Monotonic clock

diff --git a/server/server.go b/server/server.go
index 8dce69be6d77cfbbae9d73e9d96bfac4f9215445..c3bb59310b8ff28195f299b664cb0bd495c2c03c 100644 (file)
--- a/server/server.go
+++ b/server/server.go
@@ -53,7 +53,39 @@ type Store struct {
        Get chan *StoreRequest
 }
 
-// TODO: Monotonic clock
+var monotonic_clock chan chan time.Time
+
+const minimum_clock_increment = time.Millisecond
+
+func start_clock() {
+       internal_monotonic_clock := make(chan chan time.Time, 1)
+       go func() {
+               last_time := time.Now()
+       main:
+               for {
+                       select {
+                       case request, ok := <-internal_monotonic_clock:
+                               if !ok {
+                                       break main
+                               }
+                               earliest_acceptable_time := last_time.Add(minimum_clock_increment)
+                               current_time := time.Now()
+                               if current_time.Before(earliest_acceptable_time) {
+                                       current_time = earliest_acceptable_time
+                               }
+                               request <- current_time
+                               last_time = current_time
+                       }
+               }
+       }()
+       monotonic_clock = internal_monotonic_clock
+}
+
+func now() time.Time {
+       c := make(chan time.Time, 0)
+       monotonic_clock <- c
+       return <-c
+}
 
 func manage_store(store Store) {
        messages := list.New()
@@ -149,7 +181,7 @@ func start_server(store Store) {
 
        http.HandleFunc("/speak", func(w http.ResponseWriter, r *http.Request) {
                store.Add <- &Message{
-                       time.Now(),
+                       now(),
                        r.FormValue("id"),
                        r.FormValue("text")}
        })
@@ -163,7 +195,8 @@ func start_server(store Store) {
 
 func main() {
        flag.Parse()
-       start_time.Set(time.Now().UnixNano())
+       start_clock()
+       start_time.Set(now().UnixNano())
        store := start_store()
        start_server(store)
 }