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About
Title: libMagnum
Author: Fletcher T. Penney
Date: 2024-10-11
Copyright: Copyright © 2017-2024 Fletcher T. Penney.
Version: 1.3.0

Introduction

Mustache is a syntax for creating "logic-less templates". For example:

Hello {{name}}
You have just won {{value}} dollars!
{{#in_ca}}
Well, {{taxed_value}} dollars, after taxes.
{{/in_ca}}

can be combined with some data:

{
  "name": "Chris",
  "value": 10000,
  "taxed_value": 6000,
  "in_ca": true
}

to generate the following:

Hello Chris
You have just won 10000 dollars!
Well, 6000.0 dollars, after taxes.

The Mustache system is described as "logic-less", but in reality the functionality provides for a great deal of flexibility.

Read more about the Mustache syntax here.

Magnum

Magnum is a C implementation of a Mustache parser. It uses JSON to provide the data, which can be provided in the form of a text file, a text string, or a parson JSON_Value. (The command line implementation requires that the JSON data and template both come from text files.)

The magnum command line utility expects two or more arguments. The first is a JSON file to provide the data. The remaining are source template files, which are processed in order. The output is sent to stdout.

magnum data.json source.txt > output.txt

Magnum was inspired by another C implementation of Mustache, https://gitlab.com/jobol/mustach. mustach is licensed under the Apache License, version 2.0:

https://gitlab.com/jobol/mustach/blob/master/LICENSE-2.0.txt

Magnum was written in order to:

  • Fix several issues in order to provide compliance with the formal specification

  • Remove dependencies on external libraries -- parson is included to provide JSON parsing rather than using an external library

  • Add the test suite from the formal spec to ensure compliance

Differences From the Specification

There are (currently) a few divergences from the formal Mustache specification:

  • Since Magnum is written in C (and for security reasons), it does not support lambdas (an optional, not required, feature of Mustache.)

  • Tags that start with : will treat the remainder of the tag as literal characters -- this provides escaping when a tag name requires a character that is otherwise used for the Mustache syntax. This feature was developed in mustach.

  • Tags that start with $ will insert the raw JSON as a text string. This is used in the make_spec_test.must file in order to generate the test suite for example. It may not otherwise be a widely useful function. This may require additional cleaning up of the resulting text depending on the JSON content and the target language. The syntax for this feature may change in the future -- input welcome.

FAQ

Where Can I Learn More About the Mustache Syntax?

The description of the Mustache syntax is here:

http://mustache.github.io/mustache.5.html

The formal specification is here:

https://github.com/mustache/spec

Why "Magnum"?

Because he had the coolest mustache of all time, of course! ;)

How Do I Use Magnum in Conjunction With MultiMarkdown?

For now you can use magnum to preprocess a document before running it through MultiMarkdown.

magnum data.json template.mustache > text.mmd
multimarkdown text.mmd > text.html

CAUTION: The Mustache syntax {{foo}} is the same as the MultiMarkdown syntax for transclusion. Because the Mustache spec indicates that non- matching tags will be removed, running text through magnum will remove any transclusion tags from the MultiMarkdown text. In this case, you should run the file through MultiMarkdown first in order to perform transclusion:

multimarkdown -t mmd text.mmd > text.mustache
magnum data.json text.mustache > text2.mmd
multimarkdown text2.mmd > text.html

(When MMD is unable to match a transclusion command to a file, it leaves the request intact. Therefore it will not remove Mustache syntax from the file, unless the Mustache tag happens to match an existing file.)

If needed, Mustache includes the ability to change the tag delimiters to something else. This would remove the conflict with MMD transclusion.

{{=<% %>=}}
<% mustache tag %>

After some additional testing of Magnum, and experimenting with different uses, I may incorporate Magnum directly into MultiMarkdown.

How Do Partials Work in Magnum?

"Partials" allow you to reference other Mustache templates, much like transclusion works in MultiMarkdown.

For example, including {{> user.mustache}} in a template, would then cause the contents of the file user.mustache to be inserted, and then parsed for additional Mustache syntax.

This allows you split complex templates across multiple reusable files.

How Do I Iterate Over a Top-Level Array?

Given the data:

[
	"foo",
	"bar",
	"baz"
]

You can use the following Mustache template:

{{#.}}
* {{.}}
{{/.}}

And generate this output:

* foo
* bar
* baz

What are the security implications of partials?

Partials ({{> foo.mustache}}) allow arbitrary read access to the file system, IF the command line implementation is used, OR if a search_directory is passed to one of the magnum_populate commands. magnum is limited to whatever system access privileges it is provided, so it cannot read anything that you could not access via the command line already.

So the key thing is that if you are using libMagnum somewhere, pass NULL as the search_directory parameter to prevent partials from being enabled, if that is the behavior you desire.

License

The magnum project is released under the MIT License.

d_string.c and d_string.h are from the MultiMarkdown v6 project:

https://github.com/fletcher/MultiMarkdown-6/

MMD 6 is released under both the MIT License.

parson is Copyright (c) 2012 - 2017 Krzysztof Gabis and is licensed under the MIT License.

Portions inspired by mustach by José Bollo jobol@nonadev.net, licensed under the Apache License, Version 2.0:

http://www.apache.org/licenses/LICENSE-2.0

CuTest is released under the zlib/libpng license. See CuTest.c for the text of the license.

The MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.