public Currency(decimal amount)
{
if (amount == 0m)
{
this.bits = 0;
return;
}
var bits = Decimal.GetBits(amount);
Span <byte> mantissabytes = stackalloc byte[12];
System.Buffers.Binary.BinaryPrimitives.WriteInt32LittleEndian(mantissabytes.Slice(0, 4), bits[0]);
System.Buffers.Binary.BinaryPrimitives.WriteInt32LittleEndian(mantissabytes.Slice(4, 4), bits[1]);
System.Buffers.Binary.BinaryPrimitives.WriteInt32LittleEndian(mantissabytes.Slice(8, 4), bits[2]);
var bigmantissa = new System.Numerics.BigInteger(mantissabytes, true, false);
var isPositive = (bits[3] & 0xF000_0000) == 0;
var exponent = (bits[3] >> 16) & 0xFF;
// C# decimal is stored as 'mantissa / 10^exponent' where exponent must be (0, 28) and mantissa is 96 bits,
// while ripple stores decimals as 'mantissa * 10^exponent' where exponent must be (-96, 80) and mantissa is 54 bits.
// First flip the exponent (C# divides, ripple multiplies)
exponent = -exponent;
// We need to scale the mantissa to be between 1000_0000_0000_0000 and 9999_9999_9999_9999
while (bigmantissa < minMantissa)
{
exponent -= 1;
bigmantissa *= 10;
}
while (bigmantissa > maxMantissa)
{
exponent += 1;
bigmantissa /= 10;
}
// mantissa will now fit into 54 bits, exponent should be between -96 and 80.
mantissabytes.Clear();
var ok = bigmantissa.TryWriteBytes(mantissabytes, out var bytesWritten, true, false);
System.Diagnostics.Debug.Assert(ok);
System.Diagnostics.Debug.Assert(bytesWritten <= 7);
var mantissa = System.Buffers.Binary.BinaryPrimitives.ReadUInt64LittleEndian(mantissabytes);
System.Diagnostics.Debug.Assert(minExponent <= exponent && exponent <= maxExponent);
System.Diagnostics.Debug.Assert(minMantissa <= mantissa && mantissa <= maxMantissa);
this.bits = Pack(isPositive, exponent, mantissa);
}