Init 1

/*
 * MQTT packets building functions
 */

union mqtt_header *mqtt_packet_header(unsigned char byte) {
    static union mqtt_header header;
    header.byte = byte;
    return &header;
}

struct mqtt_ack *mqtt_packet_ack(unsigned char byte, unsigned short pkt_id) {
    static struct mqtt_ack ack;
    ack.header.byte = byte;
    ack.pkt_id = pkt_id;
    return &ack;
}

struct mqtt_connack *mqtt_packet_connack(unsigned char byte,
                                         unsigned char cflags,
                                         unsigned char rc) {
    static struct mqtt_connack connack;
    connack.header.byte = byte;
    connack.byte = cflags;
    connack.rc = rc;
    return &connack;
}

struct mqtt_suback *mqtt_packet_suback(unsigned char byte,
                                       unsigned short pkt_id,
                                       unsigned char *rcs,
                                       unsigned short rcslen) {
    struct mqtt_suback *suback = malloc(sizeof(*suback));
    suback->header.byte = byte;
    suback->pkt_id = pkt_id;
    suback->rcslen = rcslen;
    suback->rcs = malloc(rcslen);
    memcpy(suback->rcs, rcs, rcslen);
    return suback;
}

struct mqtt_publish *mqtt_packet_publish(unsigned char byte,
                                         unsigned short pkt_id,
                                         size_t topiclen,
                                         unsigned char *topic,
                                         size_t payloadlen,
                                         unsigned char *payload) {
    struct mqtt_publish *publish = malloc(sizeof(*publish));
    publish->header.byte = byte;
    publish->pkt_id = pkt_id;
    publish->topiclen = topiclen;
    publish->topic = topic;
    publish->payloadlen = payloadlen;
    publish->payload = payload;
    return publish;
}

void mqtt_packet_release(union mqtt_packet *pkt, unsigned type) {
    switch (type) {
        case CONNECT:
            free(pkt->connect.payload.client_id);
            if (pkt->connect.bits.username == 1)
                free(pkt->connect.payload.username);
            if (pkt->connect.bits.password == 1)
                free(pkt->connect.payload.password);
            if (pkt->connect.bits.will == 1) {
                free(pkt->connect.payload.will_message);
                free(pkt->connect.payload.will_topic);
            }
            break;
        case SUBSCRIBE:
        case UNSUBSCRIBE:
            for (unsigned i = 0; i < pkt->subscribe.tuples_len; i++)
                free(pkt->subscribe.tuples[i].topic);
            free(pkt->subscribe.tuples);
            break;
        case SUBACK:
            free(pkt->suback.rcs);
            break;
        case PUBLISH:
            free(pkt->publish.topic);
            free(pkt->publish.payload);
            break;
        default:
            break;
    }
}

/*
 * MQTT packets packing functions
 */

typedef unsigned char *mqtt_pack_handler(const union mqtt_packet *);

static mqtt_pack_handler *pack_handlers[13] = {
    NULL,
    NULL,
    pack_mqtt_connack,
    pack_mqtt_publish,
    pack_mqtt_ack,
    pack_mqtt_ack,
    pack_mqtt_ack,
    pack_mqtt_ack,
    NULL,
    pack_mqtt_suback,
    NULL,
    pack_mqtt_ack,
    NULL
};

static unsigned char *pack_mqtt_header(const union mqtt_header *hdr) {
    unsigned char *packed = malloc(MQTT_HEADER_LEN);
    unsigned char *ptr = packed;
    pack_u8(&ptr, hdr->byte);
    /* Encode 0 length bytes, message like this have only a fixed header */
    mqtt_encode_length(ptr, 0);
    return packed;
}

static unsigned char *pack_mqtt_ack(const union mqtt_packet *pkt) {
    unsigned char *packed = malloc(MQTT_ACK_LEN);
    unsigned char *ptr = packed;
    pack_u8(&ptr, pkt->ack.header.byte);
    mqtt_encode_length(ptr, MQTT_HEADER_LEN);
    ptr++;
    pack_u16(&ptr, pkt->ack.pkt_id);
    return packed;
}

static unsigned char *pack_mqtt_connack(const union mqtt_packet *pkt) {
    unsigned char *packed = malloc(MQTT_ACK_LEN);
    unsigned char *ptr = packed;
    pack_u8(&ptr, pkt->connack.header.byte);
    mqtt_encode_length(ptr, MQTT_HEADER_LEN);
    ptr++;
    pack_u8(&ptr, pkt->connack.byte);
    pack_u8(&ptr, pkt->connack.rc);
    return packed;
}

