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#
# Secret Labs' Regular Expression Engine
#
# convert re-style regular expression to sre pattern
#
# Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved.
#
# See the sre.py file for information on usage and redistribution.
#
"""Internal support module for sre"""
# XXX: show string offset and offending character for all errors
import sys
from sre_constants import *
def set(seq):
s = {}
for elem in seq:
s[elem] = 1
return s
SPECIAL_CHARS = ".\\[{()*+?^$|"
REPEAT_CHARS = "*+?{"
DIGITS = set("0123456789")
OCTDIGITS = set("01234567")
HEXDIGITS = set("0123456789abcdefABCDEF")
WHITESPACE = set(" \t\n\r\v\f")
ESCAPES = {
r"\a": (LITERAL, ord("\a")),
r"\b": (LITERAL, ord("\b")),
r"\f": (LITERAL, ord("\f")),
r"\n": (LITERAL, ord("\n")),
r"\r": (LITERAL, ord("\r")),
r"\t": (LITERAL, ord("\t")),
r"\v": (LITERAL, ord("\v")),
r"\\": (LITERAL, ord("\\"))
}
CATEGORIES = {
r"\A": (AT, AT_BEGINNING_STRING), # start of string
r"\b": (AT, AT_BOUNDARY),
r"\B": (AT, AT_NON_BOUNDARY),
r"\d": (IN, [(CATEGORY, CATEGORY_DIGIT)]),
r"\D": (IN, [(CATEGORY, CATEGORY_NOT_DIGIT)]),
r"\s": (IN, [(CATEGORY, CATEGORY_SPACE)]),
r"\S": (IN, [(CATEGORY, CATEGORY_NOT_SPACE)]),
r"\w": (IN, [(CATEGORY, CATEGORY_WORD)]),
r"\W": (IN, [(CATEGORY, CATEGORY_NOT_WORD)]),
r"\Z": (AT, AT_END_STRING), # end of string
}
FLAGS = {
# standard flags
"i": SRE_FLAG_IGNORECASE,
"L": SRE_FLAG_LOCALE,
"m": SRE_FLAG_MULTILINE,
"s": SRE_FLAG_DOTALL,
"x": SRE_FLAG_VERBOSE,
# extensions
"t": SRE_FLAG_TEMPLATE,
"u": SRE_FLAG_UNICODE,
}
class Pattern:
# master pattern object. keeps track of global attributes
def __init__(self):
self.flags = 0
self.open = []
self.groups = 1
self.groupdict = {}
def opengroup(self, name=None):
gid = self.groups
self.groups = gid + 1
if name is not None:
ogid = self.groupdict.get(name, None)
if ogid is not None:
raise error, ("redefinition of group name %s as group %d; "
"was group %d" % (repr(name), gid, ogid))
self.groupdict[name] = gid
self.open.append(gid)
return gid
def closegroup(self, gid):
self.open.remove(gid)
def checkgroup(self, gid):
return gid < self.groups and gid not in self.open
class SubPattern:
# a subpattern, in intermediate form
def __init__(self, pattern, data=None):
self.pattern = pattern
if data is None:
data = []
self.data = data
self.width = None
def dump(self, level=0):
nl = 1
seqtypes = type(()), type([])
for op, av in self.data:
print level*" " + op,; nl = 0
if op == "in":
# member sublanguage
print; nl = 1
for op, a in av:
print (level+1)*" " + op, a
elif op == "branch":
print; nl = 1
i = 0
for a in av[1]:
if i > 0:
print level*" " + "or"
a.dump(level+1); nl = 1
i = i + 1
elif type(av) in seqtypes:
for a in av:
if isinstance(a, SubPattern):
if not nl: print
a.dump(level+1); nl = 1
else:
print a, ; nl = 0
else:
print av, ; nl = 0
if not nl: print
def __repr__(self):
return repr(self.data)
def __len__(self):
return len(self.data)
def __delitem__(self, index):
del self.data[index]
def __getitem__(self, index):
if isinstance(index, slice):
return SubPattern(self.pattern, self.data[index])
return self.data[index]
def __setitem__(self, index, code):
self.data[index] = code
def insert(self, index, code):
self.data.insert(index, code)
def append(self, code):
self.data.append(code)
def getwidth(self):
# determine the width (min, max) for this subpattern
if self.width:
return self.width
lo = hi = 0L
UNITCODES = (ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY)
REPEATCODES = (MIN_REPEAT, MAX_REPEAT)
for op, av in self.data:
if op is BRANCH:
i = sys.maxint
j = 0
for av in av[1]:
l, h = av.getwidth()
i = min(i, l)
j = max(j, h)
lo = lo + i
hi = hi + j
elif op is CALL:
i, j = av.getwidth()
lo = lo + i
hi = hi + j
elif op is SUBPATTERN:
i, j = av[1].getwidth()
lo = lo + i
hi = hi + j
elif op in REPEATCODES:
i, j = av[2].getwidth()
lo = lo + long(i) * av[0]
hi = hi + long(j) * av[1]
elif op in UNITCODES:
lo = lo + 1
hi = hi + 1
elif op == SUCCESS:
break
self.width = int(min(lo, sys.maxint)), int(min(hi, sys.maxint))
return self.width
class Tokenizer:
def __init__(self, string):
self.string = string
self.index = 0
self.__next()
def __next(self):
if self.index >= len(self.string):
self.next = None
return
char = self.string[self.index]
if char[0] == "\\":
try:
c = self.string[self.index + 1]
except IndexError:
raise error, "bogus escape (end of line)"
char = char + c
self.index = self.index + len(char)
self.next = char
def match(self, char, skip=1):
if char == self.next:
if skip:
self.__next()
return 1
return 0
def get(self):
this = self.next
self.__next()
return this
def tell(self):
return self.index, self.next
def seek(self, index):
self.index, self.next = index
def isident(char):
return "a" <= char <= "z" or "A" <= char <= "Z" or char == "_"
def isdigit(char):
return "0" <= char <= "9"
def isname(name):
# check that group name is a valid string
if not isident(name[0]):
return False
for char in name[1:]:
if not isident(char) and not isdigit(char):
return False
return True
def _class_escape(source, escape):
# handle escape code inside character class
code = ESCAPES.get(escape)
if code:
return code
code = CATEGORIES.get(escape)
if code:
return code
try:
c = escape[1:2]
if c == "x":
# hexadecimal escape (exactly two digits)
while source.next in HEXDIGITS and len(escape) < 4:
escape = escape + source.get()
escape = escape[2:]
if len(escape) != 2:
raise error, "bogus escape: %s" % repr("\\" + escape)
return LITERAL, int(escape, 16) & 0xff
elif c in OCTDIGITS:
# octal escape (up to three digits)
while source.next in OCTDIGITS and len(escape) < 4:
escape = escape + source.get()
escape = escape[1:]
return LITERAL, int(escape, 8) & 0xff
elif c in DIGITS:
raise error, "bogus escape: %s" % repr(escape)
if len(escape) == 2:
return LITERAL, ord(escape[1])
except ValueError:
pass
raise error, "bogus escape: %s" % repr(escape)
def _escape(source, escape, state):
# handle escape code in expression
code = CATEGORIES.get(escape)
if code:
return code
code = ESCAPES.get(escape)
if code:
return code
try:
c = escape[1:2]
if c == "x":
# hexadecimal escape
while source.next in HEXDIGITS and len(escape) < 4:
escape = escape + source.get()
if len(escape) != 4:
raise ValueError
return LITERAL, int(escape[2:], 16) & 0xff
elif c == "0":
# octal escape
while source.next in OCTDIGITS and len(escape) < 4:
escape = escape + source.get()
return LITERAL, int(escape[1:], 8) & 0xff
elif c in DIGITS:
# octal escape *or* decimal group reference (sigh)
if source.next in DIGITS:
escape = escape + source.get()
if (escape[1] in OCTDIGITS and escape[2] in OCTDIGITS and
source.next in OCTDIGITS):
# got three octal digits; this is an octal escape
escape = escape + source.get()
return LITERAL, int(escape[1:], 8) & 0xff
# not an octal escape, so this is a group reference
group = int(escape[1:])
if group < state.groups:
if not state.checkgroup(group):
raise error, "cannot refer to open group"
return GROUPREF, group
raise ValueError
if len(escape) == 2:
return LITERAL, ord(escape[1])
except ValueError:
pass
raise error, "bogus escape: %s" % repr(escape)
def _parse_sub(source, state, nested=1):
# parse an alternation: a|b|c
items = []
itemsappend = items.append
sourcematch = source.match
while 1:
itemsappend(_parse(source, state))
if sourcematch("|"):
continue
if not nested:
break
if not source.next or sourcematch(")", 0):
break
else:
raise error, "pattern not properly closed"
if len(items) == 1:
return items[0]
subpattern = SubPattern(state)
subpatternappend = subpattern.append
# check if all items share a common prefix
while 1:
prefix = None
for item in items:
if not item:
break
if prefix is None:
prefix = item[0]
elif item[0] != prefix:
break
else:
