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package org.bouncycastle.pqc.math.linearalgebra;
/**
* This is a utility class containing data type conversions using little-endian
* byte order.
*
* @see BigEndianConversions
*/
public final class LittleEndianConversions
{
/**
* Default constructor (private).
*/
private LittleEndianConversions()
{
// empty
}
/**
* Convert an octet string of length 4 to an integer. No length checking is
* performed.
*
* @param input the byte array holding the octet string
* @return an integer representing the octet string <tt>input</tt>
* @throws ArithmeticException if the length of the given octet string is larger than 4.
*/
public static int OS2IP(byte[] input)
{
return ((input[0] & 0xff)) | ((input[1] & 0xff) << 8)
| ((input[2] & 0xff) << 16) | ((input[3] & 0xff)) << 24;
}
/**
* Convert an 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;
result |= (input[inOff++] & 0xff) << 8;
result |= (input[inOff++] & 0xff) << 16;
result |= (input[inOff] & 0xff) << 24;
return result;
}
/**
* Convert a byte array of the given length beginning at <tt>offset</tt>
* into an integer.
*
* @param input the byte array
* @param inOff the offset into the byte array
* @param inLen the length of the encoding
* @return the resulting integer
*/
public static int OS2IP(byte[] input, int inOff, int inLen)
{
int result = 0;
for (int i = inLen - 1; i >= 0; i--)
{
result |= (input[inOff + i] & 0xff) << (8 * i);
}
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 = input[inOff++] & 0xff;
result |= (input[inOff++] & 0xff) << 8;
result |= (input[inOff++] & 0xff) << 16;
result |= ((long)input[inOff++] & 0xff) << 24;
result |= ((long)input[inOff++] & 0xff) << 32;
result |= ((long)input[inOff++] & 0xff) << 40;
result |= ((long)input[inOff++] & 0xff) << 48;
result |= ((long)input[inOff++] & 0xff) << 56;
return result;
}
/**
* Convert an integer to an octet string of length 4.
*
* @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;
result[1] = (byte)(x >>> 8);
result[2] = (byte)(x >>> 16);
result[3] = (byte)(x >>> 24);
return result;
}
/**
* Convert an integer into a byte array beginning at the specified offset.
*
* @param value the integer to convert
* @param output the byte array to hold the result
* @param outOff the integer offset into the byte array
*/
public static void I2OSP(int value, byte[] output, int outOff)
{
output[outOff++] = (byte)value;
output[outOff++] = (byte)(value >>> 8);
output[outOff++] = (byte)(value >>> 16);
output[outOff++] = (byte)(value >>> 24);
}
/**
* Convert an integer to a byte array beginning at the specified offset. No
* length checking is performed (i.e., if the integer cannot be encoded with
* <tt>length</tt> octets, it is truncated).
*
* @param value the integer to convert
* @param output the byte array to hold the result
* @param outOff the integer offset into the byte array
* @param outLen the length of the encoding
*/
public static void I2OSP(int value, byte[] output, int outOff, int outLen)
{
for (int i = outLen - 1; i >= 0; i--)
{
output[outOff + i] = (byte)(value >>> (8 * i));
}
}
/**
* Convert an integer to a byte array of length 8.
*
* @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;
output[1] = (byte)(input >>> 8);
output[2] = (byte)(input >>> 16);
output[3] = (byte)(input >>> 24);
output[4] = (byte)(input >>> 32);
output[5] = (byte)(input >>> 40);
output[6] = (byte)(input >>> 48);
output[7] = (byte)(input >>> 56);
return output;
}
/**
* Convert an integer to a byte array of length 8.
*
* @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;
output[outOff++] = (byte)(input >>> 8);
output[outOff++] = (byte)(input >>> 16);
output[outOff++] = (byte)(input >>> 24);
output[outOff++] = (byte)(input >>> 32);
output[outOff++] = (byte)(input >>> 40);
output[outOff++] = (byte)(input >>> 48);
output[outOff] = (byte)(input >>> 56);
}
/**
* Convert an int array to a byte array of the specified length. No length
* checking is performed (i.e., if the last integer cannot be encoded with
* <tt>length % 4</tt> octets, it is truncated).
*
* @param input the int array
* @param outLen the length of the converted array
* @return the converted array
*/
public static byte[] toByteArray(int[] input, int outLen)
{
int intLen = input.length;
byte[] result = new byte[outLen];
int index = 0;
for (int i = 0; i <= intLen - 2; i++, index += 4)
{
I2OSP(input[i], result, index);
}
I2OSP(input[intLen - 1], result, index, outLen - index);
return result;
}
/**
* Convert a byte array to an int array.
*
* @param input the byte array
* @return the converted array
*/
public static int[] toIntArray(byte[] input)
{
int intLen = (input.length + 3) / 4;
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;
}
}
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