From 7d1bf79faa4e2725e83ab5a8d304673ef19e5c56 Mon Sep 17 00:00:00 2001
From: Erik Pellizzon <erikpellizzon1@gmail.com>
Date: Tue, 13 Sep 2022 16:04:40 +0100
Subject: [PATCH] hash/crc32: remove redundant code

Merge the CRC32 Update and Write functions using an unexported function, to avoid duplication of code and make it more readable.
The only difference between them is the check of the initialization of the IEEE table, and a boolean value specifies that.
---
 src/hash/crc32/crc32.go | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/src/hash/crc32/crc32.go b/src/hash/crc32/crc32.go
index b69359873d..e828089308 100644
--- a/src/hash/crc32/crc32.go
+++ b/src/hash/crc32/crc32.go
@@ -206,32 +206,31 @@ func readUint32(b []byte) uint32 {
 	return uint32(b[3]) | uint32(b[2])<<8 | uint32(b[1])<<16 | uint32(b[0])<<24
 }
 
-// Update returns the result of adding the bytes in p to the crc.
-func Update(crc uint32, tab *Table, p []byte) uint32 {
+func update(crc uint32, tab *Table, p []byte, checkInitIEEE bool) uint32 {
 	switch {
 	case haveCastagnoli.Load() && tab == castagnoliTable:
 		return updateCastagnoli(crc, p)
 	case tab == IEEETable:
-		// Unfortunately, because IEEETable is exported, IEEE may be used without a
-		// call to MakeTable. We have to make sure it gets initialized in that case.
-		ieeeOnce.Do(ieeeInit)
+		if checkInitIEEE {
+			ieeeOnce.Do(ieeeInit)
+		}
 		return updateIEEE(crc, p)
 	default:
 		return simpleUpdate(crc, tab, p)
 	}
 }
 
+// Update returns the result of adding the bytes in p to the crc.
+func Update(crc uint32, tab *Table, p []byte) uint32 {
+	// Unfortunately, because IEEETable is exported, IEEE may be used without a
+	// call to MakeTable. We have to make sure it gets initialized in that case.
+	return update(crc, tab, p, true)
+}
+
 func (d *digest) Write(p []byte) (n int, err error) {
-	switch {
-	case haveCastagnoli.Load() && d.tab == castagnoliTable:
-		d.crc = updateCastagnoli(d.crc, p)
-	case d.tab == IEEETable:
-		// We only create digest objects through New() which takes care of
-		// initialization in this case.
-		d.crc = updateIEEE(d.crc, p)
-	default:
-		d.crc = simpleUpdate(d.crc, d.tab, p)
-	}
+	// We only create digest objects through New() which takes care of
+	// initialization in this case.
+	d.crc = update(d.crc, d.tab, p, false)
 	return len(p), nil
 }