markdown.go (view raw)
1//
2// Blackfriday Markdown Processor
3// Available at http://github.com/russross/blackfriday
4//
5// Copyright © 2011 Russ Ross <russ@russross.com>.
6// Distributed under the Simplified BSD License.
7// See README.md for details.
8//
9
10//
11//
12// Markdown parsing and processing
13//
14//
15
16// Blackfriday markdown processor.
17//
18// Translates plain text with simple formatting rules into HTML or LaTeX.
19package blackfriday
20
21import (
22 "bytes"
23 "fmt"
24 "strings"
25 "unicode/utf8"
26)
27
28const VERSION = "1.4"
29
30type Extensions int
31
32// These are the supported markdown parsing extensions.
33// OR these values together to select multiple extensions.
34const (
35 NoExtensions Extensions = 0
36 NoIntraEmphasis Extensions = 1 << iota // Ignore emphasis markers inside words
37 Tables // Render tables
38 FencedCode // Render fenced code blocks
39 Autolink // Detect embedded URLs that are not explicitly marked
40 Strikethrough // Strikethrough text using ~~test~~
41 LaxHTMLBlocks // Loosen up HTML block parsing rules
42 SpaceHeaders // Be strict about prefix header rules
43 HardLineBreak // Translate newlines into line breaks
44 TabSizeEight // Expand tabs to eight spaces instead of four
45 Footnotes // Pandoc-style footnotes
46 NoEmptyLineBeforeBlock // No need to insert an empty line to start a (code, quote, ordered list, unordered list) block
47 HeaderIDs // specify header IDs with {#id}
48 Titleblock // Titleblock ala pandoc
49 AutoHeaderIDs // Create the header ID from the text
50 BackslashLineBreak // Translate trailing backslashes into line breaks
51 DefinitionLists // Render definition lists
52
53 commonHtmlFlags HtmlFlags = UseXHTML | UseSmartypants |
54 SmartypantsFractions | SmartypantsDashes | SmartypantsLatexDashes
55
56 commonExtensions Extensions = NoIntraEmphasis | Tables | FencedCode |
57 Autolink | Strikethrough | SpaceHeaders | HeaderIDs |
58 BackslashLineBreak | DefinitionLists
59)
60
61type LinkType int
62
63// These are the possible flag values for the link renderer.
64// Only a single one of these values will be used; they are not ORed together.
65// These are mostly of interest if you are writing a new output format.
66const (
67 LinkTypeNotAutolink LinkType = iota
68 LinkTypeNormal
69 LinkTypeEmail
70)
71
72type ListType int
73
74// These are the possible flag values for the ListItem renderer.
75// Multiple flag values may be ORed together.
76// These are mostly of interest if you are writing a new output format.
77const (
78 ListTypeOrdered ListType = 1 << iota
79 ListTypeDefinition
80 ListTypeTerm
81
82 ListItemContainsBlock
83 ListItemBeginningOfList
84 ListItemEndOfList
85)
86
87type TableFlags int
88
89// These are the possible flag values for the table cell renderer.
90// Only a single one of these values will be used; they are not ORed together.
91// These are mostly of interest if you are writing a new output format.
92const (
93 TableAlignmentLeft = 1 << iota
94 TableAlignmentRight
95 TableAlignmentCenter = (TableAlignmentLeft | TableAlignmentRight)
96)
97
98// The size of a tab stop.
99const (
100 TabSizeDefault = 4
101 TabSizeDouble = 8
102)
103
104// blockTags is a set of tags that are recognized as HTML block tags.
105// Any of these can be included in markdown text without special escaping.
