docs/examples/asiohiper.cpp - third_party/curl - Git at Google

 /***************************************************************************
  *                                  _   _ ____  _
  *  Project                     ___| | | |  _ \| |
  *                             / __| | | | |_) | |
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
  * Copyright (C) 2012 - 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>
  * demonstrate the use of multi socket interface with boost::asio
  * </DESC>
  */
 /*
  * This program is in c++ and uses boost::asio instead of libevent/libev.
  * Requires boost::asio, boost::bind and boost::system
  *
  * This is an adaptation of libcurl's "hiperfifo.c" and "evhiperfifo.c"
  * sample programs. This example implements a subset of the functionality from
  * hiperfifo.c, for full functionality refer hiperfifo.c or evhiperfifo.c
  *
  * Written by Lijo Antony based on hiperfifo.c by Jeff Pohlmeyer
  *
  * When running, the program creates an easy handle for a URL and
  * uses the curl_multi API to fetch it.
  *
  * Note:
  *  For the sake of simplicity, URL is hard coded to "www.google.com"
  *
  * This is purely a demo app, all retrieved data is simply discarded by the
  * write callback.
  *
  * ===========================================================================
  * WARNING: This example program is known to have flaws:
  * https://github.com/curl/curl/issues/2407
  *
  * It still kept in the example repository with the hope that it might be
  * useful, and maybe some day someone who knows enough about boost::asio will
  * read this text, accept the challenge and make the example code work
  * correctly. Until then: expect this example program to fail occasionally.
  * ===========================================================================
  */


 #include <curl/curl.h>
 #include <boost/asio.hpp>
 #include <boost/bind.hpp>
 #include <iostream>

 #define MSG_OUT stdout /* Send info to stdout, change to stderr if you want */

 /* boost::asio related objects
  * using global variables for simplicity
  */
 boost::asio::io_service io_service;
 boost::asio::deadline_timer timer(io_service);
 std::map<curl_socket_t, boost::asio::ip::tcp::socket *> socket_map;

 /* Global information, common to all connections */
 typedef struct _GlobalInfo
 {
   CURLM *multi;
   int still_running;
 } GlobalInfo;

 /* Information associated with a specific easy handle */
 typedef struct _ConnInfo
 {
   CURL *easy;
   char *url;
   GlobalInfo *global;
   char error[CURL_ERROR_SIZE];
 } ConnInfo;

 static void timer_cb(const boost::system::error_code & error, GlobalInfo *g);

 /* Update the event timer after curl_multi library calls */
 static int multi_timer_cb(CURLM *multi, long timeout_ms, GlobalInfo *g)
 {
   fprintf(MSG_OUT, "\nmulti_timer_cb: timeout_ms %ld", timeout_ms);

   /* cancel running timer */
   timer.cancel();

   if(timeout_ms > 0) {
     /* update timer */
     timer.expires_from_now(boost::posix_time::millisec(timeout_ms));
     timer.async_wait(boost::bind(&timer_cb, _1, g));
   }
   else if(timeout_ms == 0) {
     /* call timeout function immediately */
     boost::system::error_code error; /*success*/
     timer_cb(error, g);
   }

   return 0;
 }

 /* 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_CALL_MULTI_PERFORM:
       s = "CURLM_CALL_MULTI_PERFORM";
       break;
     case CURLM_BAD_HANDLE:
       s = "CURLM_BAD_HANDLE";
       break;
     case CURLM_BAD_EASY_HANDLE:
       s = "CURLM_BAD_EASY_HANDLE";
       break;
     case CURLM_OUT_OF_MEMORY:
       s = "CURLM_OUT_OF_MEMORY";
       break;
     case CURLM_INTERNAL_ERROR:
       s = "CURLM_INTERNAL_ERROR";
       break;
     case CURLM_UNKNOWN_OPTION:
       s = "CURLM_UNKNOWN_OPTION";
       break;
     case CURLM_LAST:
       s = "CURLM_LAST";
       break;
     default:
       s = "CURLM_unknown";
       break;
     case CURLM_BAD_SOCKET:
       s = "CURLM_BAD_SOCKET";
       fprintf(MSG_OUT, "\nERROR: %s returns %s", where, s);
       /* ignore this error */
       return;
     }

     fprintf(MSG_OUT, "\nERROR: %s returns %s", where, s);

     exit(code);
   }
 }

 /* 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, "\nREMAINING: %d", 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, "\nDONE: %s => (%d) %s", eff_url, res, conn->error);
       curl_multi_remove_handle(g->multi, easy);
       free(conn->url);
       curl_easy_cleanup(easy);
       free(conn);
     }
   }
 }

