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