Moving prepopulated search engines to a JSON file.

tools/json_to_struct/json_to_struct.py

+#!/usr/bin/env python
+# Copyright 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Format for the JSON schema file:
+# {
+#   "type_name": "DesiredCStructName",
+#   "headers": [          // Optional list of headers to be included by the .h.
+#     "path/to/header.h"
+#   ],
+#   "schema": [           // Fields of the generated structure.
+#     {
+#       "field": "my_enum_field",
+#       "type": "enum",   // Either: int, string, string16, enum, array.
+#       "default": "RED", // Optional. Cannot be used for array.
+#       "ctype": "Color"  // Only for enum, specify the C type.
+#     },
+#     {
+#       "field": "my_int_array_field",  // my_int_array_field_size will also
+#       "type": "array",                // be generated.
+#       "contents": {
+#         "type": "int"   // Either: int, string, string16, enum, array.
+#       }
+#     },
+#     ...
+#   ]
+# }
+#
+# Format for the JSON description file:
+# {
+#   "int_variables": {    // An optional list of constant int variables.
+#     "kDesiredConstantName": 45
+#   },
+#   "elements": {         // All the elements for which to create static
+#                         // initialization code in the .cc file.
+#     "my_const_variable": {
+#       "my_int_field": 10,
+#       "my_string_field": "foo bar",
+#       "my_enum_field": "BLACK",
+#       "my_int_array_field": [ 1, 2, 3, 5, 7 ],
+#     },
+#     "my_other_const_variable": {
+#       ...
+#     }
+#   }
+# }
+
+import json
+from datetime import datetime
+import os.path
+import sys
+import optparse
+import copy
+_script_path = os.path.realpath(__file__)
+_old_path = copy.copy(sys.path)
+
+sys.path.insert(0, os.path.normpath(_script_path + "/../../"))
+try:
+  import json_comment_eater
+finally:
+  sys.path = _old_path

[not at google - send to devlin, 2012/11/13 20:28:07]

nit: rather than storing _old_path use sys.path.pop(0).

[beaudoin, 2012/11/13 21:42:04]

/facepalm :)

Done.

+
+import struct_generator
+import element_generator
+
+HEAD = """// Copyright %d The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// GENERATED FROM THE SCHEMA DEFINITION AND DESCRIPTION IN
+//   %s
+//   %s
+// DO NOT EDIT.
+
+"""
+
+def _GenerateHeaderGuard(h_filename):
+  """Generates the string used in #ifndef guarding the header file.
+  """
+  return (('%s_' % h_filename)
+          .upper().replace(os.sep, '_').replace('/', '_').replace('.', '_'))
+
+def _GenerateH(fileroot, head, namespace, schema, description):
+  """Generates the .h file containing the definition of the structure specified
+  by the schema.
+
+  Args:
+    fileroot: The filename and path of the file to create, without an extension.
+    head: The string to output as the header of the .h file.
+    namespace: A string corresponding to the C++ namespace to use.
+    schema: A dict containing the schema. See comment at the top of this file.
+    description: A dict containing the description. See comment at the top of
+        this file.
+  """
+
+  h_filename = fileroot + '.h'
+  with open(h_filename, 'w') as f:
+    f.write(head)
+    header_guard = _GenerateHeaderGuard(h_filename)
+    f.write('#ifndef %s\n' % header_guard)
+    f.write('#define %s\n' % header_guard)
+    f.write('\n')
+
+    try:
+      for header in schema['headers']:
+        f.write('#include "%s"\n' % header)
+    except KeyError:

[not at google - send to devlin, 2012/11/13 20:28:07]

use schema.get('headers', []) rather than keyerror.

[beaudoin, 2012/11/13 21:42:04]

Done.

