3 The Node package for the SCons software construction utility.
5 This is, in many ways, the heart of SCons.
7 A Node is where we encapsulate all of the dependency information about
8 any thing that SCons can build, or about any thing which SCons can use
9 to build some other thing. The canonical "thing," of course, is a file,
10 but a Node can also represent something remote (like a web page) or
11 something completely abstract (like an Alias).
13 Each specific type of "thing" is specifically represented by a subclass
14 of the Node base class: Node.FS.File for files, Node.Alias for aliases,
15 etc. Dependency information is kept here in the base class, and
16 information specific to files/aliases/etc. is in the subclass. The
17 goal, if we've done this correctly, is that any type of "thing" should
18 be able to depend on any other type of "thing."
25 # Permission is hereby granted, free of charge, to any person obtaining
26 # a copy of this software and associated documentation files (the
27 # "Software"), to deal in the Software without restriction, including
28 # without limitation the rights to use, copy, modify, merge, publish,
29 # distribute, sublicense, and/or sell copies of the Software, and to
30 # permit persons to whom the Software is furnished to do so, subject to
31 # the following conditions:
33 # The above copyright notice and this permission notice shall be included
34 # in all copies or substantial portions of the Software.
36 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
37 # KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
38 # WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
39 # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
40 # LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
41 # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
42 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
45 __revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
53 from SCons.Debug import logInstanceCreation
59 # These are in "priority" order, so that the maximum value for any
60 # child/dependency of a node represents the state of that node if
61 # it has no builder of its own. The canonical example is a file
62 # system directory, which is only up to date if all of its children
69 stack = 6 # nodes that are in the current Taskmaster execution stack
71 # controls whether implicit dependencies are cached:
74 # controls whether implicit dep changes are ignored:
75 implicit_deps_unchanged = 0
77 # controls whether the cached implicit deps are ignored:
78 implicit_deps_changed = 0
80 # A variable that can be set to an interface-specific function be called
81 # to annotate a Node with information about its creation.
82 def do_nothing(node): pass
87 def __cmp__(self, other):
88 return cmp(self.__dict__, other.__dict__)
91 """The base Node class, for entities that we know how to
92 build, or use to build other Nodes.
95 __metaclass__ = SCons.Memoize.Memoized_Metaclass
101 if __debug__: logInstanceCreation(self, 'Node')
102 # Note that we no longer explicitly initialize a self.builder
103 # attribute to None here. That's because the self.builder
104 # attribute may be created on-the-fly later by a subclass (the
105 # canonical example being a builder to fetch a file from a
106 # source code system like CVS or Subversion).
108 # Each list of children that we maintain is accompanied by a
109 # dictionary used to look up quickly whether a node is already
110 # present in the list. Empirical tests showed that it was
111 # fastest to maintain them as side-by-side Node attributes in
112 # this way, instead of wrapping up each list+dictionary pair in
113 # a class. (Of course, we could always still do that in the
114 # future if we had a good reason to...).
115 self.sources = [] # source files used to build node
116 self.sources_dict = {}
117 self.depends = [] # explicit dependencies (from Depends)
118 self.depends_dict = {}
119 self.ignore = [] # dependencies to ignore
120 self.ignore_dict = {}
121 self.implicit = None # implicit (scanned) dependencies (None means not scanned yet)
122 self.waiting_parents = []
123 self.wkids = None # Kids yet to walk, when it's an array
128 self.always_build = None
129 self.found_includes = {}
131 self.attributes = self.Attrs() # Generic place to stick information about the Node.
132 self.side_effect = 0 # true iff this node is a side effect
133 self.side_effects = [] # the side effects of building this target
134 self.pre_actions = []
135 self.post_actions = []
136 self.linked = 0 # is this node linked to the build directory?
138 # Let the interface in which the build engine is embedded
139 # annotate this Node with its own info (like a description of
140 # what line in what file created the node, for example).
143 def get_suffix(self):
146 def generate_build_dict(self):
147 """Return an appropriate dictionary of values for building
151 def get_build_env(self):
152 """Fetch the appropriate Environment to build this node.
154 return self.get_executor().get_build_env()
156 def set_executor(self, executor):
157 """Set the action executor for this node."""
158 self.executor = executor
160 def get_executor(self, create=1):
161 """Fetch the action executor for this node. Create one if
162 there isn't already one, and requested to do so."""
