mirror of
https://github.com/tailscale/tailscale.git
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66 lines
1.5 KiB
Go
66 lines
1.5 KiB
Go
// Copyright (c) 2020 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 uniq provides removal of adjacent duplicate elements in slices.
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// It is similar to the unix command uniq.
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package uniq
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import (
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"fmt"
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"reflect"
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)
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type badTypeError struct {
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typ reflect.Type
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}
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func (e badTypeError) Error() string {
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return fmt.Sprintf("uniq.ModifySlice's first argument must have type *[]T, got %v", e.typ)
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}
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// ModifySlice removes adjacent duplicate elements from the slice pointed to by sliceptr.
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// It adjusts the length of the slice appropriately and zeros the tail.
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// eq reports whether (*sliceptr)[i] and (*sliceptr)[j] are equal.
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// ModifySlice does O(len(*sliceptr)) operations.
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func ModifySlice(sliceptr any, eq func(i, j int) bool) {
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rvp := reflect.ValueOf(sliceptr)
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if rvp.Type().Kind() != reflect.Ptr {
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panic(badTypeError{rvp.Type()})
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}
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rv := rvp.Elem()
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if rv.Type().Kind() != reflect.Slice {
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panic(badTypeError{rvp.Type()})
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}
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length := rv.Len()
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dst := 0
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for i := 1; i < length; i++ {
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if eq(dst, i) {
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continue
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}
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dst++
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// slice[dst] = slice[i]
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rv.Index(dst).Set(rv.Index(i))
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}
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end := dst + 1
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var zero reflect.Value
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if end < length {
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zero = reflect.Zero(rv.Type().Elem())
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}
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// for i := range slice[end:] {
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// size[i] = 0/nil/{}
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// }
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for i := end; i < length; i++ {
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// slice[i] = 0/nil/{}
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rv.Index(i).Set(zero)
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}
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// slice = slice[:end]
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if end < length {
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rv.SetLen(end)
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}
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}
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