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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package memutil provides utilities for working with shared memory files.
package memutil
import (
"reflect"
"unsafe"
"golang.org/x/sys/unix"
)
// MapSlice is like MapFile, but returns a slice instead of a uintptr.
func MapSlice(addr, size, prot, flags, fd, offset uintptr) ([]byte, error) {
addr, err := MapFile(addr, size, prot, flags, fd, offset)
if err != nil {
return nil, err
}
var slice []byte
hdr := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
hdr.Data = addr
hdr.Len = int(size)
hdr.Cap = int(size)
return slice, nil
}
// UnmapSlice unmaps a mapping returned by MapSlice.
func UnmapSlice(slice []byte) error {
hdr := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
_, _, err := unix.RawSyscall6(unix.SYS_MUNMAP, uintptr(unsafe.Pointer(hdr.Data)), uintptr(hdr.Cap), 0, 0, 0, 0)
return err
}
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