'''
Module for gathering disk information on Windows

:depends:   - win32api Python module
'''

# Import python libs
import ctypes
import string

# Import salt libs
try:
    import win32api
    IS_WINDOWS = True
except ImportError:
    IS_WINDOWS = False


def __virtual__():
    '''
    Only works on Windows systems
    '''
    if not IS_WINDOWS:
        return False
    return 'disk'


def usage():
    '''
    Return usage information for volumes mounted on this minion

    CLI Example::

        salt '*' disk.usage
    '''
    if __grains__['kernel'] == 'Windows':
        drives = []
        ret = {}
        drive_bitmask = ctypes.windll.kernel32.GetLogicalDrives()
        for letter in string.uppercase:
            if drive_bitmask & 1:
                drives.append(letter)
            drive_bitmask >>= 1
        for drive in drives:
            try:
                (sectorspercluster,
                 bytespersector,
                 freeclusters,
                 totalclusters) = win32api.GetDiskFreeSpace(
                     '{0}:\\'.format(drive)
                 )
                totalsize = sectorspercluster * bytespersector * totalclusters
                available_space = (
                    sectorspercluster * bytespersector * freeclusters
                )
                used = totalsize - available_space
                capacity = int(used / float(totalsize) * 100)
                ret['{0}:\\'.format(drive)] = {
                    'filesystem': '{0}:\\'.format(drive),
                    '1K-blocks': totalsize,
                    'used': used,
                    'available': available_space,
                    'capacity': '{0}%'.format(capacity),
                }
            except Exception:
                ret['{0}:\\'.format(drive)] = {
                    'filesystem': '{0}:\\'.format(drive),
                    '1K-blocks': None,
                    'used': None,
                    'available': None,
                    'capacity': None,
                }
        return ret

'''
Module for gathering disk information on Windows

:depends:   - win32api Python module
'''

# Import python libs
import ctypes
import string

# Import salt libs
try:
    import win32api
    IS_WINDOWS = True
except ImportError:
    IS_WINDOWS = False


def __virtual__():
    '''
    Only works on Windows systems
    '''
    if not IS_WINDOWS:
        return False
    return 'disk'


def usage():
    '''
    Return usage information for volumes mounted on this minion

    CLI Example::

        salt '*' disk.usage
    '''
    drives = []
    ret = {}
    drive_bitmask = ctypes.windll.kernel32.GetLogicalDrives()
    for letter in string.uppercase:
        if drive_bitmask & 1:
            drives.append(letter)
        drive_bitmask >>= 1
    for drive in drives:
        try:
            (sectorspercluster,
             bytespersector,
             freeclusters,
             totalclusters) = win32api.GetDiskFreeSpace(
                 '{0}:\\'.format(drive)
             )
            totalsize = sectorspercluster * bytespersector * totalclusters
            available_space = (
                sectorspercluster * bytespersector * freeclusters
            )
            used = totalsize - available_space
            capacity = int(used / float(totalsize) * 100)
            ret['{0}:\\'.format(drive)] = {
                'filesystem': '{0}:\\'.format(drive),
                '1K-blocks': totalsize,
                'used': used,
                'available': available_space,
                'capacity': '{0}%'.format(capacity),
            }
        except Exception:
            ret['{0}:\\'.format(drive)] = {
                'filesystem': '{0}:\\'.format(drive),
                '1K-blocks': None,
                'used': None,
                'available': None,
                'capacity': None,
            }
    return ret

Remove redundant os check