1 files changed, 275 insertions, 0 deletions

diff --git a/core/timer.c b/core/timer.c
new file mode 100644
index 00000000..06e25693
--- /dev/null
+++ b/core/timer.c
@@ -0,0 +1,275 @@
+#define __STDC_FORMAT_MACROS
+#include <inttypes.h>
+
+#include "timer.h"
+#include "network.h"
+
+/* 
+A nested linked list increases efficiency of insertions.
+Depending on the number of timers we have, we might need to have nested linked lists
+in order to improve insertion efficiency.
+The code below is preperation for that end, should it be necessary.
+
+typedef struct {
+    struct timer_package* _next;
+    union {
+        timer_packet* _inner;
+        timer* queue;
+    };
+    uint64_t pkgtime;
+} timer_package;
+
+timer_package* timer_package_pool;
+
+static timer_package* new_package()
+{
+    timer_package* ret;
+    if (timer_package_pool) {
+        ret = timer_package_pool;
+        timer_package_pool = timer_package_pool->_next;
+    } else {
+        ret = calloc(1, sizeof(struct timer_package));
+    }
+    return ret;
+}
+
+static void delete_package(timer_package* p)
+{
+    p->_next = timer_package_pool;
+    timer_package_pool = p;
+}
+*/
+
+enum timer_state {
+    STATE_INACTIVE = 0,
+    STATE_ACTIVE,
+    STATE_CALLBACK
+};
+
+struct timer
+{
+    enum timer_state state;
+    timer* _prev;
+    timer* _next;
+    timer_callback cb;
+    void* userdata;
+    uint64_t deadline;
+};
+
+static timer* timer_main_queue;
+static timer* timer_us_queue; /* hi-speed queue */
+
+inline static void timer_dequeue(timer* t, timer** queue)
+{
+    if (t->state == STATE_INACTIVE) return; /* not in a queue */
+    
+    if (t->_prev) {
+        t->_prev->_next = t->_next;
+    } else {
+        *queue = t->_next;
+    }
+    if (t->_next) t->_next->_prev = t->_prev;
+    t->state = STATE_INACTIVE;
+}
+
+static void timer_enqueue(timer* t, timer** queue, timer* prev)
+{
+    t->state = STATE_ACTIVE;
+    while (true) {
+        if (!*queue) {
+            t->_next = 0;
+            t->_prev = prev;
+            *queue = t;
+            return;
+        }
+
+        if ((*queue)->deadline > t->deadline) {
+            (*queue)->_prev = t;
+            t->_next = *queue;
+            t->_prev = prev;
+            *queue = t;
+            return;
+        }
+
+        prev = *queue;
+        queue = &((*queue)->_next);
+    }
+}
+
+/*** interface ***/
+
+void timer_init()
+{
+    /* Nothing needs to be done... yet. */
+}
+
+/* Do not depend on fields being zeroed */
+static timer* timer_pool; /* timer_pool is SINGLY LINKED!! */
+
+timer* new_timer(void)
+{
+    timer* ret;
+    if (timer_pool) {
+        ret = timer_pool;
+        timer_pool = timer_pool->_next;
+    } else {
+        ret = calloc(1, sizeof(struct timer));
+    }
+    ret->state = STATE_INACTIVE;
+    return ret;
+}
+
+void delete_timer(timer* t)
+{
+    timer_dequeue(t, &timer_main_queue);
+    t->_next = timer_pool;
+    t->state = STATE_INACTIVE;
+    timer_pool = t;
+}
+
+void timer_setup(timer* t, timer_callback cb, void* userarg)
+{
+    t->cb = cb;
+    t->userdata = userarg;
+}
+
+void* timer_get_userdata(timer* t)
+{
+    return t->userdata;
+}
+
+static void timer_delay_us(timer* t, int us)
+{
+    t->deadline += us;
+    timer** queue = t->_prev ? &(t->_prev->_next) : &timer_main_queue;
+    timer_dequeue(t, &timer_main_queue);
+    timer_enqueue(t, queue, t->_prev);
+}
+
+/* Starts the timer so that it's called in sec seconds in the future. 
+ * A non-positive value of sec results in the callback being called immediately.
