/usr/share/pyshared/ometa/interp.py is in python-parsley 1.2-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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from ometa.runtime import (InputStream, ParseError, EOFError, ArgInput,
joinErrors, expected, LeftRecursion)
def decomposeGrammar(grammar):
rules = {}
#XXX remove all these asserts once we have quasiterms
assert grammar.tag.name == 'Grammar'
for rule in grammar.args[2].args:
assert rule.tag.name == 'Rule'
rules[rule.args[0].data] = rule.args[1]
return rules
# after 12, i'm worse than a gremlin
_feed_me = object()
class TrampolinedGrammarInterpreter(object):
"""
An interpreter for OMeta grammars that processes input
incrementally.
"""
def __init__(self, grammar, ruleName, callback=None, globals=None):
self.grammar = grammar
self.position = 0
self.callback = callback
self.globals = globals or {}
self.rules = decomposeGrammar(grammar)
self.next = self.apply(ruleName, None, ())
self._localsStack = []
self.currentResult = None
self.input = InputStream([], 0)
self.ended = False
self._spanStart = 0
def receive(self, buf):
"""
Feed data to the parser.
"""
if not buf:
# No data. Nothing to do.
return
if self.ended:
raise ValueError("Can't feed a parser that's been ended.")
self.input.data.extend(buf)
x = None
for x in self.next:
if x is _feed_me:
return x
if self.callback:
self.callback(*x)
self.ended = True
def end(self):
"""
Close the input stream, indicating to the grammar that no more
input will arrive.
"""
if self.ended:
return
self.ended = True
x = None
for x in self.next:
pass
if self.callback:
self.callback(*x)
## Implementation note: each method, instead of being a function
## returning a value, is a generator that will yield '_feed_me' an
## arbitrary number of times, then finally yield the value of the
## expression being evaluated.
def _apply(self, rule, ruleName, args):
"""
Apply a rule method to some args.
@param rule: A method of this object.
@param ruleName: The name of the rule invoked.
@param args: A sequence of arguments to it.
"""
if args:
if ((not getattr(rule, 'func_code', None))
or rule.func_code.co_argcount - 1 != len(args)):
for arg in args[::-1]:
self.input = ArgInput(arg, self.input)
g = rule()
else:
g = rule(*args)
for x in g:
if x is _feed_me: yield x
yield x
return
memoRec = self.input.getMemo(ruleName)
if memoRec is None:
oldPosition = self.input
lr = LeftRecursion()
memoRec = self.input.setMemo(ruleName, lr)
try:
inp = self.input
for x in rule():
if x is _feed_me: yield x
memoRec = inp.setMemo(ruleName, [x, self.input])
except ParseError:
raise
if lr.detected:
sentinel = self.input
while True:
try:
self.input = oldPosition
for x in rule():
if x is _feed_me: yield x
ans = x
if (self.input == sentinel):
break
memoRec = oldPosition.setMemo(ruleName,
[ans, self.input])
except ParseError:
break
self.input = oldPosition
elif isinstance(memoRec, LeftRecursion):
memoRec.detected = True
raise self.input.nullError()
self.input = memoRec[1]
yield memoRec[0]
def _eval(self, expr):
"""
Dispatch to a parse_<term name> method for the given grammar expression.
"""
return getattr(self, "parse_" + expr.tag.name)(*expr.args)
def parse_Apply(self, ruleName, codeName, args):
for x in self.apply(ruleName.data, codeName.data, args.args):
if x is _feed_me: yield x
yield x
def apply(self, ruleName, codeName, args):
"""
Invoke a rule, optionally with arguments.
"""
argvals = []
for a in args:
for x in self._eval(a):
if x is _feed_me: yield x
argvals.append(x[0])
_locals = {}
self._localsStack.append(_locals)
try:
#XXX super
rul = self.rules.get(ruleName)
if rul:
def f():
return self._eval(rul)
else:
#ruleName may be a Twine, so gotta call str()
f = getattr(self, str('rule_' + ruleName))
for x in self._apply(f, ruleName, argvals):
if x is _feed_me: yield x
yield x
finally:
self._localsStack.pop()
def parse_Exactly(self, spec):
"""
Accept a one or more characters that equal the given spec.
"""
wanted = spec.data
result = []
for c in wanted:
try:
val, p = self.input.head()
except EOFError:
yield _feed_me
val, p = self.input.head()
result.append(val)
if val == c:
self.input = self.input.tail()
else:
raise self.err(p.withMessage(expected(None, wanted)))
yield ''.join(result), p
def parse_Token(self, spec):
"""
Consume leading whitespace then the given string.
"""
val = ' '
while val.isspace():
try:
val, p = self.input.head()
except EOFError:
yield _feed_me
val, p = self.input.head()
if val.isspace():
self.input = self.input.tail()
wanted = spec.data
result = []
for c in wanted:
try:
val, p = self.input.head()
except EOFError:
yield _feed_me
val, p = self.input.head()
result.append(val)
if val == c:
self.input = self.input.tail()
else:
raise self.err(p.withMessage(expected("token", wanted)))
yield ''.join(result), p
def parse_And(self, expr):
"""
Execute multiple subexpressions in order, returning the result
of the last one.
