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1#
2# Secret Labs' Regular Expression Engine
3#
4# re-compatible interface for the sre matching engine
5#
6# Copyright (c) 1998-2001 by Secret Labs AB.  All rights reserved.
7#
8# This version of the SRE library can be redistributed under CNRI's
9# Python 1.6 license.  For any other use, please contact Secret Labs
10# AB (info@pythonware.com).
11#
12# Portions of this engine have been developed in cooperation with
13# CNRI.  Hewlett-Packard provided funding for 1.6 integration and
14# other compatibility work.
15#
16
17r"""Support for regular expressions (RE).
18
19This module provides regular expression matching operations similar to
20those found in Perl.  It supports both 8-bit and Unicode strings; both
21the pattern and the strings being processed can contain null bytes and
22characters outside the US ASCII range.
23
24Regular expressions can contain both special and ordinary characters.
25Most ordinary characters, like "A", "a", or "0", are the simplest
26regular expressions; they simply match themselves.  You can
27concatenate ordinary characters, so last matches the string 'last'.
28
29The special characters are:
30    "."      Matches any character except a newline.
31    "^"      Matches the start of the string.
32    "$"      Matches the end of the string or just before the newline at
33             the end of the string.
34    "*"      Matches 0 or more (greedy) repetitions of the preceding RE.
35             Greedy means that it will match as many repetitions as possible.
36    "+"      Matches 1 or more (greedy) repetitions of the preceding RE.
37    "?"      Matches 0 or 1 (greedy) of the preceding RE.
38    *?,+?,?? Non-greedy versions of the previous three special characters.
39    {m,n}    Matches from m to n repetitions of the preceding RE.
40    {m,n}?   Non-greedy version of the above.
41    "\\"     Either escapes special characters or signals a special sequence.
42    []       Indicates a set of characters.
43             A "^" as the first character indicates a complementing set.
44    "|"      A|B, creates an RE that will match either A or B.
45    (...)    Matches the RE inside the parentheses.
46             The contents can be retrieved or matched later in the string.
47    (?iLmsux) Set the I, L, M, S, U, or X flag for the RE (see below).
48    (?:...)  Non-grouping version of regular parentheses.
49    (?P<name>...) The substring matched by the group is accessible by name.
50    (?P=name)     Matches the text matched earlier by the group named name.
51    (?#...)  A comment; ignored.
52    (?=...)  Matches if ... matches next, but doesn't consume the string.
53    (?!...)  Matches if ... doesn't match next.
54    (?<=...) Matches if preceded by ... (must be fixed length).
55    (?<!...) Matches if not preceded by ... (must be fixed length).
56    (?(id/name)yes|no) Matches yes pattern if the group with id/name matched,
57                       the (optional) no pattern otherwise.
58
59The special sequences consist of "\\" and a character from the list
60below.  If the ordinary character is not on the list, then the
61resulting RE will match the second character.
62    \number  Matches the contents of the group of the same number.
63    \A       Matches only at the start of the string.
64    \Z       Matches only at the end of the string.
65    \b       Matches the empty string, but only at the start or end of a word.
66    \B       Matches the empty string, but not at the start or end of a word.
67    \d       Matches any decimal digit; equivalent to the set [0-9].
68    \D       Matches any non-digit character; equivalent to the set [^0-9].
69    \s       Matches any whitespace character; equivalent to [ \t\n\r\f\v].
70    \S       Matches any non-whitespace character; equiv. to [^ \t\n\r\f\v].
71    \w       Matches any alphanumeric character; equivalent to [a-zA-Z0-9_].
72             With LOCALE, it will match the set [0-9_] plus characters defined
73             as letters for the current locale.
74    \W       Matches the complement of \w.
75    \\       Matches a literal backslash.
76
77This module exports the following functions:
78    match    Match a regular expression pattern to the beginning of a string.
79    search   Search a string for the presence of a pattern.
80    sub      Substitute occurrences of a pattern found in a string.
81    subn     Same as sub, but also return the number of substitutions made.
82    split    Split a string by the occurrences of a pattern.
83    findall  Find all occurrences of a pattern in a string.
84    finditer Return an iterator yielding a match object for each match.
85    compile  Compile a pattern into a RegexObject.
86    purge    Clear the regular expression cache.