# all subitems start with a common "prefix".
# move it out of the branch
for item in items:
del item[0]
subpatternappend(prefix)
continue # check next one
break
# check if the branch can be replaced by a character set
for item in items:
if len(item) != 1 or item[0][0] != LITERAL:
break
else:
# we can store this as a character set instead of a
# branch (the compiler may optimize this even more)
set = []
setappend = set.append
for item in items:
setappend(item[0])
subpatternappend((IN, set))
return subpattern
subpattern.append((BRANCH, (None, items)))
return subpattern
def _parse_sub_cond(source, state, condgroup):
item_yes = _parse(source, state)
if source.match("|"):
item_no = _parse(source, state)
if source.match("|"):
raise error, "conditional backref with more than two branches"
else:
item_no = None
if source.next and not source.match(")", 0):
raise error, "pattern not properly closed"
subpattern = SubPattern(state)
subpattern.append((GROUPREF_EXISTS, (condgroup, item_yes, item_no)))
return subpattern
_PATTERNENDERS = set("|)")
_ASSERTCHARS = set("=!<")
_LOOKBEHINDASSERTCHARS = set("=!")
_REPEATCODES = set([MIN_REPEAT, MAX_REPEAT])
def _parse(source, state):
# parse a simple pattern
subpattern = SubPattern(state)
# precompute constants into local variables
subpatternappend = subpattern.append
sourceget = source.get
sourcematch = source.match
_len = len
PATTERNENDERS = _PATTERNENDERS
ASSERTCHARS = _ASSERTCHARS
LOOKBEHINDASSERTCHARS = _LOOKBEHINDASSERTCHARS
REPEATCODES = _REPEATCODES
while 1:
if source.next in PATTERNENDERS:
break # end of subpattern
this = sourceget()
if this is None:
break # end of pattern
if state.flags & SRE_FLAG_VERBOSE:
# skip whitespace and comments
if this in WHITESPACE:
continue
if this == "#":
while 1:
this = sourceget()
if this in (None, "\n"):
break
continue
if this and this[0] not in SPECIAL_CHARS:
subpatternappend((LITERAL, ord(this)))
elif this == "[":
# character set
set = []
setappend = set.append
## if sourcematch(":"):
## pass # handle character classes
if sourcematch("^"):
setappend((NEGATE, None))
# check remaining characters
start = set[:]
while 1:
this = sourceget()
if this == "]" and set != start:
break
elif this and this[0] == "\\":
code1 = _class_escape(source, this)
elif this:
code1 = LITERAL, ord(this)
else:
raise error, "unexpected end of regular expression"
if sourcematch("-"):
# potential range
this = sourceget()
if this == "]":
if code1[0] is IN:
code1 = code1[1][0]
setappend(code1)
setappend((LITERAL, ord("-")))
break
elif this:
if this[0] == "\\":
code2 = _class_escape(source, this)
else:
code2 = LITERAL, ord(this)
if code1[0] != LITERAL or code2[0] != LITERAL:
raise error, "bad character range"
lo = code1[1]
hi = code2[1]
if hi < lo:
raise error, "bad character range"
setappend((RANGE, (lo, hi)))
else:
raise error, "unexpected end of regular expression"
else:
if code1[0] is IN:
code1 = code1[1][0]
setappend(code1)
