devout: add event loop and main run function

pkgs/devout/devout.fnl

@@ -1,3 +1,9 @@
+(local sock (require :minisock))
+(local { : view } (require :fennel))
+
+(fn trace [expr]
+  (doto expr (print :TRACE (view expr))))
+
 (fn parse-uevent [s]
   (let [at (string.find s "@" 1 true)
         (nl nxt) (string.find s "\0" 1 true)]
@@ -42,8 +48,80 @@
      :subscribe (fn [_ id callback terms]
                   (tset subscribers id {: callback : terms }))
      :unsubscribe (fn [_ id] (tset subscribers id nil))
-
      }))
 
+;; #define POLLIN          0x0001
+;; #define POLLPRI         0x0002
+;; #define POLLOUT         0x0004
+;; #define POLLERR         0x0008
+;; #define POLLHUP         0x0010
+;; #define POLLNVAL        0x0020
 
-{ : database }
+(fn unix-socket [name]
+  (let [addr (.. "\1\0"  name  "\0\0\0\0\0")
+        (sock err) (sock.bind addr)]
+    (assert sock err)))
+
+(fn pollfds-for [fds]
+  (table.concat (icollect [_ v (ipairs fds)] (string.pack "iHH" v 1 0))))
+
+(fn unpack-pollfds [pollfds]
+  (var i 1)
+  (let [fds {}]
+    (while (< i (# pollfds))
+      (let [(fd _ revents i_) (string.unpack "iHH" pollfds i)]
+        (if (> revents 0) (tset fds fd revents))
+        (set i i_)))
+    fds))
+
+(fn parse-terms [str]
+  (print :terms str)
+  (collect [n (string.gmatch str "([^ ]+)")]
+    (string.match n "(.-)=(.+)")))
+
+(fn handle-client [db client]
+  (match (trace (sock.read client))
+    "" (do
+         (db:unsubscribe client)
+         false)
+    s (do
+        (db:subscribe
+         client
+         (fn [e]
+           (sock.write client (view e)))
+         (parse-terms s))
+        true)
+    (nil err) (do (print err) false)))
+
+(fn event-loop []
+  (let [fds {}]
+    {
+     :register #(tset fds $2 $3)
+     :feed (fn [_ revents]
+             (each [fd revent (pairs revents)]
+               (when (not ((. fds fd) fd))
+                 (tset fds fd nil)
+                 (sock.close fd))))
+     :fds #(icollect [fd _ (pairs fds)] fd)
+    :_tbl #(do fds)                    ;exposed for tests
+     }))
+
+(fn run []
+  (let [[sockname] arg
+        s (unix-socket sockname)
+        db (database)
+        loop (event-loop)]
+    (loop:register
+     s
+     #(match (sock.accept s)
+        (client addr)
+        (do
+          (loop:register client (partial handle-client db))
+          true)))
+    (while true
+      (let [pollfds (pollfds-for (loop:fds))
+            (rpollfds numfds) (sock.poll pollfds 1000)]
+        (when (> numfds 0)
+          (loop:feed (unpack-pollfds rpollfds)))))))
+
+{ : database : run : event-loop  }