106var blockTags = map[string]struct{}{
107 "blockquote": struct{}{},
108 "del": struct{}{},
109 "div": struct{}{},
110 "dl": struct{}{},
111 "fieldset": struct{}{},
112 "form": struct{}{},
113 "h1": struct{}{},
114 "h2": struct{}{},
115 "h3": struct{}{},
116 "h4": struct{}{},
117 "h5": struct{}{},
118 "h6": struct{}{},
119 "iframe": struct{}{},
120 "ins": struct{}{},
121 "math": struct{}{},
122 "noscript": struct{}{},
123 "ol": struct{}{},
124 "pre": struct{}{},
125 "p": struct{}{},
126 "script": struct{}{},
127 "style": struct{}{},
128 "table": struct{}{},
129 "ul": struct{}{},
130
131 // HTML5
132 "address": struct{}{},
133 "article": struct{}{},
134 "aside": struct{}{},
135 "canvas": struct{}{},
136 "figcaption": struct{}{},
137 "figure": struct{}{},
138 "footer": struct{}{},
139 "header": struct{}{},
140 "hgroup": struct{}{},
141 "main": struct{}{},
142 "nav": struct{}{},
143 "output": struct{}{},
144 "progress": struct{}{},
145 "section": struct{}{},
146 "video": struct{}{},
147}
148
149// Renderer is the rendering interface.
150// This is mostly of interest if you are implementing a new rendering format.
151//
152// When a byte slice is provided, it contains the (rendered) contents of the
153// element.
154//
155// When a callback is provided instead, it will write the contents of the
156// respective element directly to the output buffer and return true on success.
157// If the callback returns false, the rendering function should reset the
158// output buffer as though it had never been called.
159//
160// Currently Html and Latex implementations are provided
161type Renderer interface {
162 // block-level callbacks
163 BlockCode(out *bytes.Buffer, text []byte, lang string)
164 BlockQuote(out *bytes.Buffer, text []byte)
165 BlockHtml(out *bytes.Buffer, text []byte)
166 BeginHeader(out *bytes.Buffer, level int, id string) int
167 EndHeader(out *bytes.Buffer, level int, id string, tocMarker int)
168 HRule(out *bytes.Buffer)
169 BeginList(out *bytes.Buffer, flags ListType)
170 EndList(out *bytes.Buffer, flags ListType)
171 ListItem(out *bytes.Buffer, text []byte, flags ListType)
172 BeginParagraph(out *bytes.Buffer)
173 EndParagraph(out *bytes.Buffer)
174 Table(out *bytes.Buffer, header []byte, body []byte, columnData []int)
175 TableRow(out *bytes.Buffer, text []byte)
176 TableHeaderCell(out *bytes.Buffer, text []byte, flags int)
177 TableCell(out *bytes.Buffer, text []byte, flags int)
178 BeginFootnotes(out *bytes.Buffer)
179 EndFootnotes(out *bytes.Buffer)
180 FootnoteItem(out *bytes.Buffer, name, text []byte, flags ListType)
181 TitleBlock(out *bytes.Buffer, text []byte)
182
183 // Span-level callbacks
184 AutoLink(out *bytes.Buffer, link []byte, kind LinkType)
185 CodeSpan(out *bytes.Buffer, text []byte)
186 DoubleEmphasis(out *bytes.Buffer, text []byte)
187 Emphasis(out *bytes.Buffer, text []byte)
188 Image(out *bytes.Buffer, link []byte, title []byte, alt []byte)
189 LineBreak(out *bytes.Buffer)
190 Link(out *bytes.Buffer, link []byte, title []byte, content []byte)
191 RawHtmlTag(out *bytes.Buffer, tag []byte)
192 TripleEmphasis(out *bytes.Buffer, text []byte)
193 StrikeThrough(out *bytes.Buffer, text []byte)
194 FootnoteRef(out *bytes.Buffer, ref []byte, id int)
195
196 // Low-level callbacks
197 Entity(out *bytes.Buffer, entity []byte)
198 NormalText(out *bytes.Buffer, text []byte)
199
200 // Header and footer
201 DocumentHeader(out *bytes.Buffer)
202 DocumentFooter(out *bytes.Buffer)
203
204 GetFlags() HtmlFlags
205}
206
207// Callback functions for inline parsing. One such function is defined
208// for each character that triggers a response when parsing inline data.
209type inlineParser func(p *parser, out *bytes.Buffer, data []byte, offset int) int
210
211// Parser holds runtime state used by the parser.
212// This is constructed by the Markdown function.
