130 lines
4.3 KiB
Markdown
130 lines
4.3 KiB
Markdown
This is an implementation of John Gruber's [markdown][] in
|
||
[Go][]. It is a translation of [peg-markdown][], written by
|
||
John MacFarlane in C, into Go. It is using a modified version
|
||
of Andrew J Snodgrass' PEG parser [peg][] -- now supporting
|
||
LEG grammars --, which is itself based on the parser used
|
||
by peg-markdown.
|
||
|
||
[markdown]: http://daringfireball.net/projects/markdown/
|
||
[peg-markdown]: https://github.com/jgm/peg-markdown
|
||
[peg]: https://github.com/pointlander/peg
|
||
[Go]: http://golang.org/
|
||
|
||
Support for HTML output is implemented, but Groff and LaTeX
|
||
output have not been ported. The output should be identical
|
||
to that of peg-markdown.
|
||
|
||
A simple benchmark has been done by comparing the
|
||
execution time of the Go binary (cmd/main.go) and the
|
||
original C implementation's binary needed for processing
|
||
a Markdown document, which had been created by
|
||
concatenating ten [Markdown syntax descriptions][syntax].
|
||
|
||
[syntax]: http://daringfireball.net/projects/markdown/syntax.text
|
||
|
||
In [December 2010][dec], the `8g` compiled Go version still was
|
||
around 3.5 times slower than the original C version.
|
||
|
||
[dec]: https://github.com/knieriem/markdown/commit/b3f7b3
|
||
|
||
In the meantime Go compilers and runtime have been improved,
|
||
which reduced the factor down to around 2.5 for both `8g` and `6g`
|
||
for the unmodified sources.
|
||
|
||
After some current changes to the peg/leg parser generator
|
||
the Markdown parser can take advantage of the *switch* optimization
|
||
now. This further reduced the execution time difference
|
||
to 1.9x for `6/8g`.
|
||
|
||
|
||
## Installation
|
||
|
||
Provided you have a recent copy of Go, and git is available,
|
||
|
||
goinstall github.com/knieriem/markdown
|
||
|
||
should install the package into
|
||
`$GOROOT/src/pkg/github.com/knieriem/markdown`, and build
|
||
it.
|
||
|
||
See doc.go for an example how to use the package.
|
||
|
||
To create the command line program *markdown,* run
|
||
|
||
cd $GOROOT/src/pkg/github.com/knieriem/markdown
|
||
gomake cmd
|
||
|
||
the binary should then be available in subdirectory *cmd.*
|
||
|
||
To run the Markdown 1.0.3 test suite, type
|
||
|
||
make mdtest
|
||
|
||
This will download peg-markdown, in case you have `git`
|
||
available, build cmd/markdown, and run the test suite.
|
||
|
||
The test suite will fail on one test, for the same reason which
|
||
applies to peg-markdown, because the grammar is the same.
|
||
See the [original README][] for details.
|
||
|
||
[original README]: https://github.com/jgm/peg-markdown/blob/master/README.markdown
|
||
|
||
## Development
|
||
|
||
[`Goinstall`][Goinstall] is creating its own Makefiles to build
|
||
packages, based on the `.go` files found in the directory.
|
||
It would not know about `parser.leg.go`, which had to be built
|
||
by `leg` from the `parser.leg` grammar source file first.
|
||
Because of this, to make *markdown* installable using
|
||
`goinstall`, `parser.leg.go` has been added to the VCS.
|
||
|
||
`Make` will update `parser.leg.go` using `leg`, which is part of
|
||
[knieriem/peg][] at github, if parser.leg has been changed. If
|
||
a copy of this package has not yet been downloaded -- i.e. no
|
||
directory `./peg` is present --, `make` will perform the
|
||
necessary steps automatically (run `make peg` to manually
|
||
download [knieriem/peg][]).
|
||
|
||
To update [knieriem/peg][] run `gomake update-peg`. This will
|
||
fetch available revisions from github, and remove the old
|
||
*leg* binary.
|
||
|
||
[goinstall]: http://golang.org/cmd/goinstall/
|
||
[knieriem/peg]: https://github.com/knieriem/peg
|
||
|
||
|
||
## Extensions
|
||
|
||
In addition to the extensions already present in peg-markdown,
|
||
this package also supports definition lists (option `-dlists`)
|
||
similar to the way they are described in the documentation of
|
||
[PHP Markdown Extra][].
|
||
|
||
Definitions (`<dd>...</dd>`) are implemented using [`ListTight`][ListTight]
|
||
and `ListLoose`, on which bullet lists and ordered lists are based
|
||
already. If there is an empty line between the definition title and
|
||
the first definition, a loose list is expected, a tight list otherwise.
|
||
|
||
As definition item markers both `:` and `~` can be used.
|
||
|
||
[PHP Markdown Extra]: http://michelf.com/projects/php-markdown/extra/#def-list
|
||
[ListTight]: https://github.com/knieriem/markdown/blob/master/parser.leg#L191
|
||
|
||
|
||
## Todo
|
||
|
||
* Implement tables
|
||
|
||
* Rename element key identifiers, so that they are not public
|
||
|
||
* Where appropriate, use more idiomatic Go code
|
||
|
||
## Subdirectory Index
|
||
|
||
* peg – PEG parser generator (modified) from Andrew J Snodgrass
|
||
|
||
* peg/leg – LEG parser generator, based on PEG
|
||
|
||
* cmd – command line program `markdown`
|
||
|