imapbackup.py

#!/usr/bin/env python -u

"""IMAP Incremental Backup Script"""
__version__ = "1.4h"
__author__ = "Rui Carmo (http://taoofmac.com)"
__copyright__ = "(C) 2006-2018 Rui Carmo. Code under MIT License.(C)"
__contributors__ = "jwagnerhki, Bob Ippolito, Michael Leonhard, Giuseppe Scrivano <gscrivano@gnu.org>, Ronan Sheth, Brandon Long, Christian Schanz, A. Bovett, Mark Feit"

# = Contributors =
# http://github.com/markfeit: Allow password to be read from a file
# http://github.com/jwagnerhki: fix for message_id checks
# A. Bovett: Modifications for Thunderbird compatibility and disabling spinner in Windows
#  Christian Schanz: added target directory parameter
# Brandon Long (Gmail team): Reminder to use BODY.PEEK instead of BODY
# Ronan Sheth: hashlib patch (this now requires Python 2.5, although reverting it back is trivial)
# Giuseppe Scrivano: Added support for folders.
# Michael Leonhard: LIST result parsing, SSL support, revamped argument processing,
#                   moved spinner into class, extended recv fix to Windows
# Bob Ippolito: fix for MemoryError on socket recv, http://python.org/sf/1092502
# Rui Carmo: original author, up to v1.2e

# = TODO =
# - Add proper exception handlers to scanFile() and downloadMessages()
# - Migrate mailbox usage from rfc822 module to email module
# - Investigate using the noseek mailbox/email option to improve speed
# - Use the email module to normalize downloaded messages
#   and add missing Message-Id
# - Test parseList() and its descendents on other imapds
# - Test bzip2 support
# - Add option to download only subscribed folders
# - Add regex option to filter folders
# - Use a single IMAP command to get Message-IDs
# - Use a single IMAP command to fetch the messages
# - Patch Python's ssl module to do proper checking of certificate chain
# - Patch Python's ssl module to raise good exceptions
# - Submit patch of socket._fileobject.read
# - Improve imaplib module with LIST parsing code, submit patch
# DONE:
# v1.4h
# - Add timeout option
# v1.3c
# - Add SSL support
# - Support host:port
# - Cleaned up code using PyLint to identify problems
#   pylint -f html --indent-string="  " --max-line-length=90 imapbackup.py > report.html
import getpass
import os
import gc
import sys
import time
import platform
import getopt
import mailbox
import imaplib
import socket
import re
import hashlib
import gzip
import bz2


class SkipFolderException(Exception):
    """Indicates aborting processing of current folder, continue with next folder."""
    pass


class Spinner:
    """Prints out message with cute spinner, indicating progress"""

    def __init__(self, message, nospinner):
        """Spinner constructor"""
        self.glyphs = "|/-\\"
        self.pos = 0
        self.message = message
        self.nospinner = nospinner
        sys.stdout.write(message)
        sys.stdout.flush()
        self.spin()

    def spin(self):
        """Rotate the spinner"""
        if sys.stdin.isatty() and not self.nospinner:
            sys.stdout.write("\r" + self.message + " " + self.glyphs[self.pos])
            sys.stdout.flush()
            self.pos = (self.pos+1) % len(self.glyphs)

    def stop(self):
        """Erase the spinner from the screen"""
        if sys.stdin.isatty() and not self.nospinner:
            sys.stdout.write("\r" + self.message + "  ")
            sys.stdout.write("\r" + self.message)
            sys.stdout.flush()


def pretty_byte_count(num):
    """Converts integer into a human friendly count of bytes, eg: 12.243 MB"""
    if num == 1:
        return "1 byte"
    elif num < 1024:
        return "%s bytes" % num
    elif num < 1048576:
        return "%.2f KB" % (num/1024.0)
    elif num < 1073741824:
        return "%.3f MB" % (num/1048576.0)
    elif num < 1099511627776:
        return "%.3f GB" % (num/1073741824.0)
    else:
        return "%.3f TB" % (num/1099511627776.0)


# Regular expressions for parsing
MSGID_RE = re.compile("^Message\-Id\: (.+)", re.IGNORECASE + re.MULTILINE)
BLANKS_RE = re.compile(r'\s+', re.MULTILINE)

# Constants
UUID = '19AF1258-1AAF-44EF-9D9A-731079D6FAD7'  # Used to generate Message-Ids


def string_from_file(value):
    """
    Read a string from a file or return the string unchanged.

