From f796c49260ad19c33b616c9543b99f7f425dc2fe Mon Sep 17 00:00:00 2001
From: apocelipes <seve3r@outlook.com>
Date: Thu, 26 Sep 2024 15:03:44 +0800
Subject: [PATCH] hash/crc32,hash/crc64: use sync.OnceFunc

Use sync.OnceFunc to simplify the code and to reduce global variables.
---
 src/hash/crc32/crc32.go | 20 +++++++++-----------
 src/hash/crc64/crc64.go |  9 +++------
 2 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/src/hash/crc32/crc32.go b/src/hash/crc32/crc32.go
index b659959959..bc1ae310dd 100644
--- a/src/hash/crc32/crc32.go
+++ b/src/hash/crc32/crc32.go
@@ -78,10 +78,9 @@ type Table [256]uint32
 var castagnoliTable *Table
 var castagnoliTable8 *slicing8Table
 var updateCastagnoli func(crc uint32, p []byte) uint32
-var castagnoliOnce sync.Once
 var haveCastagnoli atomic.Bool
 
-func castagnoliInit() {
+var castagnoliInitOnce = sync.OnceFunc(func() {
 	castagnoliTable = simpleMakeTable(Castagnoli)
 
 	if archAvailableCastagnoli() {
@@ -96,7 +95,7 @@ func castagnoliInit() {
 	}
 
 	haveCastagnoli.Store(true)
-}
+})
 
 // IEEETable is the table for the [IEEE] polynomial.
 var IEEETable = simpleMakeTable(IEEE)
@@ -104,9 +103,8 @@ var IEEETable = simpleMakeTable(IEEE)
 // ieeeTable8 is the slicing8Table for IEEE
 var ieeeTable8 *slicing8Table
 var updateIEEE func(crc uint32, p []byte) uint32
-var ieeeOnce sync.Once
 
-func ieeeInit() {
+var ieeeInitOnce = sync.OnceFunc(func() {
 	if archAvailableIEEE() {
 		archInitIEEE()
 		updateIEEE = archUpdateIEEE
@@ -117,17 +115,17 @@ func ieeeInit() {
 			return slicingUpdate(crc, ieeeTable8, p)
 		}
 	}
-}
+})
 
 // MakeTable returns a [Table] constructed from the specified polynomial.
 // The contents of this [Table] must not be modified.
 func MakeTable(poly uint32) *Table {
 	switch poly {
 	case IEEE:
-		ieeeOnce.Do(ieeeInit)
+		ieeeInitOnce()
 		return IEEETable
 	case Castagnoli:
-		castagnoliOnce.Do(castagnoliInit)
+		castagnoliInitOnce()
 		return castagnoliTable
 	default:
 		return simpleMakeTable(poly)
@@ -147,7 +145,7 @@ type digest struct {
 // marshal and unmarshal the internal state of the hash.
 func New(tab *Table) hash.Hash32 {
 	if tab == IEEETable {
-		ieeeOnce.Do(ieeeInit)
+		ieeeInitOnce()
 	}
 	return &digest{0, tab}
 }
@@ -202,7 +200,7 @@ func update(crc uint32, tab *Table, p []byte, checkInitIEEE bool) uint32 {
 		return updateCastagnoli(crc, p)
 	case tab == IEEETable:
 		if checkInitIEEE {
-			ieeeOnce.Do(ieeeInit)
+			ieeeInitOnce()
 		}
 		return updateIEEE(crc, p)
 	default:
@@ -238,7 +236,7 @@ func Checksum(data []byte, tab *Table) uint32 { return Update(0, tab, data) }
 // ChecksumIEEE returns the CRC-32 checksum of data
 // using the [IEEE] polynomial.
 func ChecksumIEEE(data []byte) uint32 {
-	ieeeOnce.Do(ieeeInit)
+	ieeeInitOnce()
 	return updateIEEE(0, data)
 }
 
diff --git a/src/hash/crc64/crc64.go b/src/hash/crc64/crc64.go
index bdfd82ed31..66e53620b0 100644
--- a/src/hash/crc64/crc64.go
+++ b/src/hash/crc64/crc64.go
@@ -30,14 +30,11 @@ const (
 type Table [256]uint64
 
 var (
-	slicing8TablesBuildOnce sync.Once
-	slicing8TableISO        *[8]Table
-	slicing8TableECMA       *[8]Table
+	slicing8TableISO  *[8]Table
+	slicing8TableECMA *[8]Table
 )
 
-func buildSlicing8TablesOnce() {
-	slicing8TablesBuildOnce.Do(buildSlicing8Tables)
-}
+var buildSlicing8TablesOnce = sync.OnceFunc(buildSlicing8Tables)
 
 func buildSlicing8Tables() {
 	slicing8TableISO = makeSlicingBy8Table(makeTable(ISO))