MOUNTMGR_MOUNT_POINTS - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTIOAPI_H

// Output structure for IOCTL_MOUNTMGR_DELETE_POINTS, IOCTL_MOUNTMGR_QUERY_POINTS, and IOCTL_MOUNTMGR_DELETE_POINTS_DBONLY.
typedef struct _MOUNTMGR_MOUNT_POINTS
{
    ULONG Size;
    ULONG NumberOfMountPoints;
    _Field_size_(NumberOfMountPoints) MOUNTMGR_MOUNT_POINT MountPoints[1];
} MOUNTMGR_MOUNT_POINTS, *PMOUNTMGR_MOUNT_POINTS;

#endif

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This structure is documented in Windows Driver Kit.