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scons-local-3.0.0/SCons/PathList.py

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+#
+# Copyright (c) 2001 - 2017 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 rel_3.0.0:4395:8972f6a2f699 2017/09/18 12:59:24 bdbaddog"
+
+__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 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(object):
+    """
+    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 '${TARGET.dir}/include',
+            which require re-evaluation for every target + source)
+
+            other objects (which may be something like an EntryProxy
+            that needs a method called to return a Node)
+
+        Pre-identifying the type of each element in the PathList up-front
+        and storing the type in the list of tuples is intended to reduce
+        the amount of calculation when we actually do the substitution
+        over and over for each target.
+        """
+        if SCons.Util.is_String(pathlist):
+            pathlist = pathlist.split(os.pathsep)
+        elif not SCons.Util.is_Sequence(pathlist):
+            pathlist = [pathlist]
+
+        pl = []
+        for p in pathlist:
+            try:
+                found = '$' in p
+            except (AttributeError, TypeError):
+                type = TYPE_OBJECT
+            else:
+                if not found:
+                    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(SCons.Util.flatten(value))
+                elif value:
+                    result.append(value)
+            elif type == TYPE_OBJECT:
+                value = node_conv(value)
+                if value:
+                    result.append(value)
+            elif value:
+                result.append(value)
+        return tuple(result)
+
+
+class PathListCache(object):
+    """
+    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.
+    """
+    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
+
+    @SCons.Memoize.CountDictCall(_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: