README.md (view raw)
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Black Friday
============
This is an implementation of John Gruber's [markdown][1] in [Go][2].
It is a translation of the [upskirt][3] library written in C with a
few minor changes. It retains the paranoia of the original (it is
careful not to trust its input, and as such it should be safe to
feed it arbitrary user-supplied inputs). It also retains the
emphasis on high performance, and the source is almost as ugly as
the original.
HTML output is currently supported, along with Smartpants
extensions.
Installation
------------
Assuming you have recent version of Go installed, along with git:
goinstall github.com/russross/blackfriday
will download, compile, and install the package into
`$GOROOT/src/pkg/github.com/russross/blackfriday`.
Check out `example/main.go` for an example of how to use it. Run
`gomake` in that directory to build a simple command-line markdown
tool:
cd $GOROOT/src/pkg/github.com/russross/blackfriday/example
gomake
will build the binary `markdown` in the `example` directory.
Features
--------
All features of upskirt are supported, including:
* The Markdown v1.0.3 test suite passes with the `--tidy` option.
Without `--tidy`, the differences appear to be bugs/dubious
features in the original.
* Common extensions, including table support, fenced code blocks,
autolinks, strikethroughs, non-strict emphasis, etc.
* Paranoid parsing, making it safe to feed untrusted used input
without fear of bad things happening. There are still some
corner cases that are untested, but it is already more strict
than upskirt (Go's bounds-checking uncovered a few off-by-one
errors that were present in the C code).
* Good performance. I have not done rigorous benchmarking, but
informal testing suggests it is around 3.5x slower than upskirt.
This is an ugly, direct translation from the C code, so
the difference is unlikely to be related to differences in
coding style. There is a lot of bounds checking that is
duplicated (by user code for the application and again by code
the compiler generates) and there is some additional memory
management overhead, since I allocate and garbage collect
buffers instead of explicitly managing them as upskirt does.
* Minimal dependencies. blackfriday only depends on standard
library packages in Go. The source code is pretty
self-contained, so it is easy to add to any project.
Extensions
----------
In addition to the extensions offered by upskirt, this package
implements two additional Smartypants options:
* LaTeX-style dash parsing, where `--` is translated into
`–`, and `---` is translated into `—`
* Generic fractions, where anything that looks like a fraction
is translated into suitable HTML (instead of just a few special
cases). For example, `4/5` becomes `<sup>4</sup>⁄<sub>5</sub>`
LaTeX Output
------------
A rudimentary LaTeX rendering backend is also included. To see an
example of its usage, comment out this link in `main.go`:
renderer := blackfriday.HtmlRenderer(html_flags)
and uncomment this line:
renderer := blackfriday.LatexRenderer(0)
It renders some basic documents, but is only experimental at this point.
Todo
----
* Code cleanup
* Better code documentation
[1]: http://daringfireball.net/projects/markdown/ "Markdown"
[2]: http://golang.org/ "Go Language"
[3]: http://github.com/tanoku/upskirt "Upskirt"
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