 /* Called by asio when there is an action on a socket */
 static void event_cb(GlobalInfo *g, curl_socket_t s,
                      int action, const boost::system::error_code & error,
                      int *fdp)
 {
   fprintf(MSG_OUT, "\nevent_cb: action=%d", action);

   if(socket_map.find(s) == socket_map.end()) {
     fprintf(MSG_OUT, "\nevent_cb: socket already closed");
     return;
   }

   /* make sure the event matches what are wanted */
   if(*fdp == action || *fdp == CURL_POLL_INOUT) {
     CURLMcode rc;
     if(error)
       action = CURL_CSELECT_ERR;
     rc = curl_multi_socket_action(g->multi, s, 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, "\nlast transfer done, kill timeout");
       timer.cancel();
     }

     /* keep on watching.
      * the socket may have been closed and/or fdp may have been changed
      * in curl_multi_socket_action(), so check them both */
     if(!error && socket_map.find(s) != socket_map.end() &&
        (*fdp == action || *fdp == CURL_POLL_INOUT)) {
       boost::asio::ip::tcp::socket *tcp_socket = socket_map.find(s)->second;

       if(action == CURL_POLL_IN) {
         tcp_socket->async_read_some(boost::asio::null_buffers(),
                                     boost::bind(&event_cb, g, s,
                                                 action, _1, fdp));
       }
       if(action == CURL_POLL_OUT) {
         tcp_socket->async_write_some(boost::asio::null_buffers(),
                                      boost::bind(&event_cb, g, s,
                                                  action, _1, fdp));
       }
     }
   }
 }

 /* Called by asio when our timeout expires */
 static void timer_cb(const boost::system::error_code & error, GlobalInfo *g)
 {
   if(!error) {
     fprintf(MSG_OUT, "\ntimer_cb: ");

     CURLMcode rc;
     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 any data */
 static void remsock(int *f, GlobalInfo *g)
 {
   fprintf(MSG_OUT, "\nremsock: ");

   if(f) {
     free(f);
   }
 }

 static void setsock(int *fdp, curl_socket_t s, CURL *e, int act, int oldact,
                     GlobalInfo *g)
 {
   fprintf(MSG_OUT, "\nsetsock: socket=%d, act=%d, fdp=%p", s, act, fdp);

   std::map<curl_socket_t, boost::asio::ip::tcp::socket *>::iterator it =
     socket_map.find(s);

   if(it == socket_map.end()) {
     fprintf(MSG_OUT, "\nsocket %d is a c-ares socket, ignoring", s);
     return;
   }

   boost::asio::ip::tcp::socket * tcp_socket = it->second;

   *fdp = act;

   if(act == CURL_POLL_IN) {
     fprintf(MSG_OUT, "\nwatching for socket to become readable");
     if(oldact != CURL_POLL_IN && oldact != CURL_POLL_INOUT) {
       tcp_socket->async_read_some(boost::asio::null_buffers(),
                                   boost::bind(&event_cb, g, s,
                                               CURL_POLL_IN, _1, fdp));
     }
   }
   else if(act == CURL_POLL_OUT) {
     fprintf(MSG_OUT, "\nwatching for socket to become writable");
     if(oldact != CURL_POLL_OUT && oldact != CURL_POLL_INOUT) {
       tcp_socket->async_write_some(boost::asio::null_buffers(),
                                    boost::bind(&event_cb, g, s,
                                                CURL_POLL_OUT, _1, fdp));
     }
   }
   else if(act == CURL_POLL_INOUT) {
     fprintf(MSG_OUT, "\nwatching for socket to become readable & writable");
     if(oldact != CURL_POLL_IN && oldact != CURL_POLL_INOUT) {
       tcp_socket->async_read_some(boost::asio::null_buffers(),
                                   boost::bind(&event_cb, g, s,
                                               CURL_POLL_IN, _1, fdp));
     }
     if(oldact != CURL_POLL_OUT && oldact != CURL_POLL_INOUT) {
       tcp_socket->async_write_some(boost::asio::null_buffers(),
                                    boost::bind(&event_cb, g, s,
                                                CURL_POLL_OUT, _1, fdp));
     }
   }
 }

