Add mg multithreaded example

PUBLISHED_FROM=8a3424ba6260b0351d7c06270dc141d804ae7f77

examples/multithreaded/Makefile

+PROG = multithreaded
+MODULE_CFLAGS=-DMG_ENABLE_THREADS
+include ../examples.mk

examples/multithreaded/multithreaded.c

+/*
+ * Copyright (c) 2014-2017 Cesanta Software Limited
+ * All rights reserved
+ */
+
+#include "mongoose.h"
+
+static sig_atomic_t s_received_signal = 0;
+static const char *s_http_port = "8000";
+static const int s_num_worker_threads = 5;
+static unsigned long s_next_id = 0;
+
+static void signal_handler(int sig_num) {
+  signal(sig_num, signal_handler);
+  s_received_signal = sig_num;
+}
+static struct mg_serve_http_opts s_http_server_opts;
+static sock_t sock[2];
+
+// This info is passed to the worker thread
+struct work_request {
+  unsigned long conn_id;  // needed to identify the connection where to send the reply
+  // optionally, more data that could be required by worker 
+};
+
+// This info is passed by the worker thread to mg_broadcast
+struct work_result {
+  unsigned long conn_id;
+  int sleep_time;
+};
+
+static void on_work_complete(struct mg_connection *nc, int ev, void *ev_data) {
+  (void) ev;
+  char s[32];
+  struct mg_connection *c;
+  for (c = mg_next(nc->mgr, NULL); c != NULL; c = mg_next(nc->mgr, c)) {
+    if (c->user_data != NULL) {
+      struct work_result *res = (struct work_result *)ev_data;
+      if ((unsigned long)c->user_data == res->conn_id) {
+        sprintf(s, "conn_id:%lu sleep:%d", res->conn_id, res->sleep_time);
+        mg_send_head(c, 200, strlen(s), "Content-Type: text/plain");
+        mg_printf(c, "%s", s);
+      }
+    }
+  }
+}
+
+void *worker_thread_proc(void *param) {
+  struct mg_mgr *mgr = (struct mg_mgr *) param;
+  struct work_request req = {0};
+  
+  while (s_received_signal == 0) {
+    if (read(sock[1], &req, sizeof(req)) < 0)
+      perror("Reading worker sock");
+    int r = rand() % 10;
+    sleep(r);
+    struct work_result res = {req.conn_id, r};
+    mg_broadcast(mgr, on_work_complete, (void *)&res, sizeof(res));
+  }
+  return NULL;
+}
+
+static void ev_handler(struct mg_connection *nc, int ev, void *ev_data) {
+  (void) nc;
+  (void) ev_data;
+  
+  switch (ev) {
+    case MG_EV_ACCEPT:
+      nc->user_data = (void *)++s_next_id;
+      break;
+    case MG_EV_HTTP_REQUEST: {
+      struct work_request req = {(unsigned long)nc->user_data};
+
+      if (write(sock[0], &req, sizeof(req)) < 0)
+        perror("Writing worker sock");
+      break;
+    }
+    case MG_EV_CLOSE: {
+      if (nc->user_data) nc->user_data = NULL;
+    }
+  }
+}
+
+int main(void) {
+  struct mg_mgr mgr;
+  struct mg_connection *nc;
+  int i;
+
+  if (mg_socketpair(sock, SOCK_STREAM) == 0) {
+    perror("Opening socket pair");
+    exit(1);
+  }
+
+  signal(SIGTERM, signal_handler);
+  signal(SIGINT, signal_handler);
+
+  mg_mgr_init(&mgr, NULL);
+
+  nc = mg_bind(&mgr, s_http_port, ev_handler);
+  if (nc == NULL) {
+    printf("Failed to create listener\n");
+    return 1;
+  }
+
+  mg_set_protocol_http_websocket(nc);
+  s_http_server_opts.document_root = ".";  // Serve current directory
+  s_http_server_opts.enable_directory_listing = "no";
+
+  for (i = 0; i < s_num_worker_threads; i++) {
+    mg_start_thread(worker_thread_proc, &mgr);
+  }
+
+  printf("Started on port %s\n", s_http_port);
+  while (s_received_signal == 0) {
+    mg_mgr_poll(&mgr, 200);
+  }
+
+  mg_mgr_free(&mgr);
+
+  closesocket(sock[0]);
+  closesocket(sock[1]);
+
+  return 0;
+}