    If the string begins with '@', the remainder of the string
    will be treated as a path to the file to be read.  Precede
    the '@' with a '\' to treat it as a literal.
    """

    assert isinstance(value, basestring)

    if not value or value[0] not in ["\\", "@"]:
        return value

    if value[0] == "\\":
        return value[1:]

    with open(os.path.expanduser(value[1:]), 'r') as content:
        return content.read().strip()


def download_messages(server, filename, messages, config):
    """Download messages from folder and append to mailbox"""

    if config['overwrite']:
        if os.path.exists(filename):
            print "Deleting", filename
            os.remove(filename)
        return []
    else:
        assert('bzip2' != config['compress'])

    # Open disk file
    if config['compress'] == 'gzip':
        mbox = gzip.GzipFile(filename, 'ab', 9)
    elif config['compress'] == 'bzip2':
        mbox = bz2.BZ2File(filename, 'wb', 512*1024, 9)
    else:
        mbox = file(filename, 'ab')

    # the folder has already been selected by scanFolder()

    # nothing to do
    if not len(messages):
        print "New messages: 0"
        mbox.close()
        return

    spinner = Spinner("Downloading %s new messages to %s" % (len(messages), filename),
                      config['nospinner'])
    total = biggest = 0

    # each new message
    for msg_id in messages.keys():

        # This "From" and the terminating newline below delimit messages
        # in mbox files.  Note that RFC 4155 specifies that the date be
        # in the same format as the output of ctime(3), which is required
        # by ISO C to use English day and month abbreviations.
        buf = "From nobody %s\n" % time.ctime()
        # If this is one of our synthesised Message-IDs, insert it before
        # the other headers
        if UUID in msg_id:
            buf = buf + "Message-Id: %s\n" % msg_id
        mbox.write(buf)

        # fetch message
        typ, data = server.fetch(messages[msg_id], "RFC822")
        assert('OK' == typ)
        text = data[0][1].strip().replace('\r', '')
        if config['thunderbird']:
            # This avoids Thunderbird mistaking a line starting "From  " as the start
            # of a new message. _Might_ also apply to other mail lients - unknown
            text = text.replace("\nFrom ", "\n From ")
        mbox.write(text)
        mbox.write('\n\n')

        size = len(text)
        biggest = max(size, biggest)
        total += size

        del data
        gc.collect()
        spinner.spin()

    mbox.close()
    spinner.stop()
    print ": %s total, %s for largest message" % (pretty_byte_count(total),
                                                  pretty_byte_count(biggest))


def scan_file(filename, compress, overwrite, nospinner):
    """Gets IDs of messages in the specified mbox file"""
    # file will be overwritten
    if overwrite:
        return []
    else:
        assert('bzip2' != compress)

    # file doesn't exist
    if not os.path.exists(filename):
        print "File %s: not found" % filename
        return []

    spinner = Spinner("File %s" % filename, nospinner)

    # open the file
    if compress == 'gzip':
        mbox = gzip.GzipFile(filename, 'rb')
    elif compress == 'bzip2':
        mbox = bz2.BZ2File(filename, 'rb')
    else:
        mbox = file(filename, 'rb')

    messages = {}

    # each message
    i = 0
    for message in mailbox.PortableUnixMailbox(mbox):
        header = ''
        # We assume all messages on disk have message-ids
        try:
            header = ''.join(message.getfirstmatchingheader('message-id'))
        except KeyError:
            # No message ID was found. Warn the user and move on
            print
            print "WARNING: Message #%d in %s" % (i, filename),
            print "has no Message-Id header."

        header = BLANKS_RE.sub(' ', header.strip())
        try:
            msg_id = MSGID_RE.match(header).group(1)
            if msg_id not in messages.keys():
                # avoid adding dupes
                messages[msg_id] = msg_id
        except AttributeError:
            # Message-Id was found but could somehow not be parsed by regexp
            # (highly bloody unlikely)
            print
            print "WARNING: Message #%d in %s" % (i, filename),
            print "has a malformed Message-Id header."
        spinner.spin()
        i = i + 1

    # done
    mbox.close()
    spinner.stop()
    print ": %d messages" % (len(messages.keys()))
    return messages


def scan_folder(server, foldername, nospinner):
    """Gets IDs of messages in the specified folder, returns id:num dict"""
    messages = {}
    spinner = Spinner("Folder %s" % foldername, nospinner)
    try:
        typ, data = server.select(foldername, readonly=True)
        if 'OK' != typ:
            raise SkipFolderException("SELECT failed: %s" % data)
        num_msgs = int(data[0])