 static void addsock(curl_socket_t s, CURL *easy, int action, GlobalInfo *g)
 {
   /* fdp is used to store current action */
   int *fdp = (int *) calloc(sizeof(int), 1);

   setsock(fdp, s, easy, action, 0, 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)
 {
   fprintf(MSG_OUT, "\nsock_cb: socket=%d, what=%d, sockp=%p", s, what, sockp);

   GlobalInfo *g = (GlobalInfo*) cbp;
   int *actionp = (int *) sockp;
   const char *whatstr[] = { "none", "IN", "OUT", "INOUT", "REMOVE"};

   fprintf(MSG_OUT,
           "\nsocket callback: s=%d e=%p what=%s ", s, e, whatstr[what]);

   if(what == CURL_POLL_REMOVE) {
     fprintf(MSG_OUT, "\n");
     remsock(actionp, g);
   }
   else {
     if(!actionp) {
       fprintf(MSG_OUT, "\nAdding data: %s", whatstr[what]);
       addsock(s, e, what, g);
     }
     else {
       fprintf(MSG_OUT,
               "\nChanging action from %s to %s",
               whatstr[*actionp], whatstr[what]);
       setsock(actionp, s, e, what, *actionp, g);
     }
   }

   return 0;
 }

 /* CURLOPT_WRITEFUNCTION */
 static size_t write_cb(void *ptr, size_t size, size_t nmemb, void *data)
 {
   size_t written = size * nmemb;
   char *pBuffer = (char *)malloc(written + 1);

   strncpy(pBuffer, (const char *)ptr, written);
   pBuffer[written] = '\0';

   fprintf(MSG_OUT, "%s", pBuffer);

   free(pBuffer);

   return written;
 }

 /* CURLOPT_PROGRESSFUNCTION */
 static int prog_cb(void *p, double dltotal, double dlnow, double ult,
                    double uln)
 {
   ConnInfo *conn = (ConnInfo *)p;

   (void)ult;
   (void)uln;

   fprintf(MSG_OUT, "\nProgress: %s (%g/%g)", conn->url, dlnow, dltotal);
   fprintf(MSG_OUT, "\nProgress: %s (%g)", conn->url, ult);

   return 0;
 }

 /* CURLOPT_OPENSOCKETFUNCTION */
 static curl_socket_t opensocket(void *clientp, curlsocktype purpose,
                                 struct curl_sockaddr *address)
 {
   fprintf(MSG_OUT, "\nopensocket :");

   curl_socket_t sockfd = CURL_SOCKET_BAD;

   /* restrict to IPv4 */
   if(purpose == CURLSOCKTYPE_IPCXN && address->family == AF_INET) {
     /* create a tcp socket object */
     boost::asio::ip::tcp::socket *tcp_socket =
       new boost::asio::ip::tcp::socket(io_service);

     /* open it and get the native handle*/
     boost::system::error_code ec;
     tcp_socket->open(boost::asio::ip::tcp::v4(), ec);

     if(ec) {
       /* An error occurred */
       std::cout << std::endl << "Couldn't open socket [" << ec << "][" <<
         ec.message() << "]";
       fprintf(MSG_OUT, "\nERROR: Returning CURL_SOCKET_BAD to signal error");
     }
     else {
       sockfd = tcp_socket->native_handle();
       fprintf(MSG_OUT, "\nOpened socket %d", sockfd);

