1 files changed, 230 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/pqc/math/linearalgebra/LittleEndianConversions.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/pqc/math/linearalgebra/LittleEndianConversions.java
new file mode 100644
index 000000000..111695218
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/pqc/math/linearalgebra/LittleEndianConversions.java
@@ -0,0 +1,230 @@
+package org.spongycastle.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;
+    }
+
+}