markdown.go (view raw)
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// // Blackfriday Markdown Processor // Available at http://github.com/russross/blackfriday // // Copyright © 2011 Russ Ross <russ@russross.com>. // Distributed under the Simplified BSD License. // See README.md for details. // // // // Markdown parsing and processing // // // Blackfriday markdown processor. // // Translates plain text with simple formatting rules into HTML or LaTeX. package blackfriday import ( "bytes" "fmt" "strings" "unicode/utf8" ) const VERSION = "1.4" type Extensions int // These are the supported markdown parsing extensions. // OR these values together to select multiple extensions. const ( NoExtensions Extensions = 0 NoIntraEmphasis Extensions = 1 << iota // Ignore emphasis markers inside words Tables // Render tables FencedCode // Render fenced code blocks Autolink // Detect embedded URLs that are not explicitly marked Strikethrough // Strikethrough text using ~~test~~ LaxHTMLBlocks // Loosen up HTML block parsing rules SpaceHeaders // Be strict about prefix header rules HardLineBreak // Translate newlines into line breaks TabSizeEight // Expand tabs to eight spaces instead of four Footnotes // Pandoc-style footnotes NoEmptyLineBeforeBlock // No need to insert an empty line to start a (code, quote, ordered list, unordered list) block HeaderIDs // specify header IDs with {#id} Titleblock // Titleblock ala pandoc AutoHeaderIDs // Create the header ID from the text BackslashLineBreak // Translate trailing backslashes into line breaks DefinitionLists // Render definition lists commonHtmlFlags HtmlFlags = UseXHTML | UseSmartypants | SmartypantsFractions | SmartypantsDashes | SmartypantsLatexDashes commonExtensions Extensions = NoIntraEmphasis | Tables | FencedCode | Autolink | Strikethrough | SpaceHeaders | HeaderIDs | BackslashLineBreak | DefinitionLists ) type LinkType int // These are the possible flag values for the link renderer. // Only a single one of these values will be used; they are not ORed together. // These are mostly of interest if you are writing a new output format. const ( LinkTypeNotAutolink LinkType = iota LinkTypeNormal LinkTypeEmail ) type ListType int // These are the possible flag values for