path: root/mako/util.py

# mako/util.py
# Copyright (C) 2006-2011 the Mako authors and contributors <see AUTHORS file>
#
# This module is part of Mako and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

import sys


py3k = getattr(sys, 'py3kwarning', False) or sys.version_info >= (3, 0)
py24 = sys.version_info >= (2, 4) and sys.version_info < (2, 5)
jython = sys.platform.startswith('java')
win32 = sys.platform.startswith('win')

if py3k:
    from io import StringIO
else:
    try:
        from cStringIO import StringIO
    except:
        from StringIO import StringIO

import codecs, re, weakref, os, time, operator

try:
    import threading
    import thread
except ImportError:
    import dummy_threading as threading
    import dummy_thread as thread

if win32 or jython:
    time_func = time.clock
else:
    time_func = time.time 
 
def function_named(fn, name):
    """Return a function with a given __name__.

    Will assign to __name__ and return the original function if possible on
    the Python implementation, otherwise a new function will be constructed.

    """
    fn.__name__ = name
    return fn

try:
    from functools import partial
except:
    def partial(func, *args, **keywords):
        def newfunc(*fargs, **fkeywords):
            newkeywords = keywords.copy()
            newkeywords.update(fkeywords)
            return func(*(args + fargs), **newkeywords)
        return newfunc

if py24:
    def exception_name(exc):
        try:
            return exc.__class__.__name__
        except AttributeError:
            return exc.__name__
else:
    def exception_name(exc):
        return exc.__class__.__name__
 
def verify_directory(dir):
    """create and/or verify a filesystem directory."""
 
    tries = 0
 
    while not os.path.exists(dir):
        try:
            tries += 1
            os.makedirs(dir, 0775)
        except:
            if tries > 5:
                raise

def to_list(x, default=None):
    if x is None:
        return default
    if not isinstance(x, (list, tuple)):
        return [x]
    else:
        return x


class memoized_property(object):
    """A read-only @property that is only evaluated once."""
    def __init__(self, fget, doc=None):
        self.fget = fget
        self.__doc__ = doc or fget.__doc__
        self.__name__ = fget.__name__

    def __get__(self, obj, cls):
        if obj is None:
            return self
        obj.__dict__[self.__name__] = result = self.fget(obj)
        return result

class SetLikeDict(dict):
    """a dictionary that has some setlike methods on it"""
    def union(self, other):
        """produce a 'union' of this dict and another (at the key level).
 
        values in the second dict take precedence over that of the first"""
        x = SetLikeDict(**self)
        x.update(other)
        return x

class FastEncodingBuffer(object):
    """a very rudimentary buffer that is faster than StringIO, 
    but doesnt crash on unicode data like cStringIO."""
 
    def __init__(self, encoding=None, errors='strict', unicode=False):
        self.data = []
        self.encoding = encoding
        if unicode:
            self.delim = u''
        else:
            self.delim = ''
        self.unicode = unicode
        self.errors = errors
        self.write = self.data.append
 
    def truncate(self):
        self.data =[]
 
    def getvalue(self):
        if self.encoding:
            return self.delim.join(self.data).encode(self.encoding, self.errors)
        else:
            return self.delim.join(self.data)

class LRUCache(dict):
    """A dictionary-like object that stores a limited number of items, discarding
    lesser used items periodically.
 
    this is a rewrite of LRUCache from Myghty to use a periodic timestamp-based
    paradigm so that synchronization is not really needed.  the size management 
    is inexact.
    """
 
    class _Item(object):
        def __init__(self, key, value):
            self.key = key
            self.value = value
            self.timestamp = time_func()
        def __repr__(self):
            return repr(self.value)
 
    def __init__(self, capacity, threshold=.5):
        self.capacity = capacity
        self.threshold = threshold
 
    def __getitem__(self, key):
        item = dict.__getitem__(self, key)
        item.timestamp = time_func()
        return item.value
 
    def values(self):
        return [i.value for i in dict.values(self)]
 
    def setdefault(self, key, value):
        if key in self:
            return self[key]
        else:
            self[key] = value
            return value
 
    def __setitem__(self, key, value):
        item = dict.get(self, key)
        if item is None:
            item = self._Item(key, value)
            dict.__setitem__(self, key, item)
        else:
            item.value = value
        self._manage_size()
 
    def _manage_size(self):
        while len(self) > self.capacity + self.capacity * self.threshold:
            bytime = sorted(dict.values(self), 
                            key=operator.attrgetter('timestamp'), reverse=True)
            for item in bytime[self.capacity:]:
                try:
                    del self[item.key]
                except KeyError:
                    # if we couldnt find a key, most likely some other thread broke in 
                    # on us. loop around and try again
                    break

# Regexp to match python magic encoding line
_PYTHON_MAGIC_COMMENT_re = re.compile(
    r'[ \t\f]* \# .* coding[=:][ \t]*([-\w.]+)',
    re.VERBOSE)

def parse_encoding(fp):
    """Deduce the encoding of a Python source file (binary mode) from magic comment.

