client: Interleave accepting new button presses & re-sends

[tattlekey] / client / tattlekey.c

diff --git a/client/tattlekey.c b/client/tattlekey.c
index aadf49dd9b58d1ad36c175128583d648c4a136c8..cd1324145e220b097578b0b67e613ca973778bd8 100644 (file)
--- a/client/tattlekey.c
+++ b/client/tattlekey.c
@@ -7,13 +7,18 @@
 #include "config.h"
 #include "net.h"
 
-enum event_type { BUTTONPRESS };
+enum event_type { BUTTONPRESS, SEND };
 typedef struct {
   enum event_type type;
   union {
     struct {
       uint32_t timestamp;
     } buttonpress;
+    struct {
+      uint32_t timestamp;
+      u16_t seq;
+      u8_t send_count;
+    } send;
   };
 } event_t;
 
@@ -21,6 +26,17 @@ queue_t queue;
 
 uint32_t time_s() { return time_us_64() / 1000000ul; }
 
+/* Often we don't bother checking for failure (full queue) because
+ *   1. The best thing to do in this unfortunate situation is to blithely
+ *      continue, dropping some events; continuing is better than stopping.
+ *   2. Neither interrupt context nor queue-processing context can block
+ *      until space is available, or even sit around & blink the LED to
+ *      signal a problem.
+ * (We also get a bit of type safety by taking event_t* rather than void*.) */
+static void queue_try_add_ignoring_errors(queue_t *q, event_t *e) {
+  queue_try_add(q, e);
+}
+
 static void button_pressed() {
   /* This runs in interrupt context; don't linger.  */
   static uint64_t last_button_press_time = 0;
@@ -31,9 +47,7 @@ static void button_pressed() {
     event_t e;
     e.type = BUTTONPRESS;
     e.buttonpress.timestamp = now;
-    /* We don't check for failure (full queue) here because there's not much to
-     * be done about it. */
-    queue_try_add(&queue, &e);
+    queue_try_add_ignoring_errors(&queue, &e);
   }
 }
 
@@ -57,16 +71,25 @@ int main() {
     event_t e;
     queue_remove_blocking(&queue, &e);
     switch (e.type) {
-    case BUTTONPRESS:
-      seq++;
-      for (int i = 0; i < config_resend_count; i++) {
-        uint32_t now = time_s();
-        uint32_t ago = now - e.buttonpress.timestamp;
-        send_report(seq, ago);
-        signal(i == 0 ? 2 : 1, 100);
-        sleep_ms(config_resend_interval_ms);
-      }
-      break;
+    case BUTTONPRESS: {
+      event_t send_e;
+      send_e.type = SEND;
+      send_e.send.timestamp = e.buttonpress.timestamp;
+      send_e.send.seq = seq++;
+      send_e.send.send_count = 0;
+      queue_try_add_ignoring_errors(&queue, &send_e);
+    } break;
+    case SEND: {
+      uint32_t now = time_s();
+      uint32_t ago = now - e.send.timestamp;
+      send_report(e.send.seq, ago);
+      e.send.send_count++;
+      if (e.send.send_count < config_resend_count)
+        queue_try_add_ignoring_errors(&queue, &e);
+      /* TODO: Sleep elsewhere. */
+      signal(e.send.send_count == 1 ? 2 : 1, 100);
+      sleep_ms(config_resend_interval_ms);
+    } break;
     default:
       signal_error_by_blinking();
     }