gopherlib.py

"""Gopher protocol client interface."""

__all__ = ["send_selector","send_query"]

# Default selector, host and port
DEF_SELECTOR = '1/'
DEF_HOST     = 'gopher.micro.umn.edu'
DEF_PORT     = 70

# Recognized file types
A_TEXT       = '0'
A_MENU       = '1'
A_CSO        = '2'
A_ERROR      = '3'
A_MACBINHEX  = '4'
A_PCBINHEX   = '5'
A_UUENCODED  = '6'
A_INDEX      = '7'
A_TELNET     = '8'
A_BINARY     = '9'
A_DUPLICATE  = '+'
A_SOUND      = 's'
A_EVENT      = 'e'
A_CALENDAR   = 'c'
A_HTML       = 'h'
A_TN3270     = 'T'
A_MIME       = 'M'
A_IMAGE      = 'I'
A_WHOIS      = 'w'
A_QUERY      = 'q'
A_GIF        = 'g'
A_HTML       = 'h'          # HTML file
A_WWW        = 'w'          # WWW address
A_PLUS_IMAGE = ':'
A_PLUS_MOVIE = ';'
A_PLUS_SOUND = '<'


_names = dir()
_type_to_name_map = {}
def type_to_name(gtype):
    """Map all file types to strings; unknown types become TYPE='x'."""
    global _type_to_name_map
    if _type_to_name_map=={}:
        for name in _names:
            if name[:2] == 'A_':
                _type_to_name_map[eval(name)] = name[2:]
    if gtype in _type_to_name_map:
        return _type_to_name_map[gtype]
    return 'TYPE=%r' % (gtype,)

# Names for characters and strings
CRLF = '\r\n'
TAB = '\t'

def send_selector(selector, host, port = 0):
    """Send a selector to a given host and port, return a file with the reply."""
    import socket
    if not port:
        i = host.find(':')
        if i >= 0:
            host, port = host[:i], int(host[i+1:])
    if not port:
        port = DEF_PORT
    elif type(port) == type(''):
        port = int(port)
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect((host, port))
    s.sendall(selector + CRLF)
    s.shutdown(1)
    return s.makefile('rb')

def send_query(selector, query, host, port = 0):
    """Send a selector and a query string."""
    return send_selector(selector + '\t' + query, host, port)

def path_to_selector(path):
    """Takes a path as returned by urlparse and returns the appropriate selector."""
    if path=="/":
        return "/"
    else:
        return path[2:] # Cuts initial slash and data type identifier

def path_to_datatype_name(path):
    """Takes a path as returned by urlparse and maps it to a string.
    See section 3.4 of RFC 1738 for details."""
    if path=="/":
        # No way to tell, although "INDEX" is likely
        return "TYPE='unknown'"
    else:
        return type_to_name(path[1])

# The following functions interpret the data returned by the gopher
# server according to the expected type, e.g. textfile or directory

def get_directory(f):
    """Get a directory in the form of a list of entries."""
    entries = []
    while 1:
        line = f.readline()
        if not line:
            print '(Unexpected EOF from server)'
            break
        if line[-2:] == CRLF:
            line = line[:-2]
        elif line[-1:] in CRLF:
            line = line[:-1]
        if line == '.':
            break
        if not line:
            print '(Empty line from server)'
            continue
        gtype = line[0]
        parts = line[1:].split(TAB)
        if len(parts) < 4:
            print '(Bad line from server: %r)' % (line,)
            continue
        if len(parts) > 4:
            if parts[4:] != ['+']:
                print '(Extra info from server:',
                print parts[4:], ')'
        else:
            parts.append('')
        parts.insert(0, gtype)
        entries.append(parts)
    return entries

def get_textfile(f):
    """Get a text file as a list of lines, with trailing CRLF stripped."""
    lines = []
    get_alt_textfile(f, lines.append)
    return lines

def get_alt_textfile(f, func):
    """Get a text file and pass each line to a function, with trailing CRLF stripped."""
    while 1:
        line = f.readline()
        if not line:
            print '(Unexpected EOF from server)'
            break
        if line[-2:] == CRLF:
            line = line[:-2]
        elif line[-1:] in CRLF:
            line = line[:-1]
        if line == '.':
            break
        if line[:2] == '..':
            line = line[1:]
        func(line)

def get_binary(f):
    """Get a binary file as one solid data block."""
    data = f.read()
    return data

def get_alt_binary(f, func, blocksize):
    """Get a binary file and pass each block to a function."""
    while 1:
        data = f.read(blocksize)
        if not data:
            break
        func(data)

def test():
    """Trivial test program."""
    import sys
    import getopt
    opts, args = getopt.getopt(sys.argv[1:], '')
    selector = DEF_SELECTOR
    type = selector[0]
    host = DEF_HOST
    if args:
        host = args[0]
        args = args[1:]
    if args:
        type = args[0]
        args = args[1:]
        if len(type) > 1:
            type, selector = type[0], type
        else:
            selector = ''
            if args:
                selector = args[0]
                args = args[1:]
        query = ''
        if args:
            query = args[0]
            args = args[1:]
    if type == A_INDEX:
        f = send_query(selector, query, host)
    else:
        f = send_selector(selector, host)
    if type == A_TEXT:
        lines = get_textfile(f)
        for item in lines: print item
    elif type in (A_MENU, A_INDEX):
        entries = get_directory(f)
        for item in entries: print item
    else:
        data = get_binary(f)
        print 'binary data:', len(data), 'bytes:', repr(data[:100])[:40]

# Run the test when run as script
if __name__ == '__main__':
    test()