httpserver.c

#include <event2/buffer.h>
#include <event2/event.h>
#include <event2/http.h>
#include <event2/keyvalq_struct.h>

const char *get_query_arg(struct evhttp_request *req, const char *name) {
	// Parse uri
	const struct evhttp_uri *uri = evhttp_request_get_evhttp_uri(req);
	const char *query = evhttp_uri_get_query(uri);

	// Parse query
	struct evkeyvalq kv;
	evhttp_parse_query_str(query, &kv);

	// Find query field
	return evhttp_find_header(&kv, name);
}

void greet_handler(struct evhttp_request *req, void *arg) {
	// Get name from query string
	const char *name = get_query_arg(req, "name");

	// Write response
	struct evbuffer *buf = evbuffer_new();
	evbuffer_add_printf(buf, "Hello %s!\n", name);
	evhttp_send_reply(req, 200, "OK", buf);

	// Cleanup
	evbuffer_free(buf);
}

int main() {
	struct event_base *base;
	struct evhttp *http;

	// Init event loop and http server
	base = event_base_new();
	http = evhttp_new(base);

	// Attach request handlers
	evhttp_set_cb(http, "/hello", greet_handler, NULL);

	// Listen for connections
	evhttp_bind_socket_with_handle(http, "0.0.0.0", 8080);

	// Run event loop
	event_base_dispatch(base);

	// Clean up
	evhttp_free(http);
	event_base_free(base);

	return 0;
}

/*
	Compile and run

	$ clang -levent httpserver.c -o httpserver
	$ ./httpserver

	Benchmarks on my MacBook Pro M1

	$ hey -c 100 -n 100000 "http://localhost:8080/hello?name=world"

	Summary:
	  Total:	1.2842 secs
	  Slowest:	0.0138 secs
	  Fastest:	0.0000 secs
	  Average:	0.0013 secs
	  Requests/sec:	77871.0496

	  Total data:	1300000 bytes
	  Size/request:	13 bytes

	Response time histogram:
	  0.000 [1]	|
	  0.001 [79859]	|■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
	  0.003 [19260]	|■■■■■■■■■■
	  0.004 [649]	|
	  0.006 [31]	|
	  0.007 [0]	|
	  0.008 [84]	|
	  0.010 [20]	|
	  0.011 [18]	|
	  0.012 [41]	|
	  0.014 [37]	|


	Latency distribution:
	  10% in 0.0010 secs
	  25% in 0.0011 secs
	  50% in 0.0012 secs
	  75% in 0.0014 secs
	  90% in 0.0016 secs
	  95% in 0.0018 secs
	  99% in 0.0028 secs

	Details (average, fastest, slowest):
	  DNS+dialup:	0.0000 secs, 0.0000 secs, 0.0138 secs
	  DNS-lookup:	0.0000 secs, 0.0000 secs, 0.0032 secs
	  req write:	0.0000 secs, 0.0000 secs, 0.0020 secs
	  resp wait:	0.0012 secs, 0.0000 secs, 0.0084 secs
	  resp read:	0.0000 secs, 0.0000 secs, 0.0020 secs

	Status code distribution:
	  [200]	100000 responses
*/