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323 lines
9.6 KiB
Python
Executable File
323 lines
9.6 KiB
Python
Executable File
#!/usr/bin/env python
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# Copyright (c) 2017-2019, The Tor Project, Inc.
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# See LICENSE for licensing information
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r"""
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This script iterates over a list of C files. For each file, it looks at the
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#if/#else C macros, and annotates them with comments explaining what they
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match.
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For example, it replaces this kind of input...
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>>> INPUT = '''
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... #ifdef HAVE_OCELOT
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... C code here
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... #if MIMSY == BOROGROVE
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... block 1
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... block 1
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... block 1
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... block 1
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... #else
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... block 2
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... block 2
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... block 2
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... block 2
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... #endif
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... #endif
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... '''
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With this kind of output:
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>>> EXPECTED_OUTPUT = '''
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... #ifdef HAVE_OCELOT
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... C code here
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... #if MIMSY == BOROGROVE
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... block 1
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... block 1
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... block 1
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... block 1
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... #else /* !(MIMSY == BOROGROVE) */
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... block 2
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... block 2
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... block 2
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... block 2
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... #endif /* MIMSY == BOROGROVE */
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... #endif /* defined(HAVE_OCELOT) */
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... '''
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Here's how to use it:
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>>> import sys
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>>> if sys.version_info.major < 3: from cStringIO import StringIO
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>>> if sys.version_info.major >= 3: from io import StringIO
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>>> OUTPUT = StringIO()
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>>> translate(StringIO(INPUT), OUTPUT)
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>>> assert OUTPUT.getvalue() == EXPECTED_OUTPUT
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Note that only #else and #endif lines are annotated. Existing comments
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on those lines are removed.
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"""
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# Future imports for Python 2.7, mandatory in 3.0
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from __future__ import division
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from __future__ import print_function
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from __future__ import unicode_literals
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import re
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# Any block with fewer than this many lines does not need annotations.
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LINE_OBVIOUSNESS_LIMIT = 4
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# Maximum line width. This includes a terminating newline character.
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#
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# (This is the maximum before encoding, so that if the the operating system
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# uses multiple characers to encode newline, that's still okay.)
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LINE_WIDTH=80
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class Problem(Exception):
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pass
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def close_parens_needed(expr):
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"""Return the number of left-parentheses needed to make 'expr'
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balanced.
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>>> close_parens_needed("1+2")
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0
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>>> close_parens_needed("(1 + 2)")
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0
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>>> close_parens_needed("(1 + 2")
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1
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>>> close_parens_needed("(1 + (2 *")
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2
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>>> close_parens_needed("(1 + (2 * 3) + (4")
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2
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"""
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return expr.count("(") - expr.count(")")
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def truncate_expression(expr, new_width):
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"""Given a parenthesized C expression in 'expr', try to return a new
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expression that is similar to 'expr', but no more than 'new_width'
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characters long.
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Try to return an expression with balanced parentheses.
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>>> truncate_expression("1+2+3", 8)
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'1+2+3'
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>>> truncate_expression("1+2+3+4+5", 8)
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'1+2+3...'
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>>> truncate_expression("(1+2+3+4)", 8)
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'(1+2...)'
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>>> truncate_expression("(1+(2+3+4))", 8)
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'(1+...)'
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>>> truncate_expression("(((((((((", 8)
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'((...))'
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"""
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if len(expr) <= new_width:
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# The expression is already short enough.
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return expr
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ellipsis = "..."
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# Start this at the minimum that we might truncate.
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n_to_remove = len(expr) + len(ellipsis) - new_width
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# Try removing characters, one by one, until we get something where
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# re-balancing the parentheses still fits within the limit.
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while n_to_remove < len(expr):
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truncated = expr[:-n_to_remove] + ellipsis
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truncated += ")" * close_parens_needed(truncated)
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if len(truncated) <= new_width:
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return truncated
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n_to_remove += 1
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return ellipsis
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def commented_line(fmt, argument, maxwidth=LINE_WIDTH):
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# (This is a raw docstring so that our doctests can use \.)
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r"""
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Return fmt%argument, for use as a commented line. If the line would
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be longer than maxwidth, truncate argument but try to keep its
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parentheses balanced.
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Requires that fmt%"..." will fit into maxwidth characters.
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Requires that fmt ends with a newline.
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>>> commented_line("/* %s */\n", "hello world", 32)
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'/* hello world */\n'
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>>> commented_line("/* %s */\n", "hello world", 15)
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'/* hello... */\n'
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>>> commented_line("#endif /* %s */\n", "((1+2) && defined(FOO))", 32)
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'#endif /* ((1+2) && defi...) */\n'
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The default line limit is 80 characters including the newline:
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>>> long_argument = "long " * 100
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>>> long_line = commented_line("#endif /* %s */\n", long_argument)
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>>> len(long_line)
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80
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>>> long_line[:40]
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'#endif /* long long long long long long '
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>>> long_line[40:]
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'long long long long long long lon... */\n'
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If a line works out to being 80 characters naturally, it isn't truncated,
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and no ellipsis is added.
