github.com/metacubex/gvisor@v0.0.0-20240320004321-933faba989ec/pkg/gohacks/slice_go113_unsafe.go (about)

     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  }