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tailscale/util/slicesx/slicesx.go

45 lines
1.1 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package slicesx contains some helpful generic slice functions.
package slicesx
import "math/rand"
// Interleave combines two slices of the form [a, b, c] and [x, y, z] into a
// slice with elements interleaved; i.e. [a, x, b, y, c, z].
func Interleave[S ~[]T, T any](a, b S) S {
// Avoid allocating an empty slice.
if a == nil && b == nil {
return nil
}
var (
i int
ret = make([]T, 0, len(a)+len(b))
)
for i = 0; i < len(a) && i < len(b); i++ {
ret = append(ret, a[i], b[i])
}
ret = append(ret, a[i:]...)
ret = append(ret, b[i:]...)
return ret
}
// Shuffle randomly shuffles a slice in-place, similar to rand.Shuffle.
func Shuffle[S ~[]T, T any](s S) {
// TODO(andrew): use a pooled Rand?
// This is the same Fisher-Yates shuffle implementation as rand.Shuffle
n := len(s)
i := n - 1
for ; i > 1<<31-1-1; i-- {
j := int(rand.Int63n(int64(i + 1)))
s[i], s[j] = s[j], s[i]
}
for ; i > 0; i-- {
j := int(rand.Int31n(int32(i + 1)))
s[i], s[j] = s[j], s[i]
}
}