Implement increment/decrement on cache storage engines, using read/write by...

Implement increment/decrement on cache storage engines, using read/write by default and using atomic command on memcache

actionpack/test/controller/session/mem_cache_store_test.rb

@@ -62,9 +62,8 @@ def test_storage
       assert_equal d, s.cache.get(session_key)[:test]
       assert_equal d, s[:test]
     end
-  end
-
-
+  end         
+  
   def test_deletion
     new_session do |s|
       session_key = 'session:' + s.session_id

activesupport/lib/active_support/cache.rb

@@ -87,8 +87,25 @@ def delete(key, options = nil)
 
       def delete_matched(matcher, options = nil)
         log("delete matched", matcher.inspect, options)
+      end       
+      
+      def increment(key, amount = 1)
+        log("incrementing", key, amount)
+        if num = read(key)
+          write(key, num + amount)
+        else
+          nil
+        end
       end
 
+      def decrement(key, amount = 1)
+        log("decrementing", key, amount)
+        if num = read(key)
+          write(key, num - amount)
+        else
+          nil
+        end
+      end
       
       private
         def log(operation, key, options)

activesupport/lib/active_support/cache/mem_cache_store.rb

@@ -48,8 +48,26 @@ def delete(key, options = nil)
       rescue MemCache::MemCacheError => e
         logger.error("MemCacheError (#{e}): #{e.message}")
         false
+      end              
+
+      def increment(key, amount = 1)       
+        log("incrementing", key, amount)
+        
+        response = @data.incr(key, amount)  
+        response == Response::NOT_FOUND ? nil : response
+      rescue MemCache::MemCacheError 
+        nil
       end
 
+      def decrement(key, amount = 1)
+        log("decrement", key, amount)
+        
+        response = data.decr(key, amount) 
+        response == Response::NOT_FOUND ? nil : response
+      rescue MemCache::MemCacheError 
+        nil
+      end        
+      
       def delete_matched(matcher, options = nil)
         super
         raise "Not supported by Memcache"