"""
seq = expr.args
x = None, self.input.nullError()
for subexpr in seq:
for x in self._eval(subexpr):
if x is _feed_me: yield x
self.currentError = x[1]
yield x
def parse_Or(self, expr):
"""
Execute multiple subexpressions, returning the result of the
first one that succeeds.
"""
errors = []
i = self.input
for subexpr in expr.args:
try:
for x in self._eval(subexpr):
if x is _feed_me: yield x
val, p = x
errors.append(p)
self.currentError = joinErrors(errors)
yield x
return
except ParseError, err:
errors.append(err)
self.input = i
raise self.err(joinErrors(errors))
def parse_Many(self, expr, ans=None):
"""
Execute an expression repeatedly until it fails to match,
collecting the results into a list. Implementation of '*'.
"""
ans = ans or []
while True:
try:
m = self.input
for x in self._eval(expr):
if x is _feed_me: yield x
ans.append(x[0])
self.currentError = x[1]
except ParseError, err:
self.input = m
break
yield ans, err
def parse_Many1(self, expr):
"""
Execute an expression one or more times, collecting the
results into a list. Implementation of '+'.
"""
for x in self._eval(expr):
if x is _feed_me: yield x
for x in self.parse_Many(expr, ans=[x[0]]):
if x is _feed_me: yield x
yield x
def parse_Repeat(self, min, max, expr):
"""
Execute an expression between C{min} and C{max} times,
collecting the results into a list. Implementation of '{}'.
"""
if min.tag.name == '.int.':
min = min.data
else:
min = self._localsStack[-1][min.data]
if max.tag.name == '.int.':
max = max.data
elif max.tag.name == 'null':
max = None
else:
max = self._localsStack[-1][max.data]
if min == max == 0:
yield '', None
return
ans = []
for i in range(min):
for x in self._eval(expr):
if x is _feed_me: yield x
v, e = x
ans.append(v)
if max is not None:
repeats = xrange(min, max)
for i in repeats:
try:
m = self.input
for x in self._eval(expr):
if x is _feed_me: yield x
v, e = x
ans.append(v)
except ParseError, e:
self.input = m
break
yield ans, e
def parse_Optional(self, expr):
"""
Execute an expression, returning None if it
fails. Implementation of '?'.
"""
i = self.input
try:
for x in self._eval(expr):
if x is _feed_me: yield x
yield x
except ParseError:
self.input = i
yield (None, self.input.nullError())
def parse_Not(self, expr):
"""
Execute an expression, returning True if it fails and failing
otherwise. Implementation of '~'.
"""
m = self.input
try:
for x in self._eval(expr):
if x is _feed_me: yield x
except ParseError:
self.input = m
yield True, self.input.nullError()
else:
raise self.err(self.input.nullError())
def parse_Label(self, expr, label_term):
"""
Execute an expression , if it fails apply the label to the exception.
"""
label = label_term.data
try:
for x in self._eval(expr):
if x is _feed_me:
yield x
print "^^", label
self.currentError = x[1].withMessage([("Custom Exception:", label, None)])
yield x[0], self.currentError
except ParseError, e:
raise self.err(e.withMessage([("Custom Exception:", label, None)]))
def parse_Lookahead(self, expr):
"""
Execute an expression, then reset the input stream to the
position before execution. Implementation of '~~'.
"""
try:
i = self.input
for x in self._eval(expr):
if x is _feed_me: yield x
finally:
self.input = i
def parse_Bind(self, name, expr):
"""
Execute an expression and bind its result to the given name.
"""
for x in self._eval(expr):
if x is _feed_me: yield x
v, err = x
if name.data:
self._localsStack[-1][name.data] = v
else:
for n, val in zip(name.args, v):
self._localsStack[-1][n.data] = val
yield v, err
def parse_Predicate(self, expr):
"""
Run a Python expression and fail if it returns False.
"""
for x in self._eval(expr):
if x is _feed_me: yield x
val, err = x
if not val:
raise self.err(err)
else:
yield True, err
def parse_Action(self, expr):
"""
Run a Python expression, return its result.
"""
val = eval(expr.data, self.globals, self._localsStack[-1])
yield val, self.input.nullError()
def parse_ConsumedBy(self, expr):
"""
Run an expression. Return the literal contents of the input
stream it consumed.
"""
oldInput = self.input
for x in self._eval(expr):
if x is _feed_me: yield x
slice = oldInput.data[oldInput.position:self.input.position]
yield "".join(slice), x[1]
def rule_anything(self):
"""
Match a single character.
"""
try:
val, p = self.input.head()
except EOFError:
yield _feed_me
val, p = self.input.head()
self.input = self.input.tail()
yield val, p
def rule_letter(self):
"""
Match a single letter.
"""
try:
val, p = self.input.head()
except EOFError:
yield _feed_me
val, p = self.input.head()
if val in string.letters:
self.input = self.input.tail()
yield val, p
else:
raise self.err(p.withMessage(expected("letter")))
def rule_digit(self):
"""
Match a digit.
