package org.bouncycastle.pqc.math.linearalgebra;
/**
* This is a utility class containing data type conversions using big-endian
* byte order.
*
* @see LittleEndianConversions
*/
public final class BigEndianConversions
{
/**
* Default constructor (private).
*/
private BigEndianConversions()
{
// empty
}
/**
* Convert an integer to an octet string of length 4 according to IEEE 1363,
* Section 5.5.3.
*
* @param x the integer to convert
* @return the converted integer
*/
public static byte[] I2OSP(int x)
{
byte[] result = new byte[4];
result[0] = (byte)(x >>> 24);
result[1] = (byte)(x >>> 16);
result[2] = (byte)(x >>> 8);
result[3] = (byte)x;
return result;
}
/**
* Convert an integer to an octet string according to IEEE 1363, Section
* 5.5.3. Length checking is performed.
*
* @param x the integer to convert
* @param oLen the desired length of the octet string
* @return an octet string of length <tt>oLen</tt> representing the
* integer <tt>x</tt>, or <tt>null</tt> if the integer is
* negative
* @throws ArithmeticException if <tt>x</tt> can't be encoded into <tt>oLen</tt>
* octets.
*/
public static byte[] I2OSP(int x, int oLen)
throws ArithmeticException
{
if (x < 0)
{
return null;
}
int octL = IntegerFunctions.ceilLog256(x);
if (octL > oLen)
{
throw new ArithmeticException(
"Cannot encode given integer into specified number of octets.");
}
byte[] result = new byte[oLen];
for (int i = oLen - 1; i >= oLen - octL; i--)
{
result[i] = (byte)(x >>> (8 * (oLen - 1 - i)));
}
return result;
}
/**
* Convert an integer to an octet string of length 4 according to IEEE 1363,
* Section 5.5.3.
*
* @param input the integer to convert
* @param output byte array holding the output
* @param outOff offset in output array where the result is stored
*/
public static void I2OSP(int input, byte[] output, int outOff)
{
output[outOff++] = (byte)(input >>> 24);
output[outOff++] = (byte)(input >>> 16);
output[outOff++] = (byte)(input >>> 8);
output[outOff] = (byte)input;
}
/**
* Convert an integer to an octet string of length 8 according to IEEE 1363,
* Section 5.5.3.
*
* @param input the integer to convert
* @return the converted integer
*/
public static byte[] I2OSP(long input)
{
byte[] output = new byte[8];
output[0] = (byte)(input >>> 56);
output[1] = (byte)(input >>> 48);
output[2] = (byte)(input >>> 40);
output[3] = (byte)(input >>> 32);
output[4] = (byte)(input >>> 24);
output[5] = (byte)(input >>> 16);
output[6] = (byte)(input >>> 8);
output[7] = (byte)input;
return output;
}
/**
* Convert an integer to an octet string of length 8 according to IEEE 1363,
* Section 5.5.3.
*
* @param input the integer to convert
* @param output byte array holding the output
* @param outOff offset in output array where the result is stored
*/
public static void I2OSP(long input, byte[] output, int outOff)
{
output[outOff++] = (byte)(input >>> 56);
output[outOff++] = (byte)(input >>> 48);
output[outOff++] = (byte)(input >>> 40);
output[outOff++] = (byte)(input >>> 32);
output[outOff++] = (byte)(input >>> 24);
output[outOff++] = (byte)(input >>> 16);
output[outOff++] = (byte)(input >>> 8);
output[outOff] = (byte)input;
}
/**
* Convert an integer to an octet string of the specified length according
* to IEEE 1363, Section 5.5.3. No length checking is performed (i.e., if
* the integer cannot be encoded into <tt>length</tt> octets, it is
* truncated).
*
* @param input the integer to convert
* @param output byte array holding the output
* @param outOff offset in output array where the result is stored
* @param length the length of the encoding
*/
public static void I2OSP(int input, byte[] output, int outOff, int length)
{
for (int i = length - 1; i >= 0; i--)
{
output[outOff + i] = (byte)(input >>> (8 * (length - 1 - i)));
}
}
/**
* Convert an octet string to an integer according to IEEE 1363, Section
* 5.5.3.
