💾 Archived View for gmi.noulin.net › markdown › md4c_README.md captured on 2024-08-25 at 06:55:44.
View Raw
More Information
⬅️ Previous capture (2023-07-10)
-=-=-=-=-=-=-
[](https://travis-ci.org/mity/md4c)
[](https://ci.appveyor.com/project/mity/md4c/branch/master)
[](https://scan.coverity.com/projects/mity-md4c)
[](https://codecov.io/github/mity/md4c)
# MD4C Readme
- Home: http://github.com/mity/md4c
- Wiki: http://github.com/mity/md4c/wiki
MD4C stands for "Markdown for C" and, unsurprisingly, it is a C Markdown parser
implementation.
## What is Markdown
In short, Markdown is the markup language this `README.md` file is written in.
The following resources can explain more if you are unfamiliar with it:
- [Wikipedia article](http://en.wikipedia.org/wiki/Markdown)
- [CommonMark site](http://commonmark.org)
## What is MD4C
MD4C is C Markdown parser with the following features:
- **Compliance:** Generally MD4C aims to be compliant to the latest version of
[CommonMark specification](http://spec.commonmark.org/). Right now we are
fully compliant to CommonMark 0.28.
- **Extensions:** MD4C supports some commonly requested and accepted extensions.
See below.
- **Compactness:** MD4C is implemented in one source file and one header file.
- **Embedding:** MD4C is easy to reuse in other projects, its API is very
straightforward: There is actually just one function, `md_parse()`.
- **Push model:** MD4C parses the complete document and calls callback
functions provided by the application for each start/end of block, start/end
of a span, and with any textual contents.
- **Portability:** MD4C builds and works on Windows and Linux, and it should
be fairly simple to make it run also on most other systems.
- **Encoding:** MD4C can be compiled to recognize ASCII-only control characters,
UTF-8 and, on Windows, also UTF-16, i.e. what is on Windows commonly called
just "Unicode". See more details below.
- **Permissive license:** MD4C is available under the MIT license.
- **Performance:** MD4C is very fast. Preliminary tests show it's quite faster
then [Hoedown](https://github.com/hoedown/hoedown) or
[Cmark](https://github.com/jgm/cmark).
## Using MD4C
The parser is implemented in a single C source file `md4c.c` and its
accompanying header `md4c.h`.
The main provided function is `md_parse()`. It takes a text in Markdown syntax
as an input and a pointer to renderer structure which holds pointers to few
callback functions.
As `md_parse()` processes the input, it calls the appropriate callbacks
allowing application to convert it into another format or render it onto
the screen.
More comprehensive guide can be found in the header `md4c.h` and also
on [MD4C wiki](http://github.com/mity/md4c/wiki).
Example implementation of simple renderer is available in the `md2html`
directory which implements a conversion utility from Markdown to HTML.
## Markdown Extensions
The default behavior is to recognize only elements defined by the [CommonMark
specification](http://spec.commonmark.org/).
However with appropriate renderer flags, the behavior can be tuned to enable
some extensions or allowing some deviations from the specification.
* With the flag `MD_FLAG_COLLAPSEWHITESPACE`, non-trivial whitespace is
collapsed into a single space.
* With the flag `MD_FLAG_TABLES`, GitHub-style tables are supported.
* With the flag `MD_FLAG_STRIKETHROUGH`, strikethrough spans are enabled
(text enclosed in tilde marks, e.g. '~foo bar~').
* With the flag `MD_FLAG_PERMISSIVEURLAUTOLINKS` permissive URL autolinks
(not enclosed in `<` and `>`) are supported.
* With the flag `MD_FLAG_PERMISSIVEAUTOLINKS`, ditto for e-mail autolinks.
* With the flag `MD_FLAG_PERMISSIVEWWWAUTOLINKS` permissive WWW autolinks
(without any scheme specified; `http:` is assumed) are supported.
* With the flag `MD_FLAG_NOHTMLSPANS` or `MD_FLAG_NOHTML`, raw inline HTML
or raw HTML blocks respectively are disabled.
* With the flag `MD_FLAG_NOINDENTEDCODEBLOCKS`, indented code blocks are
disabled.
## Input/Output Encoding
The CommonMark specification generally assumes UTF-8 input, but under closer
inspection, Unicode plays any role in few very specific situations when parsing
Markdown documents:
* For detection of word boundary when processing emphasis and strong emphasis,
some classification of Unicode character (whitespace, punctuation) is used.
* For (case-insensitive) matching of a link reference with corresponding link
reference definition, Unicode case folding is used.
* For translating HTML entities (e.g. `&`) and numeric character
references (e.g. `#` or `ಫ`) into their Unicode equivalents.
However MD4C leaves this translation on the renderer/application; as the
renderer is supposed to really know output encoding and whether it really
needs to perform this kind of translation. (Consider that a renderer
converting Markdown to HTML may leave the entities untranslated and defer
the work to a web browser.)
MD4C relies on this property of the CommonMark and the implementation is, to
a large degree, encoding-agnostic. Most of MD4C code only assumes that the
encoding of your choice is compatible with ASCII, i.e. that the codepoints
below 128 have the same numeric values as ASCII.
Any input MD4C does not understand is simply seen as part of the document text
and sent to the renderer's callback functions unchanged.
The two situations where MD4C has to understand Unicode are handled accordingly
to the following preprocessor macros:
* If preprocessor macro `MD4C_USE_UTF8` is defined, MD4C assumes UTF-8
for word boundary detection and case-folding.
* On Windows, if preprocessor macro `MD4C_USE_UTF16` is defined, MD4C uses
`WCHAR` instead of `char` and assumes UTF-16 encoding in those situations.
(UTF-16 is what Windows developers usually call just "Unicode" and what
Win32API works with.)
* By default (when none of the macros is defined), ASCII-only mode is used
even in the specific situations. That effectively means that non-ASCII
whitespace or punctuation characters won't be recognized as such and that
case-folding is performed only on ASCII letters (i.e. `[a-zA-Z]`).
(Adding support for yet another encodings should be relatively simple due
the isolation of the respective code.)
## License
MD4C is covered with MIT license, see the file `LICENSE.md`.
## Reporting Bugs
If you encounter any bug, please be so kind and report it. Unheard bugs cannot
get fixed. You can submit bug reports here:
- http://github.com/mity/md4c/issues