ext/unicorn_http/httpdate.c

   1 #include <ruby.h>
   2 #include <sys/time.h>
   3 #include <stdio.h>
   4
   5 static const size_t buf_capa = sizeof("Thu, 01 Jan 1970 00:00:00 GMT");
   6 static VALUE buf;
   7 static char *buf_ptr;
   8 static const char week[] = "Sun\0Mon\0Tue\0Wed\0Thu\0Fri\0Sat";
   9 static const char months[] = "Jan\0Feb\0Mar\0Apr\0May\0Jun\0"
  10                              "Jul\0Aug\0Sep\0Oct\0Nov\0Dec";
  11
  12 /* for people on wonky systems only */
  13 #ifndef HAVE_GMTIME_R
  14 # warning using fake gmtime_r
  15 static struct tm * my_gmtime_r(time_t *now, struct tm *tm)
  16 {
  17         struct tm *global = gmtime(now);
  18         if (global)
  19                 *tm = *global;
  20         return tm;
  21 }
  22 #  define gmtime_r my_gmtime_r
  23 #endif
  24
  25
  26 /*
  27  * Returns a string which represents the time as rfc1123-date of HTTP-date
  28  * defined by RFC 2616:
  29  *
  30  *   day-of-week, DD month-name CCYY hh:mm:ss GMT
  31  *
  32  * Note that the result is always GMT.
  33  *
  34  * This method is identical to Time#httpdate in the Ruby standard library,
  35  * except it is implemented in C for performance.  We always saw
  36  * Time#httpdate at or near the top of the profiler output so we
  37  * decided to rewrite this in C.
  38  *
  39  * Caveats: it relies on a Ruby implementation with the global VM lock,
  40  * a thread-safe version will be provided when a Unix-only, GVL-free Ruby
  41  * implementation becomes viable.
  42  */
  43 static VALUE httpdate(VALUE self)
  44 {
  45         static time_t last;
  46         struct timeval now;
  47         struct tm tm;
  48
  49         /*
  50          * Favor gettimeofday(2) over time(2), as the latter can return the
  51          * wrong value in the first 1 .. 2.5 ms of every second(!)
  52          *
  53          * https://lore.kernel.org/git/20230320230507.3932018-1-gitster@pobox.com/
  54          * https://inbox.sourceware.org/libc-alpha/20230306160321.2942372-1-adhemerval.zanella@linaro.org/T/
  55          * https://sourceware.org/bugzilla/show_bug.cgi?id=30200
  56          */
  57         if (gettimeofday(&now, NULL))
  58                 rb_sys_fail("gettimeofday");
  59
  60         if (last == now.tv_sec)
  61                 return buf;
  62         last = now.tv_sec;
  63         gmtime_r(&now.tv_sec, &tm);
  64
  65         /* we can make this thread-safe later if our Ruby loses the GVL */
  66         snprintf(buf_ptr, buf_capa,
  67                  "%s, %02d %s %4d %02d:%02d:%02d GMT",
  68                  week + (tm.tm_wday * 4),
  69                  tm.tm_mday,
  70                  months + (tm.tm_mon * 4),
  71                  tm.tm_year + 1900,
  72                  tm.tm_hour,
  73                  tm.tm_min,
  74                  tm.tm_sec);
  75
  76         return buf;
  77 }
  78
  79 void init_unicorn_httpdate(void)
  80 {
  81         VALUE mod = rb_define_module("Unicorn");
  82         mod = rb_define_module_under(mod, "HttpResponse");
  83
  84         buf = rb_str_new(0, buf_capa - 1);
  85         rb_gc_register_mark_object(buf);
  86         buf_ptr = RSTRING_PTR(buf);
  87         httpdate(Qnil);
  88
  89         rb_define_method(mod, "httpdate", httpdate, 0);
  90 }