       /* save it for monitoring */
       socket_map.insert(std::pair<curl_socket_t,
                         boost::asio::ip::tcp::socket *>(sockfd, tcp_socket));
     }
   }

   return sockfd;
 }

 /* CURLOPT_CLOSESOCKETFUNCTION */
 static int close_socket(void *clientp, curl_socket_t item)
 {
   fprintf(MSG_OUT, "\nclose_socket : %d", item);

   std::map<curl_socket_t, boost::asio::ip::tcp::socket *>::iterator it =
     socket_map.find(item);

   if(it != socket_map.end()) {
     delete it->second;
     socket_map.erase(it);
   }

   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->easy = curl_easy_init();
   if(!conn->easy) {
     fprintf(MSG_OUT, "\ncurl_easy_init() failed, exiting!");
     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, 1L);
   curl_easy_setopt(conn->easy, CURLOPT_PROGRESSFUNCTION, prog_cb);
   curl_easy_setopt(conn->easy, CURLOPT_PROGRESSDATA, conn);
   curl_easy_setopt(conn->easy, CURLOPT_LOW_SPEED_TIME, 3L);
   curl_easy_setopt(conn->easy, CURLOPT_LOW_SPEED_LIMIT, 10L);

   /* call this function to get a socket */
   curl_easy_setopt(conn->easy, CURLOPT_OPENSOCKETFUNCTION, opensocket);

   /* call this function to close a socket */
   curl_easy_setopt(conn->easy, CURLOPT_CLOSESOCKETFUNCTION, close_socket);

   fprintf(MSG_OUT,
           "\nAdding easy %p to multi %p (%s)", 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 */
 }

 int main(int argc, char **argv)
 {
   GlobalInfo g;

   (void)argc;
   (void)argv;

   memset(&g, 0, sizeof(GlobalInfo));
   g.multi = curl_multi_init();

   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);

   new_conn((char *)"www.google.com", &g);  /* add a URL */

   /* enter io_service run loop */
   io_service.run();

   curl_multi_cleanup(g.multi);

   fprintf(MSG_OUT, "\ndone.\n");

   return 0;
 }
	/***************************************************************************
	* _ _ ____ _
	* Project ___\| \| \| \| _ \\| \|
	* / __\| \| \| \| \|_) \| \|
	* \| (__\| \|_\| \| _ <\| \|___
	* \___\|\___/\|_\| \_\_____\|
	*
	* Copyright (C) 2012 - 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>
	* demonstrate the use of multi socket interface with boost::asio
	* </DESC>
	*/
	/*
	* This program is in c++ and uses boost::asio instead of libevent/libev.
	* Requires boost::asio, boost::bind and boost::system
	*
	* This is an adaptation of libcurl's "hiperfifo.c" and "evhiperfifo.c"
	* sample programs. This example implements a subset of the functionality from
	* hiperfifo.c, for full functionality refer hiperfifo.c or evhiperfifo.c
	*
	* Written by Lijo Antony based on hiperfifo.c by Jeff Pohlmeyer
	*
	* When running, the program creates an easy handle for a URL and
	* uses the curl_multi API to fetch it.
	*
	* Note:
	* For the sake of simplicity, URL is hard coded to "www.google.com"
	*
	* This is purely a demo app, all retrieved data is simply discarded by the
	* write callback.
	*
	* ===========================================================================
	* WARNING: This example program is known to have flaws:
	* https://github.com/curl/curl/issues/2407
	*
	* It still kept in the example repository with the hope that it might be
	* useful, and maybe some day someone who knows enough about boost::asio will
	* read this text, accept the challenge and make the example code work
	* correctly. Until then: expect this example program to fail occasionally.
	* ===========================================================================
	*/


	#include <curl/curl.h>
	#include <boost/asio.hpp>
	#include <boost/bind.hpp>
	#include <iostream>

	#define MSG_OUT stdout /* Send info to stdout, change to stderr if you want */

	/* boost::asio related objects
	* using global variables for simplicity
	*/
	boost::asio::io_service io_service;
	boost::asio::deadline_timer timer(io_service);
	std::map<curl_socket_t, boost::asio::ip::tcp::socket *> socket_map;

