text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2014, 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 http://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.
   *
   ***************************************************************************/
  /* This example code only builds as-is on Windows.
   *
   * While Unix/Linux user, you do not need this software.
   * You can achieve the same result as synctime using curl, awk and date.
   * Set proxy as according to your network, but beware of proxy Cache-Control.
   *
   * To set your system clock, root access is required.
   * # date -s "`curl -sI http://nist.time.gov/timezone.cgi?UTC/s/0 \
   *        | awk -F': ' '/Date: / {print $2}'`"
   *
   * To view remote webserver date and time.
   * $ curl -sI http://nist.time.gov/timezone.cgi?UTC/s/0 \
   *        | awk -F': ' '/Date: / {print $2}'
   *
   * Synchronising your computer clock via Internet time server usually relies
   * on DAYTIME, TIME, or NTP protocols. These protocols provide good accurate
   * time synchronisation but it does not work very well through a
   * firewall/proxy. Some adjustment has to be made to the firewall/proxy for
   * these protocols to work properly.
   *
   * There is an indirect method. Since most webserver provide server time in
   * their HTTP header, therefore you could synchronise your computer clock
   * using HTTP protocol which has no problem with firewall/proxy.
   *
   * For this software to work, you should take note of these items.
   * 1. Your firewall/proxy must allow your computer to surf internet.
   * 2. Webserver system time must in sync with the NTP time server,
   *    or at least provide an accurate time keeping.
   * 3. Webserver HTTP header does not provide the milliseconds units,
   *    so there is no way to get very accurate time.
   * 4. This software could only provide an accuracy of +- a few seconds,
   *    as Round-Trip delay time is not taken into consideration.
   *    Compensation of network, firewall/proxy delay cannot be simply divide
   *    the Round-Trip delay time by half.
   * 5. Win32 SetSystemTime() API will set your computer clock according to
   *    GMT/UTC time. Therefore your computer timezone must be properly set.
   * 6. Webserver data should not be cached by the proxy server. Some
   *    webserver provide Cache-Control to prevent caching.
   *
   * References:
   * http://tf.nist.gov/timefreq/service/its.htm
   * http://tf.nist.gov/timefreq/service/firewall.htm
   *
   * Usage:
   * This software will synchronise your computer clock only when you issue
   * it with --synctime. By default, it only display the webserver's clock.
   *
   * Written by: Frank (contributed to libcurl)
   *
   * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
   * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
   * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
   *
   * IN NO EVENT SHALL THE AUTHOR OF THIS SOFTWARE BE LIABLE FOR
   * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
   * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
   * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
   * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   * OF THIS SOFTWARE.
   *
   */
  
  #include <stdio.h>
  #include <time.h>
  #ifndef __CYGWIN__
  #include <windows.h>
  #endif
  #include <curl/curl.h>
  
  
  #define MAX_STRING              256
  #define MAX_STRING1             MAX_STRING+1
  
  #define SYNCTIME_UA "synctime/1.0"
  
  typedef struct
  {
    char http_proxy[MAX_STRING1];
    char proxy_user[MAX_STRING1];
    char timeserver[MAX_STRING1];
  } conf_t;
  
  const char DefaultTimeServer[3][MAX_STRING1] =
  {
    "http://pool.ntp.org/",
    "http://nist.time.gov/",
    "http://www.google.com/"
  };
  
  const char *DayStr[] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
  const char *MthStr[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
                          "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
  
  int  ShowAllHeader;
  int  AutoSyncTime;
  SYSTEMTIME SYSTime;
  SYSTEMTIME LOCALTime;
  
  #define HTTP_COMMAND_HEAD       0
  #define HTTP_COMMAND_GET        1
  
  
  size_t SyncTime_CURL_WriteOutput(void *ptr, size_t size, size_t nmemb,
                                   void *stream)
  {
    fwrite(ptr, size, nmemb, stream);
    return(nmemb*size);
  }
  
  size_t SyncTime_CURL_WriteHeader(void *ptr, size_t size, size_t nmemb,
                                   void *stream)
  {
    int   i, RetVal;
    char  TmpStr1[26], TmpStr2[26];
  
    if (ShowAllHeader == 1)
      fprintf(stderr, "%s", (char *)(ptr));
  
    if (strncmp((char *)(ptr), "Date:", 5) == 0) {
      if (ShowAllHeader == 0)
        fprintf(stderr, "HTTP Server. %s", (char *)(ptr));
  
