P4 is a domain specific language to configure packet processing pipelines in programmable dataplane switches, and is a powerful idea towards realizing the goal of flexible software-defined networks. This paper presents pcube, a framework that provides a set of primitives to simplify the development of P4-based dataplane applications. pcube provides primitives for loops, summations, and other common operations on indexed state variables, which can be embedded within P4 code and unrolled by the pcube preprocessor. pcube also provides primitives to synchronize state variables across switches in distributed dataplane applications, which are automatically translated into P4 code to send and receive synchronization messages across multiple switches by pcube. We build example dataplane applications such as a distributed load balancer in our framework, and show that using pcube reduces the programming effort (in term of lines of code) significantly-by a factor of up to 5.4x.