    It does this in the same way as the `Python interpreter`__

    .. __: http://docs.python.org/ref/encodings.html

    The ``fp`` argument should be a seekable file object in binary mode.
    """
    pos = fp.tell()
    fp.seek(0)
    try:
        line1 = fp.readline()
        has_bom = line1.startswith(codecs.BOM_UTF8)
        if has_bom:
            line1 = line1[len(codecs.BOM_UTF8):]

        m = _PYTHON_MAGIC_COMMENT_re.match(line1.decode('ascii', 'ignore'))
        if not m:
            try:
                import parser
                parser.suite(line1.decode('ascii', 'ignore'))
            except (ImportError, SyntaxError):
                # Either it's a real syntax error, in which case the source
                # is not valid python source, or line2 is a continuation of
                # line1, in which case we don't want to scan line2 for a magic
                # comment.
                pass
            else:
                line2 = fp.readline()
                m = _PYTHON_MAGIC_COMMENT_re.match(line2.decode('ascii', 'ignore'))

        if has_bom:
            if m:
                raise SyntaxError, \
                      "python refuses to compile code with both a UTF8" \
                      " byte-order-mark and a magic encoding comment"
            return 'utf_8'
        elif m:
            return m.group(1)
        else:
            return None
    finally:
        fp.seek(pos)

def sorted_dict_repr(d):
    """repr() a dictionary with the keys in order.
 
    Used by the lexer unit test to compare parse trees based on strings.
 
    """
    keys = d.keys()
    keys.sort()
    return "{" + ", ".join(["%r: %r" % (k, d[k]) for k in keys]) + "}"
 
def restore__ast(_ast):
    """Attempt to restore the required classes to the _ast module if it
    appears to be missing them
    """
    if hasattr(_ast, 'AST'):
        return
    _ast.PyCF_ONLY_AST = 2 << 9
    m = compile("""\
def foo(): pass
class Bar(object): pass
if False: pass
baz = 'mako'
1 + 2 - 3 * 4 / 5
6 // 7 % 8 << 9 >> 10
11 & 12 ^ 13 | 14
15 and 16 or 17
-baz + (not +18) - ~17
baz and 'foo' or 'bar'
(mako is baz == baz) is not baz != mako
mako > baz < mako >= baz <= mako
mako in baz not in mako""", '<unknown>', 'exec', _ast.PyCF_ONLY_AST)
    _ast.Module = type(m)

    for cls in _ast.Module.__mro__:
        if cls.__name__ == 'mod':
            _ast.mod = cls
        elif cls.__name__ == 'AST':
            _ast.AST = cls

    _ast.FunctionDef = type(m.body[0])
    _ast.ClassDef = type(m.body[1])
    _ast.If = type(m.body[2])

    _ast.Name = type(m.body[3].targets[0])
    _ast.Store = type(m.body[3].targets[0].ctx)
    _ast.Str = type(m.body[3].value)

    _ast.Sub = type(m.body[4].value.op)
    _ast.Add = type(m.body[4].value.left.op)
    _ast.Div = type(m.body[4].value.right.op)
    _ast.Mult = type(m.body[4].value.right.left.op)

    _ast.RShift = type(m.body[5].value.op)
    _ast.LShift = type(m.body[5].value.left.op)
    _ast.Mod = type(m.body[5].value.left.left.op)
    _ast.FloorDiv = type(m.body[5].value.left.left.left.op)

    _ast.BitOr = type(m.body[6].value.op)
    _ast.BitXor = type(m.body[6].value.left.op)
    _ast.BitAnd = type(m.body[6].value.left.left.op)

    _ast.Or = type(m.body[7].value.op)
    _ast.And = type(m.body[7].value.values[0].op)

    _ast.Invert = type(m.body[8].value.right.op)
    _ast.Not = type(m.body[8].value.left.right.op)
    _ast.UAdd = type(m.body[8].value.left.right.operand.op)
    _ast.USub = type(m.body[8].value.left.left.op)

    _ast.Or = type(m.body[9].value.op)
    _ast.And = type(m.body[9].value.values[0].op)

    _ast.IsNot = type(m.body[10].value.ops[0])
    _ast.NotEq = type(m.body[10].value.ops[1])
    _ast.Is = type(m.body[10].value.left.ops[0])
    _ast.Eq = type(m.body[10].value.left.ops[1])

    _ast.Gt = type(m.body[11].value.ops[0])
    _ast.Lt = type(m.body[11].value.ops[1])
    _ast.GtE = type(m.body[11].value.ops[2])
    _ast.LtE = type(m.body[11].value.ops[3])

    _ast.In = type(m.body[12].value.ops[0])
    _ast.NotIn = type(m.body[12].value.ops[1])


try:
    from inspect import CO_VARKEYWORDS, CO_VARARGS
    def inspect_func_args(fn):
        co = fn.func_code

        nargs = co.co_argcount
        names = co.co_varnames
        args = list(names[:nargs])

        varargs = None
        if co.co_flags & CO_VARARGS:
            varargs = co.co_varnames[nargs]
            nargs = nargs + 1
        varkw = None
        if co.co_flags & CO_VARKEYWORDS:
            varkw = co.co_varnames[nargs]

        return args, varargs, varkw, fn.func_defaults
except ImportError:
    import inspect
    def inspect_func_args(fn):
        return inspect.getargspec(fn)