Beginning Python - From Novice to Professional

512 CHAPTER 27 ■ PROJECT 8: FILE SHARING WITH XML-RPC
class AccessDenied(Fault):
"""
An exception that is raised if a user tries to access a
resource for which he or she is not authorized.
"""
def __init__(self, message="Access denied"):
Fault.__init__(self, ACCESS_DENIED, message)
def inside(dir, name):
"""
Checks whether a given file name lies within a given directory.
"""
dir = abspath(dir)
name = abspath(name)
return name.startswith(join(dir, ''))
def getPort(url):
"""
Extracts the port number from a URL.
"""
name = urlparse(url)[1]
parts = name.split(':')
return int(parts[-1])
class Node:
"""
A node in a peer-to-peer network.
"""
def __init__(self, url, dirname, secret):
self.url = url
self.dirname = dirname
self.secret = secret
self.known = set()
def query(self, query, history=[]):
"""
Performs a query for a file, possibly asking other known Nodes for
help. Returns the file as a string.
"""
try:
return self._handle(query)
except UnhandledQuery:
history = history + [self.url]
if len(history) >= MAX_HISTORY_LENGTH: raise
return self._broadcast(query, history)