text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
   *
   * This software is licensed as described in the file COPYING, which
   * you should have received as part of this distribution. The terms
   * are also available at https://curl.haxx.se/docs/copyright.html.
   *
   * You may opt to use, copy, modify, merge, publish, distribute and/or sell
   * copies of the Software, and permit persons to whom the Software is
   * furnished to do so, under the terms of the COPYING file.
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
   * KIND, either express or implied.
   *
   ***************************************************************************/
  /* <DESC>
   * multi socket API usage with epoll and timerfd
   * </DESC>
   */
  /* Example application source code using the multi socket interface to
   * download many files at once.
   *
   * This example features the same basic functionality as hiperfifo.c does,
   * but this uses epoll and timerfd instead of libevent.
   *
   * Written by Jeff Pohlmeyer, converted to use epoll by Josh Bialkowski
  
  Requires a linux system with epoll
  
  When running, the program creates the named pipe "hiper.fifo"
  
  Whenever there is input into the fifo, the program reads the input as a list
  of URL's and creates some new easy handles to fetch each URL via the
  curl_multi "hiper" API.
  
  
  Thus, you can try a single URL:
    % echo http://www.yahoo.com > hiper.fifo
  
  Or a whole bunch of them:
    % cat my-url-list > hiper.fifo
  
  The fifo buffer is handled almost instantly, so you can even add more URL's
  while the previous requests are still being downloaded.
  
  Note:
    For the sake of simplicity, URL length is limited to 1023 char's !
  
  This is purely a demo app, all retrieved data is simply discarded by the write
  callback.
  
  */
  
  #include <errno.h>
  #include <fcntl.h>
  #include <signal.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/epoll.h>
  #include <sys/stat.h>
  #include <sys/time.h>
  #include <sys/timerfd.h>
  #include <sys/types.h>
  #include <time.h>
  #include <unistd.h>
  
  #include <curl/curl.h>
  
  #ifdef __GNUC__
  #define _Unused __attribute__((unused))
  #else
  #define _Unused
  #endif
  
  #define MSG_OUT stdout /* Send info to stdout, change to stderr if you want */
  
  
  /* Global information, common to all connections */
  typedef struct _GlobalInfo
  {
    int epfd;    /* epoll filedescriptor */
    int tfd;     /* timer filedescriptor */
    int fifofd;  /* fifo filedescriptor */
    CURLM *multi;
    int still_running;
    FILE *input;
  } GlobalInfo;
  
  
  /* Information associated with a specific easy handle */
  typedef struct _ConnInfo
  {
    CURL *easy;
    char *url;
    GlobalInfo *global;
    char error[CURL_ERROR_SIZE];
  } ConnInfo;
  
  
  /* Information associated with a specific socket */
  typedef struct _SockInfo
  {
    curl_socket_t sockfd;
    CURL *easy;
    int action;
    long timeout;
    GlobalInfo *global;
  } SockInfo;
  
  #define __case(code) \
    case code: s = __STRING(code)
  
  /* Die if we get a bad CURLMcode somewhere */
  static void mcode_or_die(const char *where, CURLMcode code)
  {
    if(CURLM_OK != code) {
      const char *s;
      switch(code) {
        __case(CURLM_BAD_HANDLE); break;
        __case(CURLM_BAD_EASY_HANDLE); break;
        __case(CURLM_OUT_OF_MEMORY); break;
        __case(CURLM_INTERNAL_ERROR); break;
        __case(CURLM_UNKNOWN_OPTION); break;
        __case(CURLM_LAST); break;
        default: s = "CURLM_unknown"; break;
        __case(CURLM_BAD_SOCKET);
        fprintf(MSG_OUT, "ERROR: %s returns %s\n", where, s);
        /* ignore this error */
        return;
      }
      fprintf(MSG_OUT, "ERROR: %s returns %s\n", where, s);
      exit(code);
    }
  }
  
  static void timer_cb(GlobalInfo* g, int revents);
  
  /* Update the timer after curl_multi library does it's thing. Curl will
   * inform us through this callback what it wants the new timeout to be,
   * after it does some work. */
  static int multi_timer_cb(CURLM *multi, long timeout_ms, GlobalInfo *g)
  {
    struct itimerspec its;
    CURLMcode rc;
  
    fprintf(MSG_OUT, "multi_timer_cb: Setting timeout to %ld ms\n", timeout_ms);
  
