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package util
import (
"os"
"reflect"
"unsafe"
"golang.org/x/sys/windows"
)
type MappedRegion struct {
windows.Handle
Data []byte
addr uintptr
}
func MapRegion(f *os.File, offset int64, size int32) (*MappedRegion, error) {
maxSize := offset + int64(size)
h, err := windows.CreateFileMapping(
windows.Handle(f.Fd()), nil, windows.PAGE_READWRITE,
uint32(maxSize>>32), uint32(maxSize), nil)
if h == 0 {
return nil, err
}
const allocationGranularity = 64 * 1024
align := offset % allocationGranularity
offset -= align
a, err := windows.MapViewOfFile(h, windows.FILE_MAP_WRITE,
uint32(offset>>32), uint32(offset), uintptr(size)+uintptr(align))
if a == 0 {
windows.CloseHandle(h)
return nil, err
}
ret := &MappedRegion{Handle: h, addr: a}
// SliceHeader, although deprecated, avoids a go vet warning.
sh := (*reflect.SliceHeader)(unsafe.Pointer(&ret.Data))
sh.Data = a + uintptr(align)
sh.Len = int(size)
sh.Cap = int(size)
return ret, nil
}
func (r *MappedRegion) Unmap() error {
if r.Data == nil {
return nil
}
err := windows.UnmapViewOfFile(r.addr)
if err != nil {
return err
}
r.Data = nil
return windows.CloseHandle(r.Handle)
}
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