Begin libsandglass implementation.

1 files changed, 249 insertions, 0 deletions

diff --git a/src/sandglass.c b/src/sandglass.c
index 4acf983..57729f9 100644
--- a/src/sandglass.c
+++ b/src/sandglass.c
@@ -18,4 +18,253 @@
  * <http://www.gnu.org/licenses/>.                                       *
  *************************************************************************/
 
+#include "sandglass_impl.h"
 #include "sandglass.h"
+#include <unistd.h>
+#include <time.h>
+#include <errno.h>
+
+static int sandglass_real_create(sandglass_t *sandglass,
+                                 const sandglass_attributes_t *attr);
+
+/* Create a timer */
+int
+sandglass_create(sandglass_t *sandglass,
+                 const sandglass_attributes_t *min,
+                 const sandglass_attributes_t *max)
+{
+  sandglass_attributes_t realmin, realmax;
+
+  /* Get our real min and max values */
+
+  if (min)
+    realmin = *min;
+  else {
+    /* min defaults to { SANDGLASS_INTROSPECTIVE, SANDGLASS_SYSTEM } */
+    realmin.incrementation = SANDGLASS_INTROSPECTIVE;
+    realmin.resolution     = SANDGLASS_SYSTEM;
+  }
+
+  if (max)
+    realmax = *max;
+  else {
+    /* max defaults to the greater of min and { SANDGLASS_INTROSPECTIVE,
+       SANDGLASS_CPUTIME } */
+    if (realmin.incrementation > SANDGLASS_INTROSPECTIVE
+        || (realmin.incrementation == SANDGLASS_INTROSPECTIVE
+            && realmin.resolution > SANDGLASS_CPUTIME))
+      realmax = realmin;
+    else {
+      realmax.incrementation = SANDGLASS_INTROSPECTIVE;
+      realmax.resolution     = SANDGLASS_CPUTIME;
+    }
+  }
+
+  /* Ensure max >= min */
+  if (realmax.incrementation < realmin.incrementation
+      || (realmax.incrementation == realmin.incrementation
+          && realmax.resolution < realmin.resolution))
+  {
+    errno = EINVAL;
+    return -1;
+  }
+
+  /* Now search for available timers, starting from max */
+
+  while (sandglass_real_create(sandglass, &realmax) != 0) {
+    /* Once we reach the minimum attributes, bail out */
+    if (realmax.incrementation == realmin.incrementation
+        && realmax.resolution == realmin.resolution)
+    {
+      errno = ENOTSUP;
+      return -1;
+    }
+
+    /* Try the next lowest allowable settings */
+    if (realmax.resolution)
+      --realmax.resolution;
+    else {
+      if (realmax.incrementation) {
+        --realmax.incrementation;
+        realmax.resolution = SANDGLASS_CPUTIME;
+      } else {
+        errno = ENOTSUP;
+        return -1;
+      }
+    }
+  }
+
+  return 0;
+}
+
+static int
+sandglass_real_create(sandglass_t *sandglass,
+                      const sandglass_attributes_t *attr)
+{
+  switch (attr->incrementation) {
+    case SANDGLASS_MONOTONIC:
+      switch (attr->resolution) {
+        case SANDGLASS_REALTICKS:
+#ifdef SANDGLASS_TSC
+          sandglass->resolution = sandglass_tsc_resolution();
+          sandglass->loops      = sandglass_tsc_loops();
+          break;
+#else
+          return -1;
+#endif
+
+        case SANDGLASS_CPUTIME:
+#ifdef SANDGLASS_TSC
+          sandglass->resolution = sandglass_tsc_resolution();
+          sandglass->loops      = 1;
+          break;
+#else
+          return -1;
+#endif
+
+        case SANDGLASS_SYSTEM:
+          sandglass->resolution = 1e9;
+          sandglass->loops      = 1;
+          break;
+
+        default:
+          return -1;
+      }
+      break;
+
+    case SANDGLASS_INTROSPECTIVE:
+      switch (attr->resolution) {
+        case SANDGLASS_REALTICKS:
+          /* No such thing as an introspective raw TSC */
+          return -1;
+
+        case SANDGLASS_CPUTIME:
+          if (sysconf(_SC_THREAD_CPUTIME) > 0 || sysconf(_SC_CPUTIME) > 0) {
+            sandglass->resolution = 1e9;
+            sandglass->loops      = 1;
+          } else
+            return -1;
+          break;
+
+        case SANDGLASS_SYSTEM:
+          sandglass->resolution = CLOCKS_PER_SEC;
+          sandglass->loops      = 1;
+          break;
+
+        default:
+          return -1;
+      }
+      break;
+
+    default:
+      return -1;
+  }
+
+  sandglass->attributes = *attr;
+  return 0;
+}
+
+/* Store a timer value in sandglass->grains */
+static int sandglass_real_gettime(sandglass_t *sandglass);
+
+/* Start timing */
+int
+sandglass_begin(sandglass_t *sandglass)
+{
+  return sandglass_real_gettime(sandglass);
+}
+
+/* Finish timing */
+int
+sandglass_elapse(sandglass_t *sandglass)
+{
+  long oldgrains = sandglass->grains;
+
+  if (sandglass_real_gettime(sandglass) != 0)
+    return -1;
+
+  sandglass->grains -= oldgrains;
+  sandglass->grains /= sandglass->loops;
+
+  return 0;
+}
+
+/* Store a timer value in sandglass->grains */
+static int
+sandglass_real_gettime(sandglass_t *sandglass)
+{
+  struct timespec ts;
+  clock_t clock_ticks;
+
+  switch (sandglass->attributes.incrementation) {
+    case SANDGLASS_MONOTONIC:
+      switch (sandglass->attributes.resolution) {
+        case SANDGLASS_REALTICKS:
+#ifdef SANDGLASS_TSC
+          sandglass->grains = sandglass_get_tsc();
+          break;
+#else
+          return -1;
+#endif
+
+        case SANDGLASS_CPUTIME:
+#ifdef SANDGLASS_TSC
+          sandglass->grains = sandglass_get_tsc();
+          break;
+#else
+          return -1;
+#endif
+
+        case SANDGLASS_SYSTEM:
+          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;
+          }
+          break;
+
+        default:
+          return -1;
+      }
+      break;
+
+    case SANDGLASS_INTROSPECTIVE:
+      switch (sandglass->attributes.resolution) {
+        case SANDGLASS_REALTICKS:
+          /* No such thing as an introspective raw TSC */
+          return -1;
+
+        case SANDGLASS_CPUTIME:
+          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;
+          break;
+
+        case SANDGLASS_SYSTEM:
+          if ((clock_ticks = clock()) == -1)
+            return -1;
+          sandglass->grains = clock();
+          break;
+
+        default:
+          return -1;
+      }
+      break;
+
+    default:
+      return -1;
+  }
+
+  return 0;
+}