mirror of https://github.com/tailscale/tailscale/
util/mak: move tailssh's mapSet into a new package for reuse elsewhere
Change-Id: Idfe95db82275fd2be6ca88f245830731a0d5aecf Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>pull/4501/head
Brad Fitzpatrick
2 years ago
committed by
Brad Fitzpatrick
parent
c2eff20008
commit
910ae68e0b
@ -0,0 +1,53 @@
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// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package mak helps make maps. It contains generic helpers to make/assign
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// things, notably to maps, but also slices.
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package mak
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import (
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"fmt"
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"reflect"
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)
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// Set populates an entry in a map, making the map if necessary.
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//
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// That is, it assigns (*m)[k] = v, making *m if it was nil.
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func Set[K comparable, V any, T ~map[K]V](m *T, k K, v V) {
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if *m == nil {
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*m = make(map[K]V)
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}
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(*m)[k] = v
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}
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// NonNil takes a pointer to a Go data structure
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// (currently only a slice or a map) and makes sure it's non-nil for
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// JSON serialization. (In particular, JavaScript clients usually want
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// the field to be defined after they decode the JSON.)
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// MakeNonNil takes a pointer to a Go data structure
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// (currently only a slice or a map) and makes sure it's non-nil for
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// JSON serialization. (In particular, JavaScript clients usually want
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// the field to be defined after they decode the JSON.)
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func NonNil(ptr interface{}) {
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if ptr == nil {
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panic("nil interface")
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}
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rv := reflect.ValueOf(ptr)
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if rv.Kind() != reflect.Ptr {
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panic(fmt.Sprintf("kind %v, not Ptr", rv.Kind()))
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}
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if rv.Pointer() == 0 {
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panic("nil pointer")
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}
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rv = rv.Elem()
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if rv.Pointer() != 0 {
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return
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}
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switch rv.Type().Kind() {
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case reflect.Slice:
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rv.Set(reflect.MakeSlice(rv.Type(), 0, 0))
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case reflect.Map:
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rv.Set(reflect.MakeMap(rv.Type()))
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}
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}
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@ -0,0 +1,71 @@
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// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package mak contains code to help make things.
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package mak
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import (
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"reflect"
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"testing"
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)
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type M map[string]int
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func TestSet(t *testing.T) {
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t.Run("unnamed", func(t *testing.T) {
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var m map[string]int
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Set(&m, "foo", 42)
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Set(&m, "bar", 1)
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Set(&m, "bar", 2)
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want := map[string]int{
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"foo": 42,
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"bar": 2,
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}
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if got := m; !reflect.DeepEqual(got, want) {
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t.Errorf("got %v; want %v", got, want)
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}
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})
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t.Run("named", func(t *testing.T) {
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var m M
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Set(&m, "foo", 1)
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Set(&m, "bar", 1)
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Set(&m, "bar", 2)
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want := M{
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"foo": 1,
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"bar": 2,
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}
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if got := m; !reflect.DeepEqual(got, want) {
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t.Errorf("got %v; want %v", got, want)
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}
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})
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}
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func TestNonNil(t *testing.T) {
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var s []string
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NonNil(&s)
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if len(s) != 0 {
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t.Errorf("slice len = %d; want 0", len(s))
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}
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if s == nil {
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t.Error("slice still nil")
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}
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s = append(s, "foo")
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NonNil(&s)
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if len(s) != 1 {
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t.Errorf("len = %d; want 1", len(s))
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}
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if s[0] != "foo" {
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t.Errorf("value = %q; want foo", s)
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}
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var m map[string]string
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NonNil(&m)
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if len(m) != 0 {
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t.Errorf("map len = %d; want 0", len(s))
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}
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if m == nil {
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t.Error("map still nil")
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}
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}
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