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"""Configuration backend for storing settings in a simple plain text format"""
__all__ = ["FileParserError", "FileBuilderError", "FileBackend"]
import errno
import os
import re
import platform
import random
from collections import deque
from application.system import makedirs, openfile, unlink
from zope.interface import implements
from sipsimple.configuration.backend import IConfigurationBackend, ConfigurationBackendError
class FileParserError(ConfigurationBackendError):
"""Error raised when the configuration file cannot be parsed."""
class FileBuilderError(ConfigurationBackendError):
"""Error raised when the configuration data cannot be saved."""
class GroupState(object):
"""
Internal class used for keeping track of the containing groups while
parsing.
"""
def __init__(self, indentation):
self.indentation = indentation
self.data = {}
class Line(object):
"""Internal representation of lines in a configuration file"""
def __init__(self, indentation, name, separator, value):
self.indentation = indentation
self.name = name
self.separator = separator
self.value = value
def __repr__(self):
return "%s(%r, %r, %r, %r)" % (self.__class__.__name__, self.indentation, self.name, self.separator, self.value)
class FileBackend(object):
"""
Implementation of a configuration backend that stores data in a simple
plain text format.
"""
implements(IConfigurationBackend)
escape_characters_re = re.compile(r"""[,"'=: #\\\t\x0b\x0c\n\r]""")
def __init__(self, filename, encoding='utf-8'):
"""
Initialize the configuration backend with the specified file.
The file is not read at this time, but rather each time the load method
is called.
"""
self.filename = filename
self.encoding = encoding
def load(self):
"""
Read the file configured with this backend and parse it, returning a
dictionary conforming to the IConfigurationBackend specification.
"""
try:
file = open(self.filename)
except IOError as e:
if e.errno == errno.ENOENT:
return {}
else:
raise ConfigurationBackendError("failed to read configuration file: %s" % str(e))
state_stack = deque()
state_stack.appendleft(GroupState(-1))
for lineno, line in enumerate(file, 1):
line = self._parse_line(line, lineno)
if not line.name:
continue
# find the container for this declaration
while state_stack[0].indentation >= line.indentation:
state_stack.popleft()
if line.separator == ':':
new_group_state = GroupState(line.indentation)
state_stack[0].data[line.name] = new_group_state.data
state_stack.appendleft(new_group_state)
elif line.separator == '=':
state_stack[0].data[line.name] = line.value
return state_stack[-1].data
def save(self, data):
"""
Given a dictionary conforming to the IConfigurationBackend
specification, write the data to the file configured with this backend
in a format suitable to be read back using load().
"""
lines = self._build_group(data, 0)
config_directory = os.path.dirname(self.filename)
tmp_filename = '%s.%d.%08X' % (self.filename, os.getpid(), random.getrandbits(32))
try:
if config_directory:
makedirs(config_directory)
file = openfile(tmp_filename, 'wb', permissions=0o600)
file.write((os.linesep.join(lines)+os.linesep).encode(self.encoding))
file.close()
if platform.system() == 'Windows':
# os.rename does not work on Windows if the destination file already exists.
# It seems there is no atomic way to do this on Windows.
unlink(self.filename)
os.rename(tmp_filename, self.filename)
except (IOError, OSError) as e:
raise ConfigurationBackendError("failed to write configuration file: %s" % str(e))
def _parse_line(self, line, lineno):
def advance_to_next_token(line):
counter = 0
while line and line[0].isspace():
line.popleft()
counter += 1
if line and line[0] == '#':
line.clear()
return counter
def token_iterator(line, delimiter=''):
quote_char = None
while line:
if quote_char is None and line[0] in delimiter:
break
char = line.popleft()
if char in "'\"":
if quote_char is None:
quote_char = char
continue
elif quote_char == char:
quote_char = None
continue
else:
yield char
elif char == '\\':
if not line:
raise FileParserError("unexpected `\\' at end of line %d" % lineno)
char = line.popleft()
if char == 'n':
yield '\n'
elif char == 'r':
yield '\r'
else:
yield char
elif quote_char is None and char == '#':
line.clear()
break
elif quote_char is None and char.isspace():
break
else:
yield char
if quote_char is not None:
raise FileParserError("missing ending quote at line %d" % lineno)
line = deque(line.rstrip().decode(self.encoding))
indentation = advance_to_next_token(line)
if not line:
return Line(indentation, None, None, None)
name = ''.join(token_iterator(line, delimiter=':='))
advance_to_next_token(line)
if not line or line[0] not in ':=':
raise FileParserError("expected one of `:' or `=' at line %d" % lineno)
if not name:
raise FileParserError("missing setting/section name at line %d" % lineno)
separator = line.popleft()
advance_to_next_token(line)
if not line:
return Line(indentation, name, separator, None)
elif separator == ':':
raise FileParserError("unexpected characters after `:' at line %d" % lineno)
value = None
value_list = None
while line:
value = ''.join(token_iterator(line, delimiter=','))
advance_to_next_token(line)
if line:
if line[0] == ',':
line.popleft()
advance_to_next_token(line)
if value_list is None:
value_list = []
else:
raise FileParserError("unexpected characters after value at line %d" % lineno)
if value_list is not None:
value_list.append(value)
value = value_list if value_list is not None else value
return Line(indentation, name, separator, value)
def _build_group(self, group, indentation):
setting_lines = []
group_lines = []
indent_spaces = ' '*4*indentation
for name, data in sorted(group.items()):
if data is None:
setting_lines.append('%s%s =' % (indent_spaces, self._escape(name)))
elif type(data) is dict:
group_lines.append('%s%s:' % (indent_spaces, self._escape(name)))
group_lines.extend(self._build_group(data, indentation+1))
group_lines.append('')
elif type(data) is list:
list_value = ', '.join(self._escape(item) for item in data)
if len(data) == 1:
list_value += ','
setting_lines.append('%s%s = %s' % (indent_spaces, self._escape(name), list_value))
elif type(data) is str:
setting_lines.append('%s%s = %s' % (indent_spaces, self._escape(name), self._escape(data)))
else:
raise FileBuilderError("expected unicode, dict or list object, got %s" % type(data).__name__)
return setting_lines + group_lines
def _escape(self, value):
if value == '':
return '""'
elif self.escape_characters_re.search(value):
return '"%s"' % value.replace('\\', '\\\\').replace('"', '\\"').replace('\n', '\\n').replace('\r', '\\r')
else:
return value

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