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using System;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Math.EC;
namespace Org.BouncyCastle.Bcpg
{
/// <remarks>A multiple precision integer</remarks>
public sealed class MPInteger
: BcpgObject
{
private readonly BigInteger m_val;
public MPInteger(BcpgInputStream bcpgIn)
{
if (bcpgIn == null)
throw new ArgumentNullException(nameof(bcpgIn));
int lengthInBits = (bcpgIn.ReadByte() << 8) | bcpgIn.ReadByte();
int lengthInBytes = (lengthInBits + 7) / 8;
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
if (lengthInBytes <= 512)
{
Span<byte> span = stackalloc byte[lengthInBytes];
bcpgIn.ReadFully(span);
m_val = new BigInteger(1, span);
return;
}
#endif
byte[] bytes = new byte[lengthInBytes];
bcpgIn.ReadFully(bytes);
m_val = new BigInteger(1, bytes);
}
public MPInteger(BigInteger val)
{
if (val == null)
throw new ArgumentNullException(nameof(val));
if (val.SignValue < 0)
throw new ArgumentException("Values must be positive", nameof(val));
m_val = val;
}
public BigInteger Value => m_val;
public override void Encode(BcpgOutputStream bcpgOut)
{
bcpgOut.WriteShort((short)m_val.BitLength);
bcpgOut.Write(m_val.ToByteArrayUnsigned());
}
internal static BigInteger ToMpiBigInteger(ECPoint point)
{
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
Span<byte> encoding = stackalloc byte[point.GetEncodedLength(false)];
point.EncodeTo(false, encoding);
return new BigInteger(1, encoding);
#else
return new BigInteger(1, point.GetEncoded(false));
#endif
}
}
}
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