213type parser struct {
214 r Renderer
215 refOverride ReferenceOverrideFunc
216 refs map[string]*reference
217 inlineCallback [256]inlineParser
218 flags Extensions
219 nesting int
220 maxNesting int
221 insideLink bool
222
223 // Footnotes need to be ordered as well as available to quickly check for
224 // presence. If a ref is also a footnote, it's stored both in refs and here
225 // in notes. Slice is nil if footnotes not enabled.
226 notes []*reference
227}
228
229func (p *parser) getRef(refid string) (ref *reference, found bool) {
230 if p.refOverride != nil {
231 r, overridden := p.refOverride(refid)
232 if overridden {
233 if r == nil {
234 return nil, false
235 }
236 return &reference{
237 link: []byte(r.Link),
238 title: []byte(r.Title),
239 noteId: 0,
240 hasBlock: false,
241 text: []byte(r.Text)}, true
242 }
243 }
244 // refs are case insensitive
245 ref, found = p.refs[strings.ToLower(refid)]
246 return ref, found
247}
248
249//
250//
251// Public interface
252//
253//
254
255// Reference represents the details of a link.
256// See the documentation in Options for more details on use-case.
257type Reference struct {
258 // Link is usually the URL the reference points to.
259 Link string
260 // Title is the alternate text describing the link in more detail.
261 Title string
262 // Text is the optional text to override the ref with if the syntax used was
263 // [refid][]
264 Text string
265}
266
267// ReferenceOverrideFunc is expected to be called with a reference string and
268// return either a valid Reference type that the reference string maps to or
269// nil. If overridden is false, the default reference logic will be executed.
270// See the documentation in Options for more details on use-case.
271type ReferenceOverrideFunc func(reference string) (ref *Reference, overridden bool)
272
273// Options represents configurable overrides and callbacks (in addition to the
274// extension flag set) for configuring a Markdown parse.
275type Options struct {
276 // Extensions is a flag set of bit-wise ORed extension bits. See the
277 // Extensions flags defined in this package.
278 Extensions Extensions
279
280 // ReferenceOverride is an optional function callback that is called every
281 // time a reference is resolved.
282 //
283 // In Markdown, the link reference syntax can be made to resolve a link to
284 // a reference instead of an inline URL, in one of the following ways:
285 //
286 // * [link text][refid]
287 // * [refid][]
288 //
289 // Usually, the refid is defined at the bottom of the Markdown document. If
290 // this override function is provided, the refid is passed to the override
291 // function first, before consulting the defined refids at the bottom. If
292 // the override function indicates an override did not occur, the refids at
293 // the bottom will be used to fill in the link details.
294 ReferenceOverride ReferenceOverrideFunc
295}
296
297// MarkdownBasic is a convenience function for simple rendering.
298// It processes markdown input with no extensions enabled.
299func MarkdownBasic(input []byte) []byte {
300 // set up the HTML renderer
301 htmlFlags := UseXHTML
302 renderer := HtmlRenderer(htmlFlags, "", "")
303
304 // set up the parser
305 return MarkdownOptions(input, renderer, Options{Extensions: 0})
306}
307
308// Call Markdown with most useful extensions enabled
309// MarkdownCommon is a convenience function for simple rendering.
310// It processes markdown input with common extensions enabled, including:
311//
312// * Smartypants processing with smart fractions and LaTeX dashes
313//
314// * Intra-word emphasis suppression
315//
316// * Tables
317//
318// * Fenced code blocks
319//
320// * Autolinking
321//
322// * Strikethrough support
323//
324// * Strict header parsing
325//
326// * Custom Header IDs
327func MarkdownCommon(input []byte) []byte {
328 // set up the HTML renderer
329 renderer := HtmlRenderer(commonHtmlFlags, "", "")
330 return MarkdownOptions(input, renderer, Options{
331 Extensions: commonExtensions})
332}
333
334// Markdown is the main rendering function.
335// It parses and renders a block of markdown-encoded text.
336// The supplied Renderer is used to format the output, and extensions dictates
337// which non-standard extensions are enabled.
338//
339// To use the supplied Html or LaTeX renderers, see HtmlRenderer and
340// LatexRenderer, respectively.
