internal/deephash: simplify API

Reduce to just a single external endpoint.
Convert from a variadic number of interfaces to a slice there.

name    old time/op    new time/op    delta
Hash-8    14.4µs ± 0%    14.0µs ± 1%   -3.08%  (p=0.000 n=9+9)

name    old alloc/op   new alloc/op   delta
Hash-8      873B ± 0%      793B ± 0%   -9.16%  (p=0.000 n=9+6)

name    old allocs/op  new allocs/op  delta
Hash-8      18.0 ± 0%      14.0 ± 0%  -22.22%  (p=0.000 n=10+10)

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

internal/deephash/deephash.go

@@ -19,18 +19,18 @@ import (
 	"tailscale.com/types/wgkey"
 )
 
-func Hash(v ...interface{}) string {
+func calcHash(v interface{}) string {
 	h := sha256.New()
 	// 64 matches the chunk size in crypto/sha256/sha256.go
 	b := bufio.NewWriterSize(h, 64)
-	Print(b, v)
+	printTo(b, v)
 	b.Flush()
 	return fmt.Sprintf("%x", h.Sum(nil))
 }
 
 // UpdateHash sets last to the hash of v and reports whether its value changed.
 func UpdateHash(last *string, v ...interface{}) (changed bool) {
-	sig := Hash(v)
+	sig := calcHash(v)
 	if *last != sig {
 		*last = sig
 		return true
@@ -38,7 +38,7 @@ func UpdateHash(last *string, v ...interface{}) (changed bool) {
 	return false
 }
 
-func Print(w *bufio.Writer, v ...interface{}) {
+func printTo(w *bufio.Writer, v interface{}) {
 	print(w, reflect.ValueOf(v), make(map[uintptr]bool))
 }
 

internal/deephash/deephash_test.go

@@ -18,15 +18,15 @@ import (
 	"tailscale.com/wgengine/wgcfg"
 )
 
-func TestDeepPrint(t *testing.T) {
+func TestDeepHash(t *testing.T) {
 	// v contains the types of values we care about for our current callers.
 	// Mostly we're just testing that we don't panic on handled types.
 	v := getVal()
 
-	hash1 := Hash(v)
+	hash1 := calcHash(v)
 	t.Logf("hash: %v", hash1)
 	for i := 0; i < 20; i++ {
-		hash2 := Hash(getVal())
+		hash2 := calcHash(getVal())
 		if hash1 != hash2 {
 			t.Error("second hash didn't match")
 		}
@@ -80,7 +80,7 @@ func BenchmarkHash(b *testing.B) {
 	b.ReportAllocs()
 	v := getVal()
 	for i := 0; i < b.N; i++ {
-		Hash(v)
+		calcHash(v)
 	}
 }