h2load: Support subsecond rate period

This change adds subsecond rate period support to h2load.  Now
--rate-period option only accepts integer, but it can be followed by
units.  Currently, h, m, s, and ms are supported, which are hours,
minutes, seconds, and milliseconds respectively.  The underlying
functionality and usecase are already extensively used in nghttpx.

src/h2load.cc

@@ -1261,7 +1261,7 @@ std::unique_ptr<Worker> create_worker(uint32_t id, SSL_CTX *ssl_ctx,
   std::stringstream rate_report;
   if (config.is_rate_mode() && nclients > rate) {
     rate_report << "Up to " << rate << " client(s) will be created every "
-                << std::setprecision(3) << config.rate_period << " seconds. ";
+                << util::duration_str(config.rate_period) << " ";
   }
 
   std::cout << "spawning thread #" << id << ": " << nclients
@@ -1379,12 +1379,12 @@ Options:
               will run  as it  normally does, creating  connections at
               whatever variable rate it  wants.  The default value for
               this option is 0.
-  --rate-period=<N>
+  --rate-period=<DURATION>
               Specifies the time  period between creating connections.
-              The  period  must be a positive  number  greater than or
+              The period  must be a positive  number, representing the
-              equal to 1.0,  representing the length of  the period in
+              length of the period in time.  This option is ignored if
-              seconds.  This option is  ignored if the rate  option is
+              the rate option is not used.  The default value for this
-              not used. The default value for this option is 1.0.
+              option is 1s.
   -T, --connection-active-timeout=<N>
               Specifies  the maximum  time that  h2load is  willing to
               keep a  connection open,  regardless of the  activity on
@@ -1434,7 +1434,14 @@ Options:
   -v, --verbose
               Output debug information.
   --version   Display version information and exit.
-  -h, --help  Display this help and exit.)" << std::endl;
+  -h, --help  Display this help and exit.
+
+--
+
+  The <DURATION> argument is an integer and an optional unit (e.g., 1s
+  is 1 second and 500ms is 500 milliseconds).  Units are h, m, s or ms
+  (hours, minutes, seconds and milliseconds, respectively).  If a unit
+  is omitted, a second is used as unit.)" << std::endl;
 }
 } // namespace
 
@@ -1629,26 +1636,15 @@ int main(int argc, char **argv) {
         // npn-list option
         config.npn_list = util::parse_config_str_list(optarg);
         break;
-      case 5: {
+      case 5:
         // rate-period
-        const char *start = optarg;
+        config.rate_period = util::parse_duration_with_unit(optarg);
-        char *end;
+        if (!std::isfinite(config.rate_period)) {
-        errno = 0;
+          std::cerr << "--rate-period: value error " << optarg << std::endl;
-        auto v = std::strtod(start, &end);
-
-        if (v < 1.0 || !std::isfinite(v) || end == start || errno != 0) {
-          auto error = errno;
-          std::cerr << "Rate period value error " << optarg << std::endl;
-          if (error != 0) {
-            std::cerr << "\n\t" << strerror(error) << std::endl;
-          }
           exit(EXIT_FAILURE);
         }
-
-        config.rate_period = v;
         break;
       }
-      }
       break;
     default:
       break;

src/util.h

@@ -659,9 +659,10 @@ int64_t parse_uint(const std::string &s);
 // Parses NULL terminated string |s| as unsigned integer and returns
 // the parsed integer casted to double.  If |s| ends with "s", the
 // parsed value's unit is a second.  If |s| ends with "ms", the unit
-// is millisecond.  If none of them are given, the unit is second.
+// is millisecond.  Similarly, it also supports 'm' and 'h' for
-// This function returns std::numeric_limits<double>::infinity() if
+// minutes and hours respectively.  If none of them are given, the
-// error occurs.
+// unit is second.  This function returns
+// std::numeric_limits<double>::infinity() if error occurs.
 double parse_duration_with_unit(const char *s);
 
 // Returns string representation of time duration |t|.  If t has