Added Mime writer module (formerly in Grail)

Lib/MimeWriter.py

@@ -0,0 +1,131 @@
+"""Generic MIME writer.
+
+Classes:
+
+MimeWriter - the only thing here.
+
+"""
+
+__version__ = '$Revision$'
+# $Source$
+
+
+import string
+import mimetools
+
+
+class MimeWriter:
+
+    """Generic MIME writer.
+
+    Methods:
+
+    __init__()
+    addheader()
+    flushheaders()
+    startbody()
+    startmultipartbody()
+    nextpart()
+    lastpart()
+
+    A MIME writer is much more primitive than a MIME parser.  It
+    doesn't seek around on the output file, and it doesn't use large
+    amounts of buffer space, so you have to write the parts in the
+    order they should occur on the output file.  It does buffer the
+    headers you add, allowing you to rearrange their order.
+    
+    General usage is:
+
+    f = <open the output file>
+    w = MimeWriter(f)
+    ...call w.addheader(key, value) 0 or more times...
+
+    followed by either:
+
+    f = w.startbody(content_type)
+    ...call f.write(data) for body data...
+
+    or:
+
+    w.startmultipartbody(subtype)
+    for each part:
+        subwriter = w.nextpart()
+	...use the subwriter's methods to create the subpart...
+    w.lastpart()
+
+    The subwriter is another MimeWriter instance, and should be
+    treated in the same way as the toplevel MimeWriter.  This way,
+    writing recursive body parts is easy.
+
+    Warning: don't forget to call lastpart()!
+
+    XXX There should be more state so calls made in the wrong order
+    are detected.
+
+    Some special cases:
+
+    - startbody() just returns the file passed to the constructor;
+      but don't use this knowledge, as it may be changed.
+
+    - startmultipartbody() actually returns a file as well;
+      this can be used to write the initial 'if you can read this your
+      mailer is not MIME-aware' message.
+
+    - If you call flushheaders(), the headers accumulated so far are
+      written out (and forgotten); this is useful if you don't need a
+      body part at all, e.g. for a subpart of type message/rfc822
+      that's (mis)used to store some header-like information.
+
+    - Passing a keyword argument 'prefix=<flag>' to addheader(),
+      start*body() affects where the header is inserted; 0 means
+      append at the end, 1 means insert at the start; default is
+      append for addheader(), but insert for start*body(), which use
+      it to determine where the Content-Type header goes.
+
+    """
+
+    def __init__(self, fp):
+	self._fp = fp
+	self._headers = []
+
+    def addheader(self, key, value, prefix=0):
+	lines = string.splitfields(value, "\n")
+	while lines and not lines[-1]: del lines[-1]
+	while lines and not lines[0]: del lines[0]
+	for i in range(1, len(lines)):
+	    lines[i] = "    " + string.strip(lines[i])
+	value = string.joinfields(lines, "\n") + "\n"
+	line = key + ": " + value
+	if prefix:
+	    self._headers.insert(0, line)
+	else:
+	    self._headers.append(line)
+
+    def flushheaders(self):
+	self._fp.writelines(self._headers)
+	self._headers = []
+
+    def startbody(self, ctype, plist=[], prefix=1):
+	for name, value in plist:
+	    ctype = ctype + ';\n %s=\"%s\"' % (name, value)
+	self.addheader("Content-Type", ctype, prefix=prefix)
+	self.flushheaders()
+	self._fp.write("\n")
+	return self._fp
+
+    def startmultipartbody(self, subtype, boundary=None, plist=[], prefix=1):
+	self._boundary = boundary or mimetools.choose_boundary()
+	return self.startbody("multipart/" + subtype,
+			      [("boundary", self._boundary)] + plist,
+			      prefix=prefix)
+
+    def nextpart(self):
+	self._fp.write("\n--" + self._boundary + "\n")
+	return self.__class__(self._fp)
+
+    def lastpart(self):
+	self._fp.write("\n--" + self._boundary + "--\n")
+
+
+if __name__ == '__main__':
+    print "To test the MimeWriter module, run TestMimeWriter.py."