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__revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
__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
[docs]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
[docs]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 '${TARGET.dir}/include',
which require re-evaluation for every target + source)
other objects (which may be something like an EntryProxy
that needs a method called to return a Node)
Pre-identifying the type of each element in the PathList up-front
and storing the type in the list of tuples is intended to reduce
the amount of calculation when we actually do the substitution
over and over for each target.
"""
if SCons.Util.is_String(pathlist):
pathlist = pathlist.split(os.pathsep)
elif not SCons.Util.is_Sequence(pathlist):
pathlist = [pathlist]
pl = []
for p in pathlist:
try:
found = '$' 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]
[docs] 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:
"""
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
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