Libevent HTTP Router

C/C++ extension for HTTP handling with libevent

About

evhttp-router is a simple extension of the evhttp interface, with improved support for pattern based routing and per-method HTTP handler functions. It is intended to replace the existing evhttp_set_cb and evhttp_set_gencb functions.

Usage

evhttp-router has both a C and C++ interface. It is a static library with no additional dependencies besides libevent.

Integration

The most simplest way to include evhttp-router in your project is to use a vcpkg overlay port. If vcpkg is not available in your project, you can copy the source and header files and include them in your CMake build system. The only dependency is libevent.

Limitations

To avoid making this extension bloated, overcomplicated, or intrusive, most design decisions were made with a bias towards simplicity. As a result, the following limitation should be noted:

• thread safety - the underlying routing table is not protected by any synchronization primitives such that routes should be added while there are requests being served. While it is possible to add handlers at any time, it must be done on a single thread. It is therefore recommended that all routes are defined before the event_base is dispatched. Once the loop is running, requests can be served from multiple threads, as the table is only modified when new handlers are added.

• pattern validation - there are no safeguards against defining routes that are ambiguous. If two routes map to the same location in the table, the more recent handler will overwrite the existing handler. While there is a basic mechanism for rejecting invalid patterns, any valid pattern will be mapped without further validation.

• runtime safeguards - in an effort to minimize both source and binary sizes, there are no checks or assertions for errors like array boundary violations or unexpected NULL handles. This extension is intended to augment code that already works, so incorret usage will lead to crashes and segmentation faults. To mitigate potential problems in this approach, the API is thorougly documented and tested.