ext/unicorn_http/httpdate.c

   1 #include <ruby.h>
   2 #include <time.h>
   3 #include <sys/time.h>
   4 #include <stdio.h>
   5
   6 static const size_t buf_capa = sizeof("Thu, 01 Jan 1970 00:00:00 GMT");
   7 static VALUE buf;
   8 static char *buf_ptr;
   9 static const char week[] = "Sun\0Mon\0Tue\0Wed\0Thu\0Fri\0Sat";
  10 static const char months[] = "Jan\0Feb\0Mar\0Apr\0May\0Jun\0"
  11                              "Jul\0Aug\0Sep\0Oct\0Nov\0Dec";
  12
  13 /* for people on wonky systems only */
  14 #ifndef HAVE_GMTIME_R
  15 # warning using fake gmtime_r
  16 static struct tm * my_gmtime_r(time_t *now, struct tm *tm)
  17 {
  18         struct tm *global = gmtime(now);
  19         if (global)
  20                 *tm = *global;
  21         return tm;
  22 }
  23 #  define gmtime_r my_gmtime_r
  24 #endif
  25
  26
  27 /*
  28  * Returns a string which represents the time as rfc1123-date of HTTP-date
  29  * defined by RFC 2616:
  30  *
  31  *   day-of-week, DD month-name CCYY hh:mm:ss GMT
  32  *
  33  * Note that the result is always GMT.
  34  *
  35  * This method is identical to Time#httpdate in the Ruby standard library,
  36  * except it is implemented in C for performance.  We always saw
  37  * Time#httpdate at or near the top of the profiler output so we
  38  * decided to rewrite this in C.
  39  *
  40  * Caveats: it relies on a Ruby implementation with the global VM lock,
  41  * a thread-safe version will be provided when a Unix-only, GVL-free Ruby
  42  * implementation becomes viable.
  43  */
  44 static VALUE httpdate(VALUE self)
  45 {
  46         static time_t last;
  47         struct timeval now;
  48         struct tm tm;
  49
  50         /*
  51          * Favor gettimeofday(2) over time(2), as the latter can return the
  52          * wrong value in the first 1 .. 2.5 ms of every second(!)
  53          *
  54          * https://lore.kernel.org/git/20230320230507.3932018-1-gitster@pobox.com/
  55          * https://inbox.sourceware.org/libc-alpha/20230306160321.2942372-1-adhemerval.zanella@linaro.org/T/
  56          * https://sourceware.org/bugzilla/show_bug.cgi?id=30200
  57          */
  58         if (gettimeofday(&now, NULL))
  59                 rb_sys_fail("gettimeofday");
  60
  61         if (last == now.tv_sec)
  62                 return buf;
  63         last = now.tv_sec;
  64         gmtime_r(&now.tv_sec, &tm);
  65
  66         /* we can make this thread-safe later if our Ruby loses the GVL */
  67         snprintf(buf_ptr, buf_capa,
  68                  "%s, %02d %s %4d %02d:%02d:%02d GMT",
  69                  week + (tm.tm_wday * 4),
  70                  tm.tm_mday,
  71                  months + (tm.tm_mon * 4),
  72                  tm.tm_year + 1900,
  73                  tm.tm_hour,
  74                  tm.tm_min,
  75                  tm.tm_sec);
  76
  77         return buf;
  78 }
  79
  80 void init_unicorn_httpdate(void)
  81 {
  82         VALUE mod = rb_define_module("Unicorn");
  83         mod = rb_define_module_under(mod, "HttpResponse");
  84
  85         buf = rb_str_new(0, buf_capa - 1);
  86         rb_gc_register_mark_object(buf);
  87         buf_ptr = RSTRING_PTR(buf);
  88         httpdate(Qnil);
  89
  90         rb_define_method(mod, "httpdate", httpdate, 0);
  91 }