diff --git a/database.py b/database.py
index 2d970e3..12569d3 100644
--- a/database.py
+++ b/database.py
@@ -20,7 +20,7 @@ PathType = enum.Enum('PathType', 'Rule Hostname Zone Asn Ip4 Ip6')
 RulePath = typing.Union[None]
 Asn = int
 DomainPath = typing.List[str]
-Ip4Path = typing.List[int]
+Ip4Path = typing.Tuple[int, int]  # value, prefixlen
 Ip6Path = typing.List[int]
 Path = typing.Union[RulePath, DomainPath, Asn, Ip4Path, Ip6Path]
 TypedPath = typing.Tuple[PathType, Path]
@@ -139,33 +139,33 @@ class Database(Profiler):
 
     @staticmethod
     def pack_ip4address(address: str) -> Ip4Path:
-        addr: Ip4Path = [0] * 32
-        octets = [int(octet) for octet in address.split('.')]
-        for b in range(32):
-            if (octets[b//8] >> b % 8) & 0b1:
-                addr[b] = 1
-        return addr
+        addr = 0
+        for split in address.split('.'):
+            addr = addr << 4 + int(split)
+        return (addr, 32)
 
     @staticmethod
     def unpack_ip4address(address: Ip4Path) -> str:
+        addr, prefixlen = address
+        assert prefixlen == 32
+        octets: typing.List[int] = list()
         octets = [0] * 4
-        for b, bit in enumerate(address):
-            octets[b//8] = (octets[b//8] << 1) + bit
+        for o in reversed(range(4)):
+            octets[o] = addr & 0xFF
+            addr >>= 8
         return '.'.join(map(str, octets))
 
     @staticmethod
     def pack_ip4network(network: str) -> Ip4Path:
         address, prefixlen_str = network.split('/')
         prefixlen = int(prefixlen_str)
-        return Database.pack_ip4address(address)[:prefixlen]
+        addr, _ = Database.pack_ip4address(address)
+        return (addr, prefixlen)
 
     @staticmethod
     def unpack_ip4network(network: Ip4Path) -> str:
-        address = network.copy()
-        prefixlen = len(network)
-        for _ in range(32-prefixlen):
-            address.append(0)
-        addr = Database.unpack_ip4address(address)
+        address, prefixlen = network
+        addr = Database.unpack_ip4address((address, 32))
         return f'{addr}/{prefixlen}'
 
     def update_references(self) -> None:
@@ -224,20 +224,19 @@ class Database(Profiler):
 
     def get_ip4(self, ip4_str: str) -> typing.Iterable[TypedPath]:
         self.enter_step('get_ip4_pack')
-        ip4 = self.pack_ip4address(ip4_str)
+        ip4, prefixlen = self.pack_ip4address(ip4_str)
         self.enter_step('get_ip4_brws')
         dic = self.ip4tree
-        depth = 0
-        for part in ip4:
+        for i in reversed(range(prefixlen)):
+            part = (ip4 >> i) & 0b1
             if dic.match:
                 self.enter_step('get_ip4_yield')
-                yield (PathType.Ip4, ip4[:depth])
+                yield (PathType.Ip4, (ip4, 32-i))
             self.enter_step('get_ip4_brws')
             next_dic = dic.children[part]
             if next_dic is None:
                 return
             dic = next_dic
-            depth += 1
         if dic.match:
             self.enter_step('get_ip4_yield')
             yield (PathType.Ip4, ip4)
@@ -307,10 +306,11 @@ class Database(Profiler):
         self.enter_step('set_ip4add_pack')
         if is_first_party or source:
             raise NotImplementedError
+        ip4, prefixlen = self.pack_ip4address(ip4address_str)
         self.enter_step('set_ip4add_brws')
-        ip4address = self.pack_ip4address(ip4address_str)
         dic = self.ip4tree
-        for part in ip4address:
+        for i in reversed(range(prefixlen)):
+            part = (ip4 >> i) & 0b1
             if dic.match:
                 # Refuse to add ip4address whose network is already matching
                 return
@@ -330,9 +330,10 @@ class Database(Profiler):
         if is_first_party or source:
             raise NotImplementedError
         self.enter_step('set_ip4net_brws')
-        ip4network = self.pack_ip4network(ip4network_str)
+        ip4, prefixlen = self.pack_ip4network(ip4network_str)
         dic = self.ip4tree
-        for part in ip4network:
+        for i in reversed(range(prefixlen)):
+            part = (ip4 >> i) & 0b1
             if dic.match:
                 # Refuse to add ip4network whose parent network
                 # is already matching