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# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Utility functions to explore the neighbor flags.
Part of the Chrome build flags optimization.
"""
__author__ = 'yuhenglong@google.com (Yuheng Long)'
import flags
from flags import Flag
def ClimbNext(flags_dict, climb_spec):
"""Get the flags that are different from |flags_dict| by |climb_spec|.
Given a set of flags, |flags_dict|, return a new set of flags that are
adjacent along the flag spec |climb_spec|.
An example flags_dict is {foo=[1-9]:foo=5, bar=[1-5]:bar=2} and climb_spec is
bar=[1-5]. This method changes the flag that contains the spec bar=[1-5]. The
results are its neighbors dictionaries, i.e., {foo=[1-9]:foo=5,
bar=[1-5]:bar=1} and {foo=[1-9]:foo=5, bar=[1-5]:bar=3}.
Args:
flags_dict: The dictionary containing the original flags whose neighbors are
to be explored.
climb_spec: The spec in the flags_dict is to be changed. The spec is a
definition in the little language, a string with escaped sequences of the
form [<start>-<end>] where start and end is an positive integer for a
fillable value. An example of a spec is "foo[0-9]".
Returns:
List of dictionaries of neighbor flags.
"""
# This method searches for a pattern [start-end] in the spec. If the spec
# contains this pattern, it is a numeric flag. Otherwise it is a boolean flag.
# For example, -finline-limit=[1-1000] is a numeric flag and -falign-jumps is
# a boolean flag.
numeric_flag_match = flags.Search(climb_spec)
# If the flags do not contain the spec.
if climb_spec not in flags_dict:
results = flags_dict.copy()
if numeric_flag_match:
# Numeric flags.
results[climb_spec] = Flag(climb_spec,
int(numeric_flag_match.group('start')))
else:
# Boolean flags.
results[climb_spec] = Flag(climb_spec)
return [results]
# The flags contain the spec.
if not numeric_flag_match:
# Boolean flags.
results = flags_dict.copy()
# Turn off the flag. A flag is turned off if it is not presented in the
# flags_dict.
del results[climb_spec]
return [results]
# Numeric flags.
flag = flags_dict[climb_spec]
# The value of the flag having spec.
value = flag.GetValue()
results = []
if value + 1 < int(numeric_flag_match.group('end')):
# If the value is not the end value, explore the value that is 1 larger than
# the current value.
neighbor = flags_dict.copy()
neighbor[climb_spec] = Flag(climb_spec, value + 1)
results.append(neighbor)
if value > int(numeric_flag_match.group('start')):
# If the value is not the start value, explore the value that is 1 lesser
# than the current value.
neighbor = flags_dict.copy()
neighbor[climb_spec] = Flag(climb_spec, value - 1)
results.append(neighbor)
else:
# Delete the value, i.e., turn off the flag. A flag is turned off if it is
# not presented in the flags_dict.
neighbor = flags_dict.copy()
del neighbor[climb_spec]
results.append(neighbor)
return results
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