164 executor = self.executor
165 except AttributeError:
168 import SCons.Executor
169 act = self.builder.action
171 act = self.pre_actions + act
172 if self.post_actions:
173 act = act + self.post_actions
174 executor = SCons.Executor.Executor(act,
175 self.env or self.builder.env,
176 [self.builder.overrides],
179 self.executor = executor
182 def reset_executor(self):
183 "Remove cached executor; forces recompute when needed."
185 delattr(self, 'executor')
186 except AttributeError:
189 def retrieve_from_cache(self):
190 """Try to retrieve the node's content from a cache
192 This method is called from multiple threads in a parallel build,
193 so only do thread safe stuff here. Do thread unsafe stuff in
196 Returns true iff the node was successfully retrieved.
200 def build(self, **kw):
201 """Actually build the node.
203 This method is called from multiple threads in a parallel build,
204 so only do thread safe stuff here. Do thread unsafe stuff in
207 if not self.has_builder():
209 def errfunc(stat, node=self):
210 raise SCons.Errors.BuildError(node=node, errstr="Error %d" % stat)
211 executor = self.get_executor()
212 apply(executor, (self, errfunc), kw)
215 """Called just after this node is successfully built."""
217 # Clear the implicit dependency caches of any Nodes
218 # waiting for this Node to be built.
219 for parent in self.waiting_parents:
220 parent.implicit = None
224 new_binfo = self.binfo
225 except AttributeError:
226 # Node arrived here without build info; apparently it
227 # doesn't need it, so don't bother calculating or storing
231 # Reset this Node's cached state since it was just built and
232 # various state has changed.
235 # Had build info, so it should be stored in the signature
236 # cache. However, if the build info included a content
237 # signature then it should be recalculated before being
241 if hasattr(new_binfo, 'csig'):
242 new_binfo = self.gen_binfo() # sets self.binfo
244 self.binfo = new_binfo
245 self.store_info(new_binfo)
247 def add_to_waiting_parents(self, node):
248 self.waiting_parents.append(node)
250 def call_for_all_waiting_parents(self, func):
252 for parent in self.waiting_parents:
253 parent.call_for_all_waiting_parents(func)
255 def postprocess(self):
256 """Clean up anything we don't need to hang onto after we've
259 executor = self.get_executor(create=None)
260 except AttributeError:
266 """Completely clear a Node of all its cached state (so that it
267 can be re-evaluated by interfaces that do continuous integration
274 delattr(self, '_calculated_sig')
275 except AttributeError:
278 self.found_includes = {}
281 self.waiting_parents = []
284 """Called just after this node has been visited
285 without requiring a build.."""
288 def depends_on(self, nodes):
289 """Does this node depend on any of 'nodes'? __cacheable__"""
290 return reduce(lambda D,N,C=self.children(): D or (N in C), nodes, 0)
292 def builder_set(self, builder):
294 self.builder = builder
296 def has_builder(self):
297 """Return whether this Node has a builder or not.
299 In Boolean tests, this turns out to be a *lot* more efficient
300 than simply examining the builder attribute directly ("if
301 node.builder: ..."). When the builder attribute is examined
302 directly, it ends up calling __getattr__ for both the __len__
303 and __nonzero__ attributes on instances of our Builder Proxy
304 class(es), generating a bazillion extra calls and slowing
305 things down immensely.
310 except AttributeError:
311 # There was no explicit builder for this Node, so initialize
312 # the self.builder attribute to None now.
317 def has_explicit_builder(self):
318 """Return whether this Node has an explicit builder
320 This allows an internal Builder created by SCons to be marked
321 non-explicit, so that it can be overridden by an explicit
322 builder that the user supplies (the canonical example being
325 return self.has_builder() and self.builder.is_explicit
327 def get_builder(self, default_builder=None):
328 """Return the set builder, or a specified default value"""
331 except AttributeError:
332 return default_builder
334 multiple_side_effect_has_builder = has_builder
336 def is_derived(self):
338 Returns true iff this node is derived (i.e. built).
340 This should return true only for nodes whose path should be in
341 the build directory when duplicate=0 and should contribute their build
342 signatures when they are used as source files to other derived files. For
343 example: source with source builders are not derived in this sense,
344 and hence should not return true.
347 return self.has_builder() or self.side_effect
349 def is_pseudo_derived(self):
351 Returns true iff this node is built, but should use a source path
352 when duplicate=0 and should contribute a content signature (i.e.
353 source signature) when used as a source for other derived files.
357 def alter_targets(self):
358 """Return a list of alternate targets for this Node.
