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