*
* @param input the byte array holding the octet string
* @return an integer representing the octet string <tt>input</tt>, or
* <tt>0</tt> if the represented integer is negative or too large
* or the byte array is empty
* @throws ArithmeticException if the length of the given octet string is larger than 4.
*/
public static int OS2IP(byte[] input)
{
if (input.length > 4)
{
throw new ArithmeticException("invalid input length");
}
if (input.length == 0)
{
return 0;
}
int result = 0;
for (int j = 0; j < input.length; j++)
{
result |= (input[j] & 0xff) << (8 * (input.length - 1 - j));
}
return result;
}
/**
* Convert a byte array of length 4 beginning at <tt>offset</tt> into an
* integer.
*
* @param input the byte array
* @param inOff the offset into the byte array
* @return the resulting integer
*/
public static int OS2IP(byte[] input, int inOff)
{
int result = (input[inOff++] & 0xff) << 24;
result |= (input[inOff++] & 0xff) << 16;
result |= (input[inOff++] & 0xff) << 8;
result |= input[inOff] & 0xff;
return result;
}
/**
* Convert an octet string to an integer according to IEEE 1363, Section
* 5.5.3.
*
* @param input the byte array holding the octet string
* @param inOff the offset in the input byte array where the octet string
* starts
* @param inLen the length of the encoded integer
* @return an integer representing the octet string <tt>bytes</tt>, or
* <tt>0</tt> if the represented integer is negative or too large
* or the byte array is empty
*/
public static int OS2IP(byte[] input, int inOff, int inLen)
{
if ((input.length == 0) || input.length < inOff + inLen - 1)
{
return 0;
}
int result = 0;
for (int j = 0; j < inLen; j++)
{
result |= (input[inOff + j] & 0xff) << (8 * (inLen - j - 1));
}
return result;
}
/**
* Convert a byte array of length 8 beginning at <tt>inOff</tt> into a
* long integer.
*
* @param input the byte array
* @param inOff the offset into the byte array
* @return the resulting long integer
*/
public static long OS2LIP(byte[] input, int inOff)
{
long result = ((long)input[inOff++] & 0xff) << 56;
result |= ((long)input[inOff++] & 0xff) << 48;
result |= ((long)input[inOff++] & 0xff) << 40;
result |= ((long)input[inOff++] & 0xff) << 32;
result |= ((long)input[inOff++] & 0xff) << 24;
result |= (input[inOff++] & 0xff) << 16;
result |= (input[inOff++] & 0xff) << 8;
result |= input[inOff] & 0xff;
return result;
}
/**
* Convert an int array into a byte array.
*
* @param input the int array
* @return the converted array
*/
public static byte[] toByteArray(final int[] input)
{
byte[] result = new byte[input.length << 2];
for (int i = 0; i < input.length; i++)
{
I2OSP(input[i], result, i << 2);
}
return result;
}
/**
* Convert an int array into a byte array of the specified length. No length
* checking is performed (i.e., if the last integer cannot be encoded into
* <tt>length % 4</tt> octets, it is truncated).
*
* @param input the int array
* @param length the length of the converted array
* @return the converted array
*/
public static byte[] toByteArray(final int[] input, int length)
{
final int intLen = input.length;
byte[] result = new byte[length];
int index = 0;
for (int i = 0; i <= intLen - 2; i++, index += 4)
{
I2OSP(input[i], result, index);
}
I2OSP(input[intLen - 1], result, index, length - index);
return result;
}
/**
* Convert a byte array into an int array.
*
* @param input the byte array
* @return the converted array
*/
public static int[] toIntArray(byte[] input)
{
final int intLen = (input.length + 3) / 4;
final int lastLen = input.length & 0x03;
int[] result = new int[intLen];
int index = 0;
for (int i = 0; i <= intLen - 2; i++, index += 4)
{
result[i] = OS2IP(input, index);
}
if (lastLen != 0)
{
result[intLen - 1] = OS2IP(input, index, lastLen);
}
else
{
result[intLen - 1] = OS2IP(input, index);
}
return result;
}
}