    if(timeout_ms > 0) {
      its.it_interval.tv_sec = 1;
      its.it_interval.tv_nsec = 0;
      its.it_value.tv_sec = timeout_ms / 1000;
      its.it_value.tv_nsec = (timeout_ms % 1000) * 1000 * 1000;
    }
    else if(timeout_ms == 0) {
      /* libcurl wants us to timeout now, however setting both fields of
       * new_value.it_value to zero disarms the timer. The closest we can
       * do is to schedule the timer to fire in 1 ns. */
      its.it_interval.tv_sec = 1;
      its.it_interval.tv_nsec = 0;
      its.it_value.tv_sec = 0;
      its.it_value.tv_nsec = 1;
    }
    else {
      memset(&its, 0, sizeof(struct itimerspec));
    }
  
    timerfd_settime(g->tfd, /*flags=*/0, &its, NULL);
    return 0;
  }
  
  
  /* Check for completed transfers, and remove their easy handles */
  static void check_multi_info(GlobalInfo *g)
  {
    char *eff_url;
    CURLMsg *msg;
    int msgs_left;
    ConnInfo *conn;
    CURL *easy;
    CURLcode res;
  
    fprintf(MSG_OUT, "REMAINING: %d\n", g->still_running);
    while((msg = curl_multi_info_read(g->multi, &msgs_left))) {
      if(msg->msg == CURLMSG_DONE) {
        easy = msg->easy_handle;
        res = msg->data.result;
        curl_easy_getinfo(easy, CURLINFO_PRIVATE, &conn);
        curl_easy_getinfo(easy, CURLINFO_EFFECTIVE_URL, &eff_url);
        fprintf(MSG_OUT, "DONE: %s => (%d) %s\n", eff_url, res, conn->error);
        curl_multi_remove_handle(g->multi, easy);
        free(conn->url);
        curl_easy_cleanup(easy);
        free(conn);
      }
    }
  }
  
  /* Called by libevent when we get action on a multi socket filedescriptor*/
  static void event_cb(GlobalInfo *g, int fd, int revents)
  {
    CURLMcode rc;
    struct itimerspec its;
  
    int action = (revents & EPOLLIN ? CURL_CSELECT_IN : 0) |
                 (revents & EPOLLOUT ? CURL_CSELECT_OUT : 0);
  
    rc = curl_multi_socket_action(g->multi, fd, action, &g->still_running);
    mcode_or_die("event_cb: curl_multi_socket_action", rc);
  
    check_multi_info(g);
    if(g->still_running <= 0) {
      fprintf(MSG_OUT, "last transfer done, kill timeout\n");
      memset(&its, 0, sizeof(struct itimerspec));
      timerfd_settime(g->tfd, 0, &its, NULL);
    }
  }
  
  /* Called by main loop when our timeout expires */
  static void timer_cb(GlobalInfo* g, int revents)
  {
    CURLMcode rc;
    uint64_t count = 0;
    ssize_t err = 0;
  
    err = read(g->tfd, &count, sizeof(uint64_t));
    if(err == -1) {
      /* Note that we may call the timer callback even if the timerfd isn't
       * readable. It's possible that there are multiple events stored in the
       * epoll buffer (i.e. the timer may have fired multiple times). The
       * event count is cleared after the first call so future events in the
       * epoll buffer will fail to read from the timer. */
      if(errno == EAGAIN) {
        fprintf(MSG_OUT, "EAGAIN on tfd %d\n", g->tfd);
        return;
      }
    }
    if(err != sizeof(uint64_t)) {
      fprintf(stderr, "read(tfd) == %ld", err);
      perror("read(tfd)");
    }
  
    rc = curl_multi_socket_action(g->multi,
                                    CURL_SOCKET_TIMEOUT, 0, &g->still_running);
    mcode_or_die("timer_cb: curl_multi_socket_action", rc);
    check_multi_info(g);
  }
  
  
  
  /* Clean up the SockInfo structure */
  static void remsock(SockInfo *f, GlobalInfo* g)
  {
    if(f) {
      if(f->sockfd) {
        if(epoll_ctl(g->epfd, EPOLL_CTL_DEL, f->sockfd, NULL))
          fprintf(stderr, "EPOLL_CTL_DEL failed for fd: %d : %s\n",
                  f->sockfd, strerror(errno));
      }
      free(f);
    }
  }
  
  
  
  /* Assign information to a SockInfo structure */
  static void setsock(SockInfo *f, curl_socket_t s, CURL *e, int act,
                      GlobalInfo *g)
  {
    struct epoll_event ev;
    int kind = (act & CURL_POLL_IN ? EPOLLIN : 0) |
               (act & CURL_POLL_OUT ? EPOLLOUT : 0);
  
    if(f->sockfd) {
      if(epoll_ctl(g->epfd, EPOLL_CTL_DEL, f->sockfd, NULL))
        fprintf(stderr, "EPOLL_CTL_DEL failed for fd: %d : %s\n",
                f->sockfd, strerror(errno));
    }
  
    f->sockfd = s;
    f->action = act;
    f->easy = e;
  
    ev.events = kind;
    ev.data.fd = s;
    if(epoll_ctl(g->epfd, EPOLL_CTL_ADD, s, &ev))
      fprintf(stderr, "EPOLL_CTL_ADD failed for fd: %d : %s\n",
              s, strerror(errno));
  }
  
