paillierp
Class ByteUtils

java.lang.Object
  paillierp.ByteUtils

public class ByteUtils
extends java.lang.Object

A set of static utilities for manipulating Bytes. The methods used in this class are used primarily for encoding integers and BigIntegers into byte arrays and vice versa.

Author:

James Garrity

Field Summary

static java.lang.String[]

base2 A string array for representing binary numbers.

Constructor Summary

ByteUtils()

Method Summary

static byte[]	appendBigInt(byte[] b, java.math.BigInteger... bigIntegers) Returns a byte array where the first bytes are b, followed by each of bigIntegers in byte array form, each with its length encoded in 4 bytes.
static byte[]	appendInt(byte[] b, int... ints) Returns a byte array where the first bytes are b, followed by each of ints in 4-byte array form.
static java.math.BigInteger	getBigInt(byte[] b, int offset, int size) Creates a BigInteger equivalent to the size bytes given in b starting at offset.
static int	getInt(byte[] b, int offset) Determines the integer given in the first four bytes of a given array starting with the offset.
static byte[]	getLowerLayer(byte[] b) Returns the first x bytes of b, where x is the base 10 equivalent to the last four bytes of b.
static byte[]	intToByte(int i) Converts an integer into its 4-byte equivalent in Big-endan form.
static java.lang.String	printByte(byte b) Displays the given byte in a string of 0's and 1's.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

base2

public static java.lang.String[] base2

A string array for representing binary numbers.

Constructor Detail

ByteUtils

public ByteUtils()

Method Detail

intToByte

public static byte[] intToByte(int i)

Converts an integer into its 4-byte equivalent in Big-endan form.

Parameters:

i - 32 bit integer

Returns:

a byte array of size 4 with most sig. bits first

getInt

public static int getInt(byte[] b,
                         int offset)

Determines the integer given in the first four bytes of a given array starting with the offset.

Parameters:

b - Byte array of size greater than 4

offset - Index of b

Returns:

an integer equivalent to the four subsequent bytes starting at offset

getBigInt

public static java.math.BigInteger getBigInt(byte[] b,
                                             int offset,
                                             int size)

Creates a BigInteger equivalent to the size bytes given in b starting at offset.

Parameters:

b - Byte array

offset - Index of b; where to start

size - how long to go

Returns:

a BigInteger equivalent to the subsequent bytes starting at offset

getLowerLayer

public static byte[] getLowerLayer(byte[] b)

Returns the first x bytes of b, where x is the base 10 equivalent to the last four bytes of b.

Parameters:

b - A byte array, the last four of which represent an integer x

Returns:

The first x bytes of b.

appendBigInt

public static byte[] appendBigInt(byte[] b,
                                  java.math.BigInteger... bigIntegers)

Returns a byte array where the first bytes are b, followed by each of bigIntegers in byte array form, each with its length encoded in 4 bytes.

Parameters:

b - A byte array

bigIntegers - BigIntegers i₁, ... i_m

Returns:

A byte array of b || len[ i₁ ] || i₁ || ... || len[ i_m ] || i_m. A byte array of length 0 is returned if (1) the concatenation would be too large for an integer index or (2) b is of length 0.

See Also:

BigInteger.toByteArray()

appendInt

public static byte[] appendInt(byte[] b,
                               int... ints)

Returns a byte array where the first bytes are b, followed by each of ints in 4-byte array form.

Parameters:

b - A byte array

ints - Integers i₁, ... i_m

Returns:

A byte array of b || i₁ || ... || i_m. A byte array of length 0 is returned if (1) the concatenation would be too large for an integer index or (2) b is of length 0.

printByte

public static java.lang.String printByte(byte b)

Displays the given byte in a string of 0's and 1's.

Parameters:

b - A simple byte

Returns:

A string of the binary representation of b