1 """Generic MIME writer.

     2 

     3 This module defines the class MimeWriter.  The MimeWriter class implements

     4 a basic formatter for creating MIME multi-part files.  It doesn't seek around

     5 the output file nor does it use large amounts of buffer space. You must write

     6 the parts out in the order that they should occur in the final file.

     7 MimeWriter does buffer the headers you add, allowing you to rearrange their

     8 order.

     9 

    10 """

    11 

    12 

    13 import mimetools

    14 

    15 __all__ = ["MimeWriter"]

    16 

    17 class MimeWriter:

    18 

    19     """Generic MIME writer.

    20 

    21     Methods:

    22 

    23     __init__()

    24     addheader()

    25     flushheaders()

    26     startbody()

    27     startmultipartbody()

    28     nextpart()

    29     lastpart()

    30 

    31     A MIME writer is much more primitive than a MIME parser.  It

    32     doesn't seek around on the output file, and it doesn't use large

    33     amounts of buffer space, so you have to write the parts in the

    34     order they should occur on the output file.  It does buffer the

    35     headers you add, allowing you to rearrange their order.

    36 

    37     General usage is:

    38 

    39     f = <open the output file>

    40     w = MimeWriter(f)

    41     ...call w.addheader(key, value) 0 or more times...

    42 

    43     followed by either:

    44 

    45     f = w.startbody(content_type)

    46     ...call f.write(data) for body data...

    47 

    48     or:

    49 

    50     w.startmultipartbody(subtype)

    51     for each part:

    52         subwriter = w.nextpart()

    53         ...use the subwriter's methods to create the subpart...

    54     w.lastpart()

    55 

    56     The subwriter is another MimeWriter instance, and should be

    57     treated in the same way as the toplevel MimeWriter.  This way,

    58     writing recursive body parts is easy.

    59 

    60     Warning: don't forget to call lastpart()!

    61 

    62     XXX There should be more state so calls made in the wrong order

    63     are detected.

    64 

    65     Some special cases:

    66 

    67     - startbody() just returns the file passed to the constructor;

    68       but don't use this knowledge, as it may be changed.

    69 

    70     - startmultipartbody() actually returns a file as well;

    71       this can be used to write the initial 'if you can read this your

    72       mailer is not MIME-aware' message.

    73 

    74     - If you call flushheaders(), the headers accumulated so far are

    75       written out (and forgotten); this is useful if you don't need a

    76       body part at all, e.g. for a subpart of type message/rfc822

    77       that's (mis)used to store some header-like information.

    78 

    79     - Passing a keyword argument 'prefix=<flag>' to addheader(),

    80       start*body() affects where the header is inserted; 0 means

    81       append at the end, 1 means insert at the start; default is

    82       append for addheader(), but insert for start*body(), which use

    83       it to determine where the Content-Type header goes.

    84 

    85     """

    86 

    87     def __init__(self, fp):

    88         self._fp = fp

    89         self._headers = []

    90 

    91     def addheader(self, key, value, prefix=0):

    92         """Add a header line to the MIME message.

    93 

    94         The key is the name of the header, where the value obviously provides

    95         the value of the header. The optional argument prefix determines

    96         where the header is inserted; 0 means append at the end, 1 means

    97         insert at the start. The default is to append.

    98 

    99         """

   100         lines = value.split("\n")

   101         while lines and not lines[-1]: del lines[-1]

   102         while lines and not lines[0]: del lines[0]

   103         for i in range(1, len(lines)):

   104             lines[i] = "    " + lines[i].strip()

   105         value = "\n".join(lines) + "\n"

   106         line = key + ": " + value

   107         if prefix:

   108             self._headers.insert(0, line)

   109         else:

   110             self._headers.append(line)

   111 

   112     def flushheaders(self):

   113         """Writes out and forgets all headers accumulated so far.

   114 

   115         This is useful if you don't need a body part at all; for example,

   116         for a subpart of type message/rfc822 that's (mis)used to store some

   117         header-like information.

   118 

   119         """

   120         self._fp.writelines(self._headers)

   121         self._headers = []

   122 

   123     def startbody(self, ctype, plist=[], prefix=1):

   124         """Returns a file-like object for writing the body of the message.

   125 

   126         The content-type is set to the provided ctype, and the optional

   127         parameter, plist, provides additional parameters for the

   128         content-type declaration.  The optional argument prefix determines

   129         where the header is inserted; 0 means append at the end, 1 means

   130         insert at the start. The default is to insert at the start.

   131 

   132         """

   133         for name, value in plist:

   134             ctype = ctype + ';\n %s=\"%s\"' % (name, value)

   135         self.addheader("Content-Type", ctype, prefix=prefix)

   136         self.flushheaders()

   137         self._fp.write("\n")

   138         return self._fp

   139 

   140     def startmultipartbody(self, subtype, boundary=None, plist=[], prefix=1):

   141         """Returns a file-like object for writing the body of the message.

   142 

   143         Additionally, this method initializes the multi-part code, where the

   144         subtype parameter provides the multipart subtype, the boundary

   145         parameter may provide a user-defined boundary specification, and the

   146         plist parameter provides optional parameters for the subtype.  The

   147         optional argument, prefix, determines where the header is inserted;

   148         0 means append at the end, 1 means insert at the start. The default

   149         is to insert at the start.  Subparts should be created using the

   150         nextpart() method.

   151 

   152         """

   153         self._boundary = boundary or mimetools.choose_boundary()

   154         return self.startbody("multipart/" + subtype,

   155                               [("boundary", self._boundary)] + plist,

   156                               prefix=prefix)

   157 

   158     def nextpart(self):

   159         """Returns a new instance of MimeWriter which represents an

   160         individual part in a multipart message.

   161 

   162         This may be used to write the part as well as used for creating

   163         recursively complex multipart messages. The message must first be

   164         initialized with the startmultipartbody() method before using the

   165         nextpart() method.

   166 

   167         """

   168         self._fp.write("\n--" + self._boundary + "\n")

   169         return self.__class__(self._fp)

   170 

   171     def lastpart(self):

   172         """This is used to designate the last part of a multipart message.

   173 

   174         It should always be used when writing multipart messages.

   175 

   176         """

   177         self._fp.write("\n--" + self._boundary + "--\n")

   178 

   179 

   180 if __name__ == '__main__':

   181     import test.test_MimeWriter