3629 

  3630 

  3631 def _estimatememory():

  3632     """Provide an estimate for the available system memory in Bytes.

  3633 

  3634     If no estimate can be provided on the platform, returns None.

  3635     """

  3636     if pycompat.sysplatform.startswith(b'win'):

  3637         # On Windows, use the GlobalMemoryStatusEx kernel function directly.

  3638         from ctypes import c_long as DWORD, c_ulonglong as DWORDLONG

  3639         from ctypes.wintypes import Structure, byref, sizeof, windll

  3640 

  3641         class MEMORYSTATUSEX(Structure):

  3642             _fields_ = [

  3643                 ('dwLength', DWORD),

  3644                 ('dwMemoryLoad', DWORD),

  3645                 ('ullTotalPhys', DWORDLONG),

  3646                 ('ullAvailPhys', DWORDLONG),

  3647                 ('ullTotalPageFile', DWORDLONG),

  3648                 ('ullAvailPageFile', DWORDLONG),

  3649                 ('ullTotalVirtual', DWORDLONG),

  3650                 ('ullAvailVirtual', DWORDLONG),

  3651                 ('ullExtendedVirtual', DWORDLONG),

  3652             ]

  3653 

  3654         x = MEMORYSTATUSEX()

  3655         x.dwLength = sizeof(x)

  3656         windll.kernel32.GlobalMemoryStatusEx(byref(x))

  3657         return x.ullAvailPhys

  3658 

  3659     # On newer Unix-like systems and Mac OSX, the sysconf interface

  3660     # can be used. _SC_PAGE_SIZE is part of POSIX; _SC_PHYS_PAGES

  3661     # seems to be implemented on most systems.

  3662     try:

  3663         pagesize = os.sysconf(os.sysconf_names['SC_PAGE_SIZE'])

  3664         pages = os.sysconf(os.sysconf_names['SC_PHYS_PAGES'])

  3665         return pagesize * pages

  3666     except OSError:  # sysconf can fail

  3667         pass

  3668     except KeyError:  # unknown parameter

  3669         pass