1 files changed, 52 insertions, 0 deletions
diff --git a/Lib/packaging/pypi/mirrors.py b/Lib/packaging/pypi/mirrors.py
new file mode 100644
index 0000000000..a646acff3c
--- /dev/null
+++ b/Lib/packaging/pypi/mirrors.py
@@ -0,0 +1,52 @@
+"""Utilities related to the mirror infrastructure defined in PEP 381."""
+
+from string import ascii_lowercase
+import socket
+
+DEFAULT_MIRROR_URL = "last.pypi.python.org"
+
+
+def get_mirrors(hostname=None):
+    """Return the list of mirrors from the last record found on the DNS
+    entry::
+
+    >>> from packaging.pypi.mirrors import get_mirrors
+    >>> get_mirrors()
+    ['a.pypi.python.org', 'b.pypi.python.org', 'c.pypi.python.org',
+    'd.pypi.python.org']
+
+    """
+    if hostname is None:
+        hostname = DEFAULT_MIRROR_URL
+
+    # return the last mirror registered on PyPI.
+    try:
+        hostname = socket.gethostbyname_ex(hostname)[0]
+    except socket.gaierror:
+        return []
+    end_letter = hostname.split(".", 1)
+
+    # determine the list from the last one.
+    return ["%s.%s" % (s, end_letter[1]) for s in string_range(end_letter[0])]
+
+
+def string_range(last):
+    """Compute the range of string between "a" and last.
+
+    This works for simple "a to z" lists, but also for "a to zz" lists.
+    """
+    for k in range(len(last)):
+        for x in product(ascii_lowercase, repeat=(k + 1)):
+            result = ''.join(x)
+            yield result
+            if result == last:
+                return
+
+
+def product(*args, **kwds):
+    pools = [tuple(arg) for arg in args] * kwds.get('repeat', 1)
+    result = [[]]
+    for pool in pools:
+        result = [x + [y] for x in result for y in pool]
+    for prod in result:
+        yield tuple(prod)