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
378 if extensions&Autolink != 0 {
379 p.inlineCallback[':'] = autoLink
380 }
381
382 if extensions&Footnotes != 0 {
383 p.notes = make([]*reference, 0)
384 }
385
386 first := firstPass(p, input)
387 second := secondPass(p, first)
388 return second
389}
390
391// first pass:
392// - extract references
393// - expand tabs
394// - normalize newlines
395// - copy everything else
396func firstPass(p *parser, input []byte) []byte {
397 var out bytes.Buffer
398 tabSize := TabSizeDefault
399 if p.flags&TabSizeEight != 0 {
400 tabSize = TabSizeDouble
401 }
402 beg, end := 0, 0
403 lastFencedCodeBlockEnd := 0
404 for beg < len(input) { // iterate over lines
405 if end = isReference(p, input[beg:], tabSize); end > 0 {
406 beg += end
407 } else { // skip to the next line
408 end = beg
409 for end < len(input) && input[end] != '\n' && input[end] != '\r' {
410 end++
411 }
412
413 if p.flags&FencedCode != 0 {
414 // track fenced code block boundaries to suppress tab expansion
415 // inside them:
416 if beg >= lastFencedCodeBlockEnd {
417 if i := p.fencedCode(&out, input[beg:], false); i > 0 {
418 lastFencedCodeBlockEnd = beg + i
419 }
420 }
421 }
422
423 // add the line body if present
424 if end > beg {
425 if end < lastFencedCodeBlockEnd { // Do not expand tabs while inside fenced code blocks.
426 out.Write(input[beg:end])
427 } else {
428 expandTabs(&out, input[beg:end], tabSize)
429 }
430 }
431 out.WriteByte('\n')
432
433 if end < len(input) && input[end] == '\r' {
434 end++
435 }
436 if end < len(input) && input[end] == '\n' {
437 end++
438 }
439
440 beg = end
441 }
442 }
443
444 // empty input?
445 if out.Len() == 0 {
446 out.WriteByte('\n')
447 }
448
449 return out.Bytes()
450}
451
452// second pass: actual rendering
453func secondPass(p *parser, input []byte) []byte {
454 var output bytes.Buffer
455
456 p.r.DocumentHeader(&output)
457 p.block(&output, input)
458
459 if p.flags&Footnotes != 0 && len(p.notes) > 0 {
460 p.r.BeginFootnotes(&output)
461 flags := ListItemBeginningOfList
462 for i := 0; i < len(p.notes); i += 1 {
463 ref := p.notes[i]
464 var buf bytes.Buffer
465 if ref.hasBlock {
466 flags |= ListItemContainsBlock
467 p.block(&buf, ref.title)
468 } else {
469 p.inline(&buf, ref.title)
470 }
471 p.r.FootnoteItem(&output, ref.link, buf.Bytes(), flags)
472 flags &^= ListItemBeginningOfList | ListItemContainsBlock
473 }
474 p.r.EndFootnotes(&output)
475 }
476
477 p.r.DocumentFooter(&output)
478
479 if p.nesting != 0 {
480 panic("Nesting level did not end at zero")
481 }
482
483 return output.Bytes()
484}
485
486//
487// Link references
488//
489// This section implements support for references that (usually) appear
490// as footnotes in a document, and can be referenced anywhere in the document.
491// The basic format is:
492//
493// [1]: http://www.google.com/ "Google"
494// [2]: http://www.github.com/ "Github"
495//
496// Anywhere in the document, the reference can be linked by referring to its
497// label, i.e., 1 and 2 in this example, as in:
498//
499// This library is hosted on [Github][2], a git hosting site.
500//
501// Actual footnotes as specified in Pandoc and supported by some other Markdown
502// libraries such as php-markdown are also taken care of. They look like this:
503//
504// This sentence needs a bit of further explanation.[^note]
505//
506// [^note]: This is the explanation.
507//
508// Footnotes should be placed at the end of the document in an ordered list.
509// Inline footnotes such as:
510//
511// Inline footnotes^[Not supported.] also exist.
512//
513// are not yet supported.
514
515// References are parsed and stored in this struct.
516type reference struct {
517 link []byte
518 title []byte
519 noteId int // 0 if not a footnote ref
520 hasBlock bool
521 text []byte
522}
523
524func (r *reference) String() string {
525 return fmt.Sprintf("{link: %q, title: %q, text: %q, noteId: %d, hasBlock: %v}",
526 r.link, r.title, r.text, r.noteId, r.hasBlock)
527}
528
529// Check whether or not data starts with a reference link.
530// If so, it is parsed and stored in the list of references
531// (in the render struct).
532// Returns the number of bytes to skip to move past it,
533// or zero if the first line is not a reference.