        # each message
        for num in range(1, num_msgs+1):
            # Retrieve Message-Id, making sure we don't mark all messages as read
            typ, data = server.fetch(
                num, '(BODY.PEEK[HEADER.FIELDS (MESSAGE-ID)])')
            if 'OK' != typ:
                raise SkipFolderException("FETCH %s failed: %s" % (num, data))

            header = data[0][1].strip()
            # remove newlines inside Message-Id (a dumb Exchange trait)
            header = BLANKS_RE.sub(' ', header)
            try:
                msg_id = MSGID_RE.match(header).group(1)
                if msg_id not in messages.keys():
                    # avoid adding dupes
                    messages[msg_id] = num
            except (IndexError, AttributeError):
                # Some messages may have no Message-Id, so we'll synthesise one
                # (this usually happens with Sent, Drafts and .Mac news)
                typ, data = server.fetch(
                    num, '(BODY[HEADER.FIELDS (FROM TO CC DATE SUBJECT)])')
                if 'OK' != typ:
                    raise SkipFolderException(
                        "FETCH %s failed: %s" % (num, data))
                header = data[0][1].strip()
                header = header.replace('\r\n', '\t')
                messages['<' + UUID + '.' +
                         hashlib.sha1(header).hexdigest() + '>'] = num
            spinner.spin()
    finally:
        spinner.stop()
        print ":",

    # done
    print "%d messages" % (len(messages.keys()))
    return messages


def parse_paren_list(row):
    """Parses the nested list of attributes at the start of a LIST response"""
    # eat starting paren
    assert(row[0] == '(')
    row = row[1:]

    result = []

    # NOTE: RFC3501 doesn't fully define the format of name attributes
    name_attrib_re = re.compile("^\s*(\\\\[a-zA-Z0-9_]+)\s*")

    # eat name attributes until ending paren
    while row[0] != ')':
        # recurse
        if row[0] == '(':
            paren_list, row = parse_paren_list(row)
            result.append(paren_list)
        # consume name attribute
        else:
            match = name_attrib_re.search(row)
            assert(match is not None)
            name_attrib = row[match.start():match.end()]
            row = row[match.end():]
            #print "MATCHED '%s' '%s'" % (name_attrib, row)
            name_attrib = name_attrib.strip()
            result.append(name_attrib)

    # eat ending paren
    assert(')' == row[0])
    row = row[1:]

    # done!
    return result, row


def parse_string_list(row):
    """Parses the quoted and unquoted strings at the end of a LIST response"""
    slist = re.compile('\s*(?:"([^"]+)")\s*|\s*(\S+)\s*').split(row)
    return [s for s in slist if s]


def parse_list(row):
    """Prases response of LIST command into a list"""
    row = row.strip()
    paren_list, row = parse_paren_list(row)
    string_list = parse_string_list(row)
    assert(len(string_list) == 2)
    return [paren_list] + string_list


def get_hierarchy_delimiter(server):
    """Queries the imapd for the hierarchy delimiter, eg. '.' in INBOX.Sent"""
    # see RFC 3501 page 39 paragraph 4
    typ, data = server.list('', '')
    assert(typ == 'OK')
    assert(len(data) == 1)
    lst = parse_list(data[0])  # [attribs, hierarchy delimiter, root name]
    hierarchy_delim = lst[1]
    # NIL if there is no hierarchy
    if 'NIL' == hierarchy_delim:
        hierarchy_delim = '.'
    return hierarchy_delim


def get_names(server, compress, thunderbird, nospinner):
    """Get list of folders, returns [(FolderName,FileName)]"""

    spinner = Spinner("Finding Folders", nospinner)

    # Get hierarchy delimiter
    delim = get_hierarchy_delimiter(server)
    spinner.spin()

    # Get LIST of all folders
    typ, data = server.list()
    assert(typ == 'OK')
    spinner.spin()

    names = []

