Add the ability to code generated prepopulated static nested structs

tools/json_to_struct/element_generator.py

 # Copyright (c) 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.
 
 import json
 import struct_generator
 
+field_name_count = {}

[beaudoin, 2015/07/06 16:01:11]

Module-global mutable variables are against the style guide:

https://google-styleguide.googlecode.com/svn/trunk/pyguide.html#Global_variables

It's annoying but much cleaner to define it in _GenerateCC and pass into
GenerateElements. It will also make it easier for you to write a test that
validates appending a count behaves as expected. (Please add that test.)

[danduong, 2015/07/08 23:07:03]

Done.

+
 def _JSONToCString16(json_string_literal):
   """Converts a JSON string literal to a C++ UTF-16 string literal. This is
   done by converting \\u#### to \\x####.
   """
   c_string_literal = json_string_literal
   escape_index = c_string_literal.find('\\')
   while escape_index > 0:
     if c_string_literal[escape_index + 1] == 'u':
       # We close the C string literal after the 4 hex digits and reopen it right
       # after, otherwise the Windows compiler will sometimes try to get more
       # than 4 characters in the hex string.
       c_string_literal = (c_string_literal[0:escape_index + 1] + 'x' +
           c_string_literal[escape_index + 2:escape_index + 6] + '" L"' +
           c_string_literal[escape_index + 6:])
     escape_index = c_string_literal.find('\\', escape_index + 6)
   return c_string_literal
 
-def _GenerateString(content, lines):
+def _GenerateString(content, lines, indent='  '):
   """Generates an UTF-8 string to be included in a static structure initializer.
   If content is not specified, uses NULL.
   """
   if content is None:
-    lines.append('  NULL,')
+    lines.append(indent + 'NULL,')
   else:
     # json.dumps quotes the string and escape characters as required.
-    lines.append('  %s,' % json.dumps(content))
+    lines.append(indent + '%s,' % json.dumps(content))
 
-def _GenerateString16(content, lines):
+def _GenerateString16(content, lines, indent='  '):
   """Generates an UTF-16 string to be included in a static structure
   initializer. If content is not specified, uses NULL.
   """
   if content is None:
-    lines.append('  NULL,')
+    lines.append(indent + 'NULL,')
   else:
     # json.dumps quotes the string and escape characters as required.
-    lines.append('  L%s,' % _JSONToCString16(json.dumps(content)))
+    lines.append(indent + 'L%s,' % _JSONToCString16(json.dumps(content)))
 
-def _GenerateArray(element_name, field_info, content, lines):
+def _GenerateArrayVariableName(element_name, field_name):
+  # Generates a unique variable name for an array variable.
+  global field_name_count
+  var = 'array_%s_%s' % (element_name, field_name)
+  if var not in field_name_count:
+    field_name_count[var] = 0
+    return var
+  new_var = '%s_%d' % (var, field_name_count[var])
+  field_name_count[var] += 1
+  return new_var
+
+def _GenerateArray(element_name, field_info, content, lines, indent='  '):
   """Generates an array to be included in a static structure initializer. If
   content is not specified, uses NULL. The array is assigned to a temporary
   variable which is initialized before the structure.
   """
   if content is None:
-    lines.append('  NULL,')
-    lines.append('  0,')  # Size of the array.
+    lines.append(indent + 'NULL,')
+    lines.append(indent + '0,')  # Size of the array.
     return
 
   # Create a new array variable and use it in the structure initializer.
   # This prohibits nested arrays. Add a clash detection and renaming mechanism
   # to solve the problem.
-  var = 'array_%s_%s' % (element_name, field_info['field']);
-  lines.append('  %s,' % var)
-  lines.append('  %s,' % len(content))  # Size of the array.
+  var = _GenerateArrayVariableName(element_name, field_info['field'])
+  lines.append(indent + '%s,' % var)
+  lines.append(indent + '%s,' % len(content))  # Size of the array.
   # Generate the array content.
   array_lines = []
   field_info['contents']['field'] = var;
   array_lines.append(struct_generator.GenerateField(
                      field_info['contents']) + '[] = {')
   for subcontent in content:
     GenerateFieldContent(element_name, field_info['contents'], subcontent,
-                         array_lines)
+                         array_lines, indent)
   array_lines.append('};')
   # Prepend the generated array so it is initialized before the structure.
   lines.reverse()
   array_lines.reverse()
   lines.extend(array_lines)
   lines.reverse()
 
-def GenerateFieldContent(element_name, field_info, content, lines):
+def _GenerateObject(element_name, field_info, content, lines, indent='  '):
+  """Generates an object to be included in a static structure initializer. If
+  content is not specified, uses {0}.

[beaudoin, 2015/07/06 16:01:11]

Why {0}? Is this always a valid C++ object? Just for testing? Is it expected to
cause a compiling error? If the latter, shouldn't we just fail right away?

[danduong, 2015/07/08 23:07:03]

{0} should compile. That will initialize the first element of the struct to 0. A
partially initialized struct has deterministic behavior (rest of the fields will
be zero'd out). I've seen other places where this is done in our codebase.

+  """
+  if content is None:
+    lines.append(indent + '{0},')
+    return
+
+  fields = field_info['fields']
+  lines.append(indent + '{')
+  for field in fields:
+    subcontent = content.get(field['field'])
+    GenerateFieldContent(element_name, field, subcontent, lines, '  ' + indent)
+  lines.append(indent + '},')
+
+def GenerateFieldContent(element_name, field_info, content, lines, indent='  '):
   """Generate the content of a field to be included in the static structure
   initializer. If the field's content is not specified, uses the default value
   if one exists.
   """
   if content is None:
     content = field_info.get('default', None)
   type = field_info['type']
   if type == 'int' or type == 'enum':
-    lines.append('  %s,' % content)
+    lines.append('%s%s,' % (indent, content))
   elif type == 'string':
-    _GenerateString(content, lines)
+    _GenerateString(content, lines, indent)
   elif type == 'string16':
-    _GenerateString16(content, lines)
+    _GenerateString16(content, lines, indent)
   elif type == 'array':
-    _GenerateArray(element_name, field_info, content, lines)
+    _GenerateArray(element_name, field_info, content, lines, indent)
+  elif type == 'object':
+    _GenerateObject(element_name, field_info, content, lines, indent)
   else:
     raise RuntimeError('Unknown field type "%s"' % type)
 
 def GenerateElement(type_name, schema, element_name, element):
   """Generate the static structure initializer for one element.
   """
   lines = [];
   lines.append('const %s %s = {' % (type_name, element_name));
   for field_info in schema:
     content = element.get(field_info['field'], None)
@@ skipping 11 matching lines @@
   """
   result = [];
   for var_name, value in description.get('int_variables', {}).items():
     result.append('const int %s = %s;' % (var_name, value))
   result.append('')
 
   for element_name, element in description.get('elements', {}).items():
     result.append(GenerateElement(type_name, schema, element_name, element))
     result.append('')
   return '\n'.join(result)