mimetools.py

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"""Various tools used by MIME-reading or MIME-writing programs."""


import os
import rfc822
import tempfile

__all__ = ["Message","choose_boundary","encode","decode","copyliteral",
           "copybinary"]

class Message(rfc822.Message):
    """A derived class of rfc822.Message that knows about MIME headers and
    contains some hooks for decoding encoded and multipart messages."""

    def __init__(self, fp, seekable = 1):
        rfc822.Message.__init__(self, fp, seekable)
        self.encodingheader = \
                self.getheader('content-transfer-encoding')
        self.typeheader = \
                self.getheader('content-type')
        self.parsetype()
        self.parseplist()

    def parsetype(self):
        str = self.typeheader
        if str is None:
            str = 'text/plain'
        if ';' in str:
            i = str.index(';')
            self.plisttext = str[i:]
            str = str[:i]
        else:
            self.plisttext = ''
        fields = str.split('/')
        for i in range(len(fields)):
            fields[i] = fields[i].strip().lower()
        self.type = '/'.join(fields)
        self.maintype = fields[0]
        self.subtype = '/'.join(fields[1:])

    def parseplist(self):
        str = self.plisttext
        self.plist = []
        while str[:1] == ';':
            str = str[1:]
            if ';' in str:
                # XXX Should parse quotes!
                end = str.index(';')
            else:
                end = len(str)
            f = str[:end]
            if '=' in f:
                i = f.index('=')
                f = f[:i].strip().lower() + \
                        '=' + f[i+1:].strip()
            self.plist.append(f.strip())
            str = str[end:]

    def getplist(self):
        return self.plist

    def getparam(self, name):
        name = name.lower() + '='
        n = len(name)
        for p in self.plist:
            if p[:n] == name:
                return rfc822.unquote(p[n:])
        return None

    def getparamnames(self):
        result = []
        for p in self.plist:
            i = p.find('=')
            if i >= 0:
                result.append(p[:i].lower())
        return result

    def getencoding(self):
        if self.encodingheader is None:
            return '7bit'
        return self.encodingheader.lower()

    def gettype(self):
        return self.type

    def getmaintype(self):
        return self.maintype

    def getsubtype(self):
        return self.subtype




# Utility functions
# -----------------


_prefix = None

def choose_boundary():
    """Return a random string usable as a multipart boundary.
    The method used is so that it is *very* unlikely that the same
    string of characters will every occur again in the Universe,
    so the caller needn't check the data it is packing for the
    occurrence of the boundary.

    The boundary contains dots so you have to quote it in the header."""

    global _prefix
    import time
    import random
    if _prefix is None:
        import socket
        import os
        hostid = socket.gethostbyname(socket.gethostname())
        try:
            uid = `os.getuid()`
        except:
            uid = '1'
        try:
            pid = `os.getpid()`
        except:
            pid = '1'
        _prefix = hostid + '.' + uid + '.' + pid
    timestamp = '%.3f' % time.time()
    seed = `random.randint(0, 32767)`
    return _prefix + '.' + timestamp + '.' + seed


# Subroutines for decoding some common content-transfer-types

def decode(input, output, encoding):
    """Decode common content-transfer-encodings (base64, quopri, uuencode)."""
    if encoding == 'base64':
        import base64
        return base64.decode(input, output)
    if encoding == 'quoted-printable':
        import quopri
        return quopri.decode(input, output)
    if encoding in ('uuencode', 'x-uuencode', 'uue', 'x-uue'):
        import uu
        return uu.decode(input, output)
    if encoding in ('7bit', '8bit'):
        return output.write(input.read())
    if decodetab.has_key(encoding):
        pipethrough(input, decodetab[encoding], output)
    else:
        raise ValueError, \
              'unknown Content-Transfer-Encoding: %s' % encoding

def encode(input, output, encoding):
    """Encode common content-transfer-encodings (base64, quopri, uuencode)."""
    if encoding == 'base64':
        import base64
        return base64.encode(input, output)
    if encoding == 'quoted-printable':
        import quopri
        return quopri.encode(input, output, 0)
    if encoding in ('uuencode', 'x-uuencode', 'uue', 'x-uue'):
        import uu
        return uu.encode(input, output)
    if encoding in ('7bit', '8bit'):
        return output.write(input.read())
    if encodetab.has_key(encoding):
        pipethrough(input, encodetab[encoding], output)
    else:
        raise ValueError, \
              'unknown Content-Transfer-Encoding: %s' % encoding

# The following is no longer used for standard encodings

# XXX This requires that uudecode and mmencode are in $PATH

uudecode_pipe = '''(
TEMP=/tmp/@uu.$$
sed "s%^begin [0-7][0-7]* .*%begin 600 $TEMP%" | uudecode
cat $TEMP
rm $TEMP
)'''

decodetab = {
        'uuencode':             uudecode_pipe,
        'x-uuencode':           uudecode_pipe,
        'uue':                  uudecode_pipe,
        'x-uue':                uudecode_pipe,
        'quoted-printable':     'mmencode -u -q',
        'base64':               'mmencode -u -b',
}

encodetab = {
        'x-uuencode':           'uuencode tempfile',
        'uuencode':             'uuencode tempfile',
        'x-uue':                'uuencode tempfile',
        'uue':                  'uuencode tempfile',
        'quoted-printable':     'mmencode -q',
        'base64':               'mmencode -b',
}

def pipeto(input, command):
    pipe = os.popen(command, 'w')
    copyliteral(input, pipe)
    pipe.close()

def pipethrough(input, command, output):
    tempname = tempfile.mktemp()
    temp = open(tempname, 'w')
    copyliteral(input, temp)
    temp.close()
    pipe = os.popen(command + ' <' + tempname, 'r')
    copybinary(pipe, output)
    pipe.close()
    os.unlink(tempname)

def copyliteral(input, output):
    while 1:
        line = input.readline()
        if not line: break
        output.write(line)

def copybinary(input, output):
    BUFSIZE = 8192
    while 1:
        line = input.read(BUFSIZE)
        if not line: break
        output.write(line)