10 MIME: Decoding Internet Data

(require net/mime)

The net/mime library provides utilities for parsing and creating MIME encodings as described in RFC 2045 through RFC 2049.

The library was written by Francisco Solsona.

10.1 Message Decoding

(mime-analyze message-in part?) → message?

message-in : (or/c bytes? input-port)

part? : any/c

Parses message-in and returns the parsed result as a message instance.

(struct   message   (version entity fields))

version : real?

entity : entity

fields : (listof string?)

A decoded MIME message. The version is 1.0 by default. The entity field represents the message data. The fields field contains one string for each field in the message header.

(struct   entity  ( type         subtype         charset         encoding         disposition         params         id         description         other         fields         parts         body))

type : symbol?

subtype : symbol?

charset : symbol?

encoding : symbol?

disposition : disposition?

params : (listof (cons/c symbol? string?))

id : string?

description : string?

other : (listof string?)

fields : (listof string?)

parts : (listof message?)

body : (output-port? . -> . void?)

Represents the content of a message or a sub-part.

Standard values for the type field include 'text, 'image, 'audio, 'video, 'application, 'message, and 'multipart.

Standard values for the subtype field depend on the type field, and include the following:

'text		'plain		[RFC1521, NSB]
		'richtext		[RFC1521, NSB]
		'tab-separated-values		[Lindner]
'multipart		'mixed		[RFC1521, NSB]
		'alternative		[RFC1521, NSB]
		'digest		[RFC1521, NSB]
		'parallel		[RFC1521, NSB]
		'appledouble		[MacMime, Faltstrom]
		'header-set		[Crocker]
'message		'rfc822		[RFC1521, NSB]
		'partial		[RFC1521, NSB]
		'external-body		[RFC1521, NSB]
		'news		[RFC 1036, Spencer]
'application		'octet-stream		[RFC1521, NSB]
		'postscript		[RFC1521, NSB]
		'oda		[RFC1521, NSB]
		'atomicmail		[atomicmail, NSB]
		'andrew-inset		[andrew-inset, NSB]
		'slate		[slate, Crowley]
		'wita		[Wang Info Transfer, Campbell]
		'dec-dx		[Digital Doc Trans, Campbell]
		'dca-rft		[IBM Doc Content Arch, Campbell]
		'activemessage		[Shapiro]
		'rtf		[Lindner]
		'applefile		[MacMime, Faltstrom]
		'mac-binhex40		[MacMime, Faltstrom]
		'news-message-id		[RFC1036, Spencer]
		'news-transmission		[RFC1036, Spencer]
		'wordperfect5.1		[Lindner]
		'pdf		[Lindner]
		'zip		[Lindner]
		'macwriteii		[Lindner]
		'msword		[Lindner]
		'remote-printing		[RFC1486,MTR]
'image		'jpeg		[RFC1521, NSB]
		'gif		[RFC1521, NSB]
		'ief		[RFC1314]
		'tiff		[MTR]
'audio		'basic		[RFC1521, NSB]
'video		'mpeg		[RFC1521, NSB]
		'quicktime		[Lindner]

Standard values for the charset field include 'us-ascii, which is the default.

Standard values for the encoding field are '7bit, '8bit, 'binary, 'quoted-printable, and 'base64. The default is '7bit.

The params field contains a list of parameters from other MIME headers.

The id field is taken from the "Content-Id" header field.

The description field is taken from the "Content-description" header field.

The other field contains additional (non-standard) field headers whose field names start with "Content-".

The fields field contains additional field headers whose field names do not start with "Content-".

The parts contains sub-parts from multipart MIME messages. This list is non-empty only when type is 'multipart or 'message.

The body field represents the body as a function that consumes an output out and writes the decoded message to the port. No bytes are written if type is 'multipart or 'message. All of the standard values of encoding are supported. The procedure only works once (since the encoded body is pulled from a stream).

(struct   disposition  ( type         filename         creation         modification         read         size         params))

type : symbol?

filename : (or/c string? false/c)

creation : (or/c string? false/c)

modification : (or/c string? false/c)

read : (or/c string? false/c)

size : (or/c exact-nonnegative-integer? false/c)

params : (listof (cons/c symbol? string?))

Represents a "Content-Disposition" header as defined in RFC 2183.

Standard values for the type field include 'inline and 'attachment.

The filename field is drawn from the "filename" parameter of the "Content-Disposition" header, if included in the message.

The creation, modification, and read fields represent file timestamps as drawn from the "creation-date", "modification-date", and "read-date" attributes of the "Content-Disposition" header, if included in the message.

The size field is drawn from the "size" parameter of the "Content-Disposition" header, if included in the message.

The params field stores any additional attribute bindings of the "Content-Disposition" header, if included in the message.

10.2 Exceptions

(struct   mime-error   ())

The supertype of all MIME exceptions.

(struct   (unexpected-termination mime-error)   (msg))

msg : string?

Raised when an end-of-file is reached while parsing the headers of a MIME entity. It usually means that the message does not conform to RFC 2045 and friends.

(struct   (missing-multipart-boundary-parameter mime-error)   ())

Raised when a multipart type is specified, but no "Boundary" parameter is given or an end-of-file is encountered before the boundary.

(struct   (malformed-multipart-entity mime-error)   (msg))

msg : string?

Similar to unexpected-termination, but used only while scanning parts of a multipart message.

(struct   (empty-mechanism mime-error)   ())

Raised when no transport encoding mechanism was provided with the "Content-Transfer-Encoding" field.

(struct   (empty-type mime-error)   ())

Raised when no type is specified for "Content-Type", or when the specification is incorrectly formatted.

(struct   (empty-subtype mime-error)   ())

Raised when no sub-type is specified for "Content-Type", or when the specification is incorrectly formatted.

(struct   (empty-disposition-type mime-error)   ())

Raised when type specified for the "Content-Disposition" field, or when the specification is incorrectly formatted.

10.3 MIME Unit

(require net/mime-unit)

mime@ : unit?

Imports nothing, exports mime^.

10.4 MIME Signature

(require net/mime-sig)

mime^ : signature

Includes everything exported by the net/mime module.