Add API_VERSION constant storing the runtime version as a tuple of ints (#49)

* Add API_VERSION constant storing the runtime version as a tuple of ints

Part of the fix for kaitai-io/kaitai_struct#804.

* Replace shortened GitHub issue ref with full URL (for convenience)

Co-authored-by: Petr Pucil <petr.pucil@seznam.cz>

Author: dgelessus

kaitaistruct.py

@@ -5,15 +5,21 @@
 
 PY2 = sys.version_info[0] == 2
 
-# Kaitai Struct runtime streaming API version, defined as per PEP-0396
-# standard. Used for two purposes:
-#
-# * .py files generated by ksc from .ksy check that they import proper
-#   KS runtime library by this version number;
-# * distribution utils (setup.py) use this when packaging for PyPI
-#
+# Kaitai Struct runtime version, in the format defined by PEP 440.
+# Used by our setup.cfg to set the version number in
+# packaging/distribution metadata.
+# Also used in Python code generated by older ksc versions (0.7 through 0.9)
+# to check that the imported runtime is compatible with the generated code.
+# Since ksc 0.10, the compatibility check instead uses the API_VERSION constant,
+# so that the version string does not need to be parsed at runtime
+# (see https://github.com/kaitai-io/kaitai_struct/issues/804).
 __version__ = '0.10'
 
+# Kaitai Struct runtime API version, as a tuple of ints.
+# Used in generated Python code (since ksc 0.10) to check that the imported
+# runtime is compatible with the generated code.
+API_VERSION = (0, 10)
+
 
 class KaitaiStruct(object):
     def __init__(self, stream):