clock abstraction

include/ucore/ucore_clock.h

@@ -0,0 +1,99 @@
+#ifndef UCORE_CLOCK_H_
+#define UCORE_CLOCK_H_
+
+#include <sys/time.h>
+#include <time.h>
+
+
+/**
+ * An abstract clock.
+ * Instead of hardcoding calls to time()/gettimeofday() and similar,
+ * it is useful tp have a level of indirection to better facilitate
+ * testing and simulation of code that's dependent on time.
+ */
+struct ucore_clock {
+    /**
+     * Name of this clock
+     */
+    const char *name;
+    /**
+     * Wrapper for getting the current time.
+     * @param tv timeval that will be filled in
+     */
+    void (*now)(struct ucore_clock *clock, struct timeval *tv);
+};
+
+
+/** A cached clock where clock.now() returns
+ * the cached value. The cache is updated
+ * from the real_clock whenever ucore_cached_clock_update()
+ * is called.
+ */
+struct ucore_cached_clock {
+    /** The clock*/
+    struct ucore_clock clock;
+    /** The underlying real clock*/
+    struct ucore_clock *real_clock;
+    /** cached value */
+    struct timeval cache;
+};
+
+/** A settable clock where clock.now() returns
+ * the user settable value. The user updates the clock
+ * with ucore_settable_clock_set().
+ */
+struct ucore_settable_clock {
+    /** The clock*/
+    struct ucore_clock clock;
+    /** The underlying real clock*/
+    /** Current value */
+    struct timeval now;
+};
+
+
+/** A clock where now() calls gettimeofday()
+ */
+extern struct ucore_clock ucore_timeofday_clock;
+
+/**
+ * A clock where now() calls time().
+ * This clock will this just have seconds resolution.
+ */
+extern struct ucore_clock ucore_time_clock;
+
+/**
+ * Initialize a cached clock where now() calls time().
+ * This clock will this just have seconds resolution.
+ * @param clock clock to initialize
+ */
+void ucore_cached_clock_init(struct ucore_cached_clock *clock, 
+                                struct ucore_clock *real_clock);
+
+/** Update the cached clock from the real_clock
+ */
+void ucore_cached_clock_update(struct ucore_cached_clock *clock);
+
+
+/**
+ * Initialize a user settable where now() calls time().
+ * This clock will this just have seconds resolution.
+ * @param clock clock to initialize
+ */
+void ucore_settable_clock_init(struct ucore_settable_clock *clock);
+
+/**
+ * Set the new timeval this clock will return
+ **/
+void ucore_cached_clock_set_tv(struct ucore_settable_clock *clock, 
+                                const struct timeval *tv);
+
+/**
+ * Set the new timeval this clock will return
+ * Convenience function that takes seconds/microseconds as arguments
+ * instead of a struct timeval.
+ **/
+void ucore_cached_clock_set(struct ucore_settable_clock *clock, 
+                            time_t secs, suseconds_t usecs);
+
+#endif
+

src/ucore_clock.c

@@ -0,0 +1,81 @@
+#include <ucore/ucore_clock.h>
+#include <ucore/ucore_utils.h>
+
+#ifdef __GNUC__
+#define UNUSED __attribute__((__unused__))
+#else
+#define UNUSED
+#endif
+
+static void ucore_timeofday_now(struct ucore_clock *clock UNUSED, struct timeval *tv)
+{
+    gettimeofday(tv, NULL);
+}
+
+static void ucore_time_now(struct ucore_clock *clock UNUSED, struct timeval *tv)
+{
+    tv->tv_sec = time(NULL);
+    tv->tv_usec = 0;
+}
+
+struct ucore_clock ucore_timeofday_clock = {
+    .name = "gettimeofday",
+    .now = ucore_timeofday_now,
+};
+
+struct ucore_clock ucore_time_clock = {
+    .name = "time",
+    .now = ucore_time_now,
+};
+
+static void ucore_cached_clock_now(struct ucore_clock *clock UNUSED,
+                                    struct timeval *tv)
+{
+    struct ucore_cached_clock *cached_clock;
+    cached_clock = CONTAINER_OF(clock, struct ucore_cached_clock, clock),
+
+    *tv = cached_clock->cache;
+}
+
+void ucore_cached_clock_init(struct ucore_cached_clock *clock, struct ucore_clock *real_clock)
+{
+    clock->clock.name = "cached clock";
+    clock->clock.now = ucore_cached_clock_now;
+
+    clock->real_clock = real_clock;
+
+    ucore_cached_clock_update(clock);
+}
+
+void ucore_cached_clock_update(struct ucore_cached_clock *clock)
+{
+    clock->real_clock->now(&clock->clock, &clock->cache);
+}
+
+static void ucore_settable_clock_now(struct ucore_clock *clock, struct timeval *tv)
+{
+    struct ucore_settable_clock *cached_clock;
+    cached_clock = CONTAINER_OF(clock, struct ucore_settable_clock, clock),
+
+    *tv = cached_clock->now;
+}
+
+void ucore_settable_clock_init(struct ucore_settable_clock *clock)
+{
+    clock->clock.name = "settable clock";
+    clock->clock.now = ucore_settable_clock_now;
+
+    clock->now.tv_sec = 0;
+    clock->now.tv_usec = 0;
+}
+
+void ucore_settable_clock_set_tv(struct ucore_settable_clock *clock, const struct timeval *tv)
+{
+    clock->now = *tv;
+}
+
+void ucore_settable_clock_set(struct ucore_settable_clock *clock, time_t secs, suseconds_t usecs)
+{
+    clock->now.tv_sec = secs;
+    clock->now.tv_usec = usecs;
+}