--- /dev/null
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package fmtsort provides a general stable ordering mechanism
+// for maps, on behalf of the fmt and text/template packages.
+// It is not guaranteed to be efficient and works only for types
+// that are valid map keys.
+package fmtsort
+
+import (
+ "reflect"
+ "sort"
+)
+
+// Note: Throughout this package we avoid calling reflect.Value.Interface as
+// it is not always legal to do so and it's easier to avoid the issue than to face it.
+
+// SortedMap represents a map's keys and values. The keys and values are
+// aligned in index order: Value[i] is the value in the map corresponding to Key[i].
+type SortedMap struct {
+ Key []reflect.Value
+ Value []reflect.Value
+}
+
+func (o *SortedMap) Len() int { return len(o.Key) }
+func (o *SortedMap) Less(i, j int) bool { return compare(o.Key[i], o.Key[j]) < 0 }
+func (o *SortedMap) Swap(i, j int) {
+ o.Key[i], o.Key[j] = o.Key[j], o.Key[i]
+ o.Value[i], o.Value[j] = o.Value[j], o.Value[i]
+}
+
+// Sort accepts a map and returns a SortedMap that has the same keys and
+// values but in a stable sorted order according to the keys, modulo issues
+// raised by unorderable key values such as NaNs.
+//
+// The ordering rules are more general than with Go's < operator:
+//
+// - when applicable, nil compares low
+// - ints, floats, and strings order by <
+// - NaN compares less than non-NaN floats
+// - bool compares false before true
+// - complex compares real, then imag
+// - pointers compare by machine address
+// - channel values compare by machine address
+// - structs compare each field in turn
+// - arrays compare each element in turn.
+// Otherwise identical arrays compare by length.
+// - interface values compare first by reflect.Type describing the concrete type
+// and then by concrete value as described in the previous rules.
+//
+func Sort(mapValue reflect.Value) *SortedMap {
+ if mapValue.Type().Kind() != reflect.Map {
+ return nil
+ }
+ key := make([]reflect.Value, mapValue.Len())
+ value := make([]reflect.Value, len(key))
+ iter := mapValue.MapRange()
+ for i := 0; iter.Next(); i++ {
+ key[i] = iter.Key()
+ value[i] = iter.Value()
+ }
+ sorted := &SortedMap{
+ Key: key,
+ Value: value,
+ }
+ sort.Stable(sorted)
+ return sorted
+}
+
+// compare compares two values of the same type. It returns -1, 0, 1
+// according to whether a > b (1), a == b (0), or a < b (-1).
+// If the types differ, it returns -1.
+// See the comment on Sort for the comparison rules.
+func compare(aVal, bVal reflect.Value) int {
+ aType, bType := aVal.Type(), bVal.Type()
+ if aType != bType {
+ return -1 // No good answer possible, but don't return 0: they're not equal.
+ }
+ switch aVal.Kind() {
+ case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+ a, b := aVal.Int(), bVal.Int()
+ switch {
+ case a < b:
+ return -1
+ case a > b:
+ return 1
+ default:
+ return 0
+ }
+ case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+ a, b := aVal.Uint(), bVal.Uint()
+ switch {
+ case a < b:
+ return -1
+ case a > b:
+ return 1
+ default:
+ return 0
+ }
+ case reflect.String:
+ a, b := aVal.String(), bVal.String()
+ switch {
+ case a < b:
+ return -1
+ case a > b:
+ return 1
+ default:
+ return 0
+ }
+ case reflect.Float32, reflect.Float64:
+ return floatCompare(aVal.Float(), bVal.Float())
+ case reflect.Complex64, reflect.Complex128:
+ a, b := aVal.Complex(), bVal.Complex()
+ if c := floatCompare(real(a), real(b)); c != 0 {
+ return c
+ }
+ return floatCompare(imag(a), imag(b))
+ case reflect.Bool:
+ a, b := aVal.Bool(), bVal.Bool()
+ switch {
+ case a == b:
+ return 0
+ case a:
+ return 1
+ default:
+ return -1
+ }
+ case reflect.Ptr:
+ a, b := aVal.Pointer(), bVal.Pointer()
+ switch {
+ case a < b:
+ return -1
+ case a > b:
+ return 1
+ default:
+ return 0
+ }
+ case reflect.Chan:
+ if c, ok := nilCompare(aVal, bVal); ok {
+ return c
+ }
+ ap, bp := aVal.Pointer(), bVal.Pointer()
+ switch {
+ case ap < bp:
+ return -1
+ case ap > bp:
+ return 1
+ default:
+ return 0
+ }
+ case reflect.Struct:
+ for i := 0; i < aVal.NumField(); i++ {
+ if c := compare(aVal.Field(i), bVal.Field(i)); c != 0 {
+ return c
+ }
+ }
+ return 0
+ case reflect.Array:
+ for i := 0; i < aVal.Len(); i++ {
+ if c := compare(aVal.Index(i), bVal.Index(i)); c != 0 {
+ return c
+ }
+ }
+ return 0
+ case reflect.Interface:
+ if c, ok := nilCompare(aVal, bVal); ok {
+ return c
+ }
+ c := compare(reflect.ValueOf(aType), reflect.ValueOf(bType))
+ if c != 0 {
+ return c
+ }
+ return compare(aVal.Elem(), bVal.Elem())
+ default:
+ // Certain types cannot appear as keys (maps, funcs, slices), but be explicit.