362 def get_found_includes(self, env, scanner, target):
363 """Return the scanned include lines (implicit dependencies)
366 The default is no implicit dependencies. We expect this method
367 to be overridden by any subclass that can be scanned for
368 implicit dependencies.
372 def get_implicit_deps(self, env, scanner, target):
373 """Return a list of implicit dependencies for this node.
375 This method exists to handle recursive invocation of the scanner
376 on the implicit dependencies returned by the scanner, if the
377 scanner's recursive flag says that we should.
382 # Give the scanner a chance to select a more specific scanner
384 scanner = scanner.select(self)
387 recurse = scanner.recursive
388 except AttributeError:
397 d = filter(lambda x, seen=seen: not seen.has_key(x),
398 n.get_found_includes(env, scanner, target))
408 def implicit_factory(self, path):
410 Turn a cache implicit dependency path into a node.
411 This is called so many times that doing caching
412 here is a significant performance boost.
415 return self.builder.source_factory(path)
418 def get_source_scanner(self, node):
419 """Fetch the source scanner for the specified node
421 NOTE: "self" is the target being built, "node" is
422 the source file for which we want to fetch the scanner.
424 Implies self.has_builder() is true; again, expect to only be
425 called from locations where this is already verified.
427 This function may be called very often; it attempts to cache
428 the scanner found to improve performance.
431 # Called from scan() for each child (node) of this node
432 # (self). The scan() may be called multiple times, so this
433 # gets called a multiple of those times; caching results is
434 # good. Index results based on the id of the child; can
435 # ignore build_env parameter for the index because it's passed
436 # as an optimization of an already-determined value, not as a
437 # changing parameter.
439 if not self.has_builder():
443 scanner = self.builder.source_scanner
446 except AttributeError:
449 # Not cached, so go look up a scanner from env['SCANNERS']
450 # based on the node's scanner key (usually the file
453 scanner = self.get_build_env().get_scanner(node.scanner_key())
457 """Scan this node's dependents for implicit dependencies."""
458 # Don't bother scanning non-derived files, because we don't
459 # care what their dependencies are.
460 # Don't scan again, if we already have scanned.
461 if not self.implicit is None:
464 self.implicit_dict = {}
465 self._children_reset()
466 if not self.has_builder():
469 build_env = self.get_build_env()
471 # Here's where we implement --implicit-cache.
472 if implicit_cache and not implicit_deps_changed:
473 implicit = self.get_stored_implicit()
474 if implicit is not None:
475 implicit = map(self.implicit_factory, implicit)
476 self._add_child(self.implicit, self.implicit_dict, implicit)
477 calc = build_env.get_calculator()
478 if implicit_deps_unchanged or self.current(calc):
481 # one of this node's sources has changed, so
482 # we need to recalculate the implicit deps,
485 self.implicit_dict = {}
486 self._children_reset()
489 for child in self.children(scan=0):
490 scanner = self.get_source_scanner(child)
492 deps = child.get_implicit_deps(build_env, scanner, self)
493 self._add_child(self.implicit, self.implicit_dict, deps)
495 # scan this node itself for implicit dependencies
496 scanner = self.builder.target_scanner
498 deps = self.get_implicit_deps(build_env, scanner, self)
499 self._add_child(self.implicit, self.implicit_dict, deps)
501 # XXX See note above re: --implicit-cache.
503 # self.store_implicit()
505 def scanner_key(self):
508 def env_set(self, env, safe=0):
509 if safe and self.env:
513 def calculator(self):
514 import SCons.Defaults
516 env = self.env or SCons.Defaults.DefaultEnvironment()
517 return env.get_calculator()
519 def calc_signature(self, calc=None):
521 Select and calculate the appropriate build signature for a node.
525 calc - the signature calculation module
526 returns - the signature
528 if self.is_derived():
529 import SCons.Defaults
531 env = self.env or SCons.Defaults.DefaultEnvironment()
532 if env.use_build_signature():
533 return self.calc_bsig(calc)
534 elif not self.rexists():
536 return self.calc_csig(calc)
542 """Delete the bsig from this node."""
544 delattr(self, 'binfo')
545 except AttributeError:
548 def calc_bsig(self, calc=None):
550 return self.binfo.bsig
551 except AttributeError:
552 self.binfo = self.gen_binfo(calc)
553 return self.binfo.bsig
555 def gen_binfo(self, calc=None, scan=1):
557 Generate a node's build signature, the digested signatures
558 of its dependency files and build information.