	/* Global information, common to all connections */
	typedef struct _GlobalInfo
	{
	CURLM *multi;
	int still_running;
	} GlobalInfo;

	/* Information associated with a specific easy handle */
	typedef struct _ConnInfo
	{
	CURL *easy;
	char *url;
	GlobalInfo *global;
	char error[CURL_ERROR_SIZE];
	} ConnInfo;

	static void timer_cb(const boost::system::error_code & error, GlobalInfo *g);

	/* Update the event timer after curl_multi library calls */
	static int multi_timer_cb(CURLM multi, long timeout_ms, GlobalInfo g)
	{
	fprintf(MSG_OUT, "\nmulti_timer_cb: timeout_ms %ld", timeout_ms);

	/* cancel running timer */
	timer.cancel();

	if(timeout_ms > 0) {
	/* update timer */
	timer.expires_from_now(boost::posix_time::millisec(timeout_ms));
	timer.async_wait(boost::bind(&timer_cb, _1, g));
	}
	else if(timeout_ms == 0) {
	/* call timeout function immediately */
	boost::system::error_code error; /success/
	timer_cb(error, g);
	}

	return 0;
	}

	/* 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_CALL_MULTI_PERFORM:
	s = "CURLM_CALL_MULTI_PERFORM";
	break;
	case CURLM_BAD_HANDLE:
	s = "CURLM_BAD_HANDLE";
	break;
	case CURLM_BAD_EASY_HANDLE:
	s = "CURLM_BAD_EASY_HANDLE";
	break;
	case CURLM_OUT_OF_MEMORY:
	s = "CURLM_OUT_OF_MEMORY";
	break;
	case CURLM_INTERNAL_ERROR:
	s = "CURLM_INTERNAL_ERROR";
	break;
	case CURLM_UNKNOWN_OPTION:
	s = "CURLM_UNKNOWN_OPTION";
	break;
	case CURLM_LAST:
	s = "CURLM_LAST";
	break;
	default:
	s = "CURLM_unknown";
	break;
	case CURLM_BAD_SOCKET:
	s = "CURLM_BAD_SOCKET";
	fprintf(MSG_OUT, "\nERROR: %s returns %s", where, s);
	/* ignore this error */
	return;
	}

	fprintf(MSG_OUT, "\nERROR: %s returns %s", where, s);

	exit(code);
	}
	}

	/* 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, "\nREMAINING: %d", 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, "\nDONE: %s => (%d) %s", eff_url, res, conn->error);
	curl_multi_remove_handle(g->multi, easy);
	free(conn->url);
	curl_easy_cleanup(easy);
	free(conn);
	}
	}
	}

	/* Called by asio when there is an action on a socket */
	static void event_cb(GlobalInfo *g, curl_socket_t s,
	int action, const boost::system::error_code & error,
	int *fdp)
	{
	fprintf(MSG_OUT, "\nevent_cb: action=%d", action);

	if(socket_map.find(s) == socket_map.end()) {
	fprintf(MSG_OUT, "\nevent_cb: socket already closed");
	return;
	}

	/* make sure the event matches what are wanted */
	if(fdp == action \|\| fdp == CURL_POLL_INOUT) {
	CURLMcode rc;
	if(error)
	action = CURL_CSELECT_ERR;
	rc = curl_multi_socket_action(g->multi, s, 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, "\nlast transfer done, kill timeout");
	timer.cancel();
	}

	/* keep on watching.
	* the socket may have been closed and/or fdp may have been changed
	* in curl_multi_socket_action(), so check them both */
	if(!error && socket_map.find(s) != socket_map.end() &&
	(fdp == action \|\| fdp == CURL_POLL_INOUT)) {
	boost::asio::ip::tcp::socket *tcp_socket = socket_map.find(s)->second;

	if(action == CURL_POLL_IN) {
	tcp_socket->async_read_some(boost::asio::null_buffers(),
	boost::bind(&event_cb, g, s,
	action, _1, fdp));
	}
	if(action == CURL_POLL_OUT) {
	tcp_socket->async_write_some(boost::asio::null_buffers(),
	boost::bind(&event_cb, g, s,
	action, _1, fdp));
	}
	}
	}
	}

