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1# Copyright 2014 The Chromium Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4
5"""Utility functions (file reading, simple IDL parsing by regexes) for IDL build.
6
7Design doc: http://www.chromium.org/developers/design-documents/idl-build
8"""
9
10import os
11import cPickle as pickle
12import re
13import string
14
15
16class IdlBadFilenameError(Exception):
17    """Raised if an IDL filename disagrees with the interface name in the file."""
18    pass
19
20
21def idl_filename_to_interface_name(idl_filename):
22    # interface name is the root of the basename: InterfaceName.idl
23    return os.path.splitext(os.path.basename(idl_filename))[0]
24
25
26################################################################################
27# Basic file reading/writing
28################################################################################
29
30def get_file_contents(filename):
31    with open(filename) as f:
32        return f.read()
33
34
35def read_file_to_list(filename):
36    """Returns a list of (stripped) lines for a given filename."""
37    with open(filename) as f:
38        return [line.rstrip('\n') for line in f]
39
40
41def read_pickle_files(pickle_filenames):
42    for pickle_filename in pickle_filenames:
43        with open(pickle_filename) as pickle_file:
44            yield pickle.load(pickle_file)
45
46
47def write_file(new_text, destination_filename, only_if_changed):
48    if only_if_changed and os.path.isfile(destination_filename):
49        with open(destination_filename) as destination_file:
50            if destination_file.read() == new_text:
51                return
52    with open(destination_filename, 'w') as destination_file:
53        destination_file.write(new_text)
54
55
56def write_pickle_file(pickle_filename, data, only_if_changed):
57    if only_if_changed and os.path.isfile(pickle_filename):
58        with open(pickle_filename) as pickle_file:
59            try:
60                if pickle.load(pickle_file) == data:
61                    return
62            except (EOFError, pickle.UnpicklingError):
63                # If trouble unpickling, overwrite
64                pass
65    with open(pickle_filename, 'w') as pickle_file:
66        pickle.dump(data, pickle_file)
67
68
69################################################################################
70# IDL parsing
71#
72# We use regular expressions for parsing; this is incorrect (Web IDL is not a
73# regular language), but simple and sufficient in practice.
74# Leading and trailing context (e.g. following '{') used to avoid false matches.
75################################################################################
76
77def get_partial_interface_name_from_idl(file_contents):
78    match = re.search(r'partial\s+interface\s+(\w+)\s*{', file_contents)
79    return match and match.group(1)
80
81
82def get_implements_from_idl(file_contents, interface_name):
83    """Returns lists of implementing and implemented interfaces.
84
85    Rule is: identifier-A implements identifier-B;
86    i.e., implement*ing* implements implement*ed*;
87    http://www.w3.org/TR/WebIDL/#idl-implements-statements
88
89    Returns two lists of interfaces: identifier-As and identifier-Bs.
90    An 'implements' statements can be present in the IDL file for either the
91    implementing or the implemented interface, but not other files.
92    """
93    implements_re = (r'^\s*'
94                     r'(\w+)\s+'
95                     r'implements\s+'
96                     r'(\w+)\s*'
97                     r';')
98    implements_matches = re.finditer(implements_re, file_contents, re.MULTILINE)
99    implements_pairs = [match.groups() for match in implements_matches]
100
101    foreign_implements = [pair for pair in implements_pairs
102                          if interface_name not in pair]
103    if foreign_implements:
104        left, right = foreign_implements.pop()
105        raise IdlBadFilenameError(
106                'implements statement found in unrelated IDL file.\n'
107                'Statement is:\n'
108                '    %s implements %s;\n'
109                'but filename is unrelated "%s.idl"' %
110                (left, right, interface_name))
111
112    return (
113        [left for left, right in implements_pairs if right == interface_name],
114        [right for left, right in implements_pairs if left == interface_name])
115
116
117def is_callback_interface_from_idl(file_contents):
118    match = re.search(r'callback\s+interface\s+\w+\s*{', file_contents)
119    return bool(match)
120
121
122def get_parent_interface(file_contents):
123    match = re.search(r'interface\s+'
124                      r'\w+\s*'
125                      r':\s*(\w+)\s*'
126                      r'{',
127                      file_contents)
128    return match and match.group(1)
129
130
131def get_interface_extended_attributes_from_idl(file_contents):
132    # Strip comments
133    # re.compile needed b/c Python 2.6 doesn't support flags in re.sub
134    single_line_comment_re = re.compile(r'//.*$', flags=re.MULTILINE)
135    block_comment_re = re.compile(r'/\*.*?\*/', flags=re.MULTILINE | re.DOTALL)
136    file_contents = re.sub(single_line_comment_re, '', file_contents)
137    file_contents = re.sub(block_comment_re, '', file_contents)
138
139    match = re.search(r'\[(.*)\]\s*'
140                      r'((callback|partial)\s+)?'
141                      r'(interface|exception)\s+'
142                      r'\w+\s*'
143                      r'(:\s*\w+\s*)?'
144                      r'{',
145                      file_contents, flags=re.DOTALL)
146    if not match:
147        return {}
148
149    extended_attributes_string = match.group(1)
150    extended_attributes = {}
151    # FIXME: this splitting is WRONG: it fails on ExtendedAttributeArgList like
152    # 'NamedConstructor=Foo(a, b)'
153    parts = [extended_attribute.strip()
154             for extended_attribute in extended_attributes_string.split(',')
155             # Discard empty parts, which may exist due to trailing comma
156             if extended_attribute.strip()]
157    for part in parts:
158        name, _, value = map(string.strip, part.partition('='))
159        extended_attributes[name] = value
160    return extended_attributes
161
162
163def get_put_forward_interfaces_from_idl(file_contents):
164    put_forwards_pattern = (r'\[[^\]]*PutForwards=[^\]]*\]\s+'
165                            r'readonly\s+'
166                            r'attribute\s+'
167                            r'(\w+)')
168    return sorted(set(match.group(1)
169                      for match in re.finditer(put_forwards_pattern,
170                                               file_contents,
171                                               flags=re.DOTALL)))
172