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101 lines
2.5 KiB
Go
101 lines
2.5 KiB
Go
//+build windows
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package file
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import (
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"os"
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"syscall"
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"unsafe"
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"github.com/pkg/errors"
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"golang.org/x/sys/windows"
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)
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var (
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ntdll = windows.NewLazySystemDLL("ntdll.dll")
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ntQueryVolumeInformationFile = ntdll.NewProc("NtQueryVolumeInformationFile")
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ntSetInformationFile = ntdll.NewProc("NtSetInformationFile")
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)
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type fileAllocationInformation struct {
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AllocationSize uint64
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}
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type fileFsSizeInformation struct {
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TotalAllocationUnits uint64
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AvailableAllocationUnits uint64
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SectorsPerAllocationUnit uint32
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BytesPerSector uint32
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}
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type ioStatusBlock struct {
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Status, Information uintptr
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}
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// PreallocateImplemented is a constant indicating whether the
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// implementation of Preallocate actually does anything.
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const PreallocateImplemented = true
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// PreAllocate the file for performance reasons
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func PreAllocate(size int64, out *os.File) error {
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if size <= 0 {
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return nil
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}
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var (
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iosb ioStatusBlock
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fsSizeInfo fileFsSizeInformation
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allocInfo fileAllocationInformation
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)
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// Query info about the block sizes on the file system
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_, _, e1 := ntQueryVolumeInformationFile.Call(
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uintptr(out.Fd()),
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uintptr(unsafe.Pointer(&iosb)),
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uintptr(unsafe.Pointer(&fsSizeInfo)),
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uintptr(unsafe.Sizeof(fsSizeInfo)),
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uintptr(3), // FileFsSizeInformation
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)
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if e1 != nil && e1 != syscall.Errno(0) {
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return errors.Wrap(e1, "preAllocate NtQueryVolumeInformationFile failed")
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}
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// Calculate the allocation size
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clusterSize := uint64(fsSizeInfo.BytesPerSector) * uint64(fsSizeInfo.SectorsPerAllocationUnit)
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if clusterSize <= 0 {
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return errors.Errorf("preAllocate clusterSize %d <= 0", clusterSize)
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}
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allocInfo.AllocationSize = (1 + uint64(size-1)/clusterSize) * clusterSize
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// Ask for the allocation
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_, _, e1 = ntSetInformationFile.Call(
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uintptr(out.Fd()),
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uintptr(unsafe.Pointer(&iosb)),
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uintptr(unsafe.Pointer(&allocInfo)),
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uintptr(unsafe.Sizeof(allocInfo)),
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uintptr(19), // FileAllocationInformation
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)
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if e1 != nil && e1 != syscall.Errno(0) {
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return errors.Wrap(e1, "preAllocate NtSetInformationFile failed")
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}
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return nil
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}
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const (
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FSCTL_SET_SPARSE = 0x000900c4
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)
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// SetSparseImplemented is a constant indicating whether the
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// implementation of SetSparse actually does anything.
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const SetSparseImplemented = true
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// SetSparse makes the file be a sparse file
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func SetSparse(out *os.File) error {
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err := syscall.DeviceIoControl(syscall.Handle(out.Fd()), FSCTL_SET_SPARSE, nil, 0, nil, 0, nil, nil)
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if err != nil {
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return errors.Wrap(err, "DeviceIoControl FSCTL_SET_SPARSE")
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}
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return nil
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}
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