      if (AutoSyncTime == 1) {
        *TmpStr1 = 0;
        *TmpStr2 = 0;
        if (strlen((char *)(ptr)) > 50) /* Can prevent buffer overflow to
                                           TmpStr1 & 2? */
          AutoSyncTime = 0;
        else {
          RetVal = sscanf ((char *)(ptr), "Date: %s %hu %s %hu %hu:%hu:%hu",
                           TmpStr1, &SYSTime.wDay, TmpStr2, &SYSTime.wYear,
                           &SYSTime.wHour, &SYSTime.wMinute, &SYSTime.wSecond);
  
          if (RetVal == 7) {
  
            SYSTime.wMilliseconds = 500;    /* adjust to midpoint, 0.5 sec */
            for (i=0; i<12; i++) {
              if (strcmp(MthStr[i], TmpStr2) == 0) {
                SYSTime.wMonth = i+1;
                break;
              }
            }
            AutoSyncTime = 3;       /* Computer clock will be adjusted */
          }
          else {
            AutoSyncTime = 0;       /* Error in sscanf() fields conversion */
          }
        }
      }
    }
  
    if (strncmp((char *)(ptr), "X-Cache: HIT", 12) == 0) {
      fprintf(stderr, "ERROR: HTTP Server data is cached."
              " Server Date is no longer valid.\n");
      AutoSyncTime = 0;
    }
    return(nmemb*size);
  }
  
  void SyncTime_CURL_Init(CURL *curl, char *proxy_port,
                          char *proxy_user_password)
  {
    if (strlen(proxy_port) > 0)
      curl_easy_setopt(curl, CURLOPT_PROXY, proxy_port);
  
    if (strlen(proxy_user_password) > 0)
      curl_easy_setopt(curl, CURLOPT_PROXYUSERPWD, proxy_user_password);
  
  #ifdef SYNCTIME_UA
    curl_easy_setopt(curl, CURLOPT_USERAGENT, SYNCTIME_UA);
  #endif
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, *SyncTime_CURL_WriteOutput);
    curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, *SyncTime_CURL_WriteHeader);
  }
  
  int SyncTime_CURL_Fetch(CURL *curl, char *URL_Str, char *OutFileName,
                          int HttpGetBody)
  {
    FILE *outfile;
    CURLcode res;
  
    outfile = NULL;
    if (HttpGetBody == HTTP_COMMAND_HEAD)
      curl_easy_setopt(curl, CURLOPT_NOBODY, 1L);
    else {
      outfile = fopen(OutFileName, "wb");
      curl_easy_setopt(curl, CURLOPT_WRITEDATA, outfile);
    }
  
    curl_easy_setopt(curl, CURLOPT_URL, URL_Str);
    res = curl_easy_perform(curl);
    if (outfile != NULL)
      fclose(outfile);
    return res;  /* (CURLE_OK) */
  }
  
  void showUsage(void)
  {
    fprintf(stderr, "SYNCTIME: Synchronising computer clock with time server"
            " using HTTP protocol.\n");
    fprintf(stderr, "Usage   : SYNCTIME [Option]\n");
    fprintf(stderr, "Options :\n");
    fprintf(stderr, " --server=WEBSERVER        Use this time server instead"
            " of default.\n");
    fprintf(stderr, " --showall                 Show all HTTP header.\n");
    fprintf(stderr, " --synctime                Synchronising computer clock"
            " with time server.\n");
    fprintf(stderr, " --proxy-user=USER[:PASS]  Set proxy username and"
            " password.\n");
    fprintf(stderr, " --proxy=HOST[:PORT]       Use HTTP proxy on given"
            " port.\n");
    fprintf(stderr, " --help                    Print this help.\n");
    fprintf(stderr, "\n");
    return;
  }
  
  int conf_init(conf_t *conf)
  {
    int i;
  
    *conf->http_proxy       = 0;
    for (i=0; i<MAX_STRING1; i++)
      conf->proxy_user[i]     = 0;    /* Clean up password from memory */
    *conf->timeserver       = 0;
    return 1;
  }
  
  int main(int argc, char *argv[])
  {
    CURL    *curl;
    conf_t  conf[1];
    int     OptionIndex;
    struct  tm *lt;
    struct  tm *gmt;
    time_t  tt;
    time_t  tt_local;
    time_t  tt_gmt;
    double  tzonediffFloat;
    int     tzonediffWord;
    char    timeBuf[61];
    char    tzoneBuf[16];
    int     RetValue;
  
