Not sure about C++ overhead there. C++ often edges out C in the alioth benchmarks. More to the point, I highly doubt the author's parser ("parser") in http.cpp is faster than the one in nginx, which really is a thing of beauty.
I really love the trick for efficiently reading 4 chars and checking them out of a string. I like it so much I've been working towards making it happen automatically on PyPy so if you write something like:
if buf[i:i+4] == "POST":
the JIT automatically turns that into a MOVL + CMP + JMP. The magic of high level languages :)