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using System;
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[] input, 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 = input[inputOff + count];
for (int j = inputLen - count - 1; j >= 1; j--)
{ //bin in reversed order
b |= input[inputOff + count + j] << j;
}
output[pos] = (byte)b;
}
else
{
int b = input[inputOff + count];
for (int j = 7; j >= 1; j--)
{ //bin in reversed order
b |= input[inputOff + count + j] << j;
}
output[pos] = (byte)b;
}
count += 8;
pos++;
}
}
internal static void GenerateRandomByteArray(byte[] res, uint size, uint weight, IXof digest)
{
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
Span<byte> buf = stackalloc byte[4];
#else
byte[] buf = new byte[4];
#endif
for (int i = (int)weight - 1; i >= 0; i--)
{
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
digest.Output(buf);
ulong temp = Pack.LE_To_UInt32(buf);
#else
digest.Output(buf, 0, 4);
ulong temp = Pack.LE_To_UInt32(buf, 0);
#endif
temp = temp * (size - (uint)i) >> 32;
uint rand_pos = (uint)i + (uint)temp;
if (CheckBit(res, rand_pos) != 0)
{
rand_pos = (uint)i;
}
SetBit(res, rand_pos);
}
}
private static uint CheckBit(byte[] tmp, uint position)
{
uint index = position / 8;
uint pos = position % 8;
return ((uint)tmp[index] >> (int)pos) & 1U;
}
private static void SetBit(byte[] tmp, uint position)
{
uint index = position / 8;
uint pos = position % 8;
tmp[index] |= (byte)(1 << (int)pos);
}
}
}
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