"""
try:
val, p = self.input.head()
except EOFError:
yield _feed_me
val, p = self.input.head()
if val in string.digits:
self.input = self.input.tail()
yield val, p
else:
raise self.err(p.withMessage(expected("digit")))
def err(self, e):
e.input = ''.join(e.input)
raise e
class GrammarInterpreter(object):
def __init__(self, grammar, base, globals=None):
"""
grammar: A term tree representing a grammar.
"""
self.grammar = grammar
self.base = base
self.rules = {}
self._localsStack = []
self._globals = globals or {}
self.rules = decomposeGrammar(grammar)
self.run = None
self._spanStart = 0
def apply(self, input, rulename, tree=False):
self.run = self.base(input, self._globals, tree=tree)
#XXX hax, fix grammar parser to distinguish tree from nontree grammars
if not isinstance(self.run.input.data, basestring):
tree = True
self.run.tree = True
v, err = self._apply(self.run, rulename, ())
return self.run.input, v, err
def _apply(self, run, ruleName, args):
argvals = [self._eval(run, a)[0] for a in args]
_locals = {'self': run}
self._localsStack.append(_locals)
try:
if ruleName == 'super':
return run.superApply(ruleName, argvals)
else:
rul = self.rules.get(ruleName)
if rul:
return run._apply(
(lambda: self._eval(run, rul)),
ruleName, argvals)
else:
#ruleName may be a Twine, so calling str()
x = run._apply(getattr(run, str('rule_' + ruleName)),
ruleName, argvals)
return x
finally:
self._localsStack.pop()
def _eval(self, run, expr):
name = expr.tag.name
args = expr.args
if name == "Apply":
ruleName = args[0].data
return self._apply(run, ruleName, args[2].args)
elif name == "Exactly":
return run.exactly(args[0].data)
elif name == "Label":
label = args[1].data
try:
val, err = self._eval(run, args[0])
return val, err.withMessage([("Custom Exception:", label, None)])
except ParseError, e:
raise e.withMessage([("Custom Exception:", label, None)])
elif name == "Token":
if run.tree:
return run._apply(run.rule_exactly, "exactly", [args[0].data])
else:
return run._apply(run.rule_token, "token", [args[0].data])
elif name in ("Many", "Many1"):
ans = [self._eval(run, args[0])[0]] if name == "Many1" else []
while True:
try:
m = run.input
v, _ = self._eval(run, args[0])
ans.append(v)
except ParseError, err:
run.input = m
break
return ans, err
elif name == "Repeat":
if args[0].tag.name == '.int.':
min = args[0].data
else:
min = self._localsStack[-1][args[0].data]
if args[1].tag.name == '.int.':
max = args[1].data
elif args[1].tag.name == 'null':
max = None
else:
max = self._localsStack[-1][args[1].data]
if min == max == 0:
return "", None
ans = []
for i in range(min):
v, e = self._eval(run, args[2])
ans.append(v)
for i in range(min, max):
try:
m = run.input
v, e = self._eval(run, args[2])
ans.append(v)
except ParseError, e:
run.input = m
break
return ans, e
elif name == "Optional":
i = run.input
try:
return self._eval(run, args[0])
except ParseError:
run.input = i
return (None, run.input.nullError())
elif name == "Or":
errors = []
for e in args[0].args:
try:
m = run.input
x = self._eval(run, e)
ret, err = x
errors.append(err)
return ret, joinErrors(errors)
except ParseError, err:
errors.append(err)
run.input = m
raise joinErrors(errors)
elif name == "Not":
m = run.input
try:
self._eval(run, args[0])
except ParseError, err:
run.input = m
return True, run.input.nullError()
else:
raise run.input.nullError()
elif name == "Lookahead":
try:
m = run.input
return self._eval(run, args[0])
finally:
run.input = m
elif name == "And":
v = None, run.input.nullError()
for e in args[0].args:
v = self._eval(run, e)
return v
elif name == "Bind":
v, err = self._eval(run, args[1])
if args[0].data:
self._localsStack[-1][args[0].data] = v
else:
for n, val in zip(args[0].args, v):
self._localsStack[-1][n.data] = val
return v, err
elif name == "Predicate":
val, err = self._eval(run, args[0])
if not val:
raise err
else:
return True, err
elif name == "List":
v, e = run.rule_anything()
oldInput = run.input
try:
run.input = InputStream.fromIterable(v)
except TypeError:
raise e.withMessage(expected("an iterable"))
self._eval(run, args[0])
run.end()
run.input = oldInput
return v, e
elif name in ("Action", "Python"):
lo = self._localsStack[-1]
val = eval(args[0].data, self._globals, lo)
return (val, run.input.nullError())
elif name == "ConsumedBy":
oldInput = run.input
_, err = self._eval(run, args[0])
slice = oldInput.data[oldInput.position:run.input.position]
return slice, err
else:
raise ValueError("Unrecognized term: %r" % (name,))
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