# Open an arbitrary URL # # See the following document for a tentative description of URLs: # Uniform Resource Locators Tim Berners-Lee # INTERNET DRAFT CERN # IETF URL Working Group 14 July 1993 # draft-ietf-uri-url-01.txt # # The object returned by URLopener().open(file) will differ per # protocol. All you know is that is has methods read(), readline(), # readlines(), fileno(), close() and info(). The read*(), fileno() # and close() methods work like those of open files. # The info() method returns an rfc822.Message object which can be # used to query various info about the object, if available. # (rfc822.Message objects are queried with the getheader() method.) import string import socket import regex # This really consists of two pieces: # (1) a class which handles opening of all sorts of URLs # (plus assorted utilities etc.) # (2) a set of functions for parsing URLs # XXX Should these be separated out into different modules? # Shortcut for basic usage _urlopener = None def urlopen(url): global _urlopener if not _urlopener: _urlopener = URLopener() return _urlopener.open(url) def urlretrieve(url): global _urlopener if not _urlopener: _urlopener = URLopener() return _urlopener.retrieve(url) def urlcleanup(): if _urlopener: _urlopener.cleanup() # Class to open URLs. # This is a class rather than just a subroutine because we may need # more than one set of global protocol-specific options. ftpcache = {} class URLopener: # Constructor def __init__(self): self.addheaders = [] self.tempcache = None # Undocumented feature: if you assign {} to tempcache, # it is used to cache files retrieved with # self.retrieve(). This is not enabled by default # since it does not work for changing documents (and I # haven't got the logic to check expiration headers # yet). self.ftpcache = ftpcache # Undocumented feature: you can use a different # ftp cache by assigning to the .ftpcache member; # in case you want logically independent URL openers def __del__(self): self.close() def close(self): self.cleanup() def cleanup(self): import os if self.tempcache: for url in self.tempcache.keys(): try: os.unlink(self.tempcache[url][0]) except os.error: pass del self.tempcache[url] # Add a header to be used by the HTTP interface only # e.g. u.addheader('Accept', 'sound/basic') def addheader(self, *args): self.addheaders.append(args) # External interface # Use URLopener().open(file) instead of open(file, 'r') def open(self, url): type, url = splittype(unwrap(url)) if not type: type = 'file' name = 'open_' + type if '-' in name: import regsub name = regsub.gsub('-', '_', name) if not hasattr(self, name): raise IOError, ('url error', 'unknown url type', type) try: return getattr(self, name)(url) except socket.error, msg: raise IOError, ('socket error', msg) # External interface # retrieve(url) returns (filename, None) for a local object # or (tempfilename, headers) for a remote object def retrieve(self, url): if self.tempcache and self.tempcache.has_key(url): return self.tempcache[url] url1 = unwrap(url) if self.tempcache and self.tempcache.has_key(url1): self.tempcache[url] = self.tempcache[url1] return self.tempcache[url1] type, url1 = splittype(url1) if not type or type == 'file': try: fp = self.open_local_file(url1) del fp return splithost(url1)[1], None except IOError, msg: pass fp = self.open(url) headers = fp.info() import tempfile tfn = tempfile.mktemp() if self.tempcache is not None: self.tempcache[url] = result = tfn, headers tfp = open(tfn, 'w') bs = 1024*8 block = fp.read(bs) while block: tfp.write(block) block = fp.read(bs) del fp del tfp return result # Each method named open_ knows how to open that type of URL # Use HTTP protocol def open_http(self, url): import httplib host, selector = splithost(url) if not host: raise IOError, ('http error', 'no host given') h = httplib.HTTP(host) h.putrequest('GET', selector) for args in self.addheaders: apply(h.putheader, args) errcode, errmsg, headers = h.getreply() if errcode == 200: return addinfo(h.getfile(), headers) else: raise IOError, ('http error', errcode, errmsg, headers) # Use Gopher protocol def open_gopher(self, url): import gopherlib host, selector = splithost(url) if not host: raise IOError, ('gopher error', 'no host given') type, selector = splitgophertype(selector) selector, query = splitquery(selector) selector = unquote(selector) if query: query = unquote(query) fp = gopherlib.send_query(selector, query, host) else: fp = gopherlib.send_selector(selector, host) return addinfo(fp, noheaders()) # Use local file or FTP depending on form of URL def open_file(self, url): try: return self.open_local_file(url) except IOError: return self.open_ftp(url) # Use local file def open_local_file(self, url): host, file = splithost(url) if not host: return addinfo(open(file, 'r'), noheaders()) host, port = splitport(host) if not port and socket.gethostbyname(host) in ( localhost(), thishost()): file = unquote(file) return addinfo(open(file, 'r'), noheaders()) raise IOError, ('local file error', 'not on local host') # Use FTP protocol def open_ftp(self, url): host, path = splithost(url) if not host: raise IOError, ('ftp error', 'no host given') host, port = splitport(host) user, host = splituser(host) if user: user, passwd = splitpasswd(user) else: passwd = None host = socket.gethostbyname(host) if not port: import ftplib port = ftplib.FTP_PORT path, attrs = splitattr(path) dirs = string.splitfields(path, '/') dirs, file = dirs[:-1], dirs[-1] if dirs and not dirs[0]: dirs = dirs[1:] key = (user, host, port, string.joinfields(dirs, '/')) ## print 'key =', key try: if not self.ftpcache.has_key(key): self.ftpcache[key] = \ ftpwrapper(user, passwd, host, port, dirs) if not file: type = 'D' else: type = 'I' for attr in attrs: attr, value = splitvalue(attr) if string.lower(attr) == 'type' and \ value in ('a', 'A', 'i', 'I', 'd', 'D'): type = string.upper(value) return addinfo(self.ftpcache[key].retrfile(file, type), noheaders()) except ftperrors(), msg: raise IOError, ('ftp error', msg) # Utility functions # Return the IP address of the magic hostname 'localhost' _localhost = None def localhost(): global _localhost if not _localhost: _localhost = socket.gethostbyname('localhost') return _localhost # Return the IP address of the current host _thishost = None def thishost(): global _thishost if not _thishost: _thishost = socket.gethostbyname(socket.gethostname()) return _thishost # Return the set of errors raised by the FTP class _ftperrors = None def ftperrors(): global _ftperrors if not _ftperrors: import ftplib _ftperrors = (ftplib.error_reply, ftplib.error_temp, ftplib.error_perm, ftplib.error_proto) return _ftperrors # Return an empty rfc822.Message object _noheaders = None def noheaders(): global _noheaders if not _noheaders: import rfc822 _noheaders = rfc822.Message(open('/dev/null', 'r')) _noheaders.fp.close() # Recycle file descriptor return _noheaders # Utility classes # Class used by open_ftp() for cache of open FTP connections class ftpwrapper: def __init__(self, user, passwd, host, port, dirs): self.user = unquote(user or '') self.passwd = unquote(passwd or '') self.host = host self.port = port self.dirs = [] for dir in dirs: self.dirs.append(unquote(dir)) self.init() def init(self): import ftplib self.ftp = ftplib.FTP() self.ftp.connect(self.host, self.port) self.ftp.login(self.user, self.passwd) for dir in self.dirs: self.ftp.cwd(dir) def retrfile(self, file, type): import ftplib if type in ('d', 'D'): cmd = 'TYPE A'; isdir = 1 else: cmd = 'TYPE ' + type; isdir = 0 try: self.ftp.voidcmd(cmd) except ftplib.all_errors: self.init() self.ftp.voidcmd(cmd) conn = None if file and not isdir: try: cmd = 'RETR ' + file conn = self.ftp.transfercmd(cmd) except ftplib.error_perm, reason: if reason[:3] != '550': raise IOError, ('ftp error', reason) if not conn: # Try a directory listing if file: cmd = 'LIST ' + file else: cmd = 'LIST' conn = self.ftp.transfercmd(cmd) return addclosehook(conn.makefile('r'), self.ftp.voidresp) # Base class for addinfo and addclosehook class addbase: def __init__(self, fp): self.fp = fp self.read = self.fp.read self.readline = self.fp.readline self.readlines = self.fp.readlines self.fileno = self.fp.fileno def __repr__(self): return '<%s at %s whose fp = %s>' % ( self.__class__.__name__, `id(self)`, `self.fp`) def __del__(self): self.close() def close(self): self.read = None self.readline = None self.readlines = None self.fileno = None self.fp = None # Class to add a close hook to an open file class addclosehook(addbase): def __init__(self, fp, closehook, *hookargs): addbase.__init__(self, fp) self.closehook = closehook self.hookargs = hookargs def close(self): if self.closehook: apply(self.closehook, self.hookargs) self.closehook = None self.hookargs = None addbase.close(self) # class to add an info() method to an open file class addinfo(addbase): def __init__(self, fp, headers): addbase.