md5 for ruby gridfs too

lib/mongo/gridfs/grid_store.rb

@@ -67,6 +67,8 @@ module XGen
 
         attr_accessor :lineno
 
+        attr_reader :md5
+
         class << self
 
           def exist?(db, name, root_collection=DEFAULT_ROOT_COLLECTION)
@@ -142,6 +144,7 @@ module XGen
             @aliases = doc['aliases']
             @length = doc['length']
             @metadata = doc['metadata']
+            @md5 = doc['md5']
           else
             @files_id = XGen::Mongo::Driver::ObjectID.new
             @content_type = DEFAULT_CONTENT_TYPE
@@ -426,6 +429,10 @@ module XGen
           h['uploadDate'] = @upload_date
           h['aliases'] = @aliases
           h['metadata'] = @metadata
+          md5_command = OrderedHash.new
+          md5_command['filemd5'] = @files_id
+          md5_command['root'] = @root
+          h['md5'] = @db.db_command(md5_command)['md5']
           h
         end
 

tests/test_grid_store.rb

@@ -208,6 +208,23 @@ class GridStoreTest < Test::Unit::TestCase
     }
   end
 
+  def test_md5
+    GridStore.open(@@db, 'new-file', 'w') { |f| f.write("hello world\n")}
+    GridStore.open(@@db, 'new-file', 'r') { |f|
+      assert f.md5 == '6f5902ac237024bdd0c176cb93063dc4'
+      begin
+        f.md5 = 'cant do this'
+        fail "should have seen error"
+      rescue => ex
+        true
+      end
+    }
+    GridStore.open(@@db, 'new-file', 'w') {}
+    GridStore.open(@@db, 'new-file', 'r') { |f|
+      assert f.md5 == 'd41d8cd98f00b204e9800998ecf8427e'
+    }
+  end
+
   def test_upload_date
     now = Time.now
     orig_file_upload_date = nil