# Secret Labs' Regular Expression Engine
# $Id$
#
-# convert re-style regular expression to SRE template. the current
-# implementation is somewhat incomplete, and not very fast. should
-# definitely be rewritten before Python 1.6 goes beta.
+# convert re-style regular expression to sre pattern
#
# Copyright (c) 1998-2000 by Secret Labs AB. All rights reserved.
#
# other compatibility work.
#
-# FIXME: comments marked with the FIXME tag are open issues. all such
-# issues should be closed before the final beta.
-
import string, sys
+import _sre
+
from sre_constants import *
+# FIXME: should be 65535, but the array module currently chokes on
+# unsigned integers larger than 32767...
+MAXREPEAT = int(2L**(_sre.getcodesize()*8-1))-1
+
SPECIAL_CHARS = ".\\[{()*+?^$|"
REPEAT_CHARS = "*+?{"
OCTDIGITS = tuple("01234567")
HEXDIGITS = tuple("0123456789abcdefABCDEF")
+WHITESPACE = tuple(string.whitespace)
+
ESCAPES = {
"\\a": (LITERAL, chr(7)),
"\\b": (LITERAL, chr(8)),
"\\Z": (AT, AT_END), # end of string
}
-class Pattern:
- # FIXME: <fl> rename class, and store flags in here too!
+FLAGS = {
+ "i": SRE_FLAG_IGNORECASE,
+ "L": SRE_FLAG_LOCALE,
+ "m": SRE_FLAG_MULTILINE,
+ "s": SRE_FLAG_DOTALL,
+ "t": SRE_FLAG_TEMPLATE,
+ "x": SRE_FLAG_VERBOSE,
+}
+
+class State:
def __init__(self):
- self.flags = []
+ self.flags = 0
self.groups = 1
self.groupdict = {}
def getgroup(self, name=None):
if name:
self.groupdict[name] = gid
return gid
- def setflag(self, flag):
- if flag in self.flags:
- self.flags.append(flag)
class SubPattern:
# a subpattern, in intermediate form
if not data:
data = []
self.data = data
- self.flags = []
self.width = None
def __repr__(self):
return repr(self.data)
hi = hi + j
elif op in (MIN_REPEAT, MAX_REPEAT):
i, j = av[2].getwidth()
- lo = lo + i * av[0]
- hi = hi + j * av[1]
+ lo = lo + long(i) * av[0]
+ hi = hi + long(j) * av[1]
elif op in (ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY):
lo = lo + 1
hi = hi + 1
break
self.width = int(min(lo, sys.maxint)), int(min(hi, sys.maxint))
return self.width
- def set(self, flag):
- if not flag in self.flags:
- self.flags.append(flag)
- def reset(self, flag):
- if flag in self.flags:
- self.flags.remove(flag)
class Tokenizer:
def __init__(self, string):
- self.string = list(string)
+ self.index = 0
+ self.string = string
self.next = self.__next()
def __next(self):
- if not self.string:
+ if self.index >= len(self.string):
return None
- char = self.string[0]
+ char = self.string[self.index]
if char[0] == "\\":
try:
- c = self.string[1]
+ c = self.string[self.index + 1]
except IndexError:
raise SyntaxError, "bogus escape"
char = char + c
- try:
- if c == "x":
- # hexadecimal constant
- for i in xrange(2, sys.maxint):
- c = self.string[i]
- if str(c) not in HEXDIGITS:
- break
- char = char + c
- elif str(c) in DIGITS:
- # decimal (or octal) number
- for i in xrange(2, sys.maxint):
- c = self.string[i]
- # FIXME: if larger than current number of
- # groups, interpret as an octal number
- if str(c) not in DIGITS:
- break
- char = char + c
- except IndexError:
- pass # use what we've got this far
- del self.string[0:len(char)]
+ self.index = self.index + len(char)
return char
def match(self, char):
if char == self.next:
self.next = self.__next()
return this
-def _fixescape(escape, character_class=0):
- # convert escape to (type, value)
- if character_class:
- # inside a character class, we'll look in the character
- # escapes dictionary first
- code = ESCAPES.get(escape)
- if code:
- return code
- code = CATEGORIES.get(escape)
- else:
- code = CATEGORIES.get(escape)
- if code:
- return code
- code = ESCAPES.get(escape)
+def _group(escape, state):
+ # check if the escape string represents a valid group
+ try:
+ group = int(escape[1:])
+ if group and group < state.groups:
+ return group
+ except ValueError:
+ pass
+ return None # not a valid group
+
+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:
+ if escape[1:2] == "x":
+ while source.next in HEXDIGITS:
+ escape = escape + source.get()
+ escape = escape[2:]
+ # FIXME: support unicode characters!