87    escape   Backslash all non-alphanumerics in a string.
88
89Some of the functions in this module takes flags as optional parameters:
90    I  IGNORECASE  Perform case-insensitive matching.
91    L  LOCALE      Make \w, \W, \b, \B, dependent on the current locale.
92    M  MULTILINE   "^" matches the beginning of lines (after a newline)
93                   as well as the string.
94                   "$" matches the end of lines (before a newline) as well
95                   as the end of the string.
96    S  DOTALL      "." matches any character at all, including the newline.
97    X  VERBOSE     Ignore whitespace and comments for nicer looking RE's.
98    U  UNICODE     Make \w, \W, \b, \B, dependent on the Unicode locale.
99
100This module also defines an exception 'error'.
101
102"""
103
104import sys
105import sre_compile
106import sre_parse
107try:
108    import _locale
109except ImportError:
110    _locale = None
111
112# public symbols
113__all__ = [ "match", "search", "sub", "subn", "split", "findall",
114    "compile", "purge", "template", "escape", "I", "L", "M", "S", "X",
115    "U", "IGNORECASE", "LOCALE", "MULTILINE", "DOTALL", "VERBOSE",
116    "UNICODE", "error" ]
117
118__version__ = "2.2.1"
119
120# flags
121I = IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case
122L = LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale
123U = UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode locale
124M = MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline
125S = DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline
126X = VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments
127
128# sre extensions (experimental, don't rely on these)
129T = TEMPLATE = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking
130DEBUG = sre_compile.SRE_FLAG_DEBUG # dump pattern after compilation
131
132# sre exception
133error = sre_compile.error
134
135# --------------------------------------------------------------------
136# public interface
137
138def match(pattern, string, flags=0):
139    """Try to apply the pattern at the start of the string, returning
140    a match object, or None if no match was found."""
141    return _compile(pattern, flags).match(string)
142
143def search(pattern, string, flags=0):
144    """Scan through string looking for a match to the pattern, returning
145    a match object, or None if no match was found."""
146    return _compile(pattern, flags).search(string)
147
148def sub(pattern, repl, string, count=0, flags=0):
149    """Return the string obtained by replacing the leftmost
150    non-overlapping occurrences of the pattern in string by the
151    replacement repl.  repl can be either a string or a callable;
152    if a string, backslash escapes in it are processed.  If it is
153    a callable, it's passed the match object and must return
154    a replacement string to be used."""
155    return _compile(pattern, flags).sub(repl, string, count)
156
157def subn(pattern, repl, string, count=0, flags=0):
158    """Return a 2-tuple containing (new_string, number).
159    new_string is the string obtained by replacing the leftmost
160    non-overlapping occurrences of the pattern in the source
161    string by the replacement repl.  number is the number of
162    substitutions that were made. repl can be either a string or a
163    callable; if a string, backslash escapes in it are processed.
164    If it is a callable, it's passed the match object and must
165    return a replacement string to be used."""
166    return _compile(pattern, flags).subn(repl, string, count)
167
168def split(pattern, string, maxsplit=0, flags=0):
169    """Split the source string by the occurrences of the pattern,
170    returning a list containing the resulting substrings."""
171    return _compile(pattern, flags).split(string, maxsplit)
172
173def findall(pattern, string, flags=0):
174    """Return a list of all non-overlapping matches in the string.
175
176    If one or more groups are present in the pattern, return a
177    list of groups; this will be a list of tuples if the pattern
178    has more than one group.
179
180    Empty matches are included in the result."""
181    return _compile(pattern, flags).findall(string)
182
183if sys.hexversion >= 0x02020000:
184    __all__.append("finditer")
185    def finditer(pattern, string, flags=0):
186        """Return an iterator over all non-overlapping matches in the
187        string.  For each match, the iterator returns a match object.
188
189        Empty matches are included in the result."""
190        return _compile(pattern, flags).finditer(string)
191
192def compile(pattern, flags=0):
193    "Compile a regular expression pattern, returning a pattern object."
194    return _compile(pattern, flags)
195
196def purge():
197    "Clear the regular expression cache"
198    _cache.clear()
199    _cache_repl.clear()
200
201def template(pattern, flags=0):
202    "Compile a template pattern, returning a pattern object"
203    return _compile(pattern, flags|T)
204
205_alphanum = frozenset(
206    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
207
208def escape(pattern):
209    "Escape all non-alphanumeric characters in pattern."
