Merge branch 'master' of http://git.louiz.org/poezio

1 files changed, 70 insertions, 0 deletions

diff --git a/src/fifo.py b/src/fifo.py
new file mode 100644
index 00000000..8306e24b
--- /dev/null
+++ b/src/fifo.py
@@ -0,0 +1,70 @@
+# Copyright 2011 Florent Le Coz <louiz@louiz.org>
+#
+# This file is part of Poezio.
+#
+# Poezio is free software: you can redistribute it and/or modify
+# it under the terms of the zlib license. See the COPYING file.
+
+"""
+Defines the Fifo class
+"""
+
+import logging
+log = logging.getLogger(__name__)
+
+import os
+import threading
+
+class OpenTrick(threading.Thread):
+    """
+    A threaded trick to make the open for writing succeed.
+    A fifo cannot be opened for writing if it has not been
+    yet opened by the other hand for reading.
+    So, we just open the fifo for reading and close it
+    immediately afterwards.
+    Once that is done, we can freely keep the fifo open for
+    writing and write things in it. The writing can fail if
+    there’s still nothing reading that fifo, but we just yell
+    an error in that case.
+    """
+    def __init__(self, path):
+        threading.Thread.__init__(self)
+        self.path = path
+
+    def run(self):
+        open(self.path, 'r').close()
+
+
+class Fifo(object):
+    """
+    Just a simple file handler, writing and reading in a fifo.
+    Mode is either 'r' or 'w', just like the mode for the open()
+    function.
+    """
+    def __init__(self, path, mode):
+        self.trick = None
+        if not os.path.exists(path):
+            os.mkfifo(path)
+        if mode == 'w':
+            self.trick = OpenTrick(path)
+            # that thread will wait until we open it for writing
+            self.trick.start()
+        self.fd = open(path, mode)
+
+    def write(self, data):
+        """
+        Try to write on the fifo. If that fails, this means
+        that nothing has that fifo opened, so the writing is useless,
+        so we just return (and display an error telling that, somewhere).
+        """
+        self.fd.write(data)
+        self.fd.flush()
+
+    def readline(self):
+        return self.fd.readline()
+
+    def __del__(self):
+        try:
+            self.fd.close()
+        except:
+            pass