+      pass
+    f.write('\n')
+
+    if namespace:
+      f.write('namespace %s {\n' % namespace)
+      f.write('\n')
+
+    f.write(struct_generator.GenerateStruct(
+      schema['type_name'], schema['schema']))
+    f.write('\n')
+
+    try:
+      for var_name, value in description['int_variables'].items():
+        f.write('extern const int %s;\n' % var_name)
+      f.write('\n')
+    except KeyError:

[not at google - send to devlin, 2012/11/13 20:28:07]

use description.get('int_variables', []) rather than keyerror.

[beaudoin, 2012/11/13 21:42:04]

Done.

+      pass
+
+    for element_name, element in description['elements'].items():
+      f.write('extern const %s %s;\n' % (schema['type_name'], element_name))
+
+    if namespace:
+      f.write('\n')
+      f.write('}  // namespace %s\n' % namespace)
+
+    f.write('\n')
+    f.write( '#endif  // %s\n' % header_guard)
+
+def _GenerateCC(fileroot, head, namespace, schema, description):
+  """Generates the .cc file containing the static initializers for the
+  of the elements specified in the description.
+
+  Args:
+    fileroot: The filename and path of the file to create, without an extension.
+    head: The string to output as the header of the .cc file.
+    namespace: A string corresponding to the C++ namespace to use.
+    schema: A dict containing the schema. See comment at the top of this file.
+    description: A dict containing the description. See comment at the top of
+        this file.
+  """
+  with open(fileroot + '.cc', 'w') as f:
+    f.write(head)
+
+    f.write('#include <stdio.h>\n')
+    f.write('\n')
+    f.write('#include "%s"\n' % (fileroot + '.h'))
+    f.write('\n')
+
+    if namespace:
+      f.write('namespace %s {\n' % namespace)
+      f.write('\n')
+
+    f.write(element_generator.GenerateElements(schema['type_name'],

[not at google - send to devlin, 2012/11/13 20:28:07]

This distinction between the "struct generator" and the "element generator" is
confusing me. I can't parse the difference between them.

Can we do what JSON schema compiler does, and partition these into a "h
generator" and a "cc generator", and if they have common components then write
classes for those.

[beaudoin, 2012/11/13 21:42:04]

Following chat discussion: we'll keep it like this for now. Opened a bug for an
eventual merge/clean-up:
crbug.com/160809

+        schema['schema'], description))
+
+    if namespace:
+      f.write('\n')
+      f.write('}  // namespace %s\n' % namespace)
+
+def _Load(filename):
+  """Loads a JSON file int a Python object and return this object.
+  """
+  # TODO(beaudoin): When moving to Python 2.7 use object_pairs_hook=OrderedDict.
+  with open(filename, 'r') as handle:
+    result = json.loads(json_comment_eater.Nom(handle.read()))
+  return result
+
+if __name__ == '__main__':
+  parser = optparse.OptionParser(
+      description='Generates an C++ array of struct from a JSON description.',
+      usage='usage: %prog [option] -s schema description')
+  parser.add_option('-d', '--destdir',
+      help='root directory to output generated files.')
+  parser.add_option('-n', '--namespace',
+      help='C++ namespace for generated files. e.g search_providers.')
+  parser.add_option('-s', '--schema', help='path to the schema file, '
+      'mandatory.')
+  (opts, args) = parser.parse_args()
+
+  if not opts.schema:
+    parser.error('You must specify a --schema.')
+
+  description_filename = os.path.normpath(args[0])
+  root, ext = os.path.splitext(description_filename)
+  shortroot = os.path.split(root)[1]
+  if opts.destdir:
+    output_root = os.path.join(os.path.normpath(opts.destdir), shortroot)
+  else:
+    output_root = shortroot
+
+  schema = _Load(opts.schema)
+  description = _Load(description_filename)
+
+  head = HEAD % (datetime.now().year, opts.schema, description_filename)
+  _GenerateH(output_root, head, opts.namespace, schema, description)
+  _GenerateCC(output_root, head, opts.namespace, schema, description)