Caching resolver; DOESN'T work. Should remove this.

1 files changed, 39 insertions, 12 deletions

diff --git a/project2/proj2_s4498062/dns/cache.py b/project2/proj2_s4498062/dns/cache.py
index 3ef14b3..a3a9304 100644
--- a/project2/proj2_s4498062/dns/cache.py
+++ b/project2/proj2_s4498062/dns/cache.py
@@ -7,6 +7,7 @@ It is highly recommended to use these.
 """
 
 import json
+import time
 
 from dns.resource import ResourceRecord, RecordData
 from dns.types import Type
@@ -22,11 +23,12 @@ class ResourceEncoder(json.JSONEncoder):
     def default(self, obj):
         if isinstance(obj, ResourceRecord):
             return {
-                "name": obj.name,
-                "type": Type.to_string(obj.type_),
-                "class": Class.to_string(obj.class_),
-                "ttl": obj.ttl,
-                "rdata": obj.rdata.data
+                "name":       obj.name,
+                "type":       Type.to_string(obj.type_),
+                "class":      Class.to_string(obj.class_),
+                "ttl":        obj.ttl,
+                "rdata":      obj.rdata.data,
+                "timestamp":  obj.timestamp
             }
         return json.JSONEncoder.default(self, obj)
 
@@ -42,20 +44,33 @@ def resource_from_json(dct):
     class_ = Class.from_string(dct["class"])
     ttl = dct["ttl"]
     rdata = RecordData.create(type_, dct["rdata"])
-    return ResourceRecord(name, type_, class_, ttl, rdata)
+    timestamp = dct["timestamp"]
+    return ResourceRecord(name, type_, class_, ttl, rdata, timestamp)
 
 
 class RecordCache(object):
     """ Cache for ResourceRecords """
 
-    def __init__(self, ttl):
+    FILE = '.dns.cache'
+
+    def __init__(self):
         """ Initialize the RecordCache
 
         Args:
             ttl (int): TTL of cached entries (if > 0)
         """
         self.records = []
-        self.ttl = ttl
+        self.read_cache_file()
+
+    def __del__(self):
+        self.write_cache_file()
+
+    def remove_old(self):
+        """Remove entries for which the TTL has expired"""
+        now = int(time.clock())
+        for record in reversed(self.records):
+            if record.ttl + record.timestamp < now:
+                self.records.remove(record)
 
     def lookup(self, dname, type_, class_):
         """ Lookup resource records in cache
@@ -68,7 +83,12 @@ class RecordCache(object):
             type_ (Type): type
             class_ (Class): class
         """
-        pass
+        self.remove_old()
+        for record in self.records:
+            if record.name == dname and \
+                    record.type_ == type_ and \
+                    record.class_ == class_:
+                yield record
 
     def add_record(self, record):
         """ Add a new Record to the cache
@@ -76,12 +96,19 @@ class RecordCache(object):
         Args:
             record (ResourceRecord): the record added to the cache
         """
-        pass
+        self.records.append(record)
 
     def read_cache_file(self):
         """ Read the cache file from disk """
-        pass
+        try:
+            with open(self.FILE, 'r') as jsonfile:
+                self.records = json.load(
+                    jsonfile, object_hook=resource_from_json)
+        except IOError:
+            pass
 
     def write_cache_file(self):
         """ Write the cache file to disk """
-        pass
+        self.remove_old()
+        with open(self.FILE, 'w') as jsonfile:
+            json.dump(self.records, jsonfile, cls=ResourceEncoder, indent=4)