66 lines
1.5 KiB
Go
66 lines
1.5 KiB
Go
|
// 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
|
||
|
|
|
||
|
|
import (
|
||
|
|
"fmt"
|
||
|
|
"reflect"
|
||
|
|
)
|
||
|
|
|
||
|
|
type badTypeError struct {
|
||
|
|
typ reflect.Type
|
||
|
|
}
|
||
|
|
|
||
|
|
func (e badTypeError) Error() string {
|
||
|
|
return fmt.Sprintf("uniq.ModifySlice's first argument must have type *[]T, got %v", e.typ)
|
||
|
|
}
|
||
|
|
|
||
|
|
// ModifySlice removes adjacent duplicate elements from the slice pointed to by sliceptr.
|
||
|
|
// It adjusts the length of the slice appropriately and zeros the tail.
|
||
|
|
// eq reports whether (*sliceptr)[i] and (*sliceptr)[j] are equal.
|
||
|
|
// ModifySlice does O(len(*sliceptr)) operations.
|
||
|
|
func ModifySlice(sliceptr interface{}, eq func(i, j int) bool) {
|
||
|
|
rvp := reflect.ValueOf(sliceptr)
|
||
|
|
if rvp.Type().Kind() != reflect.Ptr {
|
||
|
|
panic(badTypeError{rvp.Type()})
|
||
|
|
}
|
||
|
|
rv := rvp.Elem()
|
||
|
|
if rv.Type().Kind() != reflect.Slice {
|
||
|
|
panic(badTypeError{rvp.Type()})
|
||
|
|
}
|
||
|
|
|
||
|
|
length := rv.Len()
|
||
|
|
dst := 0
|
||
|
|
for i := 1; i < length; i++ {
|
||
|
|
if eq(dst, i) {
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
dst++
|
||
|
|
// slice[dst] = slice[i]
|
||
|
|
rv.Index(dst).Set(rv.Index(i))
|
||
|
|
}
|
||
|
|
|
||
|
|
end := dst + 1
|
||
|
|
var zero reflect.Value
|
||
|
|
if end < length {
|
||
|
|
zero = reflect.Zero(rv.Type().Elem())
|
||
|
|
}
|
||
|
|
|
||
|
|
// for i := range slice[end:] {
|
||
|
|
// size[i] = 0/nil/{}
|
||
|
|
// }
|
||
|
|
for i := end; i < length; i++ {
|
||
|
|
// slice[i] = 0/nil/{}
|
||
|
|
rv.Index(i).Set(zero)
|
||
|
|
}
|
||
|
|
|
||
|
|
// slice = slice[:end]
|
||
|
|
if end < length {
|
||
|
|
rv.SetLen(end)
|
||
|
|
}
|
||
|
|
}
|