210    s = list(pattern)
211    alphanum = _alphanum
212    for i, c in enumerate(pattern):
213        if c not in alphanum:
214            if c == "\000":
215                s[i] = "\\000"
216            else:
217                s[i] = "\\" + c
218    return pattern[:0].join(s)
219
220# --------------------------------------------------------------------
221# internals
222
223_cache = {}
224_cache_repl = {}
225
226_pattern_type = type(sre_compile.compile("", 0))
227
228_MAXCACHE = 100
229
230def _compile(*key):
231    # internal: compile pattern
232    pattern, flags = key
233    bypass_cache = flags & DEBUG
234    if not bypass_cache:
235        cachekey = (type(key[0]),) + key
236        try:
237            p, loc = _cache[cachekey]
238            if loc is None or loc == _locale.setlocale(_locale.LC_CTYPE):
239                return p
240        except KeyError:
241            pass
242    if isinstance(pattern, _pattern_type):
243        if flags:
244            raise ValueError('Cannot process flags argument with a compiled pattern')
245        return pattern
246    if not sre_compile.isstring(pattern):
247        raise TypeError, "first argument must be string or compiled pattern"
248    try:
249        p = sre_compile.compile(pattern, flags)
250    except error, v:
251        raise error, v # invalid expression
252    if not bypass_cache:
253        if len(_cache) >= _MAXCACHE:
254            _cache.clear()
255        if p.flags & LOCALE:
256            if not _locale:
257                return p
258            loc = _locale.setlocale(_locale.LC_CTYPE)
259        else:
260            loc = None
261        _cache[cachekey] = p, loc
262    return p
263
264def _compile_repl(*key):
265    # internal: compile replacement pattern
266    p = _cache_repl.get(key)
267    if p is not None:
268        return p
269    repl, pattern = key
270    try:
271        p = sre_parse.parse_template(repl, pattern)
272    except error, v:
273        raise error, v # invalid expression
274    if len(_cache_repl) >= _MAXCACHE:
275        _cache_repl.clear()
276    _cache_repl[key] = p
277    return p
278
279def _expand(pattern, match, template):
280    # internal: match.expand implementation hook
281    template = sre_parse.parse_template(template, pattern)
282    return sre_parse.expand_template(template, match)
283
284def _subx(pattern, template):
285    # internal: pattern.sub/subn implementation helper
286    template = _compile_repl(template, pattern)
287    if not template[0] and len(template[1]) == 1:
288        # literal replacement
289        return template[1][0]
290    def filter(match, template=template):
291        return sre_parse.expand_template(template, match)
292    return filter
293
294# register myself for pickling
295
296import copy_reg
297
298def _pickle(p):
299    return _compile, (p.pattern, p.flags)
300
301copy_reg.pickle(_pattern_type, _pickle, _compile)
302
303# --------------------------------------------------------------------
304# experimental stuff (see python-dev discussions for details)
305
306class Scanner:
307    def __init__(self, lexicon, flags=0):
308        from sre_constants import BRANCH, SUBPATTERN
309        self.lexicon = lexicon
310        # combine phrases into a compound pattern
311        p = []
312        s = sre_parse.Pattern()
313        s.flags = flags
314        for phrase, action in lexicon:
315            p.append(sre_parse.SubPattern(s, [
316                (SUBPATTERN, (len(p)+1, sre_parse.parse(phrase, flags))),
317                ]))
318        s.groups = len(p)+1
319        p = sre_parse.SubPattern(s, [(BRANCH, (None, p))])
320        self.scanner = sre_compile.compile(p)
321    def scan(self, string):
322        result = []
323        append = result.append
324        match = self.scanner.scanner(string).match
325        i = 0
326        while 1:
327            m = match()
328            if not m:
329                break
330            j = m.end()
331            if i == j:
332                break
333            action = self.lexicon[m.lastindex-1][1]
334            if hasattr(action, '__call__'):
335                self.match = m
336                action = action(self, m.group())
337            if action is not None:
338                append(action)
339            i = j
340        return result, string[i:]
341