+ return LITERAL, chr(int(escape[-4:], 16) & 0xff)
+ elif str(escape[1:2]) in OCTDIGITS:
+ while source.next in OCTDIGITS:
+ escape = escape + source.get()
+ escape = escape[1:]
+ # FIXME: support unicode characters!
+ return LITERAL, chr(int(escape[-6:], 8) & 0xff)
+ if len(escape) == 2:
+ return LITERAL, escape[1]
+ except ValueError:
+ pass
+ raise SyntaxError, "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
- if not character_class:
- try:
- group = int(escape[1:])
- # FIXME: only valid if group <= current number of groups
- return GROUP, group
- except ValueError:
- pass
try:
if escape[1:2] == "x":
+ while source.next in HEXDIGITS:
+ escape = escape + source.get()
escape = escape[2:]
- return LITERAL, chr(int(escape[-2:], 16) & 0xff)
+ # FIXME: support unicode characters!
+ return LITERAL, chr(int(escape[-4:], 16) & 0xff)
elif str(escape[1:2]) in DIGITS:
- return LITERAL, chr(int(escape[1:], 8) & 0xff)
- elif len(escape) == 2:
+ while 1:
+ group = _group(escape, state)
+ if group:
+ if (not source.next or
+ not _group(escape + source.next, state)):
+ return GROUP, group
+ escape = escape + source.get()
+ elif source.next in OCTDIGITS:
+ escape = escape + source.get()
+ else:
+ break
+ escape = escape[1:]
+ # FIXME: support unicode characters!
+ return LITERAL, chr(int(escape[-6:], 8) & 0xff)
+ if len(escape) == 2:
return LITERAL, escape[1]
except ValueError:
pass
raise SyntaxError, "bogus escape: %s" % repr(escape)
-def _branch(subpattern, items):
+
+def _branch(pattern, items):
# form a branch operator from a set of items (FIXME: move this
# optimization to the compiler module!)
+ subpattern = SubPattern(pattern)
+
# check if all items share a common prefix
while 1:
prefix = None
for item in items:
set.append(item[0])
subpattern.append((IN, set))
- return
+ return subpattern
subpattern.append((BRANCH, (None, items)))
+ return subpattern
-def _parse(source, pattern, flags=()):
+def _parse(source, state, flags=0):
# parse regular expression pattern into an operator list.
- subpattern = SubPattern(pattern)
-
- this = None
+ subpattern = SubPattern(state)
while 1:
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 = source.get()
+ if this in (None, "\n"):
+ break
+ continue
+
if this and this[0] not in SPECIAL_CHARS:
subpattern.append((LITERAL, this))
if this == "]" and set != start:
break
elif this and this[0] == "\\":
- code1 = _fixescape(this, 1)
+ code1 = _class_escape(source, this)
elif this:
code1 = LITERAL, this
else:
break
else:
if this[0] == "\\":
- code2 = _fixescape(this, 1)
+ code2 = _class_escape(source, this)
else:
code2 = LITERAL, this
if code1[0] != LITERAL or code2[0] != LITERAL:
code1 = code1[1][0]
set.append(code1)
- # FIXME: <fl> move set optimization to support function
+ # FIXME: <fl> move set optimization to compiler!
if len(set)==1 and set[0][0] is LITERAL:
subpattern.append(set[0]) # optimization
elif len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL:
if this == "?":
min, max = 0, 1
elif this == "*":
- min, max = 0, sys.maxint
+ min, max = 0, MAXREPEAT
elif this == "+":
- min, max = 1, sys.maxint
+ min, max = 1, MAXREPEAT
elif this == "{":
- min, max = 0, sys.maxint
+ min, max = 0, MAXREPEAT
lo = hi = ""
while str(source.next) in DIGITS:
lo = lo + source.get()
else:
raise SyntaxError, "not supported"
# figure out which item to repeat
- # FIXME: should back up to the right mark, right?
