docs/examples: add hiperfifo example using linux epoll/timerfd

Closes #2804

1 files changed, 540 insertions, 0 deletions

diff --git a/docs/examples/ephiperfifo.c b/docs/examples/ephiperfifo.c
new file mode 100644
index 000000000..e11715f1c
--- /dev/null
+++ b/docs/examples/ephiperfifo.c
@@ -0,0 +1,540 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2018, 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>
+#include <curl/multi.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);
+
+  timerfd_settime(g->tfd, /*flags=*/0, &its, NULL);
+  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;
+    timerfd_settime(g->tfd, /*flags=*/0, &its, NULL);
+  } else if (timeout_ms == 0) {
+    rc = curl_multi_socket_action(g->multi,
+                                  CURL_SOCKET_TIMEOUT, 0, &g->still_running);
+    mcode_or_die("multi_timer_cb: curl_multi_socket_action", rc);
+  } 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_POLL_IN : 0) |
+               (revents & EPOLLOUT ? CURL_POLL_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) {
+      epoll_ctl(g->epfd, EPOLL_CTL_DEL, f->sockfd, NULL);
+    }
+    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){
+    epoll_ctl(g->epfd, EPOLL_CTL_DEL, f->sockfd, NULL);
+  }
+
+  f->sockfd = s;
+  f->action = act;
+  f->easy = e;
+
+  ev.events = kind;
+  ev.data.fd = s;
+  epoll_ctl(g->epfd, EPOLL_CTL_ADD, s, &ev);
+}
+
+
+
+/* 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;
+}