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#!/usr/bin/env python
# Copyright (C) 2013 Google Inc. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
# * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
import io
import itertools
import re
import sys
class BadInput(Exception):
"""Unsupported input has been found."""
class SwitchCase(object):
"""Represents a CASE block."""
def __init__(self, identifier, block):
self.identifier = identifier
self.block = block
class Optimizer(object):
"""Generates optimized identifier matching code."""
def __init__(self, output_file, array_variable, length_variable):
self.output_file = output_file
self.array_variable = array_variable
self.length_variable = length_variable
def inspect(self, cases):
lengths = list(set([len(c.identifier) for c in cases]))
lengths.sort()
def response(length):
self.inspect_array([c for c in cases if len(c.identifier) == length], range(length))
self.write_selection(self.length_variable, lengths, str, response)
def score(self, alternatives):
return -sum([len(list(count)) ** 2 for _, count in itertools.groupby(sorted(alternatives))])
def choose_selection_pos(self, cases, pending):
candidates = [pos for pos in pending if all(alternative.isalpha() for alternative in [c.identifier[pos] for c in cases])]
if not candidates:
raise BadInput('Case-insensitive switching on non-alphabetic characters not yet implemented')
return sorted(candidates, key=lambda pos: self.score([c.identifier[pos] for c in cases]))[0]
def inspect_array(self, cases, pending):
assert len(cases) >= 1
if pending:
common = [pos for pos in pending
if len(set([c.identifier[pos] for c in cases])) == 1]
if common:
identifier = cases[0].identifier
for index in xrange(len(common)):
if index == 0:
self.output_file.write(u'if (LIKELY(')
else:
self.output_file.write(u' && ')
pos = common[index]
if identifier[pos].isalpha():
self.output_file.write("(%s[%d] | 0x20) == '%s'" %
(self.array_variable, pos, identifier[pos]))
else:
self.output_file.write("%s[%d] == '%s'" %
(self.array_variable, pos, identifier[pos]))
self.output_file.write(u')) {\n')
next_pending = list(set(pending) - set(common))
next_pending.sort()
self.inspect_array(cases, next_pending)
self.output_file.write(u'}\n')
else:
pos = self.choose_selection_pos(cases, pending)
next_pending = filter(lambda p: p != pos, pending)
alternatives = list(set([c.identifier[pos] for c in cases]))
alternatives.sort()
def literal(alternative):
if isinstance(alternative, int):
return str(alternative)
else:
return "'%s'" % alternative
def response(alternative):
self.inspect_array([c for c in cases if c.identifier[pos] == alternative],
next_pending)
expression = '(%s[%d] | 0x20)' % (self.array_variable, pos)
self.write_selection(expression, alternatives, literal, response)
else:
assert len(cases) == 1
for block_line in cases[0].block:
self.output_file.write(block_line)
def write_selection(self, expression, alternatives, literal, response):
if len(alternatives) == 1:
self.output_file.write(u'if (LIKELY(%s == %s)) {\n' % (expression, literal(alternatives[0])))
response(alternatives[0])
self.output_file.write(u'}\n')
elif len(alternatives) == 2:
self.output_file.write(u'if (%s == %s) {\n' % (expression, literal(alternatives[0])))
response(alternatives[0])
self.output_file.write(u'} else if (LIKELY(%s == %s)) {\n' % (expression, literal(alternatives[1])))
response(alternatives[1])
self.output_file.write(u'}\n')
else:
self.output_file.write('switch (%s) {\n' % expression)
for alternative in alternatives:
self.output_file.write(u'case %s: {\n' % literal(alternative))
response(alternative)
self.output_file.write(u'} break;\n')
self.output_file.write(u'}\n')
class LineProcessor(object):
def process_line(self, line):
pass
class MainLineProcessor(LineProcessor):
"""Processes the contents of an input file."""
SWITCH_PATTERN = re.compile(r'\s*SWITCH\s*\((\w*),\s*(\w*)\) \{$')
def __init__(self, output_file):
self.output_file = output_file
def process_line(self, line):
match_switch = MainLineProcessor.SWITCH_PATTERN.match(line)
if match_switch:
array_variable = match_switch.group(1)
length_variable = match_switch.group(2)
return SwitchLineProcessor(self, self.output_file, array_variable, length_variable)
else:
self.output_file.write(line)
return self
class SwitchLineProcessor(LineProcessor):
"""Processes the contents of a SWITCH block."""
CASE_PATTERN = re.compile(r'\s*CASE\s*\(\"([a-z0-9_\-\(]*)\"\) \{$')
CLOSE_BRACE_PATTERN = re.compile(r'\s*\}$')
EMPTY_PATTERN = re.compile(r'\s*$')
def __init__(self, parent, output_file, array_variable, length_variable):
self.parent = parent
self.output_file = output_file
self.array_variable = array_variable
self.length_variable = length_variable
self.cases = []
def process_line(self, line):
match_case = SwitchLineProcessor.CASE_PATTERN.match(line)
match_close_brace = SwitchLineProcessor.CLOSE_BRACE_PATTERN.match(line)
match_empty = SwitchLineProcessor.EMPTY_PATTERN.match(line)
if match_case:
identifier = match_case.group(1)
return CaseLineProcessor(self, self.output_file, identifier)
elif match_close_brace:
Optimizer(self.output_file, self.array_variable, self.length_variable).inspect(self.cases)
return self.parent
elif match_empty:
return self
else:
raise BadInput('Invalid line within SWITCH: %s' % line)
def add_case(self, latest_case):
if latest_case.identifier in [c.identifier for c in self.cases]:
raise BadInput('Repeated case: %s' % latest_case.identifier)
self.cases.append(latest_case)
class CaseLineProcessor(LineProcessor):
"""Processes the contents of a CASE block."""
CLOSE_BRACE_PATTERN = re.compile(r'\s*\}$')
BREAK_PATTERN = re.compile(r'break;')
def __init__(self, parent, output_file, identifier):
self.parent = parent
self.output_file = output_file
self.identifier = identifier
self.block = []
def process_line(self, line):
match_close_brace = CaseLineProcessor.CLOSE_BRACE_PATTERN.match(line)
match_break = CaseLineProcessor.BREAK_PATTERN.search(line)
if match_close_brace:
self.parent.add_case(SwitchCase(self.identifier, self.block))
return self.parent
elif match_break:
raise BadInput('break within CASE not supported: %s' % line)
else:
self.block.append(line)
return self
def process_file(input_name, output_name):
"""Transforms input file into legal C++ source code."""
with io.open(input_name, 'r', -1, 'utf-8') as input_file:
with io.open(output_name, 'w', -1, 'utf-8') as output_file:
processor = MainLineProcessor(output_file)
input_lines = input_file.readlines()
for line in input_lines:
processor = processor.process_line(line)
if __name__ == '__main__':
process_file(sys.argv[1], sys.argv[2])
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