Change-Id: Idfe95db82275fd2be6ca88f245830731a0d5aecf Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>main
Brad Fitzpatrick
4 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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