560 node - the node whose sources will be collected
561 cache - alternate node to use for the signature cache
562 returns - the build signature
564 This no longer handles the recursive descent of the
565 node's children's signatures. We expect that they're
566 already built and updated by someone else, if that's
572 calc = self.calculator()
574 binfo = self.new_binfo()
579 sources = self.filter_ignore(self.sources)
580 depends = self.filter_ignore(self.depends)
581 if self.implicit is None:
584 implicit = self.filter_ignore(self.implicit)
586 def calc_signature(node, calc=calc):
587 return node.calc_signature(calc)
588 sourcesigs = map(calc_signature, sources)
589 dependsigs = map(calc_signature, depends)
590 implicitsigs = map(calc_signature, implicit)
592 sigs = sourcesigs + dependsigs + implicitsigs
594 if self.has_builder():
595 executor = self.get_executor()
596 binfo.bact = str(executor)
597 binfo.bactsig = calc.module.signature(executor)
598 sigs.append(binfo.bactsig)
600 binfo.bsources = map(str, sources)
601 binfo.bdepends = map(str, depends)
602 binfo.bimplicit = map(str, implicit)
604 binfo.bsourcesigs = sourcesigs
605 binfo.bdependsigs = dependsigs
606 binfo.bimplicitsigs = implicitsigs
608 binfo.bsig = calc.module.collect(filter(None, sigs))
615 except AttributeError:
618 def calc_csig(self, calc=None):
621 except AttributeError:
622 binfo = self.binfo = self.new_binfo()
625 except AttributeError:
627 calc = self.calculator()
628 binfo.csig = calc.module.signature(self)
629 self.store_info(binfo)
632 def store_info(self, obj):
633 """Make the build signature permanent (that is, store it in the
634 .sconsign file or equivalent)."""
637 def get_stored_info(self):
640 def get_stored_implicit(self):
641 """Fetch the stored implicit dependencies"""
644 def set_precious(self, precious = 1):
645 """Set the Node's precious value."""
646 self.precious = precious
648 def set_always_build(self, always_build = 1):
649 """Set the Node's always_build value."""
650 self.always_build = always_build
653 """Does this node exists?"""
654 # All node exist by default:
658 """Does this node exist locally or in a repositiory?"""
659 # There are no repositories by default:
663 """Prepare for this Node to be created.
664 The default implemenation checks that all children either exist
668 return not node.is_derived() and \
669 not node.is_pseudo_derived() and \
670 not node.linked and \
672 missing_sources = filter(missing, self.children())
674 desc = "Source `%s' not found, needed by target `%s'." % (missing_sources[0], self)
675 raise SCons.Errors.StopError, desc
678 """Remove this Node: no-op by default."""
681 def add_dependency(self, depend):
682 """Adds dependencies."""
684 self._add_child(self.depends, self.depends_dict, depend)
687 if SCons.Util.is_List(e):
691 raise SCons.Errors.UserError("attempted to add a non-Node dependency to %s:\n\t%s is a %s, not a Node" % (str(self), s, type(e)))
693 def add_ignore(self, depend):
694 """Adds dependencies to ignore."""
696 self._add_child(self.ignore, self.ignore_dict, depend)
699 if SCons.Util.is_List(e):
703 raise SCons.Errors.UserError("attempted to ignore a non-Node dependency of %s:\n\t%s is a %s, not a Node" % (str(self), s, type(e)))
705 def add_source(self, source):
708 self._add_child(self.sources, self.sources_dict, source)
711 if SCons.Util.is_List(e):
715 raise SCons.Errors.UserError("attempted to add a non-Node as source of %s:\n\t%s is a %s, not a Node" % (str(self), s, type(e)))
717 def _add_child(self, collection, dict, child):
718 """Adds 'child' to 'collection', first checking 'dict' to see
719 if it's already present."""
720 if type(child) is not type([]):
723 if not isinstance(c, Node):
727 if not dict.has_key(c):
732 self._children_reset()
734 def add_wkid(self, wkid):
735 """Add a node to the list of kids waiting to be evaluated"""
736 if self.wkids != None:
737 self.wkids.append(wkid)
739 def _children_reset(self):
743 def filter_ignore(self, nodelist):
746 for node in nodelist:
747 if node not in ignore:
751 def _children_get(self):
753 return self.filter_ignore(self.all_children(scan=0))
755 def children(self, scan=1):
756 """Return a list of the node's direct children, minus those
757 that are ignored by this node."""
