util/sha256x: rename Hash as Block512 (#5351)

Rename Hash as Block512 to indicate that this is a general-purpose
hash.Hash for any algorithm that operates on 512-bit block sizes.

While we rename the package as hashx in this commit,
a subsequent commit will move the sha256x package to hashx.
This is done separately to avoid confusing git.

Signed-off-by: Joe Tsai <joetsai@digital-static.net>

util/deephash/deephash.go

@@ -34,7 +34,7 @@ import (
 	"time"
 	"unsafe"
 
-	"tailscale.com/util/sha256x"
+	hashx "tailscale.com/util/sha256x"
 )
 
 // There is much overlap between the theory of serialization and hashing.
@@ -82,7 +82,7 @@ const scratchSize = 128
 // hasher is reusable state for hashing a value.
 // Get one via hasherPool.
 type hasher struct {
-	sha256x.Hash
+	hashx.Block512
 	scratch    [scratchSize]byte
 	visitStack visitStack
 }
@@ -111,6 +111,13 @@ func initSeed() {
 	seed = uint64(time.Now().UnixNano())
 }
 
+func (h *hasher) Reset() {
+	if h.Block512.Hash == nil {
+		h.Block512.Hash = sha256.New()
+	}
+	h.Block512.Reset()
+}
+
 func (h *hasher) sum() (s Sum) {
 	h.Sum(s.sum[:0])
 	return s

util/deephash/deephash_test.go

@@ -531,7 +531,7 @@ func TestGetTypeHasher(t *testing.T) {
 			fn := getTypeInfo(va.Type()).hasher()
 			hb := &hashBuffer{Hash: sha256.New()}
 			h := new(hasher)
-			h.Hash.H = hb
+			h.Block512.Hash = hb
 			got := fn(h, va)
 			const ptrSize = 32 << uintptr(^uintptr(0)>>63)
 			if tt.out32 != "" && ptrSize == 32 {
@@ -628,7 +628,7 @@ func TestHashMapAcyclic(t *testing.T) {
 		v := addressableValue{reflect.ValueOf(&m).Elem()}
 		hb.Reset()
 		h := new(hasher)
-		h.Hash.H = hb
+		h.Block512.Hash = hb
 		h.hashMap(v, ti, false)
 		h.sum()
 		if got[string(hb.B)] {
@@ -648,7 +648,7 @@ func TestPrintArray(t *testing.T) {
 	x := T{X: [32]byte{1: 1, 31: 31}}
 	hb := &hashBuffer{Hash: sha256.New()}
 	h := new(hasher)
-	h.Hash.H = hb
+	h.Block512.Hash = hb
 	h.hashValue(addressableValue{reflect.ValueOf(&x).Elem()}, false)
 	h.sum()
 	const want = "\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x1f"
@@ -669,7 +669,7 @@ func BenchmarkHashMapAcyclic(b *testing.B) {
 	ti := getTypeInfo(v.Type())
 
 	h := new(hasher)
-	h.Hash.H = hb
+	h.Block512.Hash = hb
 
 	for i := 0; i < b.N; i++ {
 		h.Reset()