) l;
l >>= 8;
buf[off + 2] = (byte) l;
l >>= 8;
buf[off + 3] = (byte) l;
l >>= 8;
buf[off + 4] = (byte) l;
l >>= 8;
buf[off + 5] = (byte) l;
l >>= 8;
buf[off + 6] = (byte) l;
l >>= 8;
buf[off + 7] = (byte) l;
}
}