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