Add transaction support for Tokyo Tyrant Tables

.gitignore

@@ -1,2 +1,4 @@
 .DS_Store
 *.tdb
+*.tct
+.lock

lib/cloudkit/store/memory_table.rb

@@ -59,12 +59,6 @@ def query(&block)
       q.run(self)
     end
 
-    # Simulate a transaction. This development-mode transaction merely yields
-    # to its block.
-    def transaction
-      yield
-    end
-
     protected 
 
     def valid?(record)

lib/cloudkit/store/resource.rb

@@ -49,7 +49,7 @@ def save
     # modify resources that are not current.
     def update(json, remote_user=nil)
       raise HistoricalIntegrityViolation unless current?
-      CloudKit.storage_adapter.transaction do
+      transaction do
         record = CloudKit.storage_adapter[@id]
         record['uri'] = "#{@uri.string}/versions/#{@etag}"
         record['archived'] = escape(true)
@@ -65,7 +65,7 @@ def update(json, remote_user=nil)
     # are not current.
     def delete
       raise HistoricalIntegrityViolation unless current?
-      CloudKit.storage_adapter.transaction do
+      transaction do
         original_uri = @uri
         record = CloudKit.storage_adapter[@id]
         record['uri'] = "#{@uri.string}/versions/#{@etag}"
@@ -254,5 +254,16 @@ def symbolize_keys(hash)
     def escape_values(hash)
       hash.inject({}) { |memo, pair| memo.merge({pair[0] => escape(pair[1])}) }
     end
+
+    def transaction
+      open('.lock', 'w+') do |f|
+        f.flock(File::LOCK_EX)
+        begin 
+          yield
+        ensure
+          f.flock(File::LOCK_UN)
+        end
+      end
+    end
   end
 end