760 return self._children_get()
762 def all_children(self, scan=1):
763 """Return a list of all the node's direct children."""
764 # The return list may contain duplicate Nodes, especially in
765 # source trees where there are a lot of repeated #includes
766 # of a tangle of .h files. Profiling shows, however, that
767 # eliminating the duplicates with a brute-force approach that
768 # preserves the order (that is, something like:
775 # takes more cycles than just letting the underlying methods
776 # hand back cached values if a Node's information is requested
777 # multiple times. (Other methods of removing duplicates, like
778 # using dictionary keys, lose the order, and the only ordered
779 # dictionary patterns I found all ended up using "not in"
780 # internally anyway...)
783 if self.implicit is None:
784 return self.sources + self.depends
786 return self.sources + self.depends + self.implicit
788 def set_state(self, state):
794 def current(self, calc=None):
795 """Default check for whether the Node is current: unknown Node
796 subtypes are always out of date, so they will always get built."""
799 def children_are_up_to_date(self, calc=None):
800 """Alternate check for whether the Node is current: If all of
801 our children were up-to-date, then this Node was up-to-date, too.
803 The SCons.Node.Alias and SCons.Node.Python.Value subclasses
804 rebind their current() method to this method."""
805 # Allow the children to calculate their signatures.
806 self.binfo = self.gen_binfo(calc)
807 if self.always_build:
810 for kid in self.children(None):
812 if s and (not state or s > state):
814 return (state == 0 or state == SCons.Node.up_to_date)
816 def is_literal(self):
817 """Always pass the string representation of a Node to
818 the command interpreter literally."""
821 def add_pre_action(self, act):
822 """Adds an Action performed on this Node only before
824 self.pre_actions.append(act)
825 # executor must be recomputed to include new pre-actions
826 self.reset_executor()
828 def add_post_action(self, act):
829 """Adds and Action performed on this Node only after
831 self.post_actions.append(act)
832 # executor must be recomputed to include new pre-actions
833 self.reset_executor()
835 def render_include_tree(self):
837 Return a text representation, suitable for displaying to the
838 user, of the include tree for the sources of this node.
840 if self.is_derived() and self.env:
841 env = self.get_build_env()
842 for s in self.sources:
843 scanner = self.get_source_scanner(s)
844 def f(node, env=env, scanner=scanner, target=self):
845 return node.get_found_includes(env, scanner, target)
846 return SCons.Util.render_tree(s, f, 1)
850 def get_abspath(self):
852 Return an absolute path to the Node. This will return simply
853 str(Node) by default, but for Node types that have a concept of
854 relative path, this might return something different.
858 def for_signature(self):
860 Return a string representation of the Node that will always
861 be the same for this particular Node, no matter what. This
862 is by contrast to the __str__() method, which might, for
863 instance, return a relative path for a file Node. The purpose
864 of this method is to generate a value to be used in signature
865 calculation for the command line used to build a target, and
866 we use this method instead of str() to avoid unnecessary
867 rebuilds. This method does not need to return something that
868 would actually work in a command line; it can return any kind of
869 nonsense, so long as it does not change.
873 def get_string(self, for_signature):
874 """This is a convenience function designed primarily to be
875 used in command generators (i.e., CommandGeneratorActions or
876 Environment variables that are callable), which are called
877 with a for_signature argument that is nonzero if the command
878 generator is being called to generate a signature for the
879 command line, which determines if we should rebuild or not.
881 Such command generators should use this method in preference
882 to str(Node) when converting a Node to a string, passing
883 in the for_signature parameter, such that we will call
884 Node.for_signature() or str(Node) properly, depending on whether
885 we are calculating a signature or actually constructing a
888 return self.for_signature()
891 def get_subst_proxy(self):
893 This method is expected to return an object that will function
894 exactly like this Node, except that it implements any additional
895 special features that we would like to be in effect for
896 Environment variable substitution. The principle use is that
897 some Nodes would like to implement a __getattr__() method,
898 but putting that in the Node type itself has a tendency to kill
899 performance. We instead put it in a proxy and return it from
900 this method. It is legal for this method to return self
901 if no new functionality is needed for Environment substitution.
906 if not self.exists():
907 return "building `%s' because it doesn't exist\n" % self
909 old = self.get_stored_info()
913 def dictify(result, kids, sigs):
914 for k, s in zip(kids, sigs):
918 old_bkids = old.bsources + old.bdepends + old.bimplicit
919 except AttributeError:
920 return "Cannot explain why `%s' is being rebuilt: No previous build information found\n" % self
923 dictify(osig, old.bsources, old.bsourcesigs)
924 dictify(osig, old.bdepends, old.bdependsigs)
925 dictify(osig, old.bimplicit, old.bimplicitsigs)
927 new_bsources = map(str, self.binfo.bsources)
928 new_bdepends = map(str, self.binfo.bdepends)
929 new_bimplicit = map(str, self.binfo.bimplicit)
932 dictify(nsig, new_bsources, self.binfo.bsourcesigs)
933 dictify(nsig, new_bdepends, self.binfo.bdependsigs)
934 dictify(nsig, new_bimplicit, self.binfo.bimplicitsigs)
936 new_bkids = new_bsources + new_bdepends + new_bimplicit
937 lines = map(lambda x: "`%s' is no longer a dependency\n" % x,
938 filter(lambda x, nk=new_bkids: not x in nk, old_bkids))
941 if not k in old_bkids:
942 lines.append("`%s' is a new dependency\n" % k)
943 elif osig[k] != nsig[k]:
944 lines.append("`%s' changed\n" % k)
946 if len(lines) == 0 and old_bkids != new_bkids:
947 lines.append("the dependency order changed:\n" +
948 "%sold: %s\n" % (' '*15, old_bkids) +
949 "%snew: %s\n" % (' '*15, new_bkids))
952 newact, newactsig = self.binfo.bact, self.binfo.bactsig
953 def fmt_with_title(title, strlines):
954 lines = string.split(strlines, '\n')
955 sep = '\n' + ' '*(15 + len(title))
956 return ' '*15 + title + string.join(lines, sep) + '\n'
957 if old.bactsig != newactsig:
958 if old.bact == newact:
959 lines.append("the contents of the build action changed\n" +
960 fmt_with_title('action: ', newact))
962 lines.append("the build action changed:\n" +
963 fmt_with_title('old: ', old.bact) +
964 fmt_with_title('new: ', newact))
967 return "rebuilding `%s' for unknown reasons\n" % self
969 preamble = "rebuilding `%s' because" % self
971 return "%s %s" % (preamble, lines[0])
973 lines = ["%s:\n" % preamble] + lines
974 return string.join(lines, ' '*11)
977 ul = UserList.UserList([2])
984 class NodeList(UserList.UserList):
986 return str(map(str, self.data))
990 if not SCons.Memoize.has_metaclass:
992 class Node(SCons.Memoize.Memoizer, _Base):
993 def __init__(self, *args, **kw):
994 apply(_Base.__init__, (self,)+args, kw)
995 SCons.Memoize.Memoizer.__init__(self)
998 def get_children(node, parent): return node.children()
999 def ignore_cycle(node, stack): pass
1000 def do_nothing(node, parent): pass
1003 """An iterator for walking a Node tree.
1005 This is depth-first, children are visited before the parent.
1006 The Walker object can be initialized with any node, and
1007 returns the next node on the descent with each next() call.
1008 'kids_func' is an optional function that will be called to
1009 get the children of a node instead of calling 'children'.
1010 'cycle_func' is an optional function that will be called
1011 when a cycle is detected.
1013 This class does not get caught in node cycles caused, for example,
1014 by C header file include loops.
1016 def __init__(self, node, kids_func=get_children,
1017 cycle_func=ignore_cycle,
1018 eval_func=do_nothing):
1019 self.kids_func = kids_func
1020 self.cycle_func = cycle_func
1021 self.eval_func = eval_func
1022 node.wkids = copy.copy(kids_func(node, None))
1024 self.history = {} # used to efficiently detect and avoid cycles
1025 self.history[node] = None
1028 """Return the next node for this walk of the tree.
1030 This function is intentionally iterative, not recursive,
1031 to sidestep any issues of stack size limitations.
1035 if self.stack[-1].wkids:
1036 node = self.stack[-1].wkids.pop(0)
1037 if not self.stack[-1].wkids:
1038 self.stack[-1].wkids = None
1039 if self.history.has_key(node):
1040 self.cycle_func(node, self.stack)
1042 node.wkids = copy.copy(self.kids_func(node, self.stack[-1]))
1043 self.stack.append(node)
1044 self.history[node] = None
1046 node = self.stack.pop()
1047 del self.history[node]
1050 parent = self.stack[-1]
1053 self.eval_func(node, parent)
1058 return not self.stack
1061 arg2nodes_lookups = []