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// Copyright 2016 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.
// +build ignore
package crc32
import (
"unsafe"
)
const (
vxMinLen = 64
vxAlignment = 16
vxAlignMask = vxAlignment - 1
)
// hasVectorFacility reports whether the machine has the z/Architecture
// vector facility installed and enabled.
func hasVectorFacility() bool
var hasVX = hasVectorFacility()
// vectorizedCastagnoli implements CRC32 using vector instructions.
// It is defined in crc32_s390x.s.
//go:noescape
func vectorizedCastagnoli(crc uint32, p []byte) uint32
// vectorizedIEEE implements CRC32 using vector instructions.
// It is defined in crc32_s390x.s.
//go:noescape
func vectorizedIEEE(crc uint32, p []byte) uint32
func genericCastagnoli(crc uint32, p []byte) uint32 {
// Use slicing-by-8 on larger inputs.
if len(p) >= sliceBy8Cutoff {
return updateSlicingBy8(crc, castagnoliTable8, p)
}
return update(crc, castagnoliTable, p)
}
func genericIEEE(crc uint32, p []byte) uint32 {
// Use slicing-by-8 on larger inputs.
if len(p) >= sliceBy8Cutoff {
ieeeTable8Once.Do(func() {
ieeeTable8 = makeTable8(IEEE)
})
return updateSlicingBy8(crc, ieeeTable8, p)
}
return update(crc, IEEETable, p)
}
// updateCastagnoli calculates the checksum of p using genericCastagnoli to
// align the data appropriately for vectorCastagnoli. It avoids using
// vectorCastagnoli entirely if the length of p is less than or equal to
// vxMinLen.
func updateCastagnoli(crc uint32, p []byte) uint32 {
// Use vectorized function if vector facility is available and
// data length is above threshold.
if hasVX && len(p) > vxMinLen {
pAddr := uintptr(unsafe.Pointer(&p[0]))
if pAddr&vxAlignMask != 0 {
prealign := vxAlignment - int(pAddr&vxAlignMask)
crc = genericCastagnoli(crc, p[:prealign])
p = p[prealign:]
}
aligned := len(p) & ^vxAlignMask
crc = vectorizedCastagnoli(crc, p[:aligned])
p = p[aligned:]
// process remaining data
if len(p) > 0 {
crc = genericCastagnoli(crc, p)
}
return crc
}
return genericCastagnoli(crc, p)
}
// updateIEEE calculates the checksum of p using genericIEEE to align the data
// appropriately for vectorIEEE. It avoids using vectorIEEE entirely if the length
// of p is less than or equal to vxMinLen.
func updateIEEE(crc uint32, p []byte) uint32 {
// Use vectorized function if vector facility is available and
// data length is above threshold.
if hasVX && len(p) > vxMinLen {
pAddr := uintptr(unsafe.Pointer(&p[0]))
if pAddr&vxAlignMask != 0 {
prealign := vxAlignment - int(pAddr&vxAlignMask)
crc = genericIEEE(crc, p[:prealign])
p = p[prealign:]
}
aligned := len(p) & ^vxAlignMask
crc = vectorizedIEEE(crc, p[:aligned])
p = p[aligned:]
// process remaining data
if len(p) > 0 {
crc = genericIEEE(crc, p)
}
return crc
}
return genericIEEE(crc, p)
}
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