📫 MIME Meta Language

Rust implementation of the Emacs MIME message Meta Language, as known as MML.

This library exposes a MML to MIME message compiler and a MIME to MML message interpreter. See the API documentation for more information.

For example:

From: alice@localhost
To: bob@localhost
Subject: MML examples

This is a plain text part.

<#part type=text/html>
<h1>This is a HTML part.</h1>
<#/part>

<#part filename=./examples/attachment.png description="This is an attachment."><#/part>

compiles to:

MIME-Version: 1.0
From: <alice@localhost>
To: <bob@localhost>
Subject: MML examples
Message-ID: <17886a741feef4a2.f9706245cd3a3f97.3b41d60ef9e2fbfb@soywod>
Date: Tue, 26 Sep 2023 09:58:26 +0000
Content-Type: multipart/mixed; 
	boundary="17886a741fef2cb2_97a7dbff4c84bbac_3b41d60ef9e2fbfb"


--17886a741fef2cb2_97a7dbff4c84bbac_3b41d60ef9e2fbfb
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit

This is a plain text part.


--17886a741fef2cb2_97a7dbff4c84bbac_3b41d60ef9e2fbfb
Content-Type: text/html; charset="utf-8"
Content-Transfer-Encoding: 7bit

<h1>This is a HTML part.</h1>

Content-Type: application/octet-stream
Content-Disposition: attachment; filename="attachment.png"
Content-Transfer-Encoding: base64

iVBORw0KGgo…

--17886a741fef2cb2_97a7dbff4c84bbac_3b41d60ef9e2fbfb--

Definition

From the Emacs documentation:

Creating a MIME message is boring and non-trivial. Therefore, a library called mml has been defined that parses a language called MML (MIME Meta Language) and generates MIME messages.

The MML language is very simple. It looks a bit like an SGML application, but it’s not.

The main concept of MML is the part. Each part can be of a different type or use a different charset. The way to delineate a part is with a ‘<#part ...>’ tag. Multipart parts can be introduced with the ‘<#multipart ...>’ tag. Parts are ended by the ‘<#/part>’ or ‘<#/multipart>’ tags. Parts started with the ‘<#part ...>’ tags are also closed by the next open tag.

[…]

Each tag can contain zero or more parameters on the form ‘parameter=value’. The values may be enclosed in quotation marks, but that’s not necessary unless the value contains white space. So ‘filename=/home/user/#hello$^yes’ is perfectly valid.

Features

• MML to MIME messages compilation using MmlCompilerBuilder (cargo feature compiler required, enabled by default)
• MIME to MML messages interpretation using the MimeInterpreterBuilder (cargo feature interpreter required, activated by default)
• Multiple parts support <#multipart>…<#/multipart>
• Inline part support <#part text=mime/type>…<#/part>
• Attachment support <#part disposition=attachment filename=/path/to/attachment.ext><#/part>
• Comment support <#!part>This will not be compiled<#!/part>
• PGP support:
  • Shell commands (cargo feature pgp-commands required)
  • GPG bindings (cargo feature pgp-gpg and gpgme lib required)
  • Native Rust implementation (cargo feature pgp-native required)

Examples

See ./examples:

cargo run --example

Development

The development environment is managed by Nix. Running nix-shell will spawn a shell with everything you need to get started with the lib: cargo, cargo-watch, rust-bin, rust-analyzer…

# Start a Nix shell
$ nix-shell

# then build the lib
$ cargo build -p mml-lib

Contributing

If you want to report a bug that does not exist yet, please send an email at ~soywod/pimalaya@todo.sr.ht.

If you want to propose a feature or fix a bug, please send a patch at ~soywod/pimalaya@lists.sr.ht using git send-email. Follow this guide to configure git properly.

If you just want to discuss about the project, feel free to join the Matrix workspace #pimalaya.mml or contact me directly @soywod. You can also use the mailing list [send an email|subscribe|unsubscribe].

Sponsoring

Special thanks to the NLnet foundation and the European Commission that helped the project to receive financial support from:

• NGI Assure in 2022
• NGI Zero Untrust in 2023

If you appreciate the project, feel free to donate using one of the following providers: