flags_util.py revision e896dfd76014af3c399d1b54be022fb1663a105b 
1# Copyright (c) 2013 The Chromium OS 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 to explore the neighbor flags.
6
7Part of the Chrome build flags optimization.
8"""
9
10__author__ = 'yuhenglong@google.com (Yuheng Long)'
11
12
13import flags
14from flags import Flag
15
16
17def ClimbNext(flags_dict, climb_spec):
18  """Get the flags that are different from |flags_dict| by |climb_spec|.
19
20  Given a set of flags, |flags_dict|, return a new set of flags that are
21  adjacent along the flag spec |climb_spec|.
22
23  An example flags_dict is {foo=[1-9]:foo=5, bar=[1-5]:bar=2} and climb_spec is
24  bar=[1-5]. This method changes the flag that contains the spec bar=[1-5]. The
25  results are its neighbors dictionaries, i.e., {foo=[1-9]:foo=5,
26  bar=[1-5]:bar=1} and {foo=[1-9]:foo=5, bar=[1-5]:bar=3}.
27
28  Args:
29    flags_dict: The dictionary containing the original flags whose neighbors are
30      to be explored.
31    climb_spec: The spec in the flags_dict is to be changed. The spec is a
32      definition in the little language, a string with escaped sequences of the
33      form [<start>-<end>] where start and end is an positive integer for a
34      fillable value. An example of a spec is "foo[0-9]".
35
36  Returns:
37    List of dictionaries of neighbor flags.
38  """
39
40  # This method searches for a pattern [start-end] in the spec. If the spec
41  # contains this pattern, it is a numeric flag. Otherwise it is a boolean flag.
42  # For example, -finline-limit=[1-1000] is a numeric flag and -falign-jumps is
43  # a boolean flag.
44  numeric_flag_match = flags.Search(climb_spec)
45
46  # If the flags do not contain the spec.
47  if climb_spec not in flags_dict:
48    results = flags_dict.copy()
49
50    if numeric_flag_match:
51      # Numeric flags.
52      results[climb_spec] = Flag(climb_spec,
53                                 int(numeric_flag_match.group('start')))
54    else:
55      # Boolean flags.
56      results[climb_spec] = Flag(climb_spec)
57
58    return [results]
59
60  # The flags contain the spec.
61  if not numeric_flag_match:
62    # Boolean flags.
63    results = flags_dict.copy()
64
65    # Turn off the flag. A flag is turned off if it is not presented in the
66    # flags_dict.
67    del results[climb_spec]
68    return [results]
69
70  # Numeric flags.
71  flag = flags_dict[climb_spec]
72
73  # The value of the flag having spec.
74  value = flag.GetValue()
75  results = []
76
77  if value + 1 < int(numeric_flag_match.group('end')):
78    # If the value is not the end value, explore the value that is 1 larger than
79    # the current value.
80    neighbor = flags_dict.copy()
81    neighbor[climb_spec] = Flag(climb_spec, value + 1)
82    results.append(neighbor)
83
84  if value > int(numeric_flag_match.group('start')):
85    # If the value is not the start value, explore the value that is 1 lesser
86    # than the current value.
87    neighbor = flags_dict.copy()
88    neighbor[climb_spec] = Flag(climb_spec, value - 1)
89    results.append(neighbor)
90  else:
91    # Delete the value, i.e., turn off the flag. A flag is turned off if it is
92    # not presented in the flags_dict.
93    neighbor = flags_dict.copy()
94    del neighbor[climb_spec]
95    results.append(neighbor)
96
97  return results
98