An implementation of RFC 2388 in Common Lisp
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This package contains an implementation of RFC 2388, which is used to process form data posted with HTTP POST method using enctype "multipart/form-data".

The main functions of interest are PARSE-MIME and PARSE-HEADER.

Use PARSE-MIME to parse MIME content. It can be given either a string or a stream. It returns a list of MIME parts. The second argument must be a boundary, which is a string that seperates MIME parts. See below how to obtain it.

PARSE-HEADER is used by PARSE-MIME internally, but you can use it to parse headers yourself. For instance, when data is posted to server using POST method, a header describing the content type is sent as well. Usually its content is application/x-www-form-urlencoded or something similar. But users may set it to multipart/form-data, with additional parameter named "boundary". This is how one would usually parse the posted data:

(let* ((header (parse-header <request-content-type> :value))
       (boundary (or (assoc "boundary" (header-parameters header)
                            :test #'string-equal)
                     (error "Form data is missing a boundary: ~S"
  (parse-mime <request-posted-content> boundary))

The :VALUE keyword parameter to PARSE-HEADER means that parsing should begin with header value, not name (because header name is "content-type" and the web server has already seperated them, at least in this scenario).