	/* Called by asio when our timeout expires */
	static void timer_cb(const boost::system::error_code & error, GlobalInfo *g)
	{
	if(!error) {
	fprintf(MSG_OUT, "\ntimer_cb: ");

	CURLMcode rc;
	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 any data */
	static void remsock(int f, GlobalInfo g)
	{
	fprintf(MSG_OUT, "\nremsock: ");

	if(f) {
	free(f);
	}
	}

	static void setsock(int fdp, curl_socket_t s, CURL e, int act, int oldact,
	GlobalInfo *g)
	{
	fprintf(MSG_OUT, "\nsetsock: socket=%d, act=%d, fdp=%p", s, act, fdp);

	std::map<curl_socket_t, boost::asio::ip::tcp::socket *>::iterator it =
	socket_map.find(s);

	if(it == socket_map.end()) {
	fprintf(MSG_OUT, "\nsocket %d is a c-ares socket, ignoring", s);
	return;
	}

	boost::asio::ip::tcp::socket * tcp_socket = it->second;

	*fdp = act;

	if(act == CURL_POLL_IN) {
	fprintf(MSG_OUT, "\nwatching for socket to become readable");
	if(oldact != CURL_POLL_IN && oldact != CURL_POLL_INOUT) {
	tcp_socket->async_read_some(boost::asio::null_buffers(),
	boost::bind(&event_cb, g, s,
	CURL_POLL_IN, _1, fdp));
	}
	}
	else if(act == CURL_POLL_OUT) {
	fprintf(MSG_OUT, "\nwatching for socket to become writable");
	if(oldact != CURL_POLL_OUT && oldact != CURL_POLL_INOUT) {
	tcp_socket->async_write_some(boost::asio::null_buffers(),
	boost::bind(&event_cb, g, s,
	CURL_POLL_OUT, _1, fdp));
	}
	}
	else if(act == CURL_POLL_INOUT) {
	fprintf(MSG_OUT, "\nwatching for socket to become readable & writable");
	if(oldact != CURL_POLL_IN && oldact != CURL_POLL_INOUT) {
	tcp_socket->async_read_some(boost::asio::null_buffers(),
	boost::bind(&event_cb, g, s,
	CURL_POLL_IN, _1, fdp));
	}
	if(oldact != CURL_POLL_OUT && oldact != CURL_POLL_INOUT) {
	tcp_socket->async_write_some(boost::asio::null_buffers(),
	boost::bind(&event_cb, g, s,
	CURL_POLL_OUT, _1, fdp));
	}
	}
	}

	static void addsock(curl_socket_t s, CURL easy, int action, GlobalInfo g)
	{
	/* fdp is used to store current action */
	int fdp = (int ) calloc(sizeof(int), 1);

	setsock(fdp, s, easy, action, 0, 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)
	{
	fprintf(MSG_OUT, "\nsock_cb: socket=%d, what=%d, sockp=%p", s, what, sockp);

	GlobalInfo g = (GlobalInfo) cbp;
	int actionp = (int ) sockp;
	const char *whatstr[] = { "none", "IN", "OUT", "INOUT", "REMOVE"};

	fprintf(MSG_OUT,
	"\nsocket callback: s=%d e=%p what=%s ", s, e, whatstr[what]);

	if(what == CURL_POLL_REMOVE) {
	fprintf(MSG_OUT, "\n");
	remsock(actionp, g);
	}
	else {
	if(!actionp) {
	fprintf(MSG_OUT, "\nAdding data: %s", whatstr[what]);
	addsock(s, e, what, g);
	}
	else {
	fprintf(MSG_OUT,
	"\nChanging action from %s to %s",
	whatstr[*actionp], whatstr[what]);
	setsock(actionp, s, e, what, *actionp, g);
	}
	}

	return 0;
	}

	/* CURLOPT_WRITEFUNCTION */
	static size_t write_cb(void ptr, size_t size, size_t nmemb, void data)
	{
	size_t written = size * nmemb;
	char pBuffer = (char )malloc(written + 1);

	strncpy(pBuffer, (const char *)ptr, written);
	pBuffer[written] = '\0';

	fprintf(MSG_OUT, "%s", pBuffer);

	free(pBuffer);

	return written;
	}

	/* CURLOPT_PROGRESSFUNCTION */
	static int prog_cb(void *p, double dltotal, double dlnow, double ult,
	double uln)
	{
	ConnInfo conn = (ConnInfo )p;

