util/uniq,types/lazy,*: delete code that's now in Go std

sync.OnceValue and slices.Compact were both added in Go 1.21.

cmp.Or was added in Go 1.22.

Updates #8632
Updates #11058

Change-Id: I89ba4c404f40188e1f8a9566c8aaa049be377754
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

util/uniq/slice.go

@@ -1,62 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-// Package uniq provides removal of adjacent duplicate elements in slices.
-// It is similar to the unix command uniq.
-package uniq
-
-// ModifySlice removes adjacent duplicate elements from the given slice. It
-// adjusts the length of the slice appropriately and zeros the tail.
-//
-// ModifySlice does O(len(*slice)) operations.
-func ModifySlice[E comparable](slice *[]E) {
-	// Remove duplicates
-	dst := 0
-	for i := 1; i < len(*slice); i++ {
-		if (*slice)[i] == (*slice)[dst] {
-			continue
-		}
-		dst++
-		(*slice)[dst] = (*slice)[i]
-	}
-
-	// Zero out the elements we removed at the end of the slice
-	end := dst + 1
-	var zero E
-	for i := end; i < len(*slice); i++ {
-		(*slice)[i] = zero
-	}
-
-	// Truncate the slice
-	if end < len(*slice) {
-		*slice = (*slice)[:end]
-	}
-}
-
-// ModifySliceFunc is the same as ModifySlice except that it allows using a
-// custom comparison function.
-//
-// eq should report whether the two provided elements are equal.
-func ModifySliceFunc[E any](slice *[]E, eq func(i, j E) bool) {
-	// Remove duplicates
-	dst := 0
-	for i := 1; i < len(*slice); i++ {
-		if eq((*slice)[dst], (*slice)[i]) {
-			continue
-		}
-		dst++
-		(*slice)[dst] = (*slice)[i]
-	}
-
-	// Zero out the elements we removed at the end of the slice
-	end := dst + 1
-	var zero E
-	for i := end; i < len(*slice); i++ {
-		(*slice)[i] = zero
-	}
-
-	// Truncate the slice
-	if end < len(*slice) {
-		*slice = (*slice)[:end]
-	}
-}

util/uniq/slice_test.go

@@ -1,102 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package uniq_test
-
-import (
-	"reflect"
-	"strconv"
-	"testing"
-
-	"tailscale.com/util/uniq"
-)
-
-func runTests(t *testing.T, cb func(*[]uint32)) {
-	tests := []struct {
-		// Use uint32 to be different from an int-typed slice index
-		in   []uint32
-		want []uint32
-	}{
-		{in: []uint32{0, 1, 2}, want: []uint32{0, 1, 2}},
-		{in: []uint32{0, 1, 2, 2}, want: []uint32{0, 1, 2}},
-		{in: []uint32{0, 0, 1, 2}, want: []uint32{0, 1, 2}},
-		{in: []uint32{0, 1, 0, 2}, want: []uint32{0, 1, 0, 2}},
-		{in: []uint32{0}, want: []uint32{0}},
-		{in: []uint32{0, 0}, want: []uint32{0}},
-		{in: []uint32{}, want: []uint32{}},
-	}
-
-	for _, test := range tests {
-		in := make([]uint32, len(test.in))
-		copy(in, test.in)
-		cb(&test.in)
-		if !reflect.DeepEqual(test.in, test.want) {
-			t.Errorf("uniq.Slice(%v) = %v, want %v", in, test.in, test.want)
-		}
-		start := len(test.in)
-		test.in = test.in[:cap(test.in)]
-		for i := start; i < len(in); i++ {
-			if test.in[i] != 0 {
-				t.Errorf("uniq.Slice(%v): non-0 in tail of %v at index %v", in, test.in, i)
-			}
-		}
-	}
-}
-
-func TestModifySlice(t *testing.T) {
-	runTests(t, func(slice *[]uint32) {
-		uniq.ModifySlice(slice)
-	})
-}
-
-func TestModifySliceFunc(t *testing.T) {
-	runTests(t, func(slice *[]uint32) {
-		uniq.ModifySliceFunc(slice, func(i, j uint32) bool {
-			return i == j
-		})
-	})
-}
-
-func Benchmark(b *testing.B) {
-	benches := []struct {
-		name  string
-		reset func(s []byte)
-	}{
-		{name: "AllDups",
-			reset: func(s []byte) {
-				for i := range s {
-					s[i] = '*'
-				}
-			},
-		},
-		{name: "NoDups",
-			reset: func(s []byte) {
-				for i := range s {
-					s[i] = byte(i)
-				}
-			},
-		},
-	}
-
-	for _, bb := range benches {
-		b.Run(bb.name, func(b *testing.B) {
-			for size := 1; size <= 4096; size *= 16 {
-				b.Run(strconv.Itoa(size), func(b *testing.B) {
-					benchmark(b, 64, bb.reset)
-				})
-			}
-		})
-	}
-}
-
-func benchmark(b *testing.B, size int64, reset func(s []byte)) {
-	b.ReportAllocs()
-	b.SetBytes(size)
-	s := make([]byte, size)
-	b.ResetTimer()
-	for range b.N {
-		s = s[:size]
-		reset(s)
-		uniq.ModifySlice(&s)
-	}
-}