github.com/metacubex/gvisor@v0.0.0-20240320004321-933faba989ec/pkg/memutil/memutil_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 memutil provides utilities for working with shared memory files.
    16  package memutil
    17  
    18  import (
    19  	"reflect"
    20  	"unsafe"
    21  
    22  	"golang.org/x/sys/unix"
    23  )
    24  
    25  // MapSlice is like MapFile, but returns a slice instead of a uintptr.
    26  func MapSlice(addr, size, prot, flags, fd, offset uintptr) ([]byte, error) {
    27  	addr, err := MapFile(addr, size, prot, flags, fd, offset)
    28  	if err != nil {
    29  		return nil, err
    30  	}
    31  	var slice []byte
    32  	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
    33  	hdr.Data = addr
    34  	hdr.Len = int(size)
    35  	hdr.Cap = int(size)
    36  	return slice, nil
    37  }
    38  
    39  // UnmapSlice unmaps a mapping returned by MapSlice.
    40  func UnmapSlice(slice []byte) error {
    41  	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
    42  	_, _, err := unix.RawSyscall6(unix.SYS_MUNMAP, uintptr(unsafe.Pointer(hdr.Data)), uintptr(hdr.Cap), 0, 0, 0, 0)
    43  	return err
    44  }