	(void)ult;
	(void)uln;

	fprintf(MSG_OUT, "\nProgress: %s (%g/%g)", conn->url, dlnow, dltotal);
	fprintf(MSG_OUT, "\nProgress: %s (%g)", conn->url, ult);

	return 0;
	}

	/* CURLOPT_OPENSOCKETFUNCTION */
	static curl_socket_t opensocket(void *clientp, curlsocktype purpose,
	struct curl_sockaddr *address)
	{
	fprintf(MSG_OUT, "\nopensocket :");

	curl_socket_t sockfd = CURL_SOCKET_BAD;

	/* restrict to IPv4 */
	if(purpose == CURLSOCKTYPE_IPCXN && address->family == AF_INET) {
	/* create a tcp socket object */
	boost::asio::ip::tcp::socket *tcp_socket =
	new boost::asio::ip::tcp::socket(io_service);

	/* open it and get the native handle*/
	boost::system::error_code ec;
	tcp_socket->open(boost::asio::ip::tcp::v4(), ec);

	if(ec) {
	/* An error occurred */
	std::cout << std::endl << "Couldn't open socket [" << ec << "][" <<
	ec.message() << "]";
	fprintf(MSG_OUT, "\nERROR: Returning CURL_SOCKET_BAD to signal error");
	}
	else {
	sockfd = tcp_socket->native_handle();
	fprintf(MSG_OUT, "\nOpened socket %d", sockfd);

	/* save it for monitoring */
	socket_map.insert(std::pair<curl_socket_t,
	boost::asio::ip::tcp::socket *>(sockfd, tcp_socket));
	}
	}

	return sockfd;
	}

	/* CURLOPT_CLOSESOCKETFUNCTION */
	static int close_socket(void *clientp, curl_socket_t item)
	{
	fprintf(MSG_OUT, "\nclose_socket : %d", item);

	std::map<curl_socket_t, boost::asio::ip::tcp::socket *>::iterator it =
	socket_map.find(item);

	if(it != socket_map.end()) {
	delete it->second;
	socket_map.erase(it);
	}

	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->easy = curl_easy_init();
	if(!conn->easy) {
	fprintf(MSG_OUT, "\ncurl_easy_init() failed, exiting!");
	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, 1L);
	curl_easy_setopt(conn->easy, CURLOPT_PROGRESSFUNCTION, prog_cb);
	curl_easy_setopt(conn->easy, CURLOPT_PROGRESSDATA, conn);
	curl_easy_setopt(conn->easy, CURLOPT_LOW_SPEED_TIME, 3L);
	curl_easy_setopt(conn->easy, CURLOPT_LOW_SPEED_LIMIT, 10L);

	/* call this function to get a socket */
	curl_easy_setopt(conn->easy, CURLOPT_OPENSOCKETFUNCTION, opensocket);

	/* call this function to close a socket */
	curl_easy_setopt(conn->easy, CURLOPT_CLOSESOCKETFUNCTION, close_socket);

	fprintf(MSG_OUT,
	"\nAdding easy %p to multi %p (%s)", 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 */
	}

	int main(int argc, char **argv)
	{
	GlobalInfo g;

	(void)argc;
	(void)argv;

	memset(&g, 0, sizeof(GlobalInfo));
	g.multi = curl_multi_init();

	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);

	new_conn((char )"www.google.com", &g); / add a URL */

	/* enter io_service run loop */
	io_service.run();

	curl_multi_cleanup(g.multi);

	fprintf(MSG_OUT, "\ndone.\n");

	return 0;
	}