Added last-modifed and HEAD support

lib/python/OFS/Image.py

 """Image object"""
 
-__version__='$Revision: 1.29 $'[11:-2]
+__version__='$Revision: 1.30 $'[11:-2]
 
 import Globals
 from Globals import HTMLFile, MessageDialog
@@ -8,7 +8,7 @@ from AccessControl.Role import RoleManager
 from SimpleItem import Item_w__name__
 from Persistence import Persistent
 from Acquisition import Implicit
-
+from DateTime import DateTime
 
 
 class Pdata(Persistent, Implicit):
@@ -77,18 +77,39 @@ class File(Persistent,Implicit,RoleManager,Item_w__name__):
 	self.__name__=id
 	self.title=title
 	self.size=len(self.data)
+	self.setLastModifiedHeader()
 
     def id(self): return self.__name__
 
+    def getLastModifiedHeader(self):
+	"""Return a timestamp string representing the last
+	   modification time, in a format that can used in
+           an HTTP header."""
+	if hasattr(self, 'hmod'):
+	    return self.hmod
+	self.hmodified=DateTime().toZone('GMT').rfc822()
+	return self.hmodified
+
+    def setLastModifiedHeader(self, ts=None):
+	"""Set the timestamp string representing the last
+	   modification time to the given string. The time
+           stamp string must be expressed in GMT, in rfc822
+	   format. If no string is specified, a timestamp
+	   representing the current time will be used."""
+	if ts: self.hmodified=ts
+	else:  self.hmodified=DateTime().toZone('GMT').rfc822()	    
+
     def index_html(self, RESPONSE):
 	""" """
-	RESPONSE['content-type']=self.content_type
+	RESPONSE['content-type'] =self.content_type
+	RESPONSE['last-modified']=self.getLastModifiedHeader()
         return self.data
 
     def manage_edit(self,title,content_type,REQUEST=None):
 	""" """
 	self.title=title
 	self.content_type=content_type
+	self.setLastModifiedHeader()
 	if REQUEST: return MessageDialog(
 		    title  ='Success!',
 		    message='Your changes have been saved',
@@ -100,16 +121,25 @@ class File(Persistent,Implicit,RoleManager,Item_w__name__):
 	data=file.read()
 	self.data=Pdata(data)
 	self.size=len(data)
+	self.setLastModifiedHeader()
 	if REQUEST: return MessageDialog(
 		    title  ='Success!',
 		    message='Your changes have been saved',
 		    action ='manage_main')
 
+    HEAD__roles__=None
+    def HEAD(self, REQUEST, RESPONSE):
+	""" """
+	RESPONSE['content-type'] =self.content_type
+	RESPONSE['last-modified']=self.getLastModifiedHeader()
+	return ''
+
     PUT__roles__=['Manager']
     def PUT(self, BODY, REQUEST):
 	'handle PUT requests'
 	self.data=Pdata(BODY)
 	self.size=len(BODY)
+	self.setLastModifiedHeader()
 	try:
 	    type=REQUEST['CONTENT_TYPE']
 	    if type: self.content_type=type