1 files changed, 41 insertions, 0 deletions
diff --git a/netaddr/contrib/subnet_splitter.py b/netaddr/contrib/subnet_splitter.py
new file mode 100644
index 0000000..2e39d41
--- /dev/null
+++ b/netaddr/contrib/subnet_splitter.py
@@ -0,0 +1,41 @@
+from netaddr.ip import IPNetwork, cidr_exclude, cidr_merge
+
+
+class SubnetSplitter(object):
+    """
+    A handy utility class that takes a single (large) subnet and allows
+    smaller subnet within its range to be extracted by CIDR prefix. Any
+    leaving address space is available for subsequent extractions until
+    all space is exhausted.
+    """
+    def __init__(self, base_cidr):
+        """
+        Constructor.
+
+        :param base_cidr: an IPv4 or IPv6 address with a CIDR prefix.
+            (see IPNetwork.__init__ for full details).
+        """
+        self._subnets = set([IPNetwork(base_cidr)])
+
+    def extract_subnet(self, prefix, count=None):
+        """Extract 1 or more subnets of size specified by CIDR prefix."""
+        for cidr in self.available_subnets():
+            subnets = list(cidr.subnet(prefix, count=count))
+            if not subnets:
+                continue
+            self.remove_subnet(cidr)
+            self._subnets = self._subnets.union(
+                set(
+                    cidr_exclude(cidr, cidr_merge(subnets)[0])
+                )
+            )
+            return subnets
+        return []
+
+    def available_subnets(self):
+        """Returns a list of the currently available subnets."""
+        return sorted(self._subnets, key=lambda x: x.prefixlen, reverse=True)
+
+    def remove_subnet(self, ip_network):
+        """Remove a specified IPNetwork from available address space."""
+        self._subnets.remove(ip_network)