    OptionIndex     = 0;
    ShowAllHeader   = 0;    /* Do not show HTTP Header */
    AutoSyncTime    = 0;    /* Do not synchronise computer clock */
    RetValue        = 0;    /* Successful Exit */
    conf_init(conf);
  
    if (argc > 1) {
      while (OptionIndex < argc) {
        if (strncmp(argv[OptionIndex], "--server=", 9) == 0)
          snprintf(conf->timeserver, MAX_STRING, "%s", &argv[OptionIndex][9]);
  
        if (strcmp(argv[OptionIndex], "--showall") == 0)
          ShowAllHeader = 1;
  
        if (strcmp(argv[OptionIndex], "--synctime") == 0)
          AutoSyncTime = 1;
  
        if (strncmp(argv[OptionIndex], "--proxy-user=", 13) == 0)
          snprintf(conf->proxy_user, MAX_STRING, "%s", &argv[OptionIndex][13]);
  
        if (strncmp(argv[OptionIndex], "--proxy=", 8) == 0)
          snprintf(conf->http_proxy, MAX_STRING, "%s", &argv[OptionIndex][8]);
  
        if ((strcmp(argv[OptionIndex], "--help") == 0) ||
            (strcmp(argv[OptionIndex], "/?") == 0)) {
          showUsage();
          return 0;
        }
        OptionIndex++;
      }
    }
  
    if (*conf->timeserver == 0)     /* Use default server for time information */
      snprintf(conf->timeserver, MAX_STRING, "%s", DefaultTimeServer[0]);
  
    /* Init CURL before usage */
    curl_global_init(CURL_GLOBAL_ALL);
    curl = curl_easy_init();
    if (curl) {
      SyncTime_CURL_Init(curl, conf->http_proxy, conf->proxy_user);
  
      /* Calculating time diff between GMT and localtime */
      tt       = time(0);
      lt       = localtime(&tt);
      tt_local = mktime(lt);
      gmt      = gmtime(&tt);
      tt_gmt   = mktime(gmt);
      tzonediffFloat = difftime(tt_local, tt_gmt);
      tzonediffWord  = (int)(tzonediffFloat/3600.0);
  
      if ((double)(tzonediffWord * 3600) == tzonediffFloat)
        snprintf(tzoneBuf, 15, "%+03d'00'", tzonediffWord);
      else
        snprintf(tzoneBuf, 15, "%+03d'30'", tzonediffWord);
  
      /* Get current system time and local time */
      GetSystemTime(&SYSTime);
      GetLocalTime(&LOCALTime);
      snprintf(timeBuf, 60, "%s, %02d %s %04d %02d:%02d:%02d.%03d, ",
               DayStr[LOCALTime.wDayOfWeek], LOCALTime.wDay,
               MthStr[LOCALTime.wMonth-1], LOCALTime.wYear,
               LOCALTime.wHour, LOCALTime.wMinute, LOCALTime.wSecond,
               LOCALTime.wMilliseconds);
  
      fprintf(stderr, "Fetch: %s\n\n", conf->timeserver);
      fprintf(stderr, "Before HTTP. Date: %s%s\n\n", timeBuf, tzoneBuf);
  
      /* HTTP HEAD command to the Webserver */
      SyncTime_CURL_Fetch(curl, conf->timeserver, "index.htm",
                          HTTP_COMMAND_HEAD);
  
      GetLocalTime(&LOCALTime);
      snprintf(timeBuf, 60, "%s, %02d %s %04d %02d:%02d:%02d.%03d, ",
               DayStr[LOCALTime.wDayOfWeek], LOCALTime.wDay,
               MthStr[LOCALTime.wMonth-1], LOCALTime.wYear,
               LOCALTime.wHour, LOCALTime.wMinute, LOCALTime.wSecond,
               LOCALTime.wMilliseconds);
      fprintf(stderr, "\nAfter  HTTP. Date: %s%s\n", timeBuf, tzoneBuf);
  
      if (AutoSyncTime == 3) {
        /* Synchronising computer clock */
        if (!SetSystemTime(&SYSTime)) {  /* Set system time */
          fprintf(stderr, "ERROR: Unable to set system time.\n");
          RetValue = 1;
        }
        else {
          /* Successfully re-adjusted computer clock */
          GetLocalTime(&LOCALTime);
          snprintf(timeBuf, 60, "%s, %02d %s %04d %02d:%02d:%02d.%03d, ",
                   DayStr[LOCALTime.wDayOfWeek], LOCALTime.wDay,
                   MthStr[LOCALTime.wMonth-1], LOCALTime.wYear,
                   LOCALTime.wHour, LOCALTime.wMinute, LOCALTime.wSecond,
                   LOCALTime.wMilliseconds);
          fprintf(stderr, "\nNew System's Date: %s%s\n", timeBuf, tzoneBuf);
        }
      }
  
      /* Cleanup before exit */
      conf_init(conf);
      curl_easy_cleanup(curl);
    }
    return RetValue;
  }
  