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Diffstat (limited to 'engine/SCons/PathList.py')
| -rw-r--r-- | engine/SCons/PathList.py | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/engine/SCons/PathList.py b/engine/SCons/PathList.py new file mode 100644 index 0000000..c88cda4 --- /dev/null +++ b/engine/SCons/PathList.py @@ -0,0 +1,232 @@ +# +# Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 The SCons Foundation +# +# Permission is hereby granted, free of charge, to any person obtaining +# a copy of this software and associated documentation files (the +# "Software"), to deal in the Software without restriction, including +# without limitation the rights to use, copy, modify, merge, publish, +# distribute, sublicense, and/or sell copies of the Software, and to +# permit persons to whom the Software is furnished to do so, subject to +# the following conditions: +# +# The above copyright notice and this permission notice shall be included +# in all copies or substantial portions of the Software. +# +# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY +# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE +# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND +# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE +# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION +# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION +# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. +# + +__revision__ = "src/engine/SCons/PathList.py 4577 2009/12/27 19:43:56 scons" + +__doc__ = """SCons.PathList + +A module for handling lists of directory paths (the sort of things +that get set as CPPPATH, LIBPATH, etc.) with as much caching of data and +efficiency as we can while still keeping the evaluation delayed so that we +Do the Right Thing (almost) regardless of how the variable is specified. + +""" + +import os +import string + +import SCons.Memoize +import SCons.Node +import SCons.Util + +# +# Variables to specify the different types of entries in a PathList object: +# + +TYPE_STRING_NO_SUBST = 0 # string with no '$' +TYPE_STRING_SUBST = 1 # string containing '$' +TYPE_OBJECT = 2 # other object + +def node_conv(obj): + """ + This is the "string conversion" routine that we have our substitutions + use to return Nodes, not strings. This relies on the fact that an + EntryProxy object has a get() method that returns the underlying + Node that it wraps, which is a bit of architectural dependence + that we might need to break or modify in the future in response to + additional requirements. + """ + try: + get = obj.get + except AttributeError: + if isinstance(obj, SCons.Node.Node) or SCons.Util.is_Sequence( obj ): + result = obj + else: + result = str(obj) + else: + result = get() + return result + +class _PathList: + """ + An actual PathList object. + """ + def __init__(self, pathlist): + """ + Initializes a PathList object, canonicalizing the input and + pre-processing it for quicker substitution later. + + The stored representation of the PathList is a list of tuples + containing (type, value), where the "type" is one of the TYPE_* + variables defined above. We distinguish between: + + strings that contain no '$' and therefore need no + delayed-evaluation string substitution (we expect that there + will be many of these and that we therefore get a pretty + big win from avoiding string substitution) + + strings that contain '$' and therefore need substitution + (the hard case is things like '${TARGET.dir}/include', + which require re-evaluation for every target + source) + + other objects (which may be something like an EntryProxy + that needs a method called to return a Node) + + Pre-identifying the type of each element in the PathList up-front + and storing the type in the list of tuples is intended to reduce + the amount of calculation when we actually do the substitution + over and over for each target. + """ + if SCons.Util.is_String(pathlist): + pathlist = string.split(pathlist, os.pathsep) + elif not SCons.Util.is_Sequence(pathlist): + pathlist = [pathlist] + + pl = [] + for p in pathlist: + try: + index = string.find(p, '$') + except (AttributeError, TypeError): + type = TYPE_OBJECT + else: + if index == -1: + type = TYPE_STRING_NO_SUBST + else: + type = TYPE_STRING_SUBST + pl.append((type, p)) + + self.pathlist = tuple(pl) + + def __len__(self): return len(self.pathlist) + + def __getitem__(self, i): return self.pathlist[i] + + def subst_path(self, env, target, source): + """ + Performs construction variable substitution on a pre-digested + PathList for a specific target and source. + """ + result = [] + for type, value in self.pathlist: + if type == TYPE_STRING_SUBST: + value = env.subst(value, target=target, source=source, + conv=node_conv) + if SCons.Util.is_Sequence(value): + result.extend(value) + continue + + elif type == TYPE_OBJECT: + value = node_conv(value) + if value: + result.append(value) + return tuple(result) + + +class PathListCache: + """ + A class to handle caching of PathList lookups. + + This class gets instantiated once and then deleted from the namespace, + so it's used as a Singleton (although we don't enforce that in the + usual Pythonic ways). We could have just made the cache a dictionary + in the module namespace, but putting it in this class allows us to + use the same Memoizer pattern that we use elsewhere to count cache + hits and misses, which is very valuable. + + Lookup keys in the cache are computed by the _PathList_key() method. + Cache lookup should be quick, so we don't spend cycles canonicalizing + all forms of the same lookup key. For example, 'x:y' and ['x', + 'y'] logically represent the same list, but we don't bother to + split string representations and treat those two equivalently. + (Note, however, that we do, treat lists and tuples the same.) + + The main type of duplication we're trying to catch will come from + looking up the same path list from two different clones of the + same construction environment. That is, given + + env2 = env1.Clone() + + both env1 and env2 will have the same CPPPATH value, and we can + cheaply avoid re-parsing both values of CPPPATH by using the + common value from this cache. + """ + if SCons.Memoize.use_memoizer: + __metaclass__ = SCons.Memoize.Memoized_Metaclass + + memoizer_counters = [] + + def __init__(self): + self._memo = {} + + def _PathList_key(self, pathlist): + """ + Returns the key for memoization of PathLists. + + Note that we want this to be pretty quick, so we don't completely + canonicalize all forms of the same list. For example, + 'dir1:$ROOT/dir2' and ['$ROOT/dir1', 'dir'] may logically + represent the same list if you're executing from $ROOT, but + we're not going to bother splitting strings into path elements, + or massaging strings into Nodes, to identify that equivalence. + We just want to eliminate obvious redundancy from the normal + case of re-using exactly the same cloned value for a path. + """ + if SCons.Util.is_Sequence(pathlist): + pathlist = tuple(SCons.Util.flatten(pathlist)) + return pathlist + + memoizer_counters.append(SCons.Memoize.CountDict('PathList', _PathList_key)) + + def PathList(self, pathlist): + """ + Returns the cached _PathList object for the specified pathlist, + creating and caching a new object as necessary. + """ + pathlist = self._PathList_key(pathlist) + try: + memo_dict = self._memo['PathList'] + except KeyError: + memo_dict = {} + self._memo['PathList'] = memo_dict + else: + try: + return memo_dict[pathlist] + except KeyError: + pass + + result = _PathList(pathlist) + + memo_dict[pathlist] = result + + return result + +PathList = PathListCache().PathList + + +del PathListCache + +# Local Variables: +# tab-width:4 +# indent-tabs-mode:nil +# End: +# vim: set expandtab tabstop=4 shiftwidth=4: |