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using Org.BouncyCastle.Crypto.Utilities;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Pqc.Crypto.Bike
{
internal class BikeUtilities
{
internal static int GetHammingWeight(byte[] bytes)
{
int hammingWeight = 0;
for (int i = 0; i < bytes.Length; i++)
{
hammingWeight += bytes[i];
}
return hammingWeight;
}
internal static void FromByteArrayToBitArray(byte[] output, byte[] input)
{
int max = (output.Length / 8);
for (int i = 0; i < max; i++)
{
for (int j = 0; j != 8; j++)
{
output[i * 8 + j] = (byte)((input[i] >> j) & 1);
}
}
if (output.Length % 8 != 0)
{
int off = max * 8;
int count = 0;
while (off < output.Length)
{
output[off++] = (byte)((input[max] >> count) & 1);
count++;
}
}
}
internal static void FromBitArrayToByteArray(byte[] output, byte[] inputX, int inputOff, int inputLen)
{
int count = 0;
int pos = 0;
while (count < inputLen)
{
if (count + 8 >= inputLen)
{// last set of bits cannot have enough 8 bits
int b = inputX[inputOff + count];
for (int j = inputLen - count - 1; j >= 1; j--)
{ //bin in reversed order
b |= inputX[inputOff + count + j] << j;
}
output[pos] = (byte)b;
}
else
{
int b = inputX[inputOff + count];
for (int j = 7; j >= 1; j--)
{ //bin in reversed order
b |= inputX[inputOff + count + j] << j;
}
output[pos] = (byte)b;
}
count += 8;
pos++;
}
}
internal static byte[] GenerateRandomByteArray(int mod, int size, int weight, IXof digest)
{
byte[] buf = new byte[4];
int highest = Integers.HighestOneBit(mod);
int mask = highest | (highest - 1);
byte[] res = new byte[size];
int count = 0;
while (count < weight)
{
digest.Output(buf, 0, 4);
int tmp = (int)Pack.LE_To_UInt32(buf) & mask;
if (tmp < mod && SetBit(res, tmp))
{
++count;
}
}
return res;
}
private static bool SetBit(byte[] a, int position)
{
int index = position / 8;
int pos = position % 8;
int selector = 1 << pos;
bool result = (a[index] & selector) == 0;
a[index] |= (byte)selector;
return result;
}
}
}
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