mirror of
https://github.com/opencloud-eu/opencloud.git
synced 2026-05-07 12:01:27 -05:00
Michael Barz
72 lines
2.0 KiB
Go
72 lines
2.0 KiB
Go
/*
|
|
* Copyright 2020 Dgraph Labs, Inc. and Contributors
|
|
*
|
|
* 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 z
|
|
|
|
import (
|
|
"os"
|
|
"unsafe"
|
|
|
|
"golang.org/x/sys/unix"
|
|
)
|
|
|
|
// mmap uses the mmap system call to memory-map a file. If writable is true,
|
|
// memory protection of the pages is set so that they may be written to as well.
|
|
func mmap(fd *os.File, writable bool, size int64) ([]byte, error) {
|
|
mtype := unix.PROT_READ
|
|
if writable {
|
|
mtype |= unix.PROT_WRITE
|
|
}
|
|
return unix.Mmap(int(fd.Fd()), 0, int(size), mtype, unix.MAP_SHARED)
|
|
}
|
|
|
|
// munmap unmaps a previously mapped slice.
|
|
//
|
|
// unix.Munmap maintains an internal list of mmapped addresses, and only calls munmap
|
|
// if the address is present in that list. If we use mremap, this list is not updated.
|
|
// To bypass this, we call munmap ourselves.
|
|
func munmap(data []byte) error {
|
|
if len(data) == 0 || len(data) != cap(data) {
|
|
return unix.EINVAL
|
|
}
|
|
_, _, errno := unix.Syscall(
|
|
unix.SYS_MUNMAP,
|
|
uintptr(unsafe.Pointer(&data[0])),
|
|
uintptr(len(data)),
|
|
0,
|
|
)
|
|
if errno != 0 {
|
|
return errno
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// madvise uses the madvise system call to give advise about the use of memory
|
|
// when using a slice that is memory-mapped to a file. Set the readahead flag to
|
|
// false if page references are expected in random order.
|
|
func madvise(b []byte, readahead bool) error {
|
|
flags := unix.MADV_NORMAL
|
|
if !readahead {
|
|
flags = unix.MADV_RANDOM
|
|
}
|
|
return unix.Madvise(b, flags)
|
|
}
|
|
|
|
// msync writes any modified data to persistent storage.
|
|
func msync(b []byte) error {
|
|
return unix.Msync(b, unix.MS_SYNC)
|
|
}
|