+ panic("bad type in compare: " + aType.String())
+ }
+}
+
+// nilCompare checks whether either value is nil. If not, the boolean is false.
+// If either value is nil, the boolean is true and the integer is the comparison
+// value. The comparison is defined to be 0 if both are nil, otherwise the one
+// nil value compares low. Both arguments must represent a chan, func,
+// interface, map, pointer, or slice.
+func nilCompare(aVal, bVal reflect.Value) (int, bool) {
+ if aVal.IsNil() {
+ if bVal.IsNil() {
+ return 0, true
+ }
+ return -1, true
+ }
+ if bVal.IsNil() {
+ return 1, true
+ }
+ return 0, false
+}
+
+// floatCompare compares two floating-point values. NaNs compare low.
+func floatCompare(a, b float64) int {
+ switch {
+ case isNaN(a):
+ return -1 // No good answer if b is a NaN so don't bother checking.
+ case isNaN(b):
+ return 1
+ case a < b:
+ return -1
+ case a > b:
+ return 1
+ }
+ return 0
+}
+
+func isNaN(a float64) bool {
+ return a != a
+}
--- /dev/null
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fmtsort_test
+
+import (
+ "fmt"
+ "internal/fmtsort"
+ "math"
+ "reflect"
+ "strings"
+ "testing"
+)
+
+var compareTests = [][]reflect.Value{
+ ct(reflect.TypeOf(int(0)), -1, 0, 1),
+ ct(reflect.TypeOf(int8(0)), -1, 0, 1),
+ ct(reflect.TypeOf(int16(0)), -1, 0, 1),
+ ct(reflect.TypeOf(int32(0)), -1, 0, 1),
+ ct(reflect.TypeOf(int64(0)), -1, 0, 1),
+ ct(reflect.TypeOf(uint(0)), 0, 1, 5),
+ ct(reflect.TypeOf(uint8(0)), 0, 1, 5),
+ ct(reflect.TypeOf(uint16(0)), 0, 1, 5),
+ ct(reflect.TypeOf(uint32(0)), 0, 1, 5),
+ ct(reflect.TypeOf(uint64(0)), 0, 1, 5),
+ ct(reflect.TypeOf(uintptr(0)), 0, 1, 5),
+ ct(reflect.TypeOf(string("")), "", "a", "ab"),
+ ct(reflect.TypeOf(float32(0)), math.NaN(), math.Inf(-1), -1e10, 0, 1e10, math.Inf(1)),
+ ct(reflect.TypeOf(float64(0)), math.NaN(), math.Inf(-1), -1e10, 0, 1e10, math.Inf(1)),
+ ct(reflect.TypeOf(complex64(0+1i)), -1-1i, -1+0i, -1+1i, 0-1i, 0+0i, 0+1i, 1-1i, 1+0i, 1+1i),
+ ct(reflect.TypeOf(complex128(0+1i)), -1-1i, -1+0i, -1+1i, 0-1i, 0+0i, 0+1i, 1-1i, 1+0i, 1+1i),
+ ct(reflect.TypeOf(false), false, true),
+ ct(reflect.TypeOf(&ints[0]), &ints[0], &ints[1], &ints[2]),
+ ct(reflect.TypeOf(chans[0]), chans[0], chans[1], chans[2]),
+ ct(reflect.TypeOf(toy{}), toy{0, 1}, toy{0, 2}, toy{1, -1}, toy{1, 1}),
+ ct(reflect.TypeOf([2]int{}), [2]int{1, 1}, [2]int{1, 2}, [2]int{2, 0}),
+ ct(reflect.TypeOf(interface{}(interface{}(0))), iFace, 1, 2, 3),
+}
+
+var iFace interface{}
+
+func ct(typ reflect.Type, args ...interface{}) []reflect.Value {
+ value := make([]reflect.Value, len(args))
+ for i, v := range args {
+ x := reflect.ValueOf(v)
+ if !x.IsValid() { // Make it a typed nil.
+ x = reflect.Zero(typ)
+ } else {
+ x = x.Convert(typ)
+ }
+ value[i] = x
+ }
+ return value
+}
+
+func TestCompare(t *testing.T) {
+ for _, test := range compareTests {
+ for i, v0 := range test {
+ for j, v1 := range test {
+ c := fmtsort.Compare(v0, v1)
+ var expect int
+ switch {
+ case i == j:
+ expect = 0
+ // NaNs are tricky.