341func Markdown(input []byte, renderer Renderer, extensions Extensions) []byte {
342 return MarkdownOptions(input, renderer, Options{
343 Extensions: extensions})
344}
345
346// MarkdownOptions is just like Markdown but takes additional options through
347// the Options struct.
348func MarkdownOptions(input []byte, renderer Renderer, opts Options) []byte {
349 // no point in parsing if we can't render
350 if renderer == nil {
351 return nil
352 }
353
354 extensions := opts.Extensions
355
356 // fill in the render structure
357 p := new(parser)
358 p.r = renderer
359 p.flags = extensions
360 p.refOverride = opts.ReferenceOverride
361 p.refs = make(map[string]*reference)
362 p.maxNesting = 16
363 p.insideLink = false
364
365 // register inline parsers
366 p.inlineCallback['*'] = emphasis
367 p.inlineCallback['_'] = emphasis
368 if extensions&Strikethrough != 0 {
369 p.inlineCallback['~'] = emphasis
370 }
371 p.inlineCallback['`'] = codeSpan
372 p.inlineCallback['\n'] = lineBreak
373 p.inlineCallback['['] = link
374 p.inlineCallback['<'] = leftAngle
375 p.inlineCallback['\\'] = escape
376 p.inlineCallback['&'] = entity
377 p.inlineCallback['!'] = maybeImage
378 p.inlineCallback['^'] = maybeInlineFootnote
379
380 if extensions&Autolink != 0 {
381 p.inlineCallback[':'] = autoLink
382 }
383
384 if extensions&Footnotes != 0 {
385 p.notes = make([]*reference, 0)
386 }
387
388 first := firstPass(p, input)
389 second := secondPass(p, first)
390 return second
391}
392
393// first pass:
394// - extract references
395// - expand tabs
396// - normalize newlines
397// - copy everything else
398func firstPass(p *parser, input []byte) []byte {
399 var out bytes.Buffer
400 tabSize := TabSizeDefault
401 if p.flags&TabSizeEight != 0 {
402 tabSize = TabSizeDouble
403 }
404 beg, end := 0, 0
405 lastFencedCodeBlockEnd := 0
406 for beg < len(input) { // iterate over lines
407 if end = isReference(p, input[beg:], tabSize); end > 0 {
408 beg += end
409 } else { // skip to the next line
410 end = beg
411 for end < len(input) && input[end] != '\n' && input[end] != '\r' {
412 end++
413 }
414
415 if p.flags&FencedCode != 0 {
416 // track fenced code block boundaries to suppress tab expansion
417 // inside them:
418 if beg >= lastFencedCodeBlockEnd {
419 if i := p.fencedCode(&out, input[beg:], false); i > 0 {
420 lastFencedCodeBlockEnd = beg + i
421 }
422 }
423 }
424
425 // add the line body if present
426 if end > beg {
427 if end < lastFencedCodeBlockEnd { // Do not expand tabs while inside fenced code blocks.
428 out.Write(input[beg:end])
429 } else {
430 expandTabs(&out, input[beg:end], tabSize)
431 }
432 }
433 out.WriteByte('\n')
434
435 if end < len(input) && input[end] == '\r' {
436 end++
437 }
438 if end < len(input) && input[end] == '\n' {
439 end++
440 }
441
442 beg = end
443 }
444 }
445
446 // empty input?
447 if out.Len() == 0 {
448 out.WriteByte('\n')
449 }
450
451 return out.Bytes()
452}
453
454// second pass: actual rendering
455func secondPass(p *parser, input []byte) []byte {
456 var output bytes.Buffer
457
458 p.r.DocumentHeader(&output)
459 p.block(&output, input)
460
461 if p.flags&Footnotes != 0 && len(p.notes) > 0 {
462 p.r.BeginFootnotes(&output)
463 flags := ListItemBeginningOfList
464 for i := 0; i < len(p.notes); i += 1 {
465 ref := p.notes[i]
466 var buf bytes.Buffer
467 if ref.hasBlock {
468 flags |= ListItemContainsBlock
469 p.block(&buf, ref.title)
470 } else {
471 p.inline(&buf, ref.title)
472 }
473 p.r.FootnoteItem(&output, ref.link, buf.Bytes(), flags)
474 flags &^= ListItemBeginningOfList | ListItemContainsBlock
475 }
476 p.r.EndFootnotes(&output)
477 }
478
479 p.r.DocumentFooter(&output)
480
481 if p.nesting != 0 {
482 panic("Nesting level did not end at zero")
483 }
484
485 return output.Bytes()
486}
487
488//
489// Link references
490//
491// This section implements support for references that (usually) appear
492// as footnotes in a document, and can be referenced anywhere in the document.
