From 233da97b19e81ebf5ca0bf62d8a0203b44ed70ea Mon Sep 17 00:00:00 2001
From: Kevin O'Connor <kevin@koconnor.net>
Date: Wed, 26 Jun 2019 14:05:10 -0400
Subject: [PATCH] reactor: Add support for "completions"

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---
 klippy/reactor.py | 55 +++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 46 insertions(+), 9 deletions(-)

diff --git a/klippy/reactor.py b/klippy/reactor.py
index 29ffe4f6..164f21b7 100644
--- a/klippy/reactor.py
+++ b/klippy/reactor.py
@@ -7,19 +7,45 @@ import os, select, math, time, Queue
 import greenlet
 import chelper, util
 
+_NOW = 0.
+_NEVER = 9999999999999999.
+
 class ReactorTimer:
     def __init__(self, callback, waketime):
         self.callback = callback
         self.waketime = waketime
 
+class ReactorCompletion:
+    class sentinel: pass
+    def __init__(self, reactor):
+        self.reactor = reactor
+        self.result = self.sentinel
+        self.waiting = None
+    def test(self):
+        return self.result is not self.sentinel
+    def complete(self, result):
+        self.result = result
+        if self.waiting is not None:
+            self.reactor.update_timer(self.waiting.timer, self.reactor.NOW)
+    def wait(self, waketime=_NEVER, waketime_result=None):
+        if self.result is self.sentinel:
+            self.waiting = greenlet.getcurrent()
+            self.reactor.pause(waketime)
+            self.waiting = None
+            if self.result is self.sentinel:
+                return waketime_result
+        return self.result
+
 class ReactorCallback:
     def __init__(self, reactor, callback, waketime):
         self.reactor = reactor
         self.timer = reactor.register_timer(self.invoke, waketime)
         self.callback = callback
+        self.completion = ReactorCompletion(reactor)
     def invoke(self, eventtime):
         self.reactor.unregister_timer(self.timer)
-        self.callback(eventtime)
+        res = self.callback(eventtime)
+        self.completion.complete(res)
         return self.reactor.NEVER
 
 class ReactorFileHandler:
@@ -64,8 +90,8 @@ class ReactorMutex:
         self.reactor.update_timer(self.queue[0].timer, self.reactor.NOW)
 
 class SelectReactor:
-    NOW = 0.
-    NEVER = 9999999999999999.
+    NOW = _NOW
+    NEVER = _NEVER
     def __init__(self):
         # Main code
         self._process = False
@@ -115,11 +141,22 @@ class SelectReactor:
         if eventtime >= self._next_timer:
             return 0.
         return min(1., max(.001, self._next_timer - self.monotonic()))
-    # Callbacks
+    # Callbacks and Completions
+    def completion(self):
+        return ReactorCompletion(self)
     def register_callback(self, callback, waketime=NOW):
-        ReactorCallback(self, callback, waketime)
-    def register_async_callback(self, callback):
-        self._async_queue.put_nowait(callback)
+        rcb = ReactorCallback(self, callback, waketime)
+        return rcb.completion
+    # Asynchronous (from another thread) callbacks and completions
+    def register_async_callback(self, callback, waketime=NOW):
+        self._async_queue.put_nowait(
+            (ReactorCallback, (self, callback, waketime)))
+        try:
+            os.write(self._pipe_fds[1], '.')
+        except os.error:
+            pass
+    def async_complete(self, completion, result):
+        self._async_queue.put_nowait((completion.complete, (result,)))
         try:
             os.write(self._pipe_fds[1], '.')
         except os.error:
@@ -131,10 +168,10 @@ class SelectReactor:
             pass
         while 1:
             try:
-                callback = self._async_queue.get_nowait()
+                func, args = self._async_queue.get_nowait()
             except Queue.Empty:
                 break
-            ReactorCallback(self, callback, self.NOW)
+            func(*args)
     def _setup_async_callbacks(self):
         self._pipe_fds = os.pipe()
         util.set_nonblock(self._pipe_fds[0])