static unsigned char *pack_mqtt_suback(const union mqtt_packet *pkt) {
    size_t pktlen = MQTT_HEADER_LEN + sizeof(uint16_t) + pkt->suback.rcslen;
    unsigned char *packed = malloc(pktlen + 0);
    unsigned char *ptr = packed;
    pack_u8(&ptr, pkt->suback.header.byte);
    size_t len = sizeof(uint16_t) + pkt->suback.rcslen;
    int step = mqtt_encode_length(ptr, len);
    ptr += step;
    pack_u16(&ptr, pkt->suback.pkt_id);
    for (int i = 0; i < pkt->suback.rcslen; i++)
        pack_u8(&ptr, pkt->suback.rcs[i]);
    return packed;
}

static unsigned char *pack_mqtt_publish(const union mqtt_packet *pkt) {
    /*
     * We must calculate the total length of the packet including header and
     * length field of the fixed header part
     */
    size_t pktlen = MQTT_HEADER_LEN + sizeof(uint16_t) +
        pkt->publish.topiclen + pkt->publish.payloadlen;
    // Total len of the packet excluding fixed header len
    size_t len = 0L;
    if (pkt->header.bits.qos > AT_MOST_ONCE)
        pktlen += sizeof(uint16_t);
    int remaininglen_offset = 0;
    if ((pktlen - 1) > 0x200000)
        remaininglen_offset = 3;
    else if ((pktlen - 1) > 0x4000)
        remaininglen_offset = 2;
    else if ((pktlen - 1) > 0x80)
        remaininglen_offset = 1;
    pktlen += remaininglen_offset;
    unsigned char *packed = malloc(pktlen);
    unsigned char *ptr = packed;
    pack_u8(&ptr, pkt->publish.header.byte);
    // Total len of the packet excluding fixed header len
    len += (pktlen - MQTT_HEADER_LEN - remaininglen_offset);
    /*
     * TODO handle case where step is > 1, e.g. when a message longer than 128
     * bytes is published
     */
    int step = mqtt_encode_length(ptr, len);
    ptr += step;
    // Topic len followed by topic name in bytes
    pack_u16(&ptr, pkt->publish.topiclen);
    pack_bytes(&ptr, pkt->publish.topic);
    // Packet id
    if (pkt->header.bits.qos > AT_MOST_ONCE)
        pack_u16(&ptr, pkt->publish.pkt_id);
    // Finally the payload, same way of topic, payload len -> payload
    pack_bytes(&ptr, pkt->publish.payload);
    return packed;
}

unsigned char *pack_mqtt_packet(const union mqtt_packet *pkt, unsigned type) {
    if (type == PINGREQ || type == PINGRESP)
        return pack_mqtt_header(&pkt->header);
    return pack_handlers[type](pkt);
}

#ifndef NETWORK_H
#define NETWORK_H

#include <stdio.h>
#include <stdint.h>
#include <sys/types.h>
#include "util.h"

// Socket families
#define UNIX    0
#define INET    1

/* Set non-blocking socket */
int set_nonblocking(int);

/*
 * Set TCP_NODELAY flag to true, disabling Nagle's algorithm, no more waiting
 * for incoming packets on the buffer
 */
int set_tcp_nodelay(int);

/* Auxiliary function for creating epoll server */
int create_and_bind(const char *, const char *, int);

/*
 * Create a non-blocking socket and make it listen on the specified address and
 * port
 */
int make_listen(const char *, const char *, int);

/* Accept a connection and add it to the right epollfd */
int accept_connection(int);

/* I/O management functions */

/*
 * Send all data in a loop, avoiding interruption based on the kernel buffer
 * availability
 */
ssize_t send_bytes(int, const unsigned char *, size_t);

/*
 * Receive (read) an arbitrary number of bytes from a file descriptor and
 * store them in a buffer
 */
ssize_t recv_bytes(int, unsigned char *, size_t);

#endif

#define _DEFAULT_SOURCE

// -- omitted includes

/* Set non-blocking socket */
int set_nonblocking(int fd) {
    int flags, result;
    flags = fcntl(fd, F_GETFL, 0);
    if (flags == -1)
        goto err;
    result = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
    if (result == -1)
        goto err;
    return 0;
err:
    perror("set_nonblocking");
    return -1;
}