493// The basic format is:
494//
495// [1]: http://www.google.com/ "Google"
496// [2]: http://www.github.com/ "Github"
497//
498// Anywhere in the document, the reference can be linked by referring to its
499// label, i.e., 1 and 2 in this example, as in:
500//
501// This library is hosted on [Github][2], a git hosting site.
502//
503// Actual footnotes as specified in Pandoc and supported by some other Markdown
504// libraries such as php-markdown are also taken care of. They look like this:
505//
506// This sentence needs a bit of further explanation.[^note]
507//
508// [^note]: This is the explanation.
509//
510// Footnotes should be placed at the end of the document in an ordered list.
511// Inline footnotes such as:
512//
513// Inline footnotes^[Not supported.] also exist.
514//
515// are not yet supported.
516
517// References are parsed and stored in this struct.
518type reference struct {
519 link []byte
520 title []byte
521 noteId int // 0 if not a footnote ref
522 hasBlock bool
523 text []byte
524}
525
526func (r *reference) String() string {
527 return fmt.Sprintf("{link: %q, title: %q, text: %q, noteId: %d, hasBlock: %v}",
528 r.link, r.title, r.text, r.noteId, r.hasBlock)
529}
530
531// Check whether or not data starts with a reference link.
532// If so, it is parsed and stored in the list of references
533// (in the render struct).
534// Returns the number of bytes to skip to move past it,
535// or zero if the first line is not a reference.
536func isReference(p *parser, data []byte, tabSize int) int {
537 // up to 3 optional leading spaces
538 if len(data) < 4 {
539 return 0
540 }
541 i := 0
542 for i < 3 && data[i] == ' ' {
543 i++
544 }
545
546 noteId := 0
547
548 // id part: anything but a newline between brackets
549 if data[i] != '[' {
550 return 0
551 }
552 i++
553 if p.flags&Footnotes != 0 {
554 if i < len(data) && data[i] == '^' {
555 // we can set it to anything here because the proper noteIds will
556 // be assigned later during the second pass. It just has to be != 0
557 noteId = 1
558 i++
559 }
560 }
561 idOffset := i
562 for i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != ']' {
563 i++
564 }
565 if i >= len(data) || data[i] != ']' {
566 return 0
567 }
568 idEnd := i
569
570 // spacer: colon (space | tab)* newline? (space | tab)*
571 i++
572 if i >= len(data) || data[i] != ':' {
573 return 0
574 }
575 i++
576 for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
577 i++
578 }
579 if i < len(data) && (data[i] == '\n' || data[i] == '\r') {
580 i++
581 if i < len(data) && data[i] == '\n' && data[i-1] == '\r' {
582 i++
583 }
584 }
585 for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
586 i++
587 }
588 if i >= len(data) {
589 return 0
590 }
591
592 var (
593 linkOffset, linkEnd int
594 titleOffset, titleEnd int
595 lineEnd int
596 raw []byte
597 hasBlock bool
598 )
599
600 if p.flags&Footnotes != 0 && noteId != 0 {
601 linkOffset, linkEnd, raw, hasBlock = scanFootnote(p, data, i, tabSize)
602 lineEnd = linkEnd
603 } else {
604 linkOffset, linkEnd, titleOffset, titleEnd, lineEnd = scanLinkRef(p, data, i)
605 }
606 if lineEnd == 0 {
607 return 0
608 }
609
610 // a valid ref has been found
611
612 ref := &reference{
613 noteId: noteId,
614 hasBlock: hasBlock,
615 }
616
617 if noteId > 0 {
618 // reusing the link field for the id since footnotes don't have links
619 ref.link = data[idOffset:idEnd]
620 // if footnote, it's not really a title, it's the contained text
621 ref.title = raw
622 } else {
623 ref.link = data[linkOffset:linkEnd]
624 ref.title = data[titleOffset:titleEnd]
