Profiler filter for Mongrel2

#include <filter.h>
#include <dbg.h>

#include <sys/time.h>

typedef struct ProfilerSession {
    struct timeval * profilerTimeStart;
    struct timeval * profilerTimeEnd;
} ProfilerSession;

ProfilerSession *session = NULL;

StateEvent filter_transition(StateEvent state, Connection *conn, tns_value_t *config) {
    if (session == NULL) {
        session = (ProfilerSession *)malloc(sizeof(ProfilerSession));
        session->profilerTimeStart = malloc(sizeof(struct timeval));
        session->profilerTimeEnd = malloc(sizeof(struct timeval));
    }

    if (state == REQ_RECV) {
        debug("[Profiler:OPEN] Connection opened. Sampling time with gettimeofday.");
        int rc = gettimeofday(session->profilerTimeStart, NULL);
        check(rc == 0, "Something went REALLY wrong with Profiler filter");
        struct timeval startTime = *(session->profilerTimeStart);
        debug("[Profiler:OPEN] Start of request %ldms", startTime.tv_sec * 10000 + startTime.tv_usec);
    } else if (state == RESP_SENT) {
        gettimeofday(session->profilerTimeEnd, NULL);
        struct timeval endTime = *(session->profilerTimeEnd);
        debug("[Profiler:CLOSE] End of request at %ldms", endTime.tv_sec * 10000 + endTime.tv_usec);

        struct timeval startTime = *(session->profilerTimeStart);
        long int diff = (endTime.tv_sec * 10000 + endTime.tv_usec) - (startTime.tv_sec * 10000 + startTime.tv_usec);
        debug("[Profiler:CLOSE] Request took %ldms.", diff);
    }
    return state;

error:
    return CLOSE;
}

StateEvent *filter_init(Server *srv, bstring load_path, int *out_nstates) {
    StateEvent states[] = {REQ_RECV, RESP_SENT};
    *out_nstates = Filter_states_length(states);
    check(*out_nstates == 2, "Wrong states array length.");

    debug("[Profiler:filter_init] initted filter with needed states:");
    size_t i;
    for (i = 0; i < *out_nstates; i++) {
        debug("[Profiler:filter_init] state: %d", states[i]);
    }

    return Filter_state_list(states, *out_nstates);

error:
    return NULL;
}