+ if typ := v0.Type(); (typ.Kind() == reflect.Float32 || typ.Kind() == reflect.Float64) && math.IsNaN(v0.Float()) {
+ expect = -1
+ }
+ case i < j:
+ expect = -1
+ case i > j:
+ expect = 1
+ }
+ if c != expect {
+ t.Errorf("%s: compare(%v,%v)=%d; expect %d", v0.Type(), v0, v1, c, expect)
+ }
+ }
+ }
+ }
+}
+
+type sortTest struct {
+ data interface{} // Always a map.
+ print string // Printed result using our custom printer.
+}
+
+var sortTests = []sortTest{
+ {
+ map[int]string{7: "bar", -3: "foo"},
+ "-3:foo 7:bar",
+ },
+ {
+ map[uint8]string{7: "bar", 3: "foo"},
+ "3:foo 7:bar",
+ },
+ {
+ map[string]string{"7": "bar", "3": "foo"},
+ "3:foo 7:bar",
+ },
+ {
+ map[float64]string{7: "bar", -3: "foo", math.NaN(): "nan", math.Inf(0): "inf"},
+ "NaN:nan -3:foo 7:bar +Inf:inf",
+ },
+ {
+ map[complex128]string{7 + 2i: "bar2", 7 + 1i: "bar", -3: "foo", complex(math.NaN(), 0i): "nan", complex(math.Inf(0), 0i): "inf"},
+ "(NaN+0i):nan (-3+0i):foo (7+1i):bar (7+2i):bar2 (+Inf+0i):inf",
+ },
+ {
+ map[bool]string{true: "true", false: "false"},
+ "false:false true:true",
+ },
+ {
+ chanMap(),
+ "CHAN0:0 CHAN1:1 CHAN2:2",
+ },
+ {
+ pointerMap(),
+ "PTR0:0 PTR1:1 PTR2:2",
+ },
+ {
+ map[toy]string{toy{7, 2}: "72", toy{7, 1}: "71", toy{3, 4}: "34"},
+ "{3 4}:34 {7 1}:71 {7 2}:72",
+ },
+ {
+ map[[2]int]string{{7, 2}: "72", {7, 1}: "71", {3, 4}: "34"},
+ "[3 4]:34 [7 1]:71 [7 2]:72",
+ },
+ {
+ map[interface{}]string{7: "7", 4: "4", 3: "3", nil: "nil"},
+ "<nil>:nil 3:3 4:4 7:7",
+ },
+}
+
+func sprint(data interface{}) string {
+ om := fmtsort.Sort(reflect.ValueOf(data))
+ if om == nil {
+ return "nil"
+ }
+ b := new(strings.Builder)
+ for i, key := range om.Key {
+ if i > 0 {
+ b.WriteRune(' ')
+ }
+ b.WriteString(sprintKey(key))
+ b.WriteRune(':')
+ b.WriteString(fmt.Sprint(om.Value[i]))
+ }
+ return b.String()
+}
+
+// sprintKey formats a reflect.Value but gives reproducible values for some
+// problematic types such as pointers. Note that it only does special handling
+// for the troublesome types used in the test cases; it is not a general
+// printer.
+func sprintKey(key reflect.Value) string {
+ switch str := key.Type().String(); str {
+ case "*int":
+ ptr := key.Interface().(*int)
+ for i := range ints {
+ if ptr == &ints[i] {
+ return fmt.Sprintf("PTR%d", i)
+ }
+ }
+ return "PTR???"
+ case "chan int":
+ c := key.Interface().(chan int)
+ for i := range chans {
+ if c == chans[i] {
+ return fmt.Sprintf("CHAN%d", i)
+ }
+ }
+ return "CHAN???"
+ default:
+ return fmt.Sprint(key)
+ }
+}
+
+var (
+ ints [3]int
+ chans = [3]chan int{make(chan int), make(chan int), make(chan int)}
+)
+
+func pointerMap() map[*int]string {
+ m := make(map[*int]string)
+ for i := 2; i >= 0; i-- {
+ m[&ints[i]] = fmt.Sprint(i)
+ }
+ return m
+}
+
+func chanMap() map[chan int]string {
+ m := make(map[chan int]string)
+ for i := 2; i >= 0; i-- {
+ m[chans[i]] = fmt.Sprint(i)
+ }
+ return m
+}
+
+type toy struct {
+ A int // Exported.
+ b int // Unexported.
+}
+
+func TestOrder(t *testing.T) {
+ for _, test := range sortTests {
+ got := sprint(test.data)
+ if got != test.print {
+ t.Errorf("%s: got %q, want %q", reflect.TypeOf(test.data), got, test.print)
+ }
+ }
+}