Distribution and installation

The new module setup.py handles creation of package distributions in
compressed formats, and performs installation of said distributions
after decompression. Distribution strategy for PyDTLS is in the form
of source distributions only.

Building the OpenSSL library on Windows is non-trivial. Requirements
include linking against the same version of the C runtime that is used
by the Python interpreter, or else Microsoft redistributable
installation may also need to be performed. For the convenience of
Windows users, the distribution procedure includes creation of
prebuilt versions of the OpenSSL library for both 32- and 64-bit
versions of Windows. Despite containing binaries, these are still
source distributions that are installed with "python setup.py
install."

A version of OpenSSL compiled with the MinGW toolchain is included.
cygcrypto-1.0.0.dll and cygssl-1.0.0.dll contain symbols and can be
debugged with gdb. All MinGW OpenSSL dll's link with msvcr90.dll.

In order to avoid making installation a requirement after cloning, the
package initializer looks for prebuilts of the currently executing
platform and copies them into the dtls package directory before
continuing module initialization.

A distribution containing prebuilts for all platforms as well as those
containing no prebuilts (appropriate for Linux) can be generated by
issuing "python setup.py sdist --prebuilts."

dtls/__init__.py

@@ -15,6 +15,29 @@ sockets.
 wrap_socket's parameters and their semantics have been maintained.
 """
 
+def _prep_bins():
+    """
+    Support for running straight out of a cloned source directory instead
+    of an installed distribution
+    """
+
+    from os import path
+    from sys import platform, maxsize
+    from shutil import copy
+    bit_suffix = "-x86_64" if maxsize > 2**32 else "-x86"
+    package_root = path.abspath(path.dirname(__file__))
+    prebuilt_path = path.join(package_root, "prebuilt", platform + bit_suffix)
+    config = {"MANIFEST_DIR": prebuilt_path}
+    try:
+        execfile(path.join(prebuilt_path, "manifest.pycfg"), config)
+    except IOError:
+        return  # there are no prebuilts for this platform - nothing to do
+    files = map(lambda x: path.join(prebuilt_path, x), config["FILES"])
+    for prebuilt_file in files:
+        copy(path.join(prebuilt_path, prebuilt_file), package_root)
+
+_prep_bins()  # prepare before module imports
+
 from patch import do_patch
 from sslconnection import SSLConnection
 from demux import force_routing_demux, reset_default_demux