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package azblob
import (
"os"
"reflect"
"syscall"
"unsafe"
)
type mmf []byte
func newMMF(file *os.File, writable bool, offset int64, length int) (mmf, error) {
prot, access := uint32(syscall.PAGE_READONLY), uint32(syscall.FILE_MAP_READ) // Assume read-only
if writable {
prot, access = uint32(syscall.PAGE_READWRITE), uint32(syscall.FILE_MAP_WRITE)
}
hMMF, errno := syscall.CreateFileMapping(syscall.Handle(file.Fd()), nil, prot, uint32(int64(length)>>32), uint32(int64(length)&0xffffffff), nil)
if hMMF == 0 {
return nil, os.NewSyscallError("CreateFileMapping", errno)
}
defer syscall.CloseHandle(hMMF)
addr, errno := syscall.MapViewOfFile(hMMF, access, uint32(offset>>32), uint32(offset&0xffffffff), uintptr(length))
m := mmf{}
h := (*reflect.SliceHeader)(unsafe.Pointer(&m))
h.Data = addr
h.Len = length
h.Cap = h.Len
return m, nil
}
func (m *mmf) unmap() {
addr := uintptr(unsafe.Pointer(&(([]byte)(*m)[0])))
*m = mmf{}
err := syscall.UnmapViewOfFile(addr)
if err != nil {
panic(err)
}
}
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