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#
# Plex - Transition Maps
#
# This version represents state sets direcly as dicts
# for speed.
#
from sys import maxint as maxint
class TransitionMap(object):
"""
A TransitionMap maps an input event to a set of states.
An input event is one of: a range of character codes,
the empty string (representing an epsilon move), or one
of the special symbols BOL, EOL, EOF.
For characters, this implementation compactly represents
the map by means of a list:
[code_0, states_0, code_1, states_1, code_2, states_2,
..., code_n-1, states_n-1, code_n]
where |code_i| is a character code, and |states_i| is a
set of states corresponding to characters with codes |c|
in the range |code_i| <= |c| <= |code_i+1|.
The following invariants hold:
n >= 1
code_0 == -maxint
code_n == maxint
code_i < code_i+1 for i in 0..n-1
states_0 == states_n-1
Mappings for the special events '', BOL, EOL, EOF are
kept separately in a dictionary.
"""
map = None # The list of codes and states
special = None # Mapping for special events
def __init__(self, map = None, special = None):
if not map:
map = [-maxint, {}, maxint]
if not special:
special = {}
self.map = map
self.special = special
#self.check() ###
def add(self, event, new_state,
TupleType = tuple):
"""
Add transition to |new_state| on |event|.
"""
if type(event) is TupleType:
code0, code1 = event
i = self.split(code0)
j = self.split(code1)
map = self.map
while i < j:
map[i + 1][new_state] = 1
i = i + 2
else:
self.get_special(event)[new_state] = 1
def add_set(self, event, new_set,
TupleType = tuple):
"""
Add transitions to the states in |new_set| on |event|.
"""
if type(event) is TupleType:
code0, code1 = event
i = self.split(code0)
j = self.split(code1)
map = self.map
while i < j:
map[i + 1].update(new_set)
i = i + 2
else:
self.get_special(event).update(new_set)
def get_epsilon(self,
none = None):
"""
Return the mapping for epsilon, or None.
"""
return self.special.get('', none)
def iteritems(self,
len = len):
"""
Return the mapping as an iterable of ((code1, code2), state_set) and
(special_event, state_set) pairs.
"""
result = []
map = self.map
else_set = map[1]
i = 0
n = len(map) - 1
code0 = map[0]
while i < n:
set = map[i + 1]
code1 = map[i + 2]
if set or else_set:
result.append(((code0, code1), set))
code0 = code1
i = i + 2
for event, set in self.special.iteritems():
if set:
result.append((event, set))
return iter(result)
items = iteritems
# ------------------- Private methods --------------------
def split(self, code,
len = len, maxint = maxint):
"""
Search the list for the position of the split point for |code|,
inserting a new split point if necessary. Returns index |i| such
that |code| == |map[i]|.
"""
# We use a funky variation on binary search.
map = self.map
hi = len(map) - 1
# Special case: code == map[-1]
if code == maxint:
return hi
# General case
lo = 0
# loop invariant: map[lo] <= code < map[hi] and hi - lo >= 2
while hi - lo >= 4:
# Find midpoint truncated to even index
mid = ((lo + hi) // 2) & ~1
if code < map[mid]:
hi = mid
else:
lo = mid
# map[lo] <= code < map[hi] and hi - lo == 2
if map[lo] == code:
return lo
else:
map[hi:hi] = [code, map[hi - 1].copy()]
#self.check() ###
return hi
def get_special(self, event):
"""
Get state set for special event, adding a new entry if necessary.
"""
special = self.special
set = special.get(event, None)
if not set:
set = {}
special[event] = set
return set
# --------------------- Conversion methods -----------------------
def __str__(self):
map_strs = []
map = self.map
n = len(map)
i = 0
while i < n:
code = map[i]
if code == -maxint:
code_str = "-inf"
elif code == maxint:
code_str = "inf"
else:
code_str = str(code)
map_strs.append(code_str)
i = i + 1
if i < n:
map_strs.append(state_set_str(map[i]))
i = i + 1
special_strs = {}
for event, set in self.special.iteritems():
special_strs[event] = state_set_str(set)
return "[%s]+%s" % (
','.join(map_strs),
special_strs
)
# --------------------- Debugging methods -----------------------
def check(self):
"""Check data structure integrity."""
if not self.map[-3] < self.map[-1]:
print(self)
assert 0
def dump(self, file):
map = self.map
i = 0
n = len(map) - 1
while i < n:
self.dump_range(map[i], map[i + 2], map[i + 1], file)
i = i + 2
for event, set in self.special.iteritems():
if set:
if not event:
event = 'empty'
self.dump_trans(event, set, file)
def dump_range(self, code0, code1, set, file):
if set:
if code0 == -maxint:
if code1 == maxint:
k = "any"
else:
k = "< %s" % self.dump_char(code1)
elif code1 == maxint:
k = "> %s" % self.dump_char(code0 - 1)
elif code0 == code1 - 1:
k = self.dump_char(code0)
else:
k = "%s..%s" % (self.dump_char(code0),
self.dump_char(code1 - 1))
self.dump_trans(k, set, file)
def dump_char(self, code):
if 0 <= code <= 255:
return repr(chr(code))
else:
return "chr(%d)" % code
def dump_trans(self, key, set, file):
file.write(" %s --> %s\n" % (key, self.dump_set(set)))
def dump_set(self, set):
return state_set_str(set)
#
# State set manipulation functions
#
#def merge_state_sets(set1, set2):
# for state in set2.keys():
# set1[state] = 1
def state_set_str(set):
return "[%s]" % ','.join(["S%d" % state.number for state in set])