/* Disable Nagle's algorithm by setting TCP_NODELAY */
int set_tcp_nodelay(int fd) {
    return setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &(int) {1}, sizeof(int));
}

static int create_and_bind_unix(const char *sockpath) {
    struct sockaddr_un addr;
    int fd;
    if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
        perror("socket error");
        return -1;
    }
    memset(&addr, 0, sizeof(addr));
    addr.sun_family = AF_UNIX;
    strncpy(addr.sun_path, sockpath, sizeof(addr.sun_path) - 1);
    unlink(sockpath);
    if (bind(fd, (struct sockaddr*) &addr, sizeof(addr)) == -1) {
        perror("bind error");
        return -1;
    }
    return fd;
}

static int create_and_bind_tcp(const char *host, const char *port) {
    struct addrinfo hints = {
        .ai_family = AF_UNSPEC,
        .ai_socktype = SOCK_STREAM,
        .ai_flags = AI_PASSIVE
    };
    struct addrinfo *result, *rp;
    int sfd;
    if (getaddrinfo(host, port, &hints, &result) != 0) {
        perror("getaddrinfo error");
        return -1;
    }
    for (rp = result; rp != NULL; rp = rp->ai_next) {
        sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
        if (sfd == -1) continue;
        /* set SO_REUSEADDR so the socket will be reusable after process kill */
        if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR,
                       &(int) { 1 }, sizeof(int)) < 0)
            perror("SO_REUSEADDR");
        if ((bind(sfd, rp->ai_addr, rp->ai_addrlen)) == 0) {
            /* Succesful bind */
            break;
        }
        close(sfd);
    }
    if (rp == NULL) {
        perror("Could not bind");
        return -1;
    }
    freeaddrinfo(result);
    return sfd;
}

int create_and_bind(const char *host, const char *port, int socket_family) {
    int fd;
    if (socket_family == UNIX)
        fd = create_and_bind_unix(host);
    else
        fd = create_and_bind_tcp(host, port);
    return fd;
}

/*
 * Create a non-blocking socket and make it listen on the specfied address and
 * port
 */
int make_listen(const char *host, const char *port, int socket_family) {
    int sfd;
    if ((sfd = create_and_bind(host, port, socket_family)) == -1)
        abort();
    if ((set_nonblocking(sfd)) == -1)
        abort();
    // Set TCP_NODELAY only for TCP sockets
    if (socket_family == INET)
        set_tcp_nodelay(sfd);
    if ((listen(sfd, conf->tcp_backlog)) == -1) {
        perror("listen");
        abort();
    }
    return sfd;
}

int accept_connection(int serversock) {
    int clientsock;
    struct sockaddr_in addr;
    socklen_t addrlen = sizeof(addr);
    if ((clientsock = accept(serversock,
                             (struct sockaddr *) &addr, &addrlen)) < 0)
        return -1;
    set_nonblocking(clientsock);

    // Set TCP_NODELAY only for TCP sockets
    if (conf->socket_family == INET)
        set_tcp_nodelay(clientsock);
    char ip_buff[INET_ADDRSTRLEN + 1];
    if (inet_ntop(AF_INET, &addr.sin_addr,
                  ip_buff, sizeof(ip_buff)) == NULL) {
        close(clientsock);
        return -1;
    }
    return clientsock;
}

/* Send all bytes contained in buf, updating sent bytes counter */
ssize_t send_bytes(int fd, const unsigned char *buf, size_t len) {
    size_t total = 0;
    size_t bytesleft = len;
    ssize_t n = 0;
    while (total < len) {
        n = send(fd, buf + total, bytesleft, MSG_NOSIGNAL);
        if (n == -1) {
            if (errno == EAGAIN || errno == EWOULDBLOCK)
                break;
            else
                goto err;
        }
        total += n;
        bytesleft -= n;
    }
    return total;
err:
    fprintf(stderr, "send(2) - error sending data: %s", strerror(errno));
    return -1;
}

/*
 * Receive a given number of bytes on the descriptor fd, storing the stream of
 * data into a 2 Mb capped buffer
 */
ssize_t recv_bytes(int fd, unsigned char *buf, size_t bufsize) {
    ssize_t n = 0;
    ssize_t total = 0;
    while (total < (ssize_t) bufsize) {
        if ((n = recv(fd, buf, bufsize - total, 0)) < 0) {
            if (errno == EAGAIN || errno == EWOULDBLOCK) {
                break;
            } else
                goto err;
        }
        if (n == 0)
            return 0;
        buf += n;
        total += n;
    }
    return total;
err:
    fprintf(stderr, "recv(2) - error reading data: %s", strerror(errno));
    return -1;
}

typedef union epoll_data {
   void        *ptr;
   int          fd;
   uint32_t     u32;
   uint64_t     u64;
} epoll_data_t;

