serial_for_url: add new protocol that allows the selection of the Serial class

E.g. the posix platform has more than one implmenentation. This protocol
now allows to select them without changing the application (well, if it's
already using serial_for_url)

1 files changed, 51 insertions, 0 deletions

diff --git a/serial/urlhandler/protocol_alt.py b/serial/urlhandler/protocol_alt.py
new file mode 100644
index 0000000..3a7a0e0
--- /dev/null
+++ b/serial/urlhandler/protocol_alt.py
@@ -0,0 +1,51 @@
+#! python
+#
+# Python Serial Port Extension for Win32, Linux, BSD, Jython
+# see __init__.py
+#
+# This module implements a special URL handler that allows selection of
+# alternate implementation provided by some backends.
+#
+# (C) 2015 Chris Liechti <cliechti@gmx.net>
+#
+# SPDX-License-Identifier:    BSD-3-Clause
+#
+# URL format:    alt://port[?option[=value][&option[=value]]]
+# options:
+# - class=X used class named X instead of Serial
+#
+# example:
+#   use poll based implementation on Posix (Linux):
+#   python -m serial.tools.miniterm alt:///dev/ttyUSB0?class=PosixPollSerial
+
+import sys
+import time
+
+import serial
+
+try:
+    import urlparse
+except ImportError:
+    import urllib.parse as urlparse
+
+
+def serial_class_for_url(url):
+    """extract host and port from an URL string"""
+    parts = urlparse.urlsplit(url)
+    if parts.scheme != 'alt':
+        raise serial.SerialException('expected a string in the form "alt://port[?option[=value][&option[=value]]]": not starting with alt:// (%r)' % (parts.scheme,))
+    class_name = 'Serial'
+    try:
+        for option, values in urlparse.parse_qs(parts.query, True).items():
+            if option == 'class':
+                class_name = values[0]
+            else:
+                raise ValueError('unknown option: %r' % (option,))
+    except ValueError as e:
+        raise serial.SerialException('expected a string in the form "alt://port[?option[=value][&option[=value]]]": %s' % e)
+    return (''.join([parts.netloc, parts.path]), getattr(serial, class_name))
+
+# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+if __name__ == '__main__':
+    s = serial_for_url('alt:///dev/ttyS0?class=PosixPollSerial')
+    print(s)