github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/tcpip/transport/tcp/connect_unsafe.go (about)

     1  // Copyright 2018 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  package tcp
    16  
    17  import (
    18  	"reflect"
    19  	"unsafe"
    20  )
    21  
    22  // optionsToArray converts a slice of capacity >-= maxOptionSize to an array.
    23  //
    24  // optionsToArray panics if the capacity of options is smaller than
    25  // maxOptionSize.
    26  func optionsToArray(options []byte) *[maxOptionSize]byte {
    27  	// Reslice to full capacity.
    28  	options = options[0:maxOptionSize]
    29  	return (*[maxOptionSize]byte)(unsafe.Pointer((*reflect.SliceHeader)(unsafe.Pointer(&options)).Data))
    30  }