podman

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