Improve sandglass_tsc_resolution(), and fix timespec-based grains counts.

5 files changed, 74 insertions, 9 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 476c855..519e0ea 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -21,7 +21,11 @@ lib_LTLIBRARIES = libsandglass.la
 
 nobase_include_HEADERS = sandglass.h
 
-libsandglass_la_SOURCES    = sandglass.h sandglass_impl.h sandglass.c tsc.c
+libsandglass_la_SOURCES    = sandglass.h                                       \
+                             sandglass_impl.h                                  \
+                             sandglass.c                                       \
+                             timespec.c                                        \
+                             tsc.c
 
 if X86
   libsandglass_la_SOURCES += x86/tsc-x86.s
diff --git a/src/sandglass.c b/src/sandglass.c
index 57729f9..3399b73 100644
--- a/src/sandglass.c
+++ b/src/sandglass.c
@@ -184,6 +184,9 @@ sandglass_elapse(sandglass_t *sandglass)
     return -1;
 
   sandglass->grains -= oldgrains;
+  /* Magical correction for timespec-based grains */
+  if (sandglass->grains < 0)
+    sandglass->grains += 2000000000L;
   sandglass->grains /= sandglass->loops;
 
   return 0;
@@ -219,12 +222,11 @@ sandglass_real_gettime(sandglass_t *sandglass)
           if (sysconf(_SC_MONOTONIC_CLOCK) > 0) {
             if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
               return -1;
-            sandglass->grains = ts.tv_nsec;
           } else {
             if (clock_gettime(CLOCK_REALTIME, &ts) != 0)
               return -1;
-            sandglass->grains = ts.tv_nsec;
           }
+          sandglass->grains = sandglass_timespec_grains(&ts);
           break;
 
         default:
@@ -242,13 +244,12 @@ sandglass_real_gettime(sandglass_t *sandglass)
           if (sysconf(_SC_THREAD_CPUTIME) > 0) {
             if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) != 0)
               return -1;
-            sandglass->grains = ts.tv_nsec;
           } else if (sysconf(_SC_CPUTIME) > 0) {
             if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) != 0)
               return -1;
-            sandglass->grains = ts.tv_nsec;
           } else
             return -1;
+          sandglass->grains = sandglass_timespec_grains(&ts);
           break;
 
         case SANDGLASS_SYSTEM:
diff --git a/src/sandglass_impl.h b/src/sandglass_impl.h
index 5a3650e..b618a93 100644
--- a/src/sandglass_impl.h
+++ b/src/sandglass_impl.h
@@ -26,6 +26,7 @@
 #define SANDGLASS_IMPL_H_INCLUDED
 
 #include "sandglass.h"
+#include <time.h>
 
 #ifdef SANDGLASS_TSC
 /* Read the time stamp counter */
@@ -36,4 +37,6 @@ double sandglass_tsc_resolution();
 unsigned int sandglass_tsc_loops();
 #endif
 
+long sandglass_timespec_grains(const struct timespec *ts);
+
 #endif /* SANDGLASS_IMPL_H_INCLUDED */
\ No newline at end of file
diff --git a/src/timespec.c b/src/timespec.c
new file mode 100644
index 0000000..81a5815
--- /dev/null
+++ b/src/timespec.c
@@ -0,0 +1,30 @@
+/*************************************************************************
+ * Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com>               *
+ *                                                                       *
+ * This file is part of The Sandglass Library.                           *
+ *                                                                       *
+ * The Sandglass Library is free software; you can redistribute it       *
+ * and/or modify it under the terms of the GNU Lesser General Public     *
+ * License as published by the Free Software Foundation; either version  *
+ * 3 of the License, or (at your option) any later version.              *
+ *                                                                       *
+ * The Sandglass Library is distributed in the hope that it will be      *
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+#include "sandglass_impl.h"
+#include "sandglass.h"
+#include <time.h>
+
+/* Convert a timespec to grains */
+long
+sandglass_timespec_grains(const struct timespec *ts)
+{
+  return (ts->tv_sec%2L)*1000000000L + ts->tv_nsec;
+}
\ No newline at end of file
diff --git a/src/tsc.c b/src/tsc.c
index 64fe1b1..8038c0e 100644
--- a/src/tsc.c
+++ b/src/tsc.c
@@ -21,19 +21,46 @@
 #include "sandglass_impl.h"
 #include "sandglass.h"
 #include <time.h>
+#include <unistd.h>
 
 /* Gets the number of clock ticks per second */
 double
 sandglass_tsc_resolution()
 {
-  static long tsc = 0;
-  struct timespec ts = { .tv_sec = 0, .tv_nsec = 100000000 };
+  static long tsc = 0, grains1, grains2;
+
+  int monotonic;
+  struct timespec ts;
 
   if (tsc == 0) {
+    monotonic = sysconf(_SC_MONOTONIC_CLOCK) > 0;
+    if (monotonic) {
+      if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
+        return 0.0/0.0;
+    } else {
+      if (clock_gettime(CLOCK_REALTIME, &ts) != 0)
+        return 0.0/0.0;
+    }
     tsc = sandglass_get_tsc();
-    while (nanosleep(&ts, &ts) != 0);
+    grains1 = sandglass_timespec_grains(&ts);
+    grains2 = grains1;
+
+    while (((grains2 >= grains1) ? grains2 - grains1
+                                 : 2000000000L + (grains2 - grains1))
+           < 10000000L)
+    {
+      if (monotonic) {
+        if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
+          return 0.0/0.0;
+      } else {
+        if (clock_gettime(CLOCK_REALTIME, &ts) != 0)
+          return 0.0/0.0;
+      }
+      grains2 = sandglass_timespec_grains(&ts);
+    }
+
     tsc = sandglass_get_tsc() - tsc;
   }
 
-  return tsc*10.0;
+  return tsc*1.0e9/(grains2 - grains1);
 }