625 }
626
627 // id matches are case-insensitive
628 id := string(bytes.ToLower(data[idOffset:idEnd]))
629
630 p.refs[id] = ref
631
632 return lineEnd
633}
634
635func scanLinkRef(p *parser, data []byte, i int) (linkOffset, linkEnd, titleOffset, titleEnd, lineEnd int) {
636 // link: whitespace-free sequence, optionally between angle brackets
637 if data[i] == '<' {
638 i++
639 }
640 linkOffset = i
641 for i < len(data) && data[i] != ' ' && data[i] != '\t' && data[i] != '\n' && data[i] != '\r' {
642 i++
643 }
644 if i == len(data) {
645 return
646 }
647 linkEnd = i
648 if data[linkOffset] == '<' && data[linkEnd-1] == '>' {
649 linkOffset++
650 linkEnd--
651 }
652
653 // optional spacer: (space | tab)* (newline | '\'' | '"' | '(' )
654 for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
655 i++
656 }
657 if i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != '\'' && data[i] != '"' && data[i] != '(' {
658 return
659 }
660
661 // compute end-of-line
662 if i >= len(data) || data[i] == '\r' || data[i] == '\n' {
663 lineEnd = i
664 }
665 if i+1 < len(data) && data[i] == '\r' && data[i+1] == '\n' {
666 lineEnd++
667 }
668
669 // optional (space|tab)* spacer after a newline
670 if lineEnd > 0 {
671 i = lineEnd + 1
672 for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
673 i++
674 }
675 }
676
677 // optional title: any non-newline sequence enclosed in '"() alone on its line
678 if i+1 < len(data) && (data[i] == '\'' || data[i] == '"' || data[i] == '(') {
679 i++
680 titleOffset = i
681
682 // look for EOL
683 for i < len(data) && data[i] != '\n' && data[i] != '\r' {
684 i++
685 }
686 if i+1 < len(data) && data[i] == '\n' && data[i+1] == '\r' {
687 titleEnd = i + 1
688 } else {
689 titleEnd = i
690 }
691
692 // step back
693 i--
694 for i > titleOffset && (data[i] == ' ' || data[i] == '\t') {
695 i--
696 }
697 if i > titleOffset && (data[i] == '\'' || data[i] == '"' || data[i] == ')') {
698 lineEnd = titleEnd
699 titleEnd = i
700 }
701 }
702
703 return
704}
705
706// The first bit of this logic is the same as (*parser).listItem, but the rest
707// is much simpler. This function simply finds the entire block and shifts it
708// over by one tab if it is indeed a block (just returns the line if it's not).
709// blockEnd is the end of the section in the input buffer, and contents is the
710// extracted text that was shifted over one tab. It will need to be rendered at
711// the end of the document.
712func scanFootnote(p *parser, data []byte, i, indentSize int) (blockStart, blockEnd int, contents []byte, hasBlock bool) {
713 if i == 0 || len(data) == 0 {
714 return
715 }
716
717 // skip leading whitespace on first line
718 for i < len(data) && data[i] == ' ' {
719 i++
720 }
721
722 blockStart = i
723
724 // find the end of the line
725 blockEnd = i
726 for i < len(data) && data[i-1] != '\n' {
727 i++
728 }
729
730 // get working buffer
731 var raw bytes.Buffer
732
733 // put the first line into the working buffer
734 raw.Write(data[blockEnd:i])
735 blockEnd = i
736
737 // process the following lines
738 containsBlankLine := false
739
740gatherLines:
741 for blockEnd < len(data) {
742 i++
743
744 // find the end of this line
745 for i < len(data) && data[i-1] != '\n' {
746 i++
747 }
748
749 // if it is an empty line, guess that it is part of this item
750 // and move on to the next line
751 if p.isEmpty(data[blockEnd:i]) > 0 {
752 containsBlankLine = true
753 blockEnd = i
754 continue
755 }
756
757 n := 0
758 if n = isIndented(data[blockEnd:i], indentSize); n == 0 {
759 // this is the end of the block.