if subpattern:
- index = len(subpattern)-1
- while subpattern[index][0] is MARK:
- index = index - 1
- item = subpattern[index:index+1]
+ item = subpattern[-1:]
else:
raise SyntaxError, "nothing to repeat"
if source.match("?"):
- subpattern[index] = (MIN_REPEAT, (min, max, item))
+ subpattern[-1] = (MIN_REPEAT, (min, max, item))
else:
- subpattern[index] = (MAX_REPEAT, (min, max, item))
+ subpattern[-1] = (MAX_REPEAT, (min, max, item))
+
elif this == ".":
subpattern.append((ANY, None))
+
elif this == "(":
group = 1
name = None
group = 0
# options
if source.match("P"):
- # named group: skip forward to end of name
+ # python extensions
if source.match("<"):
+ # named group: skip forward to end of name
name = ""
while 1:
char = source.get()
- if char is None or char == ">":
+ if char is None:
+ raise SyntaxError, "unterminated name"
+ if char == ">":
break
+ # FIXME: check for valid character
name = name + char
group = 1
+ elif source.match("="):
+ # named backreference
+ raise SyntaxError, "not yet implemented"
+
+ else:
+ char = source.get()
+ if char is None:
+ raise SyntaxError, "unexpected end of pattern"
+ raise SyntaxError, "unknown specifier: ?P%s" % char
elif source.match(":"):
# non-capturing group
group = 2
- elif source.match_set("iI"):
- pattern.setflag("i")
- elif source.match_set("lL"):
- pattern.setflag("l")
- elif source.match_set("mM"):
- pattern.setflag("m")
- elif source.match_set("sS"):
- pattern.setflag("s")
- elif source.match_set("xX"):
- pattern.setflag("x")
+ elif source.match("#"):
+ # comment
+ while 1:
+ char = source.get()
+ if char is None or char == ")":
+ break
+ else:
+ # flags
+ while FLAGS.has_key(source.next):
+ state.flags = state.flags | FLAGS[source.get()]
if group:
# parse group contents
b = []
# anonymous group
group = None
else:
- group = pattern.getgroup(name)
- if group:
- subpattern.append((MARK, (group-1)*2))
+ group = state.getgroup(name)
while 1:
- p = _parse(source, pattern, flags)
+ p = _parse(source, state, flags)
if source.match(")"):
if b:
b.append(p)
- _branch(subpattern, b)
- else:
- subpattern.append((SUBPATTERN, (group, p)))
+ p = _branch(state, b)
+ subpattern.append((SUBPATTERN, (group, p)))
break
elif source.match("|"):
b.append(p)
else:
raise SyntaxError, "group not properly closed"
- if group:
- subpattern.append((MARK, (group-1)*2+1))
else:
- # FIXME: should this really be a while loop?
while 1:
char = source.get()
if char is None or char == ")":
break
+ # FIXME: skip characters?
elif this == "^":
subpattern.append((AT, AT_BEGINNING))
subpattern.append((AT, AT_END))
elif this and this[0] == "\\":
- code =_fixescape(this)
+ code = _escape(source, this, state)
subpattern.append(code)
else:
return subpattern
-def parse(source, flags=()):
- s = Tokenizer(source)
- g = Pattern()
+def parse(pattern, flags=0):
+ # parse 're' pattern into list of (opcode, argument) tuples
+ source = Tokenizer(pattern)
+ state = State()
b = []
while 1:
- p = _parse(s, g, flags)
- tail = s.get()
+ p = _parse(source, state, flags)
+ tail = source.get()
if tail == "|":
b.append(p)
elif tail == ")":
elif tail is None:
if b:
b.append(p)
- p = SubPattern(g)
- _branch(p, b)
+ p = _branch(state, b)
break
else:
raise SyntaxError, "bogus characters at end of regular expression"
return p
+def parse_replacement(source, pattern):
+ # parse 're' replacement string into list of literals and
+ # group references
+ s = Tokenizer(source)
+ p = []
+ a = p.append
+ while 1:
+ this = s.get()
+ if this is None:
+ break # end of replacement string
+ if this and this[0] == "\\":
+ try:
+ a(LITERAL, ESCAPES[this])
+ except KeyError:
+ for char in this:
+ a(LITERAL, char)
+ else:
+ a(LITERAL, this)
+ return p
+
if __name__ == "__main__":
from pprint import pprint
from testpatterns import PATTERNS
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