This CL adds the poly1305.MAC type which implements a subset of the hash.Hash interface. With MAC it is possible to compute an authentication tag of data without copying it into a single byte slice. This commit modifies the reference/generic and the AMD64 assembler but not the ARM/s390x implementation to support an io.Writer interface. Updates golang/go#25219 Change-Id: I7ee5a9eadd43387cf3cd887d734c625575eee47d Reviewed-on: https://go-review.googlesource.com/c/crypto/+/111335 Run-TryBot: Filippo Valsorda <filippo@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Filippo Valsorda <filippo@golang.org>