Updated OS X support code.

* Fixed warnings in existing implementation.
* Cached port returned by host_get_clock_service().
* Added unit test for curvecpr_util_nanoseconds().

Refs #4.

Author: impl

configure.ac

@@ -55,11 +55,10 @@ AC_TYPE_UINT32_T
 AC_CHECK_TYPE([struct timespec], [], [AC_MSG_ERROR([missing struct timespec])], [[#include <time.h>]])
 
 # Checks for functions.
-AC_CHECK_FUNCS([clock_gettime], [AC_DEFINE([HAVE_CLOCK_GETTIME])], [
-    AC_CHECK_FUNCS([host_get_clock_service],
-                   [AC_DEFINE([HAVE_HOST_GET_CLOCK_SERVICE])],
-                   [AC_MSG_ERROR([no clock_gettime or host_get_clock_service])])
-])
+AC_CHECK_FUNCS([clock_gettime],
+    [AC_DEFINE([HAVE_CLOCK_GETTIME])],
+    [AC_CHECK_FUNCS([host_get_clock_service], [AC_DEFINE([HAVE_HOST_GET_CLOCK_SERVICE])], [AC_MSG_ERROR([no clock_gettime or host_get_clock_service])])]
+)
 
 # Checks for compiler flags.
 CCHECKFLAGS="-Wno-error"

libcurvecpr/lib/util.c

@@ -5,14 +5,16 @@
 #include <curvecpr/bytes.h>
 
 #include <time.h>
-
-#include <sodium/randombytes.h>
-
 #ifdef HAVE_HOST_GET_CLOCK_SERVICE
+#include <libkern/OSAtomic.h>
 #include <mach/clock.h>
 #include <mach/mach.h>
+#include <mach/mach_error.h>
+#include <stdint.h>
 #endif
 
+#include <sodium/randombytes.h>
+
 /* XXX: Current implementation is limited to n < 2^55. */
 long long curvecpr_util_random_mod_n (long long n)
 {
@@ -34,18 +36,36 @@ long long curvecpr_util_random_mod_n (long long n)
 /* XXX: Nanosecond granularity limits users to 1 terabyte per second. */
 long long curvecpr_util_nanoseconds (void)
 {
-#if defined(HAVE_CLOCK_GETTIME)
+    /* XXX: host_get_clock_service() has been officially deprecated for years;
+       this may need to be updated in the future. */
+#ifdef HAVE_HOST_GET_CLOCK_SERVICE
+    static int32_t cclock_registered = 0;
+    static volatile clock_serv_t cclock = 0;
+    mach_timespec_t t;
+
+    if (!cclock) {
+        if (OSAtomicCompareAndSwap32Barrier(0, 1, &cclock_registered) == 1) {
+            clock_serv_t cclock_actual;
+
+            if (host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock_actual) != KERN_SUCCESS) {
+                cclock_registered = 0;
+                return -1;
+            }
+
+            cclock = cclock_actual;
+        } else {
+            while (!cclock)
+                /* Wait for clock to become available */;
+        }
+    }
+
+    if (clock_get_time(cclock, &t) != KERN_SUCCESS)
+        return -1;
+#else
     struct timespec t;
+
     if (clock_gettime(CLOCK_REALTIME, &t) != 0)
         return -1;
-#elif defined(HAVE_HOST_GET_CLOCK_SERVICE)
-    clock_serv_t clock;
-    mach_timespec_t t;
-    host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &clock);
-    clock_get_time(clock, &t);
-    mach_port_deallocate(mach_task_self(), clock);
-#else
-    #error "no function for getting microseconds"
 #endif
 
     return t.tv_sec * 1000000000LL + t.tv_nsec;

libcurvecpr/test/Makefile.am

@@ -13,4 +13,7 @@ messager_test_recv_requests_removal_from_sendmarkq_SOURCES = messager/test_recv_
 check_PROGRAMS += messager/test_send_with_1_failure_moves_message_from_sendq
 messager_test_send_with_1_failure_moves_message_from_sendq_SOURCES = messager/test_send_with_1_failure_moves_message_from_sendq.c
 
+check_PROGRAMS += util/test_nanoseconds
+util_test_nanoseconds_SOURCES = util/test_nanoseconds.c
+
 TESTS = $(check_PROGRAMS)

libcurvecpr/test/util/test_nanoseconds.c

@@ -0,0 +1,22 @@
+#include <check.h>
+#include <check_extras.h>
+
+#include <curvecpr/util.h>
+
+START_TEST (test_nanoseconds)
+{
+    long long nanoseconds = curvecpr_util_nanoseconds();
+
+    fail_if(nanoseconds < 0);
+    fail_unless(nanoseconds > 1374047000000000000LL);
+
+    /* On OS X, we may cache the kernel clock reference. Make sure it still
+       works. */
+    nanoseconds = curvecpr_util_nanoseconds();
+
+    fail_if(nanoseconds < 0);
+    fail_unless(nanoseconds > 1374047000000000000LL);
+}
+END_TEST
+
+RUN_TEST (test_nanoseconds)