Standards compliant, fast, secure markdown processing library in C
Sundown is a Markdown parser based on the original code of the
Upskirt library by Natacha Porté.
Fully standards compliant
Sundown passes out of the box the official Markdown v1.0.0 and v1.0.3
test suites, and has been extensively tested with additional corner cases
to make sure its output is as sane as possible at all times.
Massive extension support
Sundown has optional support for several (unofficial) Markdown extensions,
such as non-strict emphasis, fenced code blocks, tables, autolinks,
strikethrough and more.
UTF-8 aware
Sundown is fully UTF-8 aware, both when parsing the source document and when
generating the resulting (X)HTML code.
Tested & Ready to be used on production
Sundown has been extensively security audited, and includes protection against
all possible DOS attacks (stack overflows, out of memory situations, malformed
Markdown syntax…) and against client attacks through malicious embedded HTML.
We’ve worked very hard to make Sundown never crash or run out of memory
under any input. Sundown renders all the Markdown content in GitHub and so
far hasn’t crashed a single time.
Customizable renderers
Sundown is not stuck with XHTML output: the Markdown parser of the library
is decoupled from the renderer, so it’s trivial to extend the library with
custom renderers. A fully functional (X)HTML renderer is included.
Optimized for speed
Sundown is written in C, with a special emphasis on performance. When wrapped
on a dynamic language such as Python or Ruby, it has shown to be up to 40
times faster than other native alternatives.
Zero-dependency
Sundown is a zero-dependency library composed of 3 .c files and their headers.
No dependencies, no bullshit. Only standard C99 that builds everywhere.
Sundown is based on the original Upskirt parser by Natacha Porté, with many additions
by Vicent Marti (@vmg) and contributions from the following authors:
Ben Noordhuis, Bruno Michel, Joseph Koshy, Krzysztof Kowalczyk, Samuel Bronson,
Shuhei Tanuma
Sundown is available from other programming languages thanks to these bindings developed
by our awesome contributors.
Sundown is all about security. If you find a (potential) security vulnerability in the
library, or a way to make it crash through malicious input, please report it to us,
either directly via email or by opening an Issue on GitHub, and help make the web safer
for everybody.
Given that the Markdown spec makes no provision for Unicode character handling, Sundown
takes a conservative approach towards deciding which extended characters trigger Markdown
features:
Punctuation characters outside of the U+007F codepoint are not handled as punctuation.
They are considered as normal, in-word characters for word-boundary checks.
Whitespace characters outside of the U+007F codepoint are not considered as
whitespace. They are considered as normal, in-word characters for word-boundary checks.
There is nothing to install. Sundown is composed of 3 .c files (markdown.c,
buffer.c and array.c), so just throw them in your project. Zero-dependency means
zero-dependency. You might want to include render/html.c if you want to use the
included XHTML renderer, or write your own renderer. Either way, it’s all fun and joy.
If you are hardcore, you can use the included Makefile to build Sundown into a dynamic
library, or to build the sample sundown executable, which is just a commandline
Markdown to XHTML parser. (If gcc gives you grief about -fPIC, e.g. with MinGW, try
make MFLAGS= instead of just make.)
Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.