util/deephash: remove Tailscale toolchain compatibility shim

The future is now.

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

util/deephash/deephash.go

@@ -328,19 +328,21 @@ func (c *valueCache) get(t reflect.Type) reflect.Value {
 func (h *hasher) hashMap(v reflect.Value) {
 	mh := mapHasherPool.Get().(*mapHasher)
 	defer mapHasherPool.Put(mh)
-	iter := mapIter(&mh.iter, v)
-	defer mapIter(&mh.iter, reflect.Value{}) // avoid pinning v from mh.iter when we return
+
+	iter := &mh.iter
+	iter.Reset(v)
+	defer iter.Reset(reflect.Value{}) // avoid pinning v from mh.iter when we return
 
 	var sum Sum
 	k := mh.val.get(v.Type().Key())
 	e := mh.val.get(v.Type().Elem())
 	mh.h.visitStack = h.visitStack // always use the parent's visit stack to avoid cycles
 	for iter.Next() {
-		key := iterKey(iter, k)
-		val := iterVal(iter, e)
+		k.SetIterKey(iter)
+		e.SetIterValue(iter)
 		mh.h.reset()
-		mh.h.hashValue(key)
-		mh.h.hashValue(val)
+		mh.h.hashValue(k)
+		mh.h.hashValue(v)
 		sum.xor(mh.h.sum())
 	}
 	h.bw.Write(append(h.scratch[:0], sum.sum[:]...)) // append into scratch to avoid heap allocation

util/deephash/mapiter.go

@@ -1,38 +0,0 @@
-// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !tailscale_go
-// +build !tailscale_go
-
-package deephash
-
-import "reflect"
-
-// iterKey returns the current iter key.
-// scratch is a re-usable reflect.Value.
-// iterKey may store the iter key in scratch and return scratch,
-// or it may allocate and return a new reflect.Value.
-func iterKey(iter *reflect.MapIter, _ reflect.Value) reflect.Value {
-	return iter.Key()
-}
-
-// iterVal returns the current iter val.
-// scratch is a re-usable reflect.Value.
-// iterVal may store the iter val in scratch and return scratch,
-// or it may allocate and return a new reflect.Value.
-func iterVal(iter *reflect.MapIter, _ reflect.Value) reflect.Value {
-	return iter.Value()
-}
-
-// mapIter returns a map iterator for mapVal.
-// scratch is a re-usable reflect.MapIter.
-// mapIter may re-use scratch and return it,
-// or it may allocate and return a new *reflect.MapIter.
-// If mapVal is the zero reflect.Value, mapIter may return nil.
-func mapIter(_ *reflect.MapIter, mapVal reflect.Value) *reflect.MapIter {
-	if !mapVal.IsValid() {
-		return nil
-	}
-	return mapVal.MapRange()
-}

util/deephash/mapiter_future.go

@@ -1,43 +0,0 @@
-// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build tailscale_go
-// +build tailscale_go
-
-package deephash
-
-import "reflect"
-
-// iterKey returns the current iter key.
-// scratch is a re-usable reflect.Value.
-// iterKey may store the iter key in scratch and return scratch,
-// or it may allocate and return a new reflect.Value.
-func iterKey(iter *reflect.MapIter, scratch reflect.Value) reflect.Value {
-	iter.SetKey(scratch)
-	return scratch
-}
-
-// iterVal returns the current iter val.
-// scratch is a re-usable reflect.Value.
-// iterVal may store the iter val in scratch and return scratch,
-// or it may allocate and return a new reflect.Value.
-func iterVal(iter *reflect.MapIter, scratch reflect.Value) reflect.Value {
-	iter.SetValue(scratch)
-	return scratch
-}
-
-// mapIter returns a map iterator for mapVal.
-// scratch is a re-usable reflect.MapIter.
-// mapIter may re-use scratch and return it,
-// or it may allocate and return a new *reflect.MapIter.
-// If mapVal is the zero reflect.Value, mapIter may return nil.
-func mapIter(scratch *reflect.MapIter, mapVal reflect.Value) *reflect.MapIter {
-	scratch.Reset(mapVal) // always Reset, to allow the caller to avoid pinning memory
-	if !mapVal.IsValid() {
-		// Returning scratch would also be OK.
-		// Do this for consistency with the non-optimized version.
-		return nil
-	}
-	return scratch
-}