shutil: Add disk_usage function.

Signed-off-by: Patrick Joy <patrick@joytech.com.au>

python-stdlib/shutil/manifest.py

@@ -1,3 +1,3 @@
-metadata(version="0.0.3")
+metadata(version="0.0.4")
 
 module("shutil.py")

python-stdlib/shutil/shutil.py

@@ -1,5 +1,8 @@
 # Reimplement, because CPython3.3 impl is rather bloated
 import os
+from collections import namedtuple
+
+_ntuple_diskusage = namedtuple("usage", ("total", "used", "free"))
 
 
 def rmtree(top):
@@ -27,3 +30,13 @@ def copyfileobj(src, dest, length=512):
             if not buf:
                 break
             dest.write(buf)
+
+
+def disk_usage(path):
+    bit_tuple = os.statvfs(path)
+    blksize = bit_tuple[0]  # system block size
+    total = bit_tuple[2] * blksize
+    free = bit_tuple[3] * blksize
+    used = total - free
+
+    return _ntuple_diskusage(total, used, free)