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mmap_unix.go
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mmap_unix.go
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package mmap
import (
"errors"
"fmt"
"math/rand"
"os"
"syscall"
"unsafe"
)
const (
PROT_READ = syscall.PROT_READ
PROT_WRITE = syscall.PROT_WRITE
PROT_EXEC = syscall.PROT_EXEC
MAP_SHARED = syscall.MAP_SHARED
MAP_PRIVATE = syscall.MAP_PRIVATE
MAP_COPY = MAP_PRIVATE
)
// Offset returns the valid offset.
func Offset(offset int64) int64 {
pageSize := int64(os.Getpagesize())
return offset / pageSize * pageSize
}
func protFlags(p Prot) (prot int, flags int) {
prot = PROT_READ
flags = MAP_SHARED
if p&WRITE != 0 {
prot |= PROT_WRITE
}
if p© != 0 {
flags = MAP_COPY
}
if p&EXEC != 0 {
prot |= PROT_EXEC
}
return
}
func (m *File) mmap(fd int, offset int64, length int, prot int, flags int) (*File, error) {
data, err := syscall.Mmap(fd, offset, length, prot, flags)
if err != nil {
return nil, err
}
key := byte(rand.Uint32())
m.key = &key
m.data[m.key] = data
m.length = int64(length)
return m, nil
}
func (m *File) Flush() error {
if !m.dirty {
return nil
}
_, _, err := syscall.Syscall(syscall.SYS_MSYNC, uintptr(unsafe.Pointer(&m.data[m.key][0])), uintptr(m.length), uintptr(syscall.MS_SYNC))
if err != 0 {
return err
}
m.dirty = false
return nil
}
func (m *File) fLock() error {
if err := syscall.Flock(int(m.rawFile.Fd()), syscall.LOCK_SH|syscall.LOCK_NB); err != nil {
return errors.New(fmt.Sprintf("add checkpoint exclusive lock failed: %v", err))
}
return nil
}
func (m *File) fUnLock() error {
return syscall.Flock(int(m.rawFile.Fd()), syscall.LOCK_UN)
}
func (m *File) unmap() (err error) {
return syscall.Munmap(m.data[m.key])
}