misc.c: add a few basic clock functions

src/chessdefs.h

@@ -134,5 +134,35 @@ typedef enum {
     NORTH_WEST = (NORTH + WEST),
 } dir_t;
 
+#include <time.h>
+
+typedef struct mclock {
+    clockid_t clocktype;
+    ulong elapsed_l;
+    double elapsed_f;
+    struct timespec start;
+} mclock_t;
+
+#define CLOCK_WALL    CLOCK_REALTIME
+#define CLOCK_SYSTEM  CLOCK_MONOTONIC_RAW
+#define CLOCK_PROCESS CLOCK_PROCESS_CPUTIME_ID
+#define CLOCK_THREAD  CLOCK_THREAD_CPUTIME_ID
+
+/**
+ * CLOCK_DEFINE - define a clock type.
+ * @name: clock name
+ * @type: clock type
+ *
+ * This macro is equivalent to:
+ *   mclock_t name;
+ *   clock_init(&name, type);
+ */
+#define CLOCK_DEFINE(name, type) struct mclock name = { .clocktype = type }
+
+void clock_init(mclock_t *clock, clockid_t type);
+void clock_start(mclock_t *clock);
+s64 clock_elapsed_μs(mclock_t *clock);
+s64 clock_elapsed_ms(mclock_t *clock);
+double clock_elapsed_sec(mclock_t *clock);
 
 #endif  /* _CHESSDEFS_H */