README.md (view raw)
1Blackfriday
2===========
3
4Blackfriday is a [Markdown][1] processor implemented in [Go][2]. It
5is paranoid about its input (so you can safely feed it user-supplied
6data), it is fast, it supports common extensions (tables, smart
7punctuation substitutions, etc.), and it is safe for all utf-8
8(unicode) input.
9
10HTML output is currently supported, along with Smartypants
11extensions. An experimental LaTeX output engine is also included.
12
13It started as a translation from C of [upskirt][3].
14
15
16Installation
17------------
18
19Assuming you have recent version of Go installed, along with git:
20
21 goinstall github.com/russross/blackfriday
22
23will download, compile, and install the package into
24`$GOROOT/src/pkg/github.com/russross/blackfriday`.
25
26For basic usage, it is as simple as getting your input into a byte
27slice and calling:
28
29 output := blackfriday.MarkdownBasic(input)
30
31This renders it with no extensions enabled. To get a more useful
32feature set, use this instead:
33
34 output := blackfriday.MarkdownCommon(input)
35
36If you want to customize the set of options, first get a renderer
37(currently either the HTML or LaTeX output engines), then use it to
38call the more general `Markdown` function. For examples, see the
39implementations of `MarkdownBasic` and `MarkdownCommon` in
40`markdown.go`.
41
42You can also check out `example/main.go` for a more complete example
43of how to use it. Run `gomake` in that directory to build a simple
44command-line markdown tool:
45
46 cd $GOROOT/src/pkg/github.com/russross/blackfriday/example
47 gomake
48
49will build the binary `markdown` in the `example` directory. This is
50a statically-linked binary that can be copied to wherever you need
51it without worrying about dependencies and library versions.
52
53
54Features
55--------
56
57All features of upskirt are supported, including:
58
59* **Compatibility**. The Markdown v1.0.3 test suite passes with
60 the `--tidy` option. Without `--tidy`, the differences are
61 mostly in whitespace and entity escaping, where blackfriday is
62 more consistent and cleaner.
63
64* **Common extensions**, including table support, fenced code
65 blocks, autolinks, strikethroughs, non-strict emphasis, etc.
66
67* **Safety**. Blackfriday is paranoid when parsing, making it safe
68 to feed untrusted user input without fear of bad things
69 happening. The test suite stress tests this and there are no
70 known inputs that make it crash. If you find one, please let me
71 know and send me the input that does it.
72
73* **Fast processing**. It is fast enough to render on-demand in
74 most web applications without having to cache the output.
75
76* **Thread safety**. You can run multiple parsers is different
77 goroutines without ill effect. There is no dependence on global
78 shared state.
79
80* **Minimal dependencies**. Blackfriday only depends on standard
81 library packages in Go. The source code is pretty
82 self-contained, so it is easy to add to any project, including
83 Google App Engine projects.
84
85* **Standards compliant**. Output successfully validates using the
86 W3C validation tool for HTML 4.01 and XHTML 1.0 Transitional.
87
88
89Extensions
90----------
91
92In addition to the standard markdown syntax, this package
93implements the following extensions:
94
95* **Intra-word emphasis supression**. The `_` character is
96 commonly used inside words when discussing code, so having
97 markdown interpret it as an emphasis command is usually the
98 wrong thing. Blackfriday lets you treat all emphasis markers as
99 normal characters when they occur inside a word.
100
101* **Tables**. Tables can be created by drawing them in the input
102 using a simple syntax:
103
104 Name | Age
105 --------|------
106 Bob | 27
107 Alice | 23
108
109* **Fenced code blocks**. In addition to the normal 4-space
110 indentation to mark code blocks, you can explicitly mark them
111 and supply a language (to make syntax highlighting simple). Just
112 mark it like this:
113
114 ``` go
115 func getTrue() bool {
116 return true
117 }
118 ```
119
120 You can use 3 or more backticks to mark the beginning of the
121 block, and the same number to mark the end of the block.
122
123* **Autolinking**. Blackfriday can find URLs that have not been
124 explicitly marked as links and turn them into links.
125
126* **Strikethrough**. Use two tildes (`~~`) to mark text that
127 should be crossed out.
128
129* **Hard line breaks**. With this extension enabled (it is off by
130 default in the `MarkdownBasic` and `MarkdownCommon` convenience
131 functions), newlines in the input translate into line breaks in
132 the output.
133
134* **Smart quotes**. Smartypants-style punctuation substitution is
135 supported, turning normal double- and single-quote marks into
136 curly quotes, etc.
137
138* **LaTeX-style dash parsing** is an additional option, where `--`
139 is translated into `–`, and `---` is translated into
140 `—`. This differs from most smartypants processors, which
141 turn a single hyphen into an ndash and a double hyphen into an
142 mdash.
143
144* **Smart fractions**, where anything that looks like a fraction
145 is translated into suitable HTML (instead of just a few special
146 cases like most smartypant processors). For example, `4/5`
147 becomes `<sup>4</sup>⁄<sub>5</sub>`, which renders as
148 <sup>4</sup>⁄<sub>5</sub>.
149
150
151LaTeX Output
152------------
153
154A rudimentary LaTeX rendering backend is also included. To see an
155example of its usage, see `main.go`:
156
157It renders some basic documents, but is only experimental at this
158point. In particular, it does not do any inline escaping, so input
159that happens to look like LaTeX code will be passed through without
160modification.
161
162
163Todo
164----
165
166* More unit testing
167* Markdown pretty-printer output engine
168* Improve unicode support. It does not understand all unicode
169 rules (about what constitutes a letter, a punctuation symbol,
170 etc.), so it may fail to detect word boundaries correctly in
171 some instances. It is safe on all utf-8 input.
172
173
174License
175-------
176
177Blackfriday is distributed under the Simplified BSD License:
178
179> Copyright © 2011 Russ Ross. All rights reserved.
180>
181> Redistribution and use in source and binary forms, with or without modification, are
182> permitted provided that the following conditions are met:
183>
184> 1. Redistributions of source code must retain the above copyright notice, this list of
185> conditions and the following disclaimer.
186>
187> 2. Redistributions in binary form must reproduce the above copyright notice, this list
188> of conditions and the following disclaimer in the documentation and/or other materials
189> provided with the distribution.
190>
191> THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER ``AS IS'' AND ANY EXPRESS OR IMPLIED
192> WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
193> FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> OR
194> CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
195> CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
196> SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
197> ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
198> NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
199> ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
200>
201> The views and conclusions contained in the software and documentation are those of the
202> authors and should not be interpreted as representing official policies, either expressed
203> or implied, of the copyright holder.
204
205
206 [1]: http://daringfireball.net/projects/markdown/ "Markdown"
207 [2]: http://golang.org/ "Go Language"
208 [3]: http://github.com/tanoku/upskirt "Upskirt"