org.bouncycastle.pqc.math.linearalgebra.IntUtils Maven / Gradle / Ivy
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package org.bouncycastle.pqc.math.linearalgebra;
import org.bouncycastle.util.Pack;
import org.bouncycastle.util.encoders.Hex;
public final class IntUtils
{
/**
* Default constructor (private).
*/
private IntUtils()
{
// empty
}
/**
* Compare two int arrays. No null checks are performed.
*
* @param left the first int array
* @param right the second int array
* @return the result of the comparison
*/
public static boolean equals(int[] left, int[] right)
{
if (left.length != right.length)
{
return false;
}
boolean result = true;
for (int i = left.length - 1; i >= 0; i--)
{
result &= left[i] == right[i];
}
return result;
}
/**
* Return a clone of the given int array. No null checks are performed.
*
* @param array the array to clone
* @return the clone of the given array
*/
public static int[] clone(int[] array)
{
int[] result = new int[array.length];
System.arraycopy(array, 0, result, 0, array.length);
return result;
}
/**
* Fill the given int array with the given value.
*
* @param array the array
* @param value the value
*/
public static void fill(int[] array, int value)
{
for (int i = array.length - 1; i >= 0; i--)
{
array[i] = value;
}
}
/**
* Sorts this array of integers according to the Quicksort algorithm. After
* calling this method this array is sorted in ascending order with the
* smallest integer taking position 0 in the array.
*
* This implementation is based on the quicksort algorithm as described in
* Data Structures In Java by Thomas A. Standish, Chapter 10,
* ISBN 0-201-30564-X.
*
* @param source the array of integers that needs to be sorted.
*/
public static void quicksort(int[] source)
{
quicksort(source, 0, source.length - 1);
}
/**
* Sort a subarray of a source array. The subarray is specified by its start
* and end index.
*
* @param source the int array to be sorted
* @param left the start index of the subarray
* @param right the end index of the subarray
*/
public static void quicksort(int[] source, int left, int right)
{
if (right > left)
{
int index = partition(source, left, right, right);
quicksort(source, left, index - 1);
quicksort(source, index + 1, right);
}
}
/**
* Split a subarray of a source array into two partitions. The left
* partition contains elements that have value less than or equal to the
* pivot element, the right partition contains the elements that have larger
* value.
*
* @param source the int array whose subarray will be splitted
* @param left the start position of the subarray
* @param right the end position of the subarray
* @param pivotIndex the index of the pivot element inside the array
* @return the new index of the pivot element inside the array
*/
private static int partition(int[] source, int left, int right,
int pivotIndex)
{
int pivot = source[pivotIndex];
source[pivotIndex] = source[right];
source[right] = pivot;
int index = left;
for (int i = left; i < right; i++)
{
if (source[i] <= pivot)
{
int tmp = source[index];
source[index] = source[i];
source[i] = tmp;
index++;
}
}
int tmp = source[index];
source[index] = source[right];
source[right] = tmp;
return index;
}
/**
* Generates a subarray of a given int array.
*
* @param input -
* the input int array
* @param start -
* the start index
* @param end -
* the end index
* @return a subarray of input, ranging from start to
* end
*/
public static int[] subArray(final int[] input, final int start,
final int end)
{
int[] result = new int[end - start];
System.arraycopy(input, start, result, 0, end - start);
return result;
}
/**
* @param input an int array
* @return a human readable form of the given int array
*/
public static String toString(int[] input)
{
String result = "";
for (int i = 0; i < input.length; i++)
{
result += input[i] + " ";
}
return result;
}
/**
* @param input an int arary
* @return the int array as hex string
*/
public static String toHexString(int[] input)
{
// -DM Hex.toHexString
return Hex.toHexString(toByteArray(input));
}
public static byte[] toByteArray(final int[] input)
{
byte[] result = new byte[input.length << 2];
for (int i = 0; i < input.length; i++)
{
Pack.intToBigEndian(input[i], result, i << 2);
}
return result;
}
}