2 files changed, 71 insertions, 3 deletions

diff --git a/lib/git/index.py b/lib/git/index.py
index d8ba6e18..9a55da15 100644
--- a/lib/git/index.py
+++ b/lib/git/index.py
@@ -15,6 +15,7 @@ import tempfile
 import os
 import stat
 from git.objects import Blob, Tree
+from git.utils import SHA1Writer
 
 class _TemporaryFileSwap(object):
 	"""
@@ -205,11 +206,20 @@ class Index(object):
 		count = 0
 		while count < num_entries:
 			entry = self._read_entry(stream)
-			self.entries[(entry.path,entry.stage)] = entry
+			self.entries[(entry.path, entry.stage)] = entry
 			count += 1
 		# END for each entry
-		# this data chunk is the footer of the index, don't yet know what it is for
+		
+		# the footer contains extension data and a sha on the content so far
+		# Keep the extension footer,and verify we have a sha in the end
 		self._extension_data = stream.read(~0)
+		assert len(self._extension_data) > 19, "Index Footer was not at least a sha on content as it was only %i bytes in size" % len(self._extension_data)
+		
+		content_sha = self._extension_data[-20:]
+		
+		# truncate the sha in the end as we will dynamically create it anyway 
+		self._extension_data = self._extension_data[:-20]
+		
 	
 	@classmethod
 	def from_file(cls, repo, file_path):
@@ -296,6 +306,8 @@ class Index(object):
 		Note
 			Index writing based on the dulwich implementation
 		"""
+		stream = SHA1Writer(stream)
+		
 		# header
 		stream.write("DIRC")
 		stream.write(struct.pack(">LL", self.version, len(self.entries)))
@@ -306,9 +318,13 @@ class Index(object):
 		for entry in entries_sorted:
 			self._write_cache_entry(stream, entry)
 		# END for each entry
-		# write extension_data which we currently cannot interprete
+		
+		# write previously cached extensions data
 		stream.write(self._extension_data)
 		
+		# write the sha over the content
+		stream.write_sha()
+		
 	
 	@classmethod
 	def from_tree(cls, repo, *treeish, **kwargs):
diff --git a/lib/git/utils.py b/lib/git/utils.py
index 2aa8d33e..cdc7c55b 100644
--- a/lib/git/utils.py
+++ b/lib/git/utils.py
@@ -6,6 +6,58 @@
 
 import os
 
+try:
+    import hashlib
+except ImportError:
+    import sha
+
+def make_sha(source=''):
+    """
+    A python2.4 workaround for the sha/hashlib module fiasco
+    
+	Note
+		From the dulwich project
+	"""
+    try:
+        return hashlib.sha1(source)
+    except NameError:
+        sha1 = sha.sha(source)
+        return sha1
+
+
+class SHA1Writer(object):
+    """
+    Wrapper around a file-like object that remembers the SHA1 of 
+    the data written to it. It will write a sha when the stream is closed
+    or if the asked for explicitly usign write_sha.
+    
+    Note:
+    	Based on the dulwich project
+    """
+    __slots__ = ("f", "sha1")
+    
+    def __init__(self, f):
+        self.f = f
+        self.sha1 = make_sha("")
+
+    def write(self, data):
+        self.sha1.update(data)
+        self.f.write(data)
+
+    def write_sha(self):
+        sha = self.sha1.digest()
+        self.f.write(sha)
+        return sha
+
+    def close(self):
+        sha = self.write_sha()
+        self.f.close()
+        return sha
+
+    def tell(self):
+        return self.f.tell()
+
+
 class LazyMixin(object):
 	"""
 	Base class providing an interface to lazily retrieve attribute values upon