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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build gc && !purego
// +build gc,!purego
package poly1305
import (
"golang.org/x/sys/cpu"
)
// updateVX is an assembly implementation of Poly1305 that uses vector
// instructions. It must only be called if the vector facility (vx) is
// available.
//
//go:noescape
func updateVX(state *macState, msg []byte)
// mac is a replacement for macGeneric that uses a larger buffer and redirects
// calls that would have gone to updateGeneric to updateVX if the vector
// facility is installed.
//
// A larger buffer is required for good performance because the vector
// implementation has a higher fixed cost per call than the generic
// implementation.
type mac struct {
macState
buffer [16 * TagSize]byte // size must be a multiple of block size (16)
offset int
}
func (h *mac) Write(p []byte) (int, error) {
nn := len(p)
if h.offset > 0 {
n := copy(h.buffer[h.offset:], p)
if h.offset+n < len(h.buffer) {
h.offset += n
return nn, nil
}
p = p[n:]
h.offset = 0
if cpu.S390X.HasVX {
updateVX(&h.macState, h.buffer[:])
} else {
updateGeneric(&h.macState, h.buffer[:])
}
}
tail := len(p) % len(h.buffer) // number of bytes to copy into buffer
body := len(p) - tail // number of bytes to process now
if body > 0 {
if cpu.S390X.HasVX {
updateVX(&h.macState, p[:body])
} else {
updateGeneric(&h.macState, p[:body])
}
}
h.offset = copy(h.buffer[:], p[body:]) // copy tail bytes - can be 0
return nn, nil
}
func (h *mac) Sum(out *[TagSize]byte) {
state := h.macState
remainder := h.buffer[:h.offset]
// Use the generic implementation if we have 2 or fewer blocks left
// to sum. The vector implementation has a higher startup time.
if cpu.S390X.HasVX && len(remainder) > 2*TagSize {
updateVX(&state, remainder)
} else if len(remainder) > 0 {
updateGeneric(&state, remainder)
}
finalize(out, &state.h, &state.s)
}
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