blackfriday/README.md

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>&frasl;<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"