1 files changed, 107 insertions, 0 deletions
diff --git a/src/leap/util/coroutines.py b/src/leap/util/coroutines.py
new file mode 100644
index 00000000..5e25eb63
--- /dev/null
+++ b/src/leap/util/coroutines.py
@@ -0,0 +1,107 @@
+# the problem of watching a stdout pipe from
+# openvpn binary: using subprocess and coroutines
+# acting as event consumers
+
+from __future__ import division, print_function
+
+from subprocess import PIPE, Popen
+import sys
+from threading import Thread
+
+ON_POSIX = 'posix' in sys.builtin_module_names
+
+
+#
+# Coroutines goodies
+#
+
+def coroutine(func):
+    def start(*args, **kwargs):
+        cr = func(*args, **kwargs)
+        cr.next()
+        return cr
+    return start
+
+
+@coroutine
+def process_events(callback):
+    """
+    coroutine loop that receives
+    events sent and dispatch the callback.
+    :param callback: callback to be called\
+for each event
+    :type callback: callable
+    """
+    try:
+        while True:
+            m = (yield)
+            if callable(callback):
+                callback(m)
+            else:
+                #XXX log instead
+                print('not a callable passed')
+    except GeneratorExit:
+        return
+
+#
+# Threads
+#
+
+
+def launch_thread(target, args):
+    """
+    launch and demonize thread.
+    :param target: target function that will run in thread
+    :type target: function
+    :param args: args to be passed to thread
+    :type args: list
+    """
+    t = Thread(target=target,
+               args=args)
+    t.daemon = True
+    t.start()
+    return t
+
+
+def watch_output(out, observers):
+    """
+    initializes dict of observer coroutines
+    and pushes lines to each of them as they are received
+    from the watched output.
+    :param out: stdout of a process.
+    :type out: fd
+    :param observers: tuple of coroutines to send data\
+for each event
+    :type ovservers: tuple
+    """
+    observer_dict = {observer: process_events(observer)
+                     for observer in observers}
+    for line in iter(out.readline, b''):
+        for obs in observer_dict:
+            observer_dict[obs].send(line)
+    out.close()
+
+
+def spawn_and_watch_process(command, args, observers=None):
+    """
+    spawns a subprocess with command, args, and launch
+    a watcher thread.
+    :param command: command to be executed in the subprocess
+    :type command: str
+    :param args: arguments
+    :type args: list
+    :param observers: tuple of observer functions to be called \
+for each line in the subprocess output.
+    :type observers: tuple
+    :return: a tuple containing the child process instance, and watcher_thread,
+    :rtype: (Subprocess, Thread)
+    """
+    subp = Popen([command] + args,
+                 stdout=PIPE,
+                 stderr=PIPE,
+                 bufsize=1,
+                 close_fds=ON_POSIX)
+    watcher = launch_thread(
+        watch_output,
+        (subp.stdout, observers))
+    return subp, watcher