    # parse each LIST, find folder name
    for row in data:
        lst = parse_list(row)
        foldername = lst[2]
        suffix = {'none': '', 'gzip': '.gz', 'bzip2': '.bz2'}[compress]
        if thunderbird:
            filename = '.sbd/'.join(foldername.split(delim)) + suffix
            if filename.startswith("INBOX"):
                filename = filename.replace("INBOX", "Inbox")
        else:
            filename = '.'.join(foldername.split(delim)) + '.mbox' + suffix
        # print "\n*** Folder:", foldername # *DEBUG
        # print "***   File:", filename # *DEBUG
        names.append((foldername, filename))

    # done
    spinner.stop()
    print ": %s folders" % (len(names))
    return names


def print_usage():
    """Prints usage, exits"""
    #     "                                                                               "
    print "Usage: imapbackup [OPTIONS] -s HOST -u USERNAME [-p PASSWORD]"
    print " -a --append-to-mboxes     Append new messages to mbox files. (default)"
    print " -y --yes-overwrite-mboxes Overwite existing mbox files instead of appending."
    print " -n --compress=none        Use one plain mbox file for each folder. (default)"
    print " -z --compress=gzip        Use mbox.gz files.  Appending may be very slow."
    print " -b --compress=bzip2       Use mbox.bz2 files. Appending not supported: use -y."
    print " -f --=folder              Specifify which folders use.  Comma separated list."
    print " -e --ssl                  Use SSL.  Port defaults to 993."
    print " -k KEY --key=KEY          PEM private key file for SSL.  Specify cert, too."
    print " -c CERT --cert=CERT       PEM certificate chain for SSL.  Specify key, too."
    print "                           Python's SSL module doesn't check the cert chain."
    print " -s HOST --server=HOST     Address of server, port optional, eg. mail.com:143"
    print " -u USER --user=USER       Username to log into server"
    print " -p PASS --pass=PASS       Prompts for password if not specified.  If the first"
    print "                           character is '@', treat the rest as a path to a file"
    print "                           containing the password.  Leading '\' makes it literal."
    print " -t SECS --timeout=SECS    Sets socket timeout to SECS seconds."
    print " --thunderbird             Create Mozilla Thunderbird compatible mailbox"
    print " --nospinner               Disable spinner (makes output log-friendly)"
    print "\nNOTE: mbox files are created in the current working directory."
    sys.exit(2)


def process_cline():
    """Uses getopt to process command line, returns (config, warnings, errors)"""
    # read command line
    try:
        short_args = "aynzbekt:c:s:u:p:f:"
        long_args = ["append-to-mboxes", "yes-overwrite-mboxes", "compress=",
                     "ssl", "timeout", "keyfile=", "certfile=", "server=", "user=", "pass=",
                     "folders=", "thunderbird", "nospinner"]
        opts, extraargs = getopt.getopt(sys.argv[1:], short_args, long_args)
    except getopt.GetoptError:
        print_usage()

    warnings = []
    config = {'compress': 'none', 'overwrite': False, 'usessl': False,
              'thunderbird': False, 'nospinner': False}
    errors = []

    # empty command line
    if not len(opts) and not len(extraargs):
        print_usage()

    # process each command line option, save in config
    for option, value in opts:
        if option in ("-a", "--append-to-mboxes"):
            config['overwrite'] = False
        elif option in ("-y", "--yes-overwrite-mboxes"):
            warnings.append("Existing mbox files will be overwritten!")
            config["overwrite"] = True
        elif option == "-n":
            config['compress'] = 'none'
        elif option == "-z":
            config['compress'] = 'gzip'
        elif option == "-b":
            config['compress'] = 'bzip2'
        elif option == "--compress":
            if value in ('none', 'gzip', 'bzip2'):
                config['compress'] = value
            else:
                errors.append("Invalid compression type specified.")
        elif option in ("-e", "--ssl"):
            config['usessl'] = True
        elif option in ("-k", "--keyfile"):
            config['keyfilename'] = value
        elif option in ("-f", "--folders"):
            config['folders'] = value
        elif option in ("-c", "--certfile"):
            config['certfilename'] = value
        elif option in ("-s", "--server"):
            config['server'] = value
        elif option in ("-u", "--user"):
            config['user'] = value
        elif option in ("-p", "--pass"):
            try:
                config['pass'] = string_from_file(value)
            except Exception as ex:
                errors.append("Can't read password: %s" % (str(ex)))
        elif option in ("-t", "--timeout"):
            config['timeout'] = value
        elif option == "--thunderbird":
            config['thunderbird'] = True
        elif option == "--nospinner":
            config['nospinner'] = True
        else:
            errors.append("Unknown option: " + option)

