New parser set_option function for controlling independent size limits
on headers and body. By default request and response parsers are set up
with reasonable limits to prevent resource exhaustion attacks.
* Parser adheres strictly to rfc7230
* Increased test coverage
* Headers and body maximum size limit options
Core:
* Test buffer_cat iterator move members
HTTP:
* Fixed yield / resume in writer
* Fixed message serialization with chunked encoding
* Test yield / resume in writer
* Test all conditional branches during message serialization
* Test chunked encoding
* Increase coverage on parse_error
* Add parse_error::general
WebSocket:
* Add error::general
* Increase coverage in error
The basic_parser is rewritten to be header-only. The nodejs parser is
removed from the include subtree and placed into the test directory.
Other changes:
* Parser specific error codes in parse_error.hpp
* Add parser-bench performance testing, nodejs vs beast
* New random message generator for fuzz tests
* Test for header-only parser using random message generator
* Augmented some existing message tests to check more cases
