1 // Copyright 2023 The gVisor Authors.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 15 //go:build go1.13 && !go1.20
16 // +build go1.13,!go1.20
17 18 // TODO(go.dev/issue/8422): Remove this once Go 1.19 is no longer supported,
19 // and update callers to use unsafe.Slice directly.
20 21 package gohacks
22 23 import (
24 "unsafe"
25 )
26 27 // sliceHeader is equivalent to reflect.SliceHeader, but represents the pointer
28 // to the underlying array as unsafe.Pointer rather than uintptr, allowing
29 // sliceHeaders to be directly converted to slice objects.
30 type sliceHeader struct {
31 Data unsafe.Pointer
32 Len int
33 Cap int
34 }
35 36 // Slice returns a slice whose underlying array starts at ptr an which length
37 // and capacity are len.
38 func Slice[T any](ptr *T, length int) []T {
39 var s []T
40 hdr := (*sliceHeader)(unsafe.Pointer(&s))
41 hdr.Data = unsafe.Pointer(ptr)
42 hdr.Len = length
43 hdr.Cap = length
44 return s
45 }
46