Initial version of code generating plugin

The plugin generates higher performance compiled versions of the structs

capnp/_gen.py

@@ -0,0 +1,37 @@
+from __future__ import print_function
+
+import capnp
+import schema_capnp
+import sys
+from jinja2 import Environment, PackageLoader
+
+def main():
+  env = Environment(loader=PackageLoader('capnp', 'templates'))
+  env.filters['format_name'] = lambda name: name[name.find(':')+1:]
+
+  code = schema_capnp.CodeGeneratorRequest.read(sys.stdin)
+  code=code.to_dict()
+  code['nodes'] = [node for node in code['nodes'] if 'struct' in node]
+  for node in code['nodes']:
+    displayName = node['displayName']
+    parent, path = displayName.split(':')
+    node['module_path'] = parent.replace('.', '_') + '.' + '.'.join([x[0].upper() + x[1:] for x in path.split('.')])
+    node['module_name'] = path.replace('.', '_')
+    node['schema'] = '_{}_Schema'.format(node['module_name'])
+    is_union = False
+    for field in node['struct']['fields']:
+      if field['discriminantValue'] != 65535:
+        is_union = True
+    node['is_union'] = is_union
+
+  module = env.get_template('module.pyx')
+  filename = code['requestedFiles'][0]['filename'].replace('.', '_') + '_cython.pyx'
+  # TODO: handle multiple files
+  with open(filename, 'w') as out:
+    out.write(module.render(code=code))
+
+  setup = env.get_template('setup.py')
+  with open('setup_capnp.py', 'w') as out:
+    out.write(setup.render(code=code))
+  print('You now need to build the cython module by running `python setup_capnp.py build_ext --inplace`.')
+  print()