  
  
  /* Initialize a new SockInfo structure */
  static void addsock(curl_socket_t s, CURL *easy, int action, GlobalInfo *g)
  {
    SockInfo *fdp = (SockInfo*)calloc(sizeof(SockInfo), 1);
  
    fdp->global = g;
    setsock(fdp, s, easy, action, g);
    curl_multi_assign(g->multi, s, fdp);
  }
  
  /* CURLMOPT_SOCKETFUNCTION */
  static int sock_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *sockp)
  {
    GlobalInfo *g = (GlobalInfo*) cbp;
    SockInfo *fdp = (SockInfo*) sockp;
    const char *whatstr[]={ "none", "IN", "OUT", "INOUT", "REMOVE" };
  
    fprintf(MSG_OUT,
            "socket callback: s=%d e=%p what=%s ", s, e, whatstr[what]);
    if(what == CURL_POLL_REMOVE) {
      fprintf(MSG_OUT, "\n");
      remsock(fdp, g);
    }
    else {
      if(!fdp) {
        fprintf(MSG_OUT, "Adding data: %s\n", whatstr[what]);
        addsock(s, e, what, g);
      }
      else {
        fprintf(MSG_OUT,
                "Changing action from %s to %s\n",
                whatstr[fdp->action], whatstr[what]);
        setsock(fdp, s, e, what, g);
      }
    }
    return 0;
  }
  
  
  
  /* CURLOPT_WRITEFUNCTION */
  static size_t write_cb(void *ptr _Unused, size_t size, size_t nmemb,
                         void *data)
  {
    size_t realsize = size * nmemb;
    ConnInfo *conn _Unused = (ConnInfo*) data;
  
    return realsize;
  }
  
  
  /* CURLOPT_PROGRESSFUNCTION */
  static int prog_cb(void *p, double dltotal, double dlnow, double ult _Unused,
                     double uln _Unused)
  {
    ConnInfo *conn = (ConnInfo *)p;
  
    fprintf(MSG_OUT, "Progress: %s (%g/%g)\n", conn->url, dlnow, dltotal);
    return 0;
  }
  
  
  /* Create a new easy handle, and add it to the global curl_multi */
  static void new_conn(char *url, GlobalInfo *g)
  {
    ConnInfo *conn;
    CURLMcode rc;
  
    conn = (ConnInfo*)calloc(1, sizeof(ConnInfo));
    conn->error[0]='\0';
  
    conn->easy = curl_easy_init();
    if(!conn->easy) {
      fprintf(MSG_OUT, "curl_easy_init() failed, exiting!\n");
      exit(2);
    }
    conn->global = g;
    conn->url = strdup(url);
    curl_easy_setopt(conn->easy, CURLOPT_URL, conn->url);
    curl_easy_setopt(conn->easy, CURLOPT_WRITEFUNCTION, write_cb);
    curl_easy_setopt(conn->easy, CURLOPT_WRITEDATA, conn);
    curl_easy_setopt(conn->easy, CURLOPT_VERBOSE, 1L);
    curl_easy_setopt(conn->easy, CURLOPT_ERRORBUFFER, conn->error);
    curl_easy_setopt(conn->easy, CURLOPT_PRIVATE, conn);
    curl_easy_setopt(conn->easy, CURLOPT_NOPROGRESS, 0L);
    curl_easy_setopt(conn->easy, CURLOPT_PROGRESSFUNCTION, prog_cb);
    curl_easy_setopt(conn->easy, CURLOPT_PROGRESSDATA, conn);
    curl_easy_setopt(conn->easy, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_setopt(conn->easy, CURLOPT_LOW_SPEED_TIME, 3L);
    curl_easy_setopt(conn->easy, CURLOPT_LOW_SPEED_LIMIT, 10L);
    fprintf(MSG_OUT,
            "Adding easy %p to multi %p (%s)\n", conn->easy, g->multi, url);
    rc = curl_multi_add_handle(g->multi, conn->easy);
    mcode_or_die("new_conn: curl_multi_add_handle", rc);
  
    /* note that the add_handle() will set a time-out to trigger very soon so
       that the necessary socket_action() call will be called by this app */
  }
  
  /* This gets called whenever data is received from the fifo */
  static void fifo_cb(GlobalInfo* g, int revents)
  {
    char s[1024];
    long int rv = 0;
    int n = 0;
  
    do {
      s[0]='\0';
      rv = fscanf(g->input, "%1023s%n", s, &n);
      s[n]='\0';
      if(n && s[0]) {
        new_conn(s, g); /* if we read a URL, go get it! */
      }
      else
        break;
    } while(rv != EOF);
  }
  