534func isReference(p *parser, data []byte, tabSize int) int {
535 // up to 3 optional leading spaces
536 if len(data) < 4 {
537 return 0
538 }
539 i := 0
540 for i < 3 && data[i] == ' ' {
541 i++
542 }
543
544 noteId := 0
545
546 // id part: anything but a newline between brackets
547 if data[i] != '[' {
548 return 0
549 }
550 i++
551 if p.flags&Footnotes != 0 {
552 if i < len(data) && data[i] == '^' {
553 // we can set it to anything here because the proper noteIds will
554 // be assigned later during the second pass. It just has to be != 0
555 noteId = 1
556 i++
557 }
558 }
559 idOffset := i
560 for i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != ']' {
561 i++
562 }
563 if i >= len(data) || data[i] != ']' {
564 return 0
565 }
566 idEnd := i
567
568 // spacer: colon (space | tab)* newline? (space | tab)*
569 i++
570 if i >= len(data) || data[i] != ':' {
571 return 0
572 }
573 i++
574 for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
575 i++
576 }
577 if i < len(data) && (data[i] == '\n' || data[i] == '\r') {
578 i++
579 if i < len(data) && data[i] == '\n' && data[i-1] == '\r' {
580 i++
581 }
582 }
583 for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
584 i++
585 }
586 if i >= len(data) {
587 return 0
588 }
589
590 var (
591 linkOffset, linkEnd int
592 titleOffset, titleEnd int
593 lineEnd int
594 raw []byte
595 hasBlock bool
596 )
597
598 if p.flags&Footnotes != 0 && noteId != 0 {
599 linkOffset, linkEnd, raw, hasBlock = scanFootnote(p, data, i, tabSize)
600 lineEnd = linkEnd
601 } else {
602 linkOffset, linkEnd, titleOffset, titleEnd, lineEnd = scanLinkRef(p, data, i)
603 }
604 if lineEnd == 0 {
605 return 0
606 }
607
608 // a valid ref has been found
609
610 ref := &reference{
611 noteId: noteId,
612 hasBlock: hasBlock,
613 }
614
615 if noteId > 0 {
616 // reusing the link field for the id since footnotes don't have links
617 ref.link = data[idOffset:idEnd]
618 // if footnote, it's not really a title, it's the contained text
619 ref.title = raw
620 } else {
621 ref.link = data[linkOffset:linkEnd]
622 ref.title = data[titleOffset:titleEnd]
623 }
624
625 // id matches are case-insensitive
626 id := string(bytes.ToLower(data[idOffset:idEnd]))
627
628 p.refs[id] = ref
629
630 return lineEnd
631}
632
633func scanLinkRef(p *parser, data []byte, i int) (linkOffset, linkEnd, titleOffset, titleEnd, lineEnd int) {
634 // link: whitespace-free sequence, optionally between angle brackets
635 if data[i] == '<' {
636 i++
637 }
638 linkOffset = i
639 for i < len(data) && data[i] != ' ' && data[i] != '\t' && data[i] != '\n' && data[i] != '\r' {
640 i++
641 }
642 if i == len(data) {
643 return
644 }
645 linkEnd = i
646 if data[linkOffset] == '<' && data[linkEnd-1] == '>' {
647 linkOffset++
648 linkEnd--
649 }
650
651 // optional spacer: (space | tab)* (newline | '\'' | '"' | '(' )
652 for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
653 i++
654 }
655 if i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != '\'' && data[i] != '"' && data[i] != '(' {
656 return
657 }
658
659 // compute end-of-line
660 if i >= len(data) || data[i] == '\r' || data[i] == '\n' {
661 lineEnd = i
662 }
663 if i+1 < len(data) && data[i] == '\r' && data[i+1] == '\n' {
664 lineEnd++
665 }
666
667 // optional (space|tab)* spacer after a newline
668 if lineEnd > 0 {
669 i = lineEnd + 1
670 for i < len(data) && (data[i] == ' ' || data[i] == '\t') {
671 i++
672 }
673 }
674
675 // optional title: any non-newline sequence enclosed in '"() alone on its line
676 if i+1 < len(data) && (data[i] == '\'' || data[i] == '"' || data[i] == '(') {
677 i++
678 titleOffset = i
679
680 // look for EOL
681 for i < len(data) && data[i] != '\n' && data[i] != '\r' {
682 i++
683 }
684 if i+1 < len(data) && data[i] == '\n' && data[i+1] == '\r' {
685 titleEnd = i + 1
686 } else {
687 titleEnd = i
688 }
689
690 // step back
691 i--
692 for i > titleOffset && (data[i] == ' ' || data[i] == '\t') {
693 i--
694 }
695 if i > titleOffset && (data[i] == '\'' || data[i] == '"' || data[i] == ')') {
696 lineEnd = titleEnd
697 titleEnd = i
698 }
699 }
700
701 return
702}
703
704// The first bit of this logic is the same as (*parser).listItem, but the rest
705// is much simpler. This function simply finds the entire block and shifts it
706// over by one tab if it is indeed a block (just returns the line if it's not).
707// blockEnd is the end of the section in the input buffer, and contents is the
708// extracted text that was shifted over one tab. It will need to be rendered at
709// the end of the document.