# XXX: <fl> should move set optimization to compiler!
if _len(set)==1 and set[0][0] is LITERAL:
subpatternappend(set[0]) # optimization
elif _len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL:
subpatternappend((NOT_LITERAL, set[1][1])) # optimization
else:
# XXX: <fl> should add charmap optimization here
subpatternappend((IN, set))
elif this and this[0] in REPEAT_CHARS:
# repeat previous item
if this == "?":
min, max = 0, 1
elif this == "*":
min, max = 0, MAXREPEAT
elif this == "+":
min, max = 1, MAXREPEAT
elif this == "{":
if source.next == "}":
subpatternappend((LITERAL, ord(this)))
continue
here = source.tell()
min, max = 0, MAXREPEAT
lo = hi = ""
while source.next in DIGITS:
lo = lo + source.get()
if sourcematch(","):
while source.next in DIGITS:
hi = hi + sourceget()
else:
hi = lo
if not sourcematch("}"):
subpatternappend((LITERAL, ord(this)))
source.seek(here)
continue
if lo:
min = int(lo)
if hi:
max = int(hi)
if max < min:
raise error, "bad repeat interval"
else:
raise error, "not supported"
# figure out which item to repeat
if subpattern:
item = subpattern[-1:]
else:
item = None
if not item or (_len(item) == 1 and item[0][0] == AT):
raise error, "nothing to repeat"
if item[0][0] in REPEATCODES:
raise error, "multiple repeat"
if sourcematch("?"):
subpattern[-1] = (MIN_REPEAT, (min, max, item))
else:
subpattern[-1] = (MAX_REPEAT, (min, max, item))
elif this == ".":
subpatternappend((ANY, None))
elif this == "(":
group = 1
name = None
condgroup = None
if sourcematch("?"):
group = 0
# options
if sourcematch("P"):
# python extensions
if sourcematch("<"):
# named group: skip forward to end of name
name = ""
while 1:
char = sourceget()
if char is None:
raise error, "unterminated name"
if char == ">":
break
name = name + char
group = 1
if not isname(name):
raise error, "bad character in group name"
elif sourcematch("="):
# named backreference
name = ""
while 1:
char = sourceget()
if char is None:
raise error, "unterminated name"
if char == ")":
break
name = name + char
if not isname(name):
raise error, "bad character in group name"
gid = state.groupdict.get(name)
if gid is None:
raise error, "unknown group name"
subpatternappend((GROUPREF, gid))
continue
else:
char = sourceget()
if char is None:
raise error, "unexpected end of pattern"
raise error, "unknown specifier: ?P%s" % char
elif sourcematch(":"):
# non-capturing group
group = 2
elif sourcematch("#"):
# comment
while 1:
if source.next is None or source.next == ")":
break
sourceget()
if not sourcematch(")"):
raise error, "unbalanced parenthesis"
continue
elif source.next in ASSERTCHARS:
# lookahead assertions
char = sourceget()
dir = 1
if char == "<":
if source.next not in LOOKBEHINDASSERTCHARS:
raise error, "syntax error"
dir = -1 # lookbehind
char = sourceget()
p = _parse_sub(source, state)
if not sourcematch(")"):
raise error, "unbalanced parenthesis"
if char == "=":
subpatternappend((ASSERT, (dir, p)))
else:
subpatternappend((ASSERT_NOT, (dir, p)))
continue
elif sourcematch("("):
# conditional backreference group
condname = ""
while 1:
char = sourceget()
if char is None:
raise error, "unterminated name"
if char == ")":
break
condname = condname + char
group = 2
if isname(condname):
condgroup = state.groupdict.get(condname)
if condgroup is None:
raise error, "unknown group name"
else:
try:
condgroup = int(condname)
except ValueError:
raise error, "bad character in group name"
else:
# flags
if not source.next in FLAGS:
raise error, "unexpected end of pattern"
while source.next in FLAGS:
state.flags = state.flags | FLAGS[sourceget()]
if group:
# parse group contents
if group == 2:
# anonymous group
group = None
else:
group = state.opengroup(name)
if condgroup:
p = _parse_sub_cond(source, state, condgroup)
else:
p = _parse_sub(source, state)
if not sourcematch(")"):
raise error, "unbalanced parenthesis"
if group is not None:
state.closegroup(group)
subpatternappend((SUBPATTERN, (group, p)))
else:
while 1:
char = sourceget()
if char is None:
raise error, "unexpected end of pattern"
if char == ")":
break
raise error, "unknown extension"
elif this == "^":
subpatternappend((AT, AT_BEGINNING))
elif this == "$":
subpattern.append((AT, AT_END))
elif this and this[0] == "\\":
code = _escape(source, this, state)
subpatternappend(code)
else:
raise error, "parser error"
return subpattern
def parse(str, flags=0, pattern=None):
# parse 're' pattern into list of (opcode, argument) tuples
source = Tokenizer(str)
if pattern is None:
pattern = Pattern()
pattern.flags = flags
pattern.str = str
p = _parse_sub(source, pattern, 0)
tail = source.get()
if tail == ")":
raise error, "unbalanced parenthesis"
elif tail:
raise error, "bogus characters at end of regular expression"
if flags & SRE_FLAG_DEBUG:
p.dump()
if not (flags & SRE_FLAG_VERBOSE) and p.pattern.flags & SRE_FLAG_VERBOSE:
# the VERBOSE flag was switched on inside the pattern. to be
# on the safe side, we'll parse the whole thing again...
return parse(str, p.pattern.flags)
return p
def parse_template(source, pattern):
# parse 're' replacement string into list of literals and
# group references
s = Tokenizer(source)
sget = s.get
p = []
a = p.append
def literal(literal, p=p, pappend=a):
if p and p[-1][0] is LITERAL:
p[-1] = LITERAL, p[-1][1] + literal
else:
pappend((LITERAL, literal))
sep = source[:0]
if type(sep) is type(""):
makechar = chr
else:
makechar = unichr
while 1:
this = sget()
if this is None:
break # end of replacement string
if this and this[0] == "\\":
# group
c = this[1:2]
if c == "g":
name = ""
if s.match("<"):
while 1:
char = sget()
if char is None:
raise error, "unterminated group name"
if char == ">":
break
name = name + char
if not name:
raise error, "bad group name"
try:
index = int(name)
if index < 0:
raise error, "negative group number"
except ValueError:
if not isname(name):
raise error, "bad character in group name"
try:
index = pattern.groupindex[name]
except KeyError:
raise IndexError, "unknown group name"
a((MARK, index))
elif c == "0":
if s.next in OCTDIGITS:
this = this + sget()
if s.next in OCTDIGITS:
this = this + sget()
literal(makechar(int(this[1:], 8) & 0xff))
elif c in DIGITS:
isoctal = False
if s.next in DIGITS:
this = this + sget()
if (c in OCTDIGITS and this[2] in OCTDIGITS and
s.next in OCTDIGITS):
this = this + sget()
isoctal = True
literal(makechar(int(this[1:], 8) & 0xff))
if not isoctal:
a((MARK, int(this[1:])))
else:
try:
this = makechar(ESCAPES[this][1])
except KeyError:
pass
literal(this)
else:
literal(this)
# convert template to groups and literals lists
i = 0
groups = []
groupsappend = groups.append
literals = [None] * len(p)
for c, s in p:
if c is MARK:
groupsappend((i, s))
# literal[i] is already None
else:
literals[i] = s
i = i + 1
return groups, literals
def expand_template(template, match):
g = match.group
sep = match.string[:0]
groups, literals = template
literals = literals[:]
try:
for index, group in groups:
literals[index] = s = g(group)
if s is None:
raise error, "unmatched group"
except IndexError:
raise error, "invalid group reference"
return sep.join(literals)