+ * This function may be called again after a timer has been started to adjust 
+ * the expiry time. */
+void timer_start(timer* t, int sec)
+{
+    uint64_t newdeadline = current_time() + sec * US_PER_SECOND;
+    if (timer_is_active(t)){
+        if (t->deadline < newdeadline) {
+            timer_delay_us(t, newdeadline - t->deadline);
+            return;
+        }
+        timer_dequeue(t, &timer_main_queue);
+    }
+    t->deadline = newdeadline;
+    timer_enqueue(t, &timer_main_queue, 0);
+}
+
+/* Stops the timer. Returns -1 if the timer was not active. */
+int timer_stop(timer* t)
+{
+    int ret = timer_is_active(t) ? -1 : 0;
+    timer_dequeue(t, &timer_main_queue);
+    return ret;
+}
+
+/* Adds additionalsec seconds to the timer. 
+ * Returns -1 and does nothing if the timer was not active. */
+int timer_delay(timer* t, int additonalsec)
+{
+    if (!timer_is_active(t)) return -1;
+    timer_delay_us(t, additonalsec * US_PER_SECOND);
+    return 0;
+}
+
+static uint64_t timer_diff(timer* t, uint64_t time)
+{
+    if (t->deadline <= time) return 0;
+    return time - t->deadline;
+}
+
+/* Returns the time remaining on a timer in seconds.
+ * Returns -1 if the timer is not active.
+ * Returns 0 if the timer has expired and will be called upon the next call to timer_poll. */
+int timer_time_remaining(timer* t)
+{
+    if (!timer_is_active(t)) return -1;
+    return timer_diff(t, current_time()) / US_PER_SECOND;
+}
+
+bool timer_is_active(timer* t)
+{
+    return t->state != STATE_INACTIVE;
+}
+
+/* Single-use timer.
+ * Creates a new timer, preforms setup and starts it. */
+void timer_single(timer_callback cb, void* userarg, int sec)
+{
+    timer* t = new_timer();
+    timer_setup(t, cb, userarg);
+    timer_start(t, sec);
+}
+
+/* Single-use microsecond timer. */
+void timer_us(timer_callback cb, void* userarg, int us)
+{
+    timer* t = new_timer();
+    timer_setup(t, cb, userarg);
+    t->deadline = current_time() + us;
+    t->state = STATE_ACTIVE;
+    timer_enqueue(t, &timer_us_queue, 0);
+}
+
+uint64_t prevtime = 0;
+void timer_poll(void)
+{
+    uint64_t time = current_time();
+
+    /* Handle millisecond timers */
+    while (timer_us_queue) {
+        if (timer_diff(timer_us_queue, time) != 0) break;
+        timer* t = timer_us_queue;
+        timer_dequeue(t, &timer_us_queue);
+        t->cb(0, t->userdata);
+        delete_timer(t);
+    }
+
+    if (time - prevtime > US_PER_SECOND || prevtime == 0 || prevtime > time) { 
+        /* time moving backwards is just a sanity check */
+        prevtime = time;
+        
+        while (timer_main_queue) {
+            if (timer_diff(timer_main_queue, time) != 0) break;
+            timer* t = timer_main_queue;
+            t->state = STATE_CALLBACK;
+            int rv = t->cb(t, t->userdata);
+            if (rv != 0) {
+                timer_dequeue(t, &timer_main_queue);
+                delete_timer(t);
+                continue;
+            }
+            if (t->state != STATE_ACTIVE) {
+                timer_dequeue(t, &timer_main_queue);
+            }
+        }
+    }
+}
+
+/*** Internal Testing ***/
+
+/* I do not want to expose internals to the public, 
+ * which is why internals testing is done this way. */
+void timer_internal_tests(bool (*assert)(bool, char*))
+{
+    
+}
+
+void timer_debug_print()
+{
+    timer* t = timer_main_queue;
+    printf("Queue:\n");
+    while (t) {
+        printf("%" PRIu64 " (%" PRIu64 ") : %s\n", t->deadline, t->deadline/US_PER_SECOND, (char*)t->userdata);
+        t = t->_next;
+    }
+}