Lib/MimeWriter.py

   1 """Generic MIME writer.
   2
   3 Classes:
   4
   5 MimeWriter - the only thing here.
   6
   7 """
   8
   9
  10 import mimetools
  11
  12 __all__ = ["MimeWriter"]
  13
  14 class MimeWriter:
  15
  16     """Generic MIME writer.
  17
  18     Methods:
  19
  20     __init__()
  21     addheader()
  22     flushheaders()
  23     startbody()
  24     startmultipartbody()
  25     nextpart()
  26     lastpart()
  27
  28     A MIME writer is much more primitive than a MIME parser.  It
  29     doesn't seek around on the output file, and it doesn't use large
  30     amounts of buffer space, so you have to write the parts in the
  31     order they should occur on the output file.  It does buffer the
  32     headers you add, allowing you to rearrange their order.
  33
  34     General usage is:
  35
  36     f = <open the output file>
  37     w = MimeWriter(f)
  38     ...call w.addheader(key, value) 0 or more times...
  39
  40     followed by either:
  41
  42     f = w.startbody(content_type)
  43     ...call f.write(data) for body data...
  44
  45     or:
  46
  47     w.startmultipartbody(subtype)
  48     for each part:
  49         subwriter = w.nextpart()
  50         ...use the subwriter's methods to create the subpart...
  51     w.lastpart()
  52
  53     The subwriter is another MimeWriter instance, and should be
  54     treated in the same way as the toplevel MimeWriter.  This way,
  55     writing recursive body parts is easy.
  56
  57     Warning: don't forget to call lastpart()!
  58
  59     XXX There should be more state so calls made in the wrong order
  60     are detected.
  61
  62     Some special cases:
  63
  64     - startbody() just returns the file passed to the constructor;
  65       but don't use this knowledge, as it may be changed.
  66
  67     - startmultipartbody() actually returns a file as well;
  68       this can be used to write the initial 'if you can read this your
  69       mailer is not MIME-aware' message.
  70
  71     - If you call flushheaders(), the headers accumulated so far are
  72       written out (and forgotten); this is useful if you don't need a
  73       body part at all, e.g. for a subpart of type message/rfc822
  74       that's (mis)used to store some header-like information.
  75
  76     - Passing a keyword argument 'prefix=<flag>' to addheader(),
  77       start*body() affects where the header is inserted; 0 means
  78       append at the end, 1 means insert at the start; default is
  79       append for addheader(), but insert for start*body(), which use
  80       it to determine where the Content-Type header goes.
  81
  82     """
  83
  84     def __init__(self, fp):
  85         self._fp = fp
  86         self._headers = []
  87
  88     def addheader(self, key, value, prefix=0):
  89         lines = value.split("\n")
  90         while lines and not lines[-1]: del lines[-1]
  91         while lines and not lines[0]: del lines[0]
  92         for i in range(1, len(lines)):
  93             lines[i] = "    " + lines[i].strip()
  94         value = "\n".join(lines) + "\n"
  95         line = key + ": " + value
  96         if prefix:
  97             self._headers.insert(0, line)
  98         else:
  99             self._headers.append(line)
 100
 101     def flushheaders(self):
 102         self._fp.writelines(self._headers)
 103         self._headers = []
 104
 105     def startbody(self, ctype, plist=[], prefix=1):
 106         for name, value in plist:
 107             ctype = ctype + ';\n %s=\"%s\"' % (name, value)
 108         self.addheader("Content-Type", ctype, prefix=prefix)
 109         self.flushheaders()
 110         self._fp.write("\n")
 111         return self._fp
 112
 113     def startmultipartbody(self, subtype, boundary=None, plist=[], prefix=1):
 114         self._boundary = boundary or mimetools.choose_boundary()
 115         return self.startbody("multipart/" + subtype,
 116                               [("boundary", self._boundary)] + plist,
 117                               prefix=prefix)
 118
 119     def nextpart(self):
 120         self._fp.write("\n--" + self._boundary + "\n")
 121         return self.__class__(self._fp)
 122
 123     def lastpart(self):
 124         self._fp.write("\n--" + self._boundary + "--\n")
 125
 126
 127 if __name__ == '__main__':
 128     import test.test_MimeWriter