  /* Create a named pipe and tell libevent to monitor it */
  static const char *fifo = "hiper.fifo";
  static int init_fifo(GlobalInfo *g)
  {
    struct stat st;
    curl_socket_t sockfd;
    struct epoll_event epev;
  
    fprintf(MSG_OUT, "Creating named pipe \"%s\"\n", fifo);
    if(lstat (fifo, &st) == 0) {
      if((st.st_mode & S_IFMT) == S_IFREG) {
        errno = EEXIST;
        perror("lstat");
        exit(1);
      }
    }
    unlink(fifo);
    if(mkfifo (fifo, 0600) == -1) {
      perror("mkfifo");
      exit(1);
    }
    sockfd = open(fifo, O_RDWR | O_NONBLOCK, 0);
    if(sockfd == -1) {
      perror("open");
      exit(1);
    }
  
    g->fifofd = sockfd;
    g->input = fdopen(sockfd, "r");
  
    epev.events = EPOLLIN;
    epev.data.fd = sockfd;
    epoll_ctl(g->epfd, EPOLL_CTL_ADD, sockfd, &epev);
  
    fprintf(MSG_OUT, "Now, pipe some URL's into > %s\n", fifo);
    return 0;
  }
  
  static void clean_fifo(GlobalInfo *g)
  {
      epoll_ctl(g->epfd, EPOLL_CTL_DEL, g->fifofd, NULL);
      fclose(g->input);
      unlink(fifo);
  }
  
  
  int g_should_exit_ = 0;
  
  void SignalHandler(int signo)
  {
    if(signo == SIGINT) {
      g_should_exit_ = 1;
    }
  }
  
  int main(int argc _Unused, char **argv _Unused)
  {
    GlobalInfo g;
    int err;
    int idx;
    struct itimerspec its;
    struct epoll_event ev;
    struct epoll_event events[10];
  
    g_should_exit_ = 0;
    signal(SIGINT, SignalHandler);
  
    memset(&g, 0, sizeof(GlobalInfo));
    g.epfd = epoll_create1(EPOLL_CLOEXEC);
    if(g.epfd == -1) {
      perror("epoll_create1 failed");
      exit(1);
    }
  
    g.tfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK | TFD_CLOEXEC);
    if(g.tfd == -1) {
      perror("timerfd_create failed");
      exit(1);
    }
  
    memset(&its, 0, sizeof(struct itimerspec));
    its.it_interval.tv_sec = 1;
    its.it_value.tv_sec = 1;
    timerfd_settime(g.tfd, 0, &its, NULL);
  
    ev.events = EPOLLIN;
    ev.data.fd = g.tfd;
    epoll_ctl(g.epfd, EPOLL_CTL_ADD, g.tfd, &ev);
  
    init_fifo(&g);
    g.multi = curl_multi_init();
  
    /* setup the generic multi interface options we want */
    curl_multi_setopt(g.multi, CURLMOPT_SOCKETFUNCTION, sock_cb);
    curl_multi_setopt(g.multi, CURLMOPT_SOCKETDATA, &g);
    curl_multi_setopt(g.multi, CURLMOPT_TIMERFUNCTION, multi_timer_cb);
    curl_multi_setopt(g.multi, CURLMOPT_TIMERDATA, &g);
  
    /* we don't call any curl_multi_socket*() function yet as we have no handles
       added! */
  
    fprintf(MSG_OUT, "Entering wait loop\n");
    fflush(MSG_OUT);
    while(!g_should_exit_) {
      /* TODO(josh): use epoll_pwait to avoid a race on the signal. Mask the
       * signal before the while loop, and then re-enable the signal during
       * epoll wait. Mask at the end of the loop. */
      err = epoll_wait(g.epfd, events, sizeof(events)/sizeof(struct epoll_event),
                       10000);
      if(err == -1) {
        if(errno == EINTR) {
          fprintf(MSG_OUT, "note: wait interrupted\n");
          continue;
        }
        else {
          perror("epoll_wait");
          exit(1);
        }
      }
  
      for(idx = 0; idx < err; ++idx) {
        if(events[idx].data.fd == g.fifofd) {
          fifo_cb(&g, events[idx].events);
        }
        else if(events[idx].data.fd == g.tfd) {
          timer_cb(&g, events[idx].events);
        }
        else {
          event_cb(&g, events[idx].data.fd, events[idx].events);
        }
      }
    }
  
    fprintf(MSG_OUT, "Exiting normally.\n");
    fflush(MSG_OUT);
  
    curl_multi_cleanup(g.multi);
    return 0;
  }
  