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#-----------------------------------------------------------------
# _ast_gen.py
#
# Generates the AST Node classes from a specification given in
# a configuration file
#
# The design of this module was inspired by astgen.py from the
# Python 2.5 code-base.
#
# Copyright (C) 2008-2015, Eli Bendersky
# License: BSD
#-----------------------------------------------------------------
import pprint
from string import Template
class ASTCodeGenerator(object):
def __init__(self, cfg_filename='_c_ast.cfg'):
""" Initialize the code generator from a configuration
file.
"""
self.cfg_filename = cfg_filename
self.node_cfg = [NodeCfg(name, contents)
for (name, contents) in self.parse_cfgfile(cfg_filename)]
def generate(self, file=None):
""" Generates the code into file, an open file buffer.
"""
src = Template(_PROLOGUE_COMMENT).substitute(
cfg_filename=self.cfg_filename)
src += _PROLOGUE_CODE
for node_cfg in self.node_cfg:
src += node_cfg.generate_source() + '\n\n'
file.write(src)
def parse_cfgfile(self, filename):
""" Parse the configuration file and yield pairs of
(name, contents) for each node.
"""
with open(filename, "r") as f:
for line in f:
line = line.strip()
if not line or line.startswith('#'):
continue
colon_i = line.find(':')
lbracket_i = line.find('[')
rbracket_i = line.find(']')
if colon_i < 1 or lbracket_i <= colon_i or rbracket_i <= lbracket_i:
raise RuntimeError("Invalid line in %s:\n%s\n" % (filename, line))
name = line[:colon_i]
val = line[lbracket_i + 1:rbracket_i]
vallist = [v.strip() for v in val.split(',')] if val else []
yield name, vallist
class NodeCfg(object):
""" Node configuration.
name: node name
contents: a list of contents - attributes and child nodes
See comment at the top of the configuration file for details.
"""
def __init__(self, name, contents):
self.name = name
self.all_entries = []
self.attr = []
self.child = []
self.seq_child = []
for entry in contents:
clean_entry = entry.rstrip('*')
self.all_entries.append(clean_entry)
if entry.endswith('**'):
self.seq_child.append(clean_entry)
elif entry.endswith('*'):
self.child.append(clean_entry)
else:
self.attr.append(entry)
def generate_source(self):
src = self._gen_init()
src += '\n' + self._gen_children()
src += '\n' + self._gen_attr_names()
return src
def _gen_init(self):
src = "class %s(Node):\n" % self.name
if self.all_entries:
args = ', '.join(self.all_entries)
slots = ', '.join("'{0}'".format(e) for e in self.all_entries)
slots += ", 'coord', '__weakref__'"
arglist = '(self, %s, coord=None)' % args
else:
slots = "'coord', '__weakref__'"
arglist = '(self, coord=None)'
src += " __slots__ = (%s)\n" % slots
src += " def __init__%s:\n" % arglist
for name in self.all_entries + ['coord']:
src += " self.%s = %s\n" % (name, name)
return src
def _gen_children(self):
src = ' def children(self):\n'
if self.all_entries:
src += ' nodelist = []\n'
for child in self.child:
src += (
' if self.%(child)s is not None:' +
' nodelist.append(("%(child)s", self.%(child)s))\n') % (
dict(child=child))
for seq_child in self.seq_child:
src += (
' for i, child in enumerate(self.%(child)s or []):\n'
' nodelist.append(("%(child)s[%%d]" %% i, child))\n') % (
dict(child=seq_child))
src += ' return tuple(nodelist)\n'
else:
src += ' return ()\n'
return src
def _gen_attr_names(self):
src = " attr_names = (" + ''.join("%r, " % nm for nm in self.attr) + ')'
return src
_PROLOGUE_COMMENT = \
r'''#-----------------------------------------------------------------
# ** ATTENTION **
# This code was automatically generated from the file:
# $cfg_filename
#
# Do not modify it directly. Modify the configuration file and
# run the generator again.
# ** ** *** ** **
#
# pycparser: c_ast.py
#
# AST Node classes.
#
# Copyright (C) 2008-2015, Eli Bendersky
# License: BSD
#-----------------------------------------------------------------
'''
_PROLOGUE_CODE = r'''
import sys
class Node(object):
__slots__ = ()
""" Abstract base class for AST nodes.
"""
def children(self):
""" A sequence of all children that are Nodes
"""
pass
def show(self, buf=sys.stdout, offset=0, attrnames=False, nodenames=False, showcoord=False, _my_node_name=None):
""" Pretty print the Node and all its attributes and
children (recursively) to a buffer.
buf:
Open IO buffer into which the Node is printed.
offset:
Initial offset (amount of leading spaces)
attrnames:
True if you want to see the attribute names in
name=value pairs. False to only see the values.
nodenames:
True if you want to see the actual node names
within their parents.
showcoord:
Do you want the coordinates of each Node to be
displayed.
"""
lead = ' ' * offset
if nodenames and _my_node_name is not None:
buf.write(lead + self.__class__.__name__+ ' <' + _my_node_name + '>: ')
else:
buf.write(lead + self.__class__.__name__+ ': ')
if self.attr_names:
if attrnames:
nvlist = [(n, getattr(self,n)) for n in self.attr_names]
attrstr = ', '.join('%s=%s' % nv for nv in nvlist)
else:
vlist = [getattr(self, n) for n in self.attr_names]
attrstr = ', '.join('%s' % v for v in vlist)
buf.write(attrstr)
if showcoord:
buf.write(' (at %s)' % self.coord)
buf.write('\n')
for (child_name, child) in self.children():
child.show(
buf,
offset=offset + 2,
attrnames=attrnames,
nodenames=nodenames,
showcoord=showcoord,
_my_node_name=child_name)
class NodeVisitor(object):
""" A base NodeVisitor class for visiting c_ast nodes.
Subclass it and define your own visit_XXX methods, where
XXX is the class name you want to visit with these
methods.
For example:
class ConstantVisitor(NodeVisitor):
def __init__(self):
self.values = []
def visit_Constant(self, node):
self.values.append(node.value)
Creates a list of values of all the constant nodes
encountered below the given node. To use it:
cv = ConstantVisitor()
cv.visit(node)
Notes:
* generic_visit() will be called for AST nodes for which
no visit_XXX method was defined.
* The children of nodes for which a visit_XXX was
defined will not be visited - if you need this, call
generic_visit() on the node.
You can use:
NodeVisitor.generic_visit(self, node)
* Modeled after Python's own AST visiting facilities
(the ast module of Python 3.0)
"""
def visit(self, node):
""" Visit a node.
"""
method = 'visit_' + node.__class__.__name__
visitor = getattr(self, method, self.generic_visit)
return visitor(node)
def generic_visit(self, node):
""" Called if no explicit visitor function exists for a
node. Implements preorder visiting of the node.
"""
for c_name, c in node.children():
self.visit(c)
'''
if __name__ == "__main__":
import sys
ast_gen = ASTCodeGenerator('_c_ast.cfg')
ast_gen.generate(open('c_ast.py', 'w'))