/// <summary>
/// Compute xxHash for the async stream
/// </summary>
/// <param name="stream">The stream of data</param>
/// <param name="bufferSize">The buffer size</param>
/// <param name="seed">The seed number</param>
/// <param name="cancellationToken">The cancellation token</param>
/// <returns>The hash</returns>
public static async ValueTask <uint> ComputeHashAsync(Stream stream, int bufferSize, uint seed, CancellationToken cancellationToken)
{
if (stream == null)
{
throw new ArgumentNullException(nameof(stream));
}
Debug.Assert(stream != null);
Debug.Assert(bufferSize > 16);
// Optimizing memory allocation
byte[] buffer = ArrayPool <byte> .Shared.Rent(bufferSize + 16);
int readBytes;
int offset = 0;
long length = 0;
// Prepare the seed vector
uint v1 = seed + p1 + p2;
uint v2 = seed + p2;
uint v3 = seed + 0;
uint v4 = seed - p1;
try
{
// Read flow of bytes
while ((readBytes = await stream.ReadAsync(buffer, offset, bufferSize, cancellationToken).ConfigureAwait(true)) > 0)
{
// Exit if the operation is canceled
if (cancellationToken.IsCancellationRequested)
{
return(await Task.FromCanceled <uint>(cancellationToken).ConfigureAwait(true));
}
length += readBytes;
offset += readBytes;
if (offset < 16)
{
continue;
}
int r = offset % 16; // remain
int l = offset - r; // length
// Process the next chunk
UnsafeAlign(buffer, l, ref v1, ref v2, ref v3, ref v4);
// Put remaining bytes to buffer
UnsafeBuffer.BlockCopy(buffer, l, buffer, 0, r);
offset = r;
}
// Process the final chunk
uint h32 = UnsafeFinal(buffer, offset, ref v1, ref v2, ref v3, ref v4, length, seed);
return(h32);
}
finally
{
// Free memory
ArrayPool <byte> .Shared.Return(buffer);
}
}
