tools/json_to_struct/json_to_struct.py

   1 #!/usr/bin/env python
   2 # Copyright 2012 The Chromium Authors. All rights reserved.
   3 # Use of this source code is governed by a BSD-style license that can be
   4 # found in the LICENSE file.
   5
   6 # Format for the JSON schema file:
   7 # {
   8 #   "type_name": "DesiredCStructName",
   9 #   "headers": [          // Optional list of headers to be included by the .h.
  10 #     "path/to/header.h"
  11 #   ],
  12 #   "schema": [           // Fields of the generated structure.
  13 #     {
  14 #       "field": "my_enum_field",
  15 #       "type": "enum",   // Either: int, string, string16, enum, array.
  16 #       "default": "RED", // Optional. Cannot be used for array.
  17 #       "ctype": "Color"  // Only for enum, specify the C type.
  18 #     },
  19 #     {
  20 #       "field": "my_int_array_field",  // my_int_array_field_size will also
  21 #       "type": "array",                // be generated.
  22 #       "contents": {
  23 #         "type": "int"   // Either: int, string, string16, enum, array.
  24 #       }
  25 #     },
  26 #     ...
  27 #   ]
  28 # }
  29 #
  30 # Format for the JSON description file:
  31 # {
  32 #   "int_variables": {    // An optional list of constant int variables.
  33 #     "kDesiredConstantName": 45
  34 #   },
  35 #   "elements": {         // All the elements for which to create static
  36 #                         // initialization code in the .cc file.
  37 #     "my_const_variable": {
  38 #       "my_int_field": 10,
  39 #       "my_string_field": "foo bar",
  40 #       "my_enum_field": "BLACK",
  41 #       "my_int_array_field": [ 1, 2, 3, 5, 7 ],
  42 #     },
  43 #     "my_other_const_variable": {
  44 #       ...
  45 #     }
  46 #   }
  47 # }
  48
  49 import json
  50 from datetime import datetime
  51 import os.path
  52 import sys
  53 import optparse
  54 import re
  55 _script_path = os.path.realpath(__file__)
  56
  57 sys.path.insert(0, os.path.normpath(_script_path + "/../../json_comment_eater"))
  58 try:
  59   import json_comment_eater
  60 finally:
  61   sys.path.pop(0)
  62
  63 import struct_generator
  64 import element_generator
  65
  66 HEAD = """// Copyright %d The Chromium Authors. All rights reserved.
  67 // Use of this source code is governed by a BSD-style license that can be
  68 // found in the LICENSE file.
  69
  70 // GENERATED FROM THE SCHEMA DEFINITION AND DESCRIPTION IN
  71 //   %s
  72 //   %s
  73 // DO NOT EDIT.
  74
  75 """
  76
  77 def _GenerateHeaderGuard(h_filename):
  78   """Generates the string used in #ifndef guarding the header file.
  79   """
  80   result = re.sub('[%s\\\\.]' % os.sep, '_', h_filename.upper())
  81   return re.sub('^_*', '', result) + '_'  # Remove leading underscores.
  82
  83 def _GenerateH(basepath, fileroot, head, namespace, schema, description):
  84   """Generates the .h file containing the definition of the structure specified
  85   by the schema.
  86
  87   Args:
  88     basepath: The base directory in which files are generated.
  89     fileroot: The filename and path, relative to basepath, of the file to
  90         create, without an extension.
  91     head: The string to output as the header of the .h file.
  92     namespace: A string corresponding to the C++ namespace to use.
  93     schema: A dict containing the schema. See comment at the top of this file.
  94     description: A dict containing the description. See comment at the top of
  95         this file.