/* Event loop wrapper structure, define an EPOLL loop and his status. The
 * EPOLL instance use EPOLLONESHOT for each event and must be re-armed
 * manually, in order to allow future uses on a multithreaded architecture.
 */
struct evloop {
    int epollfd;
    int max_events;
    int timeout;
    int status;
    struct epoll_event *events;
    /* Dynamic array of periodic tasks, a pair descriptor - closure */
    int periodic_maxsize;
    int periodic_nr;
    struct {
        int timerfd;
        struct closure *closure;
    } **periodic_tasks;
} evloop;

typedef void callback(struct evloop *, void *);

/*
 * Callback object, represents a callback function with an associated
 * descriptor if needed, args is a void pointer which can be a structure
 * pointing to callback parameters and closure_id is a UUID for the closure
 * itself.
 * The last two fields are payload, a serialized version of the result of
 * a callback, ready to be sent through wire and a function pointer to the
 * callback function to execute.
 */
struct closure {
    int fd;
    void *obj;
    void *args;
    char closure_id[UUID_LEN];
    struct bytestring *payload;
    callback *call;
};

struct evloop *evloop_create(int, int);
void evloop_init(struct evloop *, int, int);
void evloop_free(struct evloop *);

/*
 * Blocks in a while(1) loop awaiting for events to be raised on monitored
 * file descriptors and executing the paired callback previously registered
 */
int evloop_wait(struct evloop *);

/*
 * Register a closure with a function to be executed every time the
 * paired descriptor is re-armed.
 */
void evloop_add_callback(struct evloop *, struct closure *);

/*
 * Register a periodic closure with a function to be executed every
 * defined interval of time.
 */
void evloop_add_periodic_task(struct evloop *,
                              int,
                              unsigned long long,
                              struct closure *);

/*
 * Unregister a closure by removing the associated descriptor from the
 * EPOLL loop
 */
int evloop_del_callback(struct evloop *, struct closure *);

/*
 * Rearm the file descriptor associated with a closure for read action,
 * making the event loop to monitor the callback for reading events
 */
int evloop_rearm_callback_read(struct evloop *, struct closure *);

/*
 * Rearm the file descriptor associated with a closure for write action,
 * making the event loop to monitor the callback for writing events
 */
int evloop_rearm_callback_write(struct evloop *, struct closure *);

/* Epoll management functions */
int epoll_add(int, int, int, void *);

/*
 * Modify an epoll-monitored descriptor, automatically set `EPOLLONESHOT` in
 * addition to the other flags, which can be `EPOLLIN` for read and EPOLLOUT for
 * write
 */
int epoll_mod(int, int, int, void *);

/*
 * Remove a descriptor from an epoll descriptor, making it no-longer monitored
 * for events
 */
int epoll_del(int, int);

/******************************
 *         EPOLL APIS         *
 ******************************/

#define EVLOOP_INITIAL_SIZE 4

struct evloop *evloop_create(int max_events, int timeout) {
    struct evloop *loop = malloc(sizeof(*loop));
    evloop_init(loop, max_events, timeout);
    return loop;
}

void evloop_init(struct evloop *loop, int max_events, int timeout) {
    loop->max_events = max_events;
    loop->events = malloc(sizeof(struct epoll_event) * max_events);
    loop->epollfd = epoll_create1(0);
    loop->timeout = timeout;
    loop->periodic_maxsize = EVLOOP_INITIAL_SIZE;
    loop->periodic_nr = 0;
    loop->periodic_tasks =
        malloc(EVLOOP_INITIAL_SIZE * sizeof(*loop->periodic_tasks));
    loop->status = 0;
}

void evloop_free(struct evloop *loop) {
    free(loop->events);
    for (int i = 0; i < loop->periodic_nr; i++)
        free(loop->periodic_tasks[i]);
    free(loop->periodic_tasks);
    free(loop);
}

int epoll_add(int efd, int fd, int evs, void *data) {
    struct epoll_event ev;
    ev.data.fd = fd;
    // Being ev.data a union, in case of data != NULL, fd will be set to random
    if (data)
        ev.data.ptr = data;
    ev.events = evs | EPOLLET | EPOLLONESHOT;
    return epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ev);
}

int epoll_mod(int efd, int fd, int evs, void *data) {
    struct epoll_event ev;
    ev.data.fd = fd;
    // Being ev.data a union, in case of data != NULL, fd will be set to random
    if (data)
        ev.data.ptr = data;
    ev.events = evs | EPOLLET | EPOLLONESHOT;
    return epoll_ctl(efd, EPOLL_CTL_MOD, fd, &ev);
}

