import os
import platform
import resource

_scale = {'kB': 1024, 'mB': 1024*1024,
    'KB': 1024, 'MB': 1024*1024}

def resident():
    if platform.system() == 'Windows':
        from wmi import WMI
        w = WMI('.')
        result = w.query("SELECT WorkingSet FROM Win32_PerfRawData_PerfProc_Process WHERE IDProcess=%d" % os.getpid())
        return int(result[0].WorkingSet)
    elif platform.system() == 'SunOS':
        with open('/proc/%d/as' % os.getpid()) as f:
            f.seek( 0, 2 )
            v = f.tell()
        return float(v)
    elif platform.system() == 'FreeBSD':
        return resource.getrusage(resource.RUSAGE_SELF).ru_maxrss * 1024
    else:
        with open('/proc/%d/status' % os.getpid()) as f:
            v = f.read()
        i = v.index('VmRSS:')
        v = v[i:].split(None, 3)
        #assert len(v) == 3, v
        return float(v[1]) * _scale[v[2]]