710func scanFootnote(p *parser, data []byte, i, indentSize int) (blockStart, blockEnd int, contents []byte, hasBlock bool) {
711 if i == 0 || len(data) == 0 {
712 return
713 }
714
715 // skip leading whitespace on first line
716 for i < len(data) && data[i] == ' ' {
717 i++
718 }
719
720 blockStart = i
721
722 // find the end of the line
723 blockEnd = i
724 for i < len(data) && data[i-1] != '\n' {
725 i++
726 }
727
728 // get working buffer
729 var raw bytes.Buffer
730
731 // put the first line into the working buffer
732 raw.Write(data[blockEnd:i])
733 blockEnd = i
734
735 // process the following lines
736 containsBlankLine := false
737
738gatherLines:
739 for blockEnd < len(data) {
740 i++
741
742 // find the end of this line
743 for i < len(data) && data[i-1] != '\n' {
744 i++
745 }
746
747 // if it is an empty line, guess that it is part of this item
748 // and move on to the next line
749 if p.isEmpty(data[blockEnd:i]) > 0 {
750 containsBlankLine = true
751 blockEnd = i
752 continue
753 }
754
755 n := 0
756 if n = isIndented(data[blockEnd:i], indentSize); n == 0 {
757 // this is the end of the block.
758 // we don't want to include this last line in the index.
759 break gatherLines
760 }
761
762 // if there were blank lines before this one, insert a new one now
763 if containsBlankLine {
764 raw.WriteByte('\n')
765 containsBlankLine = false
766 }
767
768 // get rid of that first tab, write to buffer
769 raw.Write(data[blockEnd+n : i])
770 hasBlock = true
771
772 blockEnd = i
773 }
774
775 if data[blockEnd-1] != '\n' {
776 raw.WriteByte('\n')
777 }
778
779 contents = raw.Bytes()
780
781 return
782}
783
784//
785//
786// Miscellaneous helper functions
787//
788//
789
790// Test if a character is a punctuation symbol.
791// Taken from a private function in regexp in the stdlib.
792func ispunct(c byte) bool {
793 for _, r := range []byte("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~") {
794 if c == r {
795 return true
796 }
797 }
798 return false
799}
800
801// Test if a character is a whitespace character.
802func isspace(c byte) bool {
803 return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v'
804}
805
806// Test if a character is letter.
807func isletter(c byte) bool {
808 return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
809}
810
811// Test if a character is a letter or a digit.
812// TODO: check when this is looking for ASCII alnum and when it should use unicode
813func isalnum(c byte) bool {
814 return (c >= '0' && c <= '9') || isletter(c)
815}
816
817// Replace tab characters with spaces, aligning to the next TAB_SIZE column.
818// always ends output with a newline
819func expandTabs(out *bytes.Buffer, line []byte, tabSize int) {
820 // first, check for common cases: no tabs, or only tabs at beginning of line
821 i, prefix := 0, 0
822 slowcase := false
823 for i = 0; i < len(line); i++ {
824 if line[i] == '\t' {
825 if prefix == i {
826 prefix++
827 } else {
828 slowcase = true
829 break
830 }
831 }
832 }
833
834 // no need to decode runes if all tabs are at the beginning of the line
835 if !slowcase {
836 for i = 0; i < prefix*tabSize; i++ {
837 out.WriteByte(' ')
838 }
839 out.Write(line[prefix:])
840 return
841 }
842
843 // the slow case: we need to count runes to figure out how
844 // many spaces to insert for each tab
845 column := 0
846 i = 0
847 for i < len(line) {
848 start := i
849 for i < len(line) && line[i] != '\t' {
850 _, size := utf8.DecodeRune(line[i:])
851 i += size
852 column++
853 }
854
855 if i > start {
856 out.Write(line[start:i])
857 }
858
859 if i >= len(line) {
860 break
861 }
862
863 for {
864 out.WriteByte(' ')
865 column++
866 if column%tabSize == 0 {
867 break
868 }
869 }
870
871 i++
872 }
873}
874
875// Find if a line counts as indented or not.
876// Returns number of characters the indent is (0 = not indented).
877func isIndented(data []byte, indentSize int) int {
878 if len(data) == 0 {
879 return 0
880 }
881 if data[0] == '\t' {
882 return 1
883 }
884 if len(data) < indentSize {
885 return 0
886 }
887 for i := 0; i < indentSize; i++ {
888 if data[i] != ' ' {
889 return 0
890 }
891 }
892 return indentSize
893}
894
895// Create a url-safe slug for fragments
896func slugify(in []byte) []byte {
897 if len(in) == 0 {
898 return in
899 }
900 out := make([]byte, 0, len(in))
901 sym := false
902
903 for _, ch := range in {
904 if isalnum(ch) {
905 sym = false
906 out = append(out, ch)
907 } else if sym {
908 continue
909 } else {
910 out = append(out, '-')
911 sym = true
912 }
913 }
914 var a, b int
915 var ch byte
916 for a, ch = range out {
917 if ch != '-' {
918 break
919 }
920 }
921 for b = len(out) - 1; b > 0; b-- {
922 if out[b] != '-' {
923 break
924 }
925 }
926 return out[a : b+1]
927}