int epoll_del(int efd, int fd) {
    return epoll_ctl(efd, EPOLL_CTL_DEL, fd, NULL);
}

void evloop_add_callback(struct evloop *loop, struct closure *cb) {
    if (epoll_add(loop->epollfd, cb->fd, EPOLLIN, cb) < 0)
        perror("Epoll register callback: ");
}

void evloop_add_periodic_task(struct evloop *loop,
                              int seconds,
                              unsigned long long ns,
                              struct closure *cb) {
    struct itimerspec timervalue;
    int timerfd = timerfd_create(CLOCK_MONOTONIC, 0);
    memset(&timervalue, 0x00, sizeof(timervalue));
    // Set initial expire time and periodic interval
    timervalue.it_value.tv_sec = seconds;
    timervalue.it_value.tv_nsec = ns;
    timervalue.it_interval.tv_sec = seconds;
    timervalue.it_interval.tv_nsec = ns;
    if (timerfd_settime(timerfd, 0, &timervalue, NULL) < 0) {
        perror("timerfd_settime");
        return;
    }
    // Add the timer to the event loop
    struct epoll_event ev;
    ev.data.fd = timerfd;
    ev.events = EPOLLIN;
    if (epoll_ctl(loop->epollfd, EPOLL_CTL_ADD, timerfd, &ev) < 0) {
        perror("epoll_ctl(2): EPOLLIN");
        return;
    }
    /* Store it into the event loop */
    if (loop->periodic_nr + 1 > loop->periodic_maxsize) {
        loop->periodic_maxsize *= 2;
        loop->periodic_tasks =
            realloc(loop->periodic_tasks,
                    loop->periodic_maxsize * sizeof(*loop->periodic_tasks));
    }
    loop->periodic_tasks[loop->periodic_nr] =
        malloc(sizeof(*loop->periodic_tasks[loop->periodic_nr]));
    loop->periodic_tasks[loop->periodic_nr]->closure = cb;
    loop->periodic_tasks[loop->periodic_nr]->timerfd = timerfd;
    loop->periodic_nr++;
}

int evloop_wait(struct evloop *el) {
    int rc = 0;
    int events = 0;
    long int timer = 0L;
    int periodic_done = 0;
    while (1) {
        events = epoll_wait(el->epollfd, el->events,
                            el->max_events, el->timeout);
        if (events < 0) {
            /* Signals to all threads. Ignore it for now */
            if (errno == EINTR)
                continue;
            /* Error occured, break the loop */
            rc = -1;
            el->status = errno;
            break;
        }
        for (int i = 0; i < events; i++) {
            /* Check for errors */
            if ((el->events[i].events & EPOLLERR) ||
                (el->events[i].events & EPOLLHUP) ||
                (!(el->events[i].events & EPOLLIN) &&
                 !(el->events[i].events & EPOLLOUT))) {
                /* An error has occured on this fd, or the socket is not
                   ready for reading, closing connection */
                perror ("epoll_wait(2)");
                shutdown(el->events[i].data.fd, 0);
                close(el->events[i].data.fd);
                el->status = errno;
                continue;
            }
            struct closure *closure = el->events[i].data.ptr;
            periodic_done = 0;
            for (int i = 0; i < el->periodic_nr && periodic_done == 0; i++) {
                if (el->events[i].data.fd == el->periodic_tasks[i]->timerfd) {
                    struct closure *c = el->periodic_tasks[i]->closure;
                    (void) read(el->events[i].data.fd, &timer, 8);
                    c->call(el, c->args);
                    periodic_done = 1;
                }
            }
            if (periodic_done == 1)
                continue;
            /* No error events, proceed to run callback */
            closure->call(el, closure->args);
        }
    }
    return rc;
}

int evloop_rearm_callback_read(struct evloop *el, struct closure *cb) {
    return epoll_mod(el->epollfd, cb->fd, EPOLLIN, cb);
}

int evloop_rearm_callback_write(struct evloop *el, struct closure *cb) {
    return epoll_mod(el->epollfd, cb->fd, EPOLLOUT, cb);
}

int evloop_del_callback(struct evloop *el, struct closure *cb) {
    return epoll_del(el->epollfd, cb->fd);
}

sol/
 ├── src/
 │    ├── mqtt.h
 |    ├── mqtt.c
 │    ├── network.h
 │    ├── network.c
 │    ├── pack.h
 │    └── pack.c
 ├── CHANGELOG
 ├── CMakeLists.txt
 ├── COPYING
 └── README.md