760 // we don't want to include this last line in the index.
761 break gatherLines
762 }
763
764 // if there were blank lines before this one, insert a new one now
765 if containsBlankLine {
766 raw.WriteByte('\n')
767 containsBlankLine = false
768 }
769
770 // get rid of that first tab, write to buffer
771 raw.Write(data[blockEnd+n : i])
772 hasBlock = true
773
774 blockEnd = i
775 }
776
777 if data[blockEnd-1] != '\n' {
778 raw.WriteByte('\n')
779 }
780
781 contents = raw.Bytes()
782
783 return
784}
785
786//
787//
788// Miscellaneous helper functions
789//
790//
791
792// Test if a character is a punctuation symbol.
793// Taken from a private function in regexp in the stdlib.
794func ispunct(c byte) bool {
795 for _, r := range []byte("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~") {
796 if c == r {
797 return true
798 }
799 }
800 return false
801}
802
803// Test if a character is a whitespace character.
804func isspace(c byte) bool {
805 return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v'
806}
807
808// Test if a character is letter.
809func isletter(c byte) bool {
810 return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
811}
812
813// Test if a character is a letter or a digit.
814// TODO: check when this is looking for ASCII alnum and when it should use unicode
815func isalnum(c byte) bool {
816 return (c >= '0' && c <= '9') || isletter(c)
817}
818
819// Replace tab characters with spaces, aligning to the next TAB_SIZE column.
820// always ends output with a newline
821func expandTabs(out *bytes.Buffer, line []byte, tabSize int) {
822 // first, check for common cases: no tabs, or only tabs at beginning of line
823 i, prefix := 0, 0
824 slowcase := false
825 for i = 0; i < len(line); i++ {
826 if line[i] == '\t' {
827 if prefix == i {
828 prefix++
829 } else {
830 slowcase = true
831 break
832 }
833 }
834 }
835
836 // no need to decode runes if all tabs are at the beginning of the line
837 if !slowcase {
838 for i = 0; i < prefix*tabSize; i++ {
839 out.WriteByte(' ')
840 }
841 out.Write(line[prefix:])
842 return
843 }
844
845 // the slow case: we need to count runes to figure out how
846 // many spaces to insert for each tab
847 column := 0
848 i = 0
849 for i < len(line) {
850 start := i
851 for i < len(line) && line[i] != '\t' {
852 _, size := utf8.DecodeRune(line[i:])
853 i += size
854 column++
855 }
856
857 if i > start {
858 out.Write(line[start:i])
859 }
860
861 if i >= len(line) {
862 break
863 }
864
865 for {
866 out.WriteByte(' ')
867 column++
868 if column%tabSize == 0 {
869 break
870 }
871 }
872
873 i++
874 }
875}
876
877// Find if a line counts as indented or not.
878// Returns number of characters the indent is (0 = not indented).
879func isIndented(data []byte, indentSize int) int {
880 if len(data) == 0 {
881 return 0
882 }
883 if data[0] == '\t' {
884 return 1
885 }
886 if len(data) < indentSize {
887 return 0
888 }
889 for i := 0; i < indentSize; i++ {
890 if data[i] != ' ' {
891 return 0
892 }
893 }
894 return indentSize
895}
896
897// Create a url-safe slug for fragments
898func slugify(in []byte) []byte {
899 if len(in) == 0 {
900 return in
901 }
902 out := make([]byte, 0, len(in))
903 sym := false
904
905 for _, ch := range in {
906 if isalnum(ch) {
907 sym = false
908 out = append(out, ch)
909 } else if sym {
910 continue
911 } else {
912 out = append(out, '-')
913 sym = true
914 }
915 }
916 var a, b int
917 var ch byte
918 for a, ch = range out {
919 if ch != '-' {
920 break
921 }
922 }
923 for b = len(out) - 1; b > 0; b-- {
924 if out[b] != '-' {
925 break
926 }
927 }
928 return out[a : b+1]
929}