restic/internal/fs/preallocate_darwin.go

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package fs
import (
"os"
"golang.org/x/sys/unix"
)
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func PreallocateFile(wr *os.File, size int64) error {
// try contiguous first
fst := unix.Fstore_t{
Flags: unix.F_ALLOCATECONTIG | unix.F_ALLOCATEALL,
Posmode: unix.F_PEOFPOSMODE,
Offset: 0,
Length: size,
}
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err := unix.FcntlFstore(wr.Fd(), unix.F_PREALLOCATE, &fst)
if err == nil {
return nil
}
// just take preallocation in any form, but still ask for everything
fst.Flags = unix.F_ALLOCATEALL
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err = unix.FcntlFstore(wr.Fd(), unix.F_PREALLOCATE, &fst)
return err
}