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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 itself is based on the parser used by peg-markdown.
Support for HTML output is implemented, but Groff and LaTeX output have not been ported. The output is identical to that of peg-markdown.
I try to keep the grammar in sync with the C version, by cherry-picking relevant changes. In the commit history the corresponding revisions have a suffix [jgm/peg-markdown].
A simple benchmark has been done by comparing the execution times 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.
The C version is still around 1.3x faster than the Go version.
Installation
Provided you have a copy of Go 1, and git is available,
go get github.com/knieriem/markdown
should download and install the package according to your GOPATH settings.
See doc.go for an example how to use the package. There has been an API change recently: Where you previously wrote
buf, err := ioutil.ReadAll(os.Stdin)
...
doc := markdown.Parse(string(buf), markdown.Extensions{Smart: true})
doc.WriteHtml(w)
you would now write:
p := markdown.NewParser(&markdown.Extensions{Smart: true})
w := bufio.NewWriter(os.Stdout)
p.Markdown(os.Stdin, markdown.ToHTML(w))
w.Flush()
One purpose of the change is to have a Parser that can be reused between invocations of the converter.
To create the command line program markdown, run
go build github.com/knieriem/markdown/cmd/markdown
the binary should then be available in the current directory.
To run tests, type
go test github.com/knieriem/markdown
At the moment, tests are based on the .text files from the Markdown 1.0.3 test suite created by John Gruber, imported from peg-markdown. The output of the conversion of these .text files to html is compared to the output of peg-markdown.
Development
There is not yet a way to create a Go source file like
parser.leg.go automatically from another file, parser.leg,
when building packages and commands using the Go tool. To make
markdown installable using go get, parser.leg.go has
been added to the VCS.
Make parser will update parser.leg.go using leg – which
is part of knieriem/peg at github –, if parser.leg has
been changed, or if the Go file is missing. If a copy of peg
is not yet present on your system, run
go get github.com/knieriem/peg
Then make parser should succeed.
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
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.
Todo
- Port tables and perhaps other extensions from fletcher/peg-multimarkdown.
Subdirectory Index
- cmd/markdown – command line program
markdown