__init__(self, fp) self.headers = headers def info(self): return self.headers # Utility to combine a URL with a base URL to form a new URL def basejoin(base, url): type, path = splittype(url) if type: return url host, path = splithost(path) basetype, basepath = splittype(base) basehost, basepath = splithost(basepath) basepath, basetag = splittag(basepath) basepath, basequery = splitquery(basepath) type = basetype or 'file' if path[:1] != '/': i = string.rfind(basepath, '/') if i < 0: basepath = '/' else: basepath = basepath[:i+1] path = basepath + path if not host: host = basehost if host: return type + '://' + host + path else: return type + ':' + path # Utilities to parse URLs (most of these return None for missing parts): # unwrap('') --> 'type//host/path' # splittype('type:opaquestring') --> 'type', 'opaquestring' # splithost('//host[:port]/path') --> 'host[:port]', '/path' # splituser('user[:passwd]@host[:port]') --> 'user[:passwd]', 'host[:port]' # splitpasswd('user:passwd') -> 'user', 'passwd' # splitport('host:port') --> 'host', 'port' # splitquery('/path?query') --> '/path', 'query' # splittag('/path#tag') --> '/path', 'tag' # splitattr('/path;attr1=value1;attr2=value2;...') -> # '/path', ['attr1=value1', 'attr2=value2', ...] # splitvalue('attr=value') --> 'attr', 'value' # splitgophertype('/Xselector') --> 'X', 'selector' # unquote('abc%20def') -> 'abc def' # quote('abc def') -> 'abc%20def') def unwrap(url): url = string.strip(url) if url[:1] == '<' and url[-1:] == '>': url = string.strip(url[1:-1]) if url[:4] == 'URL:': url = string.strip(url[4:]) return url _typeprog = regex.compile('^$[^/:]+$:$.*$$') def splittype(url): if _typeprog.match(url) >= 0: return _typeprog.group(1, 2) return None, url _hostprog = regex.compile('^//$[^/]+$$.*$$') def splithost(url): if _hostprog.match(url) >= 0: return _hostprog.group(1, 2) return None, url _userprog = regex.compile('^$[^@]*$@$.*$$') def splituser(host): if _userprog.match(host) >= 0: return _userprog.group(1, 2) return None, host _passwdprog = regex.compile('^$[^:]*$:$.*$$') def splitpasswd(user): if _passwdprog.match(user) >= 0: return _passwdprog.group(1, 2) return user, None _portprog = regex.compile('^$.*$:$[0-9]+$$') def splitport(host): if _portprog.match(host) >= 0: return _portprog.group(1, 2) return host, None _queryprog = regex.compile('^$.*$\?$[^?]*$$') def splitquery(url): if _queryprog.match(url) >= 0: return _queryprog.group(1, 2) return url, None _tagprog = regex.compile('^$.*$#$[^#]*$$') def splittag(url): if _tagprog.match(url) >= 0: return _tagprog.group(1, 2) return url, None def splitattr(url): words = string.splitfields(url, ';') return words[0], words[1:] _valueprog = regex.compile('^$[^=]*$=$.*$$') def splitvalue(attr): if _valueprog.match(attr) >= 0: return _valueprog.group(1, 2) return attr, None def splitgophertype(selector): if selector[:1] == '/' and selector[1:2]: return selector[1], selector[2:] return None, selector _quoteprog = regex.compile('%[0-9a-fA-F][0-9a-fA-F]') def unquote(s): i = 0 n = len(s) res = '' while 0 <= i < n: j = _quoteprog.search(s, i) if j < 0: res = res + s[i:] break res = res + (s[i:j] + chr(eval('0x' + s[j+1:j+3]))) i = j+3 return res always_safe = string.letters + string.digits + '_,.-' def quote(s, safe = '/'): safe = always_safe + safe res = '' for c in s: if c in safe: res = res + c else: res = res + '%%%02x' % ord(c) return res # Test and time quote() and unquote() def test1(): import time s = '' for i in range(256): s = s + chr(i) s = s*4 t0 = time.time() qs = quote(s) uqs = unquote(qs) t1 = time.time() if uqs != s: print 'Wrong!' print `s` print `qs` print `uqs` print round(t1 - t0, 3), 'sec' # Test program def test(): import sys import regsub args = sys.argv[1:] if not args: args = [ '/etc/passwd', 'file:/etc/passwd', 'file://localhost/etc/passwd', 'ftp://ftp.cwi.nl/etc/passwd', 'gopher://gopher.cwi.nl/11/', 'http://www.cwi.nl/index.html', ] try: for url in args: print '-'*10, url, '-'*10 fn, h = urlretrieve(url) print fn, h if h: print '======' for k in h.keys(): print k + ':', h[k] print '======' fp = open(fn, 'r') data = fp.read() del fp print regsub.gsub('\r', '', data) fn, h = None, None print '-'*40 finally: urlcleanup() # Run test program when run as a script if __name__ == '__main__': ## test1() test()