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// Copyright 2017 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.
package crc32
import (
"unsafe"
)
const (
vecMinLen = 16
vecAlignMask = 15 // align to 16 bytes
crcIEEE = 1
crcCast = 2
)
//go:noescape
func ppc64SlicingUpdateBy8(crc uint32, table8 *slicing8Table, p []byte) uint32
// this function requires the buffer to be 16 byte aligned and > 16 bytes long
//go:noescape
func vectorCrc32(crc uint32, poly uint32, p []byte) uint32
var archCastagnoliTable8 *slicing8Table
func archInitCastagnoli() {
archCastagnoliTable8 = slicingMakeTable(Castagnoli)
}
func archUpdateCastagnoli(crc uint32, p []byte) uint32 {
if len(p) >= 4*vecMinLen {
// If not aligned then process the initial unaligned bytes
if uint64(uintptr(unsafe.Pointer(&p[0])))&uint64(vecAlignMask) != 0 {
align := uint64(uintptr(unsafe.Pointer(&p[0]))) & uint64(vecAlignMask)
newlen := vecMinLen - align
crc = ppc64SlicingUpdateBy8(crc, archCastagnoliTable8, p[:newlen])
p = p[newlen:]
}
// p should be aligned now
aligned := len(p) & ^vecAlignMask
crc = vectorCrc32(crc, crcCast, p[:aligned])
p = p[aligned:]
}
if len(p) == 0 {
return crc
}
return ppc64SlicingUpdateBy8(crc, archCastagnoliTable8, p)
}
func archAvailableIEEE() bool {
return true
}
func archAvailableCastagnoli() bool {
return true
}
var archIeeeTable8 *slicing8Table
func archInitIEEE() {
// We still use slicing-by-8 for small buffers.
archIeeeTable8 = slicingMakeTable(IEEE)
}
// archUpdateIEEE calculates the checksum of p using vectorizedIEEE.
func archUpdateIEEE(crc uint32, p []byte) uint32 {
// Check if vector code should be used. If not aligned, then handle those
// first up to the aligned bytes.
if len(p) >= 4*vecMinLen {
if uint64(uintptr(unsafe.Pointer(&p[0])))&uint64(vecAlignMask) != 0 {
align := uint64(uintptr(unsafe.Pointer(&p[0]))) & uint64(vecAlignMask)
newlen := vecMinLen - align
crc = ppc64SlicingUpdateBy8(crc, archIeeeTable8, p[:newlen])
p = p[newlen:]
}
aligned := len(p) & ^vecAlignMask
crc = vectorCrc32(crc, crcIEEE, p[:aligned])
p = p[aligned:]
}
if len(p) == 0 {
return crc
}
return ppc64SlicingUpdateBy8(crc, archIeeeTable8, p)
}
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