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>>> medium_argument = "a"*66
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>>> medium_line = commented_line("#endif /* %s */\n", medium_argument)
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>>> len(medium_line)
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80
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>>> "..." in medium_line
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False
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>>> medium_line[:40]
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'#endif /* aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
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>>> medium_line[40:]
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'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa */\n'
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"""
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assert fmt.endswith("\n")
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result = fmt % argument
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if len(result) <= maxwidth:
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return result
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else:
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# How long can we let the argument be? Try filling in the
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# format with an empty argument to find out.
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max_arg_width = maxwidth - len(fmt % "")
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result = fmt % truncate_expression(argument, max_arg_width)
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assert len(result) <= maxwidth
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return result
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def negate(expr):
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"""Return a negated version of expr; try to avoid double-negation.
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We usually wrap expressions in parentheses and add a "!".
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>>> negate("A && B")
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'!(A && B)'
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But if we recognize the expression as negated, we can restore it.
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>>> negate(negate("A && B"))
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'A && B'
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The same applies for defined(FOO).
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>>> negate("defined(FOO)")
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'!defined(FOO)'
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>>> negate(negate("defined(FOO)"))
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'defined(FOO)'
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Internal parentheses don't confuse us:
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>>> negate("!(FOO) && !(BAR)")
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'!(!(FOO) && !(BAR))'
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"""
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expr = expr.strip()
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# See whether we match !(...), with no intervening close-parens.
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m = re.match(r'^!\s*\(([^\)]*)\)$', expr)
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if m:
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return m.group(1)
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# See whether we match !?defined(...), with no intervening close-parens.
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m = re.match(r'^(!?)\s*(defined\([^\)]*\))$', expr)
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if m:
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if m.group(1) == "!":
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prefix = ""
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else:
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prefix = "!"
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return prefix + m.group(2)
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return "!(%s)" % expr
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def uncomment(s):
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"""
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Remove existing trailing comments from an #else or #endif line.
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"""
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s = re.sub(r'//.*','',s)
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s = re.sub(r'/\*.*','',s)
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return s.strip()
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def translate(f_in, f_out):
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"""
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Read a file from f_in, and write its annotated version to f_out.
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"""
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# A stack listing our current if/else state. Each member of the stack
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# is a list of directives. Each directive is a 3-tuple of
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# (command, rest, lineno)
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# where "command" is one of if/ifdef/ifndef/else/elif, and where
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# "rest" is an expression in a format suitable for use with #if, and where
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# lineno is the line number where the directive occurred.
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stack = []
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# the stack element corresponding to the top level of the file.
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whole_file = []
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cur_level = whole_file
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lineno = 0
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for line in f_in:
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lineno += 1
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m = re.match(r'\s*#\s*(if|ifdef|ifndef|else|endif|elif)\b\s*(.*)',
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line)
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if not m:
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# no directive, so we can just write it out.
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f_out.write(line)
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continue
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command,rest = m.groups()
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if command in ("if", "ifdef", "ifndef"):
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# The #if directive pushes us one level lower on the stack.
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if command == 'ifdef':
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rest = "defined(%s)"%uncomment(rest)
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elif command == 'ifndef':
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rest = "!defined(%s)"%uncomment(rest)
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elif rest.endswith("\\"):
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rest = rest[:-1]+"..."
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rest = uncomment(rest)
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new_level = [ (command, rest, lineno) ]
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stack.append(cur_level)
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cur_level = new_level
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f_out.write(line)
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elif command in ("else", "elif"):
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# We stay at the same level on the stack. If we have an #else,
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# we comment it.
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if len(cur_level) == 0 or cur_level[-1][0] == 'else':
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raise Problem("Unexpected #%s on %d"% (command,lineno))
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if (len(cur_level) == 1 and command == 'else' and
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lineno > cur_level[0][2] + LINE_OBVIOUSNESS_LIMIT):
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f_out.write(commented_line("#else /* %s */\n",
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negate(cur_level[0][1])))
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else:
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f_out.write(line)
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cur_level.append((command, rest, lineno))
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else:
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# We pop one element on the stack, and comment an endif.
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assert command == 'endif'
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if len(stack) == 0:
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raise Problem("Unmatched #%s on %s"% (command,lineno))
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if lineno <= cur_level[0][2] + LINE_OBVIOUSNESS_LIMIT:
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f_out.write(line)
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elif len(cur_level) == 1 or (
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len(cur_level) == 2 and cur_level[1][0] == 'else'):
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f_out.write(commented_line("#endif /* %s */\n",
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cur_level[0][1]))
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else:
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f_out.write(commented_line("#endif /* %s || ... */\n",
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cur_level[0][1]))
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cur_level = stack.pop()
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if len(stack) or cur_level != whole_file:
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raise Problem("Missing #endif")
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if __name__ == '__main__':
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import sys,os
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if sys.argv[1] == "--self-test":
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import doctest
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doctest.testmod()
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sys.exit(0)
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for fn in sys.argv[1:]:
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with open(fn+"_OUT", 'w') as output_file:
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translate(open(fn, 'r'), output_file)
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os.rename(fn+"_OUT", fn)
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