    # don't ignore extra arguments
    for arg in extraargs:
        errors.append("Unknown argument: " + arg)

    # done processing command line
    return config, warnings, errors


def check_config(config, warnings, errors):
    """Checks the config for consistency, returns (config, warnings, errors)"""

    if config['compress'] == 'bzip2' and config['overwrite'] is False:
        errors.append(
            "Cannot append new messages to mbox.bz2 files.  Please specify -y.")
    if config['compress'] == 'gzip' and config['overwrite'] is False:
        warnings.append(
            "Appending new messages to mbox.gz files is very slow.  Please Consider\n"
            "  using -y and compressing the files yourself with gzip -9 *.mbox")
    if 'server' not in config:
        errors.append("No server specified.")
    if 'user' not in config:
        errors.append("No username specified.")
    if ('keyfilename' in config) ^ ('certfilename' in config):
        errors.append("Please specify both key and cert or neither.")
    if 'keyfilename' in config and not config['usessl']:
        errors.append("Key specified without SSL.  Please use -e or --ssl.")
    if 'certfilename' in config and not config['usessl']:
        errors.append(
            "Certificate specified without SSL.  Please use -e or --ssl.")
    if 'server' in config and ':' in config['server']:
        # get host and port strings
        bits = config['server'].split(':', 1)
        config['server'] = bits[0]
        # port specified, convert it to int
        if len(bits) > 1 and len(bits[1]) > 0:
            try:
                port = int(bits[1])
                if port > 65535 or port < 0:
                    raise ValueError
                config['port'] = port
            except ValueError:
                errors.append(
                    "Invalid port.  Port must be an integer between 0 and 65535.")
    if 'timeout' in config:
        try:
            timeout = int(config['timeout'])
            if timeout <= 0:
                raise ValueError
            config['timeout'] = timeout
        except ValueError:
            errors.append(
                "Invalid timeout value.  Must be an integer greater than 0.")
    return config, warnings, errors


def get_config():
    """Gets config from command line and console, returns config"""
    # config = {
    #   'compress': 'none' or 'gzip' or 'bzip2'
    #   'overwrite': True or False
    #   'server': String
    #   'port': Integer
    #   'user': String
    #   'pass': String
    #   'usessl': True or False
    #   'keyfilename': String or None
    #   'certfilename': String or None
    # }

    config, warnings, errors = process_cline()
    config, warnings, errors = check_config(config, warnings, errors)

    # show warnings
    for warning in warnings:
        print "WARNING:", warning

    # show errors, exit
    for error in errors:
        print "ERROR", error
    if len(errors):
        sys.exit(2)

    # prompt for password, if necessary
    if 'pass' not in config:
        config['pass'] = getpass.getpass()

    # defaults
    if 'port' not in config:
        if config['usessl']:
            config['port'] = 993
        else:
            config['port'] = 143
    if 'timeout' not in config:
        config['timeout'] = 60

    # done!
    return config


def connect_and_login(config):
    """Connects to the server and logs in.  Returns IMAP4 object."""
    try:
        assert(not (('keyfilename' in config) ^ ('certfilename' in config)))
        if config['timeout']:
            socket.setdefaulttimeout(config['timeout'])

        if config['usessl'] and 'keyfilename' in config:
            print "Connecting to '%s' TCP port %d," % (
                config['server'], config['port']),
            print "SSL, key from %s," % (config['keyfilename']),
            print "cert from %s " % (config['certfilename'])
            server = imaplib.IMAP4_SSL(config['server'], config['port'],
                                       config['keyfilename'], config['certfilename'])
        elif config['usessl']:
            print "Connecting to '%s' TCP port %d, SSL" % (
                config['server'], config['port'])
            server = imaplib.IMAP4_SSL(config['server'], config['port'])
        else:
            print "Connecting to '%s' TCP port %d" % (
                config['server'], config['port'])
            server = imaplib.IMAP4(config['server'], config['port'])

