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Viewing changes to Lib/lib2to3/pgen2/literals.py

  • Committer: Bazaar Package Importer
  • Author(s): Matthias Klose
  • Date: 2009-03-23 00:01:27 UTC
  • Revision ID: james.westby@ubuntu.com-20090323000127-5fstfxju4ufrhthq
Tags: upstream-3.1~a1+20090322
Import upstream version 3.1~a1+20090322

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Lib/lib2to3/pgen2/literals.py
 
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# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
 
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# Licensed to PSF under a Contributor Agreement.
 
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"""Safely evaluate Python string literals without using eval()."""
 
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import re
 
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simple_escapes = {"a": "\a",
 
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                  "b": "\b",
 
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                  "f": "\f",
 
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                  "n": "\n",
 
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                  "r": "\r",
 
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                  "t": "\t",
 
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                  "v": "\v",
 
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                  "'": "'",
 
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                  '"': '"',
 
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                  "\\": "\\"}
 
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def escape(m):
 
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    all, tail = m.group(0, 1)
 
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    assert all.startswith("\\")
 
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    esc = simple_escapes.get(tail)
 
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    if esc is not None:
 
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        return esc
 
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    if tail.startswith("x"):
 
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        hexes = tail[1:]
 
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        if len(hexes) < 2:
 
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            raise ValueError("invalid hex string escape ('\\%s')" % tail)
 
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        try:
 
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            i = int(hexes, 16)
 
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        except ValueError:
 
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            raise ValueError("invalid hex string escape ('\\%s')" % tail)
 
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    else:
 
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        try:
 
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            i = int(tail, 8)
 
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        except ValueError:
 
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            raise ValueError("invalid octal string escape ('\\%s')" % tail)
 
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    return chr(i)
 
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def evalString(s):
 
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    assert s.startswith("'") or s.startswith('"'), repr(s[:1])
 
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    q = s[0]
 
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    if s[:3] == q*3:
 
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        q = q*3
 
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    assert s.endswith(q), repr(s[-len(q):])
 
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    assert len(s) >= 2*len(q)
 
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    s = s[len(q):-len(q)]
 
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    return re.sub(r"\\(\'|\"|\\|[abfnrtv]|x.{0,2}|[0-7]{1,3})", escape, s)
 
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def test():
 
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    for i in range(256):
 
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        c = chr(i)
 
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        s = repr(c)
 
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        e = evalString(s)
 
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        if e != c:
 
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            print(i, c, s, e)
 
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if __name__ == "__main__":
 
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    test()