- fixed issue #133 by adding a new SubnetSplitter class

5 files changed, 155 insertions, 0 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 78a8406..dd3746c 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,4 +1,35 @@
 ---------------
+Release: 0.7.19
+---------------
+Date: ? Sep 2016
+
+^^^^^^^^^^^^^^^^^^^^
+Changes since 0.7.18
+^^^^^^^^^^^^^^^^^^^^
+
+* added a new SubnetSplitter class for those looking to divide up subnets.
+  Thanks alanwill and RyPeck and those on (Stack Overflow discussion).
+
+* removed bundled pytest dependency code for "python setup.py test".
+
+* setup.py now uses setuptools only (no more distutils) and setup_egg.py removed.
+
+* cleaned up INSTALL docs so they accurately reflect current Python packaging.
+
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Specific bug fixes addressed in this release
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+FIXED Issue 133: https://github.com/drkjam/netaddr/issues/133
+    - Splitting a single network into multiple prefixed networks
+
+FIXED Issue 129: https://github.com/drkjam/netaddr/issues/129
+    - fix IPAddress().netmask_bits to return 0 for 0.0.0.0 and [::] addresses
+
+FIXED Issue 117: https://github.com/drkjam/netaddr/issues/117
+    - (python setup.py test) failing with python3 >= 3.5
+
+---------------
 Release: 0.7.18
 ---------------
 Date: 4 Sep 2015
diff --git a/netaddr/__init__.py b/netaddr/__init__.py
index 3b81257..383f75c 100644
--- a/netaddr/__init__.py
+++ b/netaddr/__init__.py
@@ -44,3 +44,5 @@ from netaddr.strategy.eui48 import (mac_eui48, mac_unix, mac_unix_expanded,
 
 from netaddr.strategy.eui64 import (eui64_base, eui64_unix, eui64_unix_expanded,
         eui64_cisco, eui64_bare, valid_str as valid_eui64)
+
+from netaddr.contrib.subnet_splitter import SubnetSplitter
diff --git a/netaddr/contrib/__init__.py b/netaddr/contrib/__init__.py
new file mode 100644
index 0000000..c5d098b
--- /dev/null
+++ b/netaddr/contrib/__init__.py
@@ -0,0 +1,7 @@
+"""
+The netaddr.contrib namespace for non-core code contributed by users.
+
+It is a testing ground for new ideas. Depending on the interest in
+functionality found here, code may find its way into the core in various
+ways, either as is or as additions to existing APIs.
+"""
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)
diff --git a/netaddr/tests/ip/test_ip_splitter.py b/netaddr/tests/ip/test_ip_splitter.py
new file mode 100644
index 0000000..0db4bf7
--- /dev/null
+++ b/netaddr/tests/ip/test_ip_splitter.py
@@ -0,0 +1,74 @@
+import pytest
+
+from netaddr.ip import IPNetwork
+from netaddr.contrib.subnet_splitter import SubnetSplitter
+
+
+def test_ip_splitter():
+    splitter = SubnetSplitter('172.24.0.0/16')
+    assert splitter.available_subnets() == [IPNetwork('172.24.0.0/16')]
+
+    assert splitter.extract_subnet(23, count=4) == [
+        IPNetwork('172.24.0.0/23'),
+        IPNetwork('172.24.2.0/23'),
+        IPNetwork('172.24.4.0/23'),
+        IPNetwork('172.24.6.0/23'),
+    ]
+
+    assert splitter.available_subnets() == [
+        IPNetwork('172.24.8.0/21'),
+        IPNetwork('172.24.16.0/20'),
+        IPNetwork('172.24.32.0/19'),
+        IPNetwork('172.24.64.0/18'),
+        IPNetwork('172.24.128.0/17'),
+    ]
+
+    assert splitter.extract_subnet(28, count=10) == [
+        IPNetwork('172.24.8.0/28'),
+        IPNetwork('172.24.8.16/28'),
+        IPNetwork('172.24.8.32/28'),
+        IPNetwork('172.24.8.48/28'),
+        IPNetwork('172.24.8.64/28'),
+        IPNetwork('172.24.8.80/28'),
+        IPNetwork('172.24.8.96/28'),
+        IPNetwork('172.24.8.112/28'),
+        IPNetwork('172.24.8.128/28'),
+        IPNetwork('172.24.8.144/28'),
+    ]
+
+    splitter.available_subnets() ==  [
+        IPNetwork('172.24.8.128/25'),
+        IPNetwork('172.24.9.0/24'),
+        IPNetwork('172.24.10.0/23'),
+        IPNetwork('172.24.12.0/22'),
+        IPNetwork('172.24.16.0/20'),
+        IPNetwork('172.24.32.0/19'),
+        IPNetwork('172.24.64.0/18'),
+        IPNetwork('172.24.128.0/17'),
+    ]
+
+
+def test_ip_splitter_remove_same_input_range():
+    s = SubnetSplitter('172.24.0.0/16')
+    assert s.available_subnets() == [IPNetwork('172.24.0.0/16')]
+
+    assert s.extract_subnet(16, count=1) == [
+        IPNetwork('172.24.0.0/16'),
+    ]
+
+    assert s.available_subnets() == []
+
+
+def test_ip_splitter_remove_more_than_input_range():
+    s = SubnetSplitter('172.24.0.0/16')
+    assert s.available_subnets() == [IPNetwork('172.24.0.0/16')]
+
+    with pytest.raises(ValueError):
+        s.extract_subnet(16, count=2)
+
+
+def test_ip_splitter_remove_prefix_larger_than_input_range():
+    s = SubnetSplitter('172.24.0.0/16')
+    assert s.available_subnets() == [IPNetwork('172.24.0.0/16')]
+    assert s.extract_subnet(15, count=1) == []
+    assert s.available_subnets() == [IPNetwork('172.24.0.0/16')]