tailscale/util/uniq/slice.go

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// Copyright (c) 2020 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.
// 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]
}
}