        # speed up interactions on TCP connections using small packets
        server.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)

        print "Logging in as '%s'" % (config['user'])
        server.login(config['user'], config['pass'])
    except socket.gaierror, e:
        (err, desc) = e
        print "ERROR: problem looking up server '%s' (%s %s)" % (
            config['server'], err, desc)
        sys.exit(3)
    except socket.error, e:
        if str(e) == "SSL_CTX_use_PrivateKey_file error":
            print "ERROR: error reading private key file '%s'" % (
                config['keyfilename'])
        elif str(e) == "SSL_CTX_use_certificate_chain_file error":
            print "ERROR: error reading certificate chain file '%s'" % (
                config['keyfilename'])
        else:
            print "ERROR: could not connect to '%s' (%s)" % (
                config['server'], e)

        sys.exit(4)

    return server


def create_folder_structure(names):
    """ Create the folder structure on disk """
    for imap_foldername, filename in sorted(names):
        disk_foldername = os.path.split(filename)[0]
        if disk_foldername:
            try:
                # print "*** mkdir:", disk_foldername  # *DEBUG
                os.mkdir(disk_foldername)
            except OSError, e:
                if e.errno != 17:
                    raise


def main():
    """Main entry point"""
    try:
        config = get_config()
        server = connect_and_login(config)
        names = get_names(server, config['compress'], config['thunderbird'],
                          config['nospinner'])
        if config.get('folders'):
            dirs = map(lambda x: x.strip(), config.get('folders').split(','))
            if config['thunderbird']:
                dirs = [i.replace("Inbox", "INBOX", 1) if i.startswith("Inbox") else i
                        for i in dirs]
            names = filter(lambda x: x[0] in dirs, names)

        # for n, name in enumerate(names): # *DEBUG
        #   print n, name # *DEBUG

        create_folder_structure(names)

        for name_pair in names:
            try:
                foldername, filename = name_pair
                fol_messages = scan_folder(
                    server, foldername, config['nospinner'])
                fil_messages = scan_file(filename, config['compress'],
                                         config['overwrite'], config['nospinner'])
                new_messages = {}
                for msg_id in fol_messages.keys():
                    if msg_id not in fil_messages:
                        new_messages[msg_id] = fol_messages[msg_id]

                # for f in new_messages:
                #  print "%s : %s" % (f, new_messages[f])

                download_messages(server, filename, new_messages, config)

            except SkipFolderException, e:
                print e

        print "Disconnecting"
        server.logout()
    except socket.error, e:
        (err, desc) = e
        print "ERROR: %s %s" % (err, desc)
        sys.exit(4)
    except imaplib.IMAP4.error, e:
        print "ERROR:", e
        sys.exit(5)


# From http://www.pixelbeat.org/talks/python/spinner.py
def cli_exception(typ, value, traceback):
    """Handle CTRL-C by printing newline instead of ugly stack trace"""
    if not issubclass(typ, KeyboardInterrupt):
        sys.__excepthook__(typ, value, traceback)
    else:
        sys.stdout.write("\n")
        sys.stdout.flush()


if sys.stdin.isatty():
    sys.excepthook = cli_exception


# Hideous fix to counteract http://python.org/sf/1092502
# (which should have been fixed ages ago.)
# Also see http://python.org/sf/1441530
def _fixed_socket_read(self, size=-1):
    data = self._rbuf
    if size < 0:
        # Read until EOF
        buffers = []
        if data:
            buffers.append(data)
        self._rbuf = ""
        if self._rbufsize <= 1:
            recv_size = self.default_bufsize
        else:
            recv_size = self._rbufsize
        while True:
            data = self._sock.recv(recv_size)
            if not data:
                break
            buffers.append(data)
        return "".join(buffers)
    else:
        # Read until size bytes or EOF seen, whichever comes first
        buf_len = len(data)
        if buf_len >= size:
            self._rbuf = data[size:]
            return data[:size]
        buffers = []
        if data:
            buffers.append(data)
        self._rbuf = ""
        while True:
            left = size - buf_len
            recv_size = min(self._rbufsize, left)  # the actual fix
            data = self._sock.recv(recv_size)
            if not data:
                break
            buffers.append(data)
            n = len(data)
            if n >= left:
                self._rbuf = data[left:]
                buffers[-1] = data[:left]
                break
            buf_len += n
        return "".join(buffers)


# Platform detection to enable socket patch
if 'Darwin' in platform.platform() and '2.3.5' == platform.python_version():
    socket._fileobject.read = _fixed_socket_read
# 20181212: Windows 10 + Python 2.7 doesn't need this fix
# (fix leads to error: object of type 'cStringIO.StringO' has no len())
if 'Windows' in platform.platform() and '2.3.5' == platform.python_version():
    socket._fileobject.read = _fixed_socket_read

if __name__ == '__main__':
    gc.enable()
    main()