  96   """
  97
  98   h_filename = fileroot + '.h'
  99   with open(os.path.join(basepath, h_filename), 'w') as f:
 100     f.write(head)
 101
 102     f.write('#include <cstddef>\n')
 103     f.write('\n')
 104
 105     header_guard = _GenerateHeaderGuard(h_filename)
 106     f.write('#ifndef %s\n' % header_guard)
 107     f.write('#define %s\n' % header_guard)
 108     f.write('\n')
 109
 110     for header in schema.get('headers', []):
 111       f.write('#include "%s"\n' % header)
 112     f.write('\n')
 113
 114     if namespace:
 115       f.write('namespace %s {\n' % namespace)
 116       f.write('\n')
 117
 118     f.write(struct_generator.GenerateStruct(
 119       schema['type_name'], schema['schema']))
 120     f.write('\n')
 121
 122     for var_name, value in description.get('int_variables', []).items():
 123       f.write('extern const int %s;\n' % var_name)
 124     f.write('\n')
 125
 126     for element_name, element in description['elements'].items():
 127       f.write('extern const %s %s;\n' % (schema['type_name'], element_name))
 128
 129     if namespace:
 130       f.write('\n')
 131       f.write('}  // namespace %s\n' % namespace)
 132
 133     f.write('\n')
 134     f.write( '#endif  // %s\n' % header_guard)
 135
 136 def _GenerateCC(basepath, fileroot, head, namespace, schema, description):
 137   """Generates the .cc file containing the static initializers for the
 138   of the elements specified in the description.
 139
 140   Args:
 141     basepath: The base directory in which files are generated.
 142     fileroot: The filename and path, relative to basepath, of the file to
 143         create, without an extension.
 144     head: The string to output as the header of the .cc file.
 145     namespace: A string corresponding to the C++ namespace to use.
 146     schema: A dict containing the schema. See comment at the top of this file.
 147     description: A dict containing the description. See comment at the top of
 148         this file.
 149   """
 150
 151   with open(os.path.join(basepath, fileroot + '.cc'), 'w') as f:
 152     f.write(head)
 153
 154     f.write('#include "%s"\n' % (fileroot + '.h'))
 155     f.write('\n')
 156
 157     if namespace:
 158       f.write('namespace %s {\n' % namespace)
 159       f.write('\n')
 160
 161     f.write(element_generator.GenerateElements(schema['type_name'],
 162         schema['schema'], description))
 163
 164     if namespace:
 165       f.write('\n')
 166       f.write('}  // namespace %s\n' % namespace)
 167
 168 def _Load(filename):
 169   """Loads a JSON file int a Python object and return this object.
 170   """
 171   # TODO(beaudoin): When moving to Python 2.7 use object_pairs_hook=OrderedDict.
 172   with open(filename, 'r') as handle:
 173     result = json.loads(json_comment_eater.Nom(handle.read()))
 174   return result
 175
 176 if __name__ == '__main__':
 177   parser = optparse.OptionParser(
 178       description='Generates an C++ array of struct from a JSON description.',
 179       usage='usage: %prog [option] -s schema description')
 180   parser.add_option('-b', '--destbase',
 181       help='base directory of generated files.')
 182   parser.add_option('-d', '--destdir',
 183       help='directory to output generated files, relative to destbase.')
 184   parser.add_option('-n', '--namespace',
 185       help='C++ namespace for generated files. e.g search_providers.')
 186   parser.add_option('-s', '--schema', help='path to the schema file, '
 187       'mandatory.')
 188   (opts, args) = parser.parse_args()
 189
 190   if not opts.schema:
 191     parser.error('You must specify a --schema.')
 192
 193   description_filename = os.path.normpath(args[0])
 194   root, ext = os.path.splitext(description_filename)
 195   shortroot = os.path.split(root)[1]
 196   if opts.destdir:
 197     output_root = os.path.join(os.path.normpath(opts.destdir), shortroot)
 198   else:
 199     output_root = shortroot
 200
 201   if opts.destbase:
 202     basepath = os.path.normpath(opts.destbase)
 203   else:
 204     basepath = ''
 205
 206   schema = _Load(opts.schema)
 207   description = _Load(description_filename)
 208
 209   head = HEAD % (datetime.now().year, opts.schema, description_filename)
 210   _GenerateH(basepath, output_root, head, opts.namespace, schema, description)
 211   _GenerateCC(basepath, output_root, head, opts.namespace, schema, description)