From 06820530048a9570390b5501350d4fbe6c621f07 Mon Sep 17 00:00:00 2001
From: Adam Sampson <ats@offog.org>
Date: Mon, 5 May 2003 02:52:54 +0000
Subject: [PATCH] Abstract persistability out into a couple of classes.

---
 rawdoglib/__init__.py  |  2 +-
 rawdoglib/persister.py | 61 ++++++++++++++++++++++++++++++++++++++++++
 rawdoglib/rawdog.py    | 27 ++++++-------------
 3 files changed, 70 insertions(+), 20 deletions(-)
 create mode 100644 rawdoglib/persister.py

diff --git a/rawdoglib/__init__.py b/rawdoglib/__init__.py
index 0b2a0f1..e191d68 100644
--- a/rawdoglib/__init__.py
+++ b/rawdoglib/__init__.py
@@ -1 +1 @@
-__all__ = ['rssparser', 'timeoutsocket', 'rawdog']
+__all__ = ['rssparser', 'timeoutsocket', 'rawdog', 'persister']
diff --git a/rawdoglib/persister.py b/rawdoglib/persister.py
new file mode 100644
index 0000000..2ed830f
--- /dev/null
+++ b/rawdoglib/persister.py
@@ -0,0 +1,61 @@
+# rawdog: RSS aggregator without delusions of grandeur.
+# Copyright 2003 Adam Sampson <azz@us-lot.org>
+#
+# rawdog is free software; you can redistribute and/or modify it
+# under the terms of that license as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option)
+# any later version.
+#
+# rawdog is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with rawdog; see the file COPYING. If not, write to the
+# Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+# MA 02111-1307 USA, or see http://www.gnu.org/.
+
+import pickle, fcntl
+
+class Persistable:
+	"""Something which can be persisted. When a subclass of this wants to
+	   indicate that it has been modified, it should call
+	   self.modified()."""
+	def __init__(self): self._modified = 0
+	def modified(self, state = 1): self._modified = state
+	def is_modified(self): return self._modified
+
+class Persister:
+	"""Persist another class to a file, safely. The class being persisted
+	   must derive from Persistable (although this isn't enforced)."""
+
+	def __init__(self, filename, klass):
+		self.filename = filename
+		self.klass = klass
+		self.file = None
+		self.object = None
+
+	def load(self):
+		"""Load the persisted object from the file, or create a new one
+		   if this isn't possible. Returns the loaded object."""
+		try:
+			self.file = open(self.filename, "r+")
+			fcntl.lockf(self.file.fileno(), fcntl.LOCK_EX)
+			self.object = pickle.load(self.file)
+			self.object.modified(0)
+		except IOError:
+			self.file = open(self.filename, "w+")
+			fcntl.lockf(self.file.fileno(), fcntl.LOCK_EX)
+			self.object = self.klass()
+			self.object.modified()
+		return self.object
+
+	def save(self):
+		"""Save the persisted object back to the file if necessary."""
+		if self.object.is_modified():
+			self.file.seek(0)
+			self.file.truncate(0)
+			pickle.dump(self.object, self.file)
+		self.file.close()
+
diff --git a/rawdoglib/rawdog.py b/rawdoglib/rawdog.py
index 02f7e7d..c22e53a 100644
--- a/rawdoglib/rawdog.py
+++ b/rawdoglib/rawdog.py
@@ -18,7 +18,8 @@
 
 VERSION = "0.4"
 import rssparser
-import pickle, os, fcntl, time, sha
+from persister import Persistable, Persister
+import os, time, sha
 
 def format_time(secs, config):
 	"""Format a time and date nicely."""
@@ -204,7 +205,7 @@ class Config:
 		else:
 			raise ConfigError("Unknown config command: " + l[0])
 
-class Rawdog:
+class Rawdog(Persistable):
 	"""The aggregator itself."""
 
 	def __init__(self):
@@ -240,7 +241,7 @@ class Rawdog:
 				del self.articles[key]
 
 		self.last_update = now
-		self.changed = 1
+		self.modified()
 
 	def write(self, config):
 		outputfile = config["outputfile"]
@@ -370,17 +371,9 @@ def main(argv):
 	except ConfigError, err:
 		print err
 		return 1
-	
-	try:
-		f = open("state", "r+")
-		fcntl.lockf(f.fileno(), fcntl.LOCK_EX)
-		rawdog = pickle.load(f)
-		rawdog.changed = 0
-	except IOError:
-		f = open("state", "w+")
-		fcntl.lockf(f.fileno(), fcntl.LOCK_EX)
-		rawdog = Rawdog()
-		rawdog.changed = 1
+
+	persister = Persister("state", Rawdog)	
+	rawdog = persister.load()
 
 	for action in argv:
 		if action == "list":
@@ -393,11 +386,7 @@ def main(argv):
 			print "Unknown action: " + action
 			return 1
 
-	if rawdog.changed:
-		f.seek(0)
-		f.truncate(0)
-		pickle.dump(rawdog, f)
-	f.close()
+	persister.save()
 
 	return 0
 
-- 
2.35.1