|
| 1 | +import sys |
| 2 | + |
| 3 | + |
| 4 | +class Spec(object): |
| 5 | + sep = '/' |
| 6 | + |
| 7 | + def __new__(cls, *args): |
| 8 | + return cls._from_parts(args) |
| 9 | + |
| 10 | + @classmethod |
| 11 | + def _parse_args(cls, args): |
| 12 | + # This is useful when you don't want to create an instance, just |
| 13 | + # canonicalize some constructor arguments. |
| 14 | + parts = [] |
| 15 | + for a in args: |
| 16 | + if isinstance(a, Spec): |
| 17 | + parts += a._parts |
| 18 | + else: |
| 19 | + if isinstance(a, str): |
| 20 | + # Force-cast str subclasses to str (issue #21127) |
| 21 | + parts.append(str(a)) |
| 22 | + else: |
| 23 | + raise TypeError( |
| 24 | + "argument should be a str object or a Spec " |
| 25 | + "object returning str, not %r" |
| 26 | + % type(a)) |
| 27 | + return cls.parse_parts(parts) |
| 28 | + |
| 29 | + @classmethod |
| 30 | + def parse_parts(cls, parts): |
| 31 | + parsed = [] |
| 32 | + sep = cls.sep |
| 33 | + root = '' |
| 34 | + it = reversed(parts) |
| 35 | + for part in it: |
| 36 | + if not part: |
| 37 | + continue |
| 38 | + root, rel = cls.splitroot(part) |
| 39 | + if sep in rel: |
| 40 | + for x in reversed(rel.split(sep)): |
| 41 | + if x and x != '.': |
| 42 | + parsed.append(sys.intern(x)) |
| 43 | + else: |
| 44 | + if rel and rel != '.': |
| 45 | + parsed.append(sys.intern(rel)) |
| 46 | + parsed.reverse() |
| 47 | + return root, parsed |
| 48 | + |
| 49 | + @classmethod |
| 50 | + def splitroot(cls, part, sep=sep): |
| 51 | + if part and part[0] == sep: |
| 52 | + stripped_part = part.lstrip(sep) |
| 53 | + # According to POSIX path resolution: |
| 54 | + # http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap04.html#tag_04_11 |
| 55 | + # "A pathname that begins with two successive slashes may be |
| 56 | + # interpreted in an implementation-defined manner, although more |
| 57 | + # than two leading slashes shall be treated as a single slash". |
| 58 | + if len(part) - len(stripped_part) == 2: |
| 59 | + return sep * 2, stripped_part |
| 60 | + else: |
| 61 | + return sep, stripped_part |
| 62 | + else: |
| 63 | + return '', part |
| 64 | + |
| 65 | + @classmethod |
| 66 | + def _from_parts(cls, args): |
| 67 | + self = object.__new__(cls) |
| 68 | + root, parts = cls._parse_args(args) |
| 69 | + self._root = root |
| 70 | + self._parts = parts |
| 71 | + return self |
| 72 | + |
| 73 | + @classmethod |
| 74 | + def _from_parsed_parts(cls, root, parts): |
| 75 | + self = object.__new__(cls) |
| 76 | + self._root = root |
| 77 | + self._parts = parts |
| 78 | + return self |
| 79 | + |
| 80 | + def join_parsed_parts(self, root, parts, root2, parts2): |
| 81 | + """ |
| 82 | + Join the two paths represented by the respective |
| 83 | + (root, parts) tuples. Return a new (root, parts) tuple. |
| 84 | + """ |
| 85 | + if root2: |
| 86 | + return root2, root2 + parts2[1:] |
| 87 | + elif parts: |
| 88 | + return root, parts + parts2 |
| 89 | + return root2, parts2 |
| 90 | + |
| 91 | + def _make_child(self, args): |
| 92 | + root, parts = self._parse_args(args) |
| 93 | + root, parts = self.join_parsed_parts( |
| 94 | + self._root, self._parts, root, parts) |
| 95 | + return self._from_parsed_parts(root, parts) |
| 96 | + |
| 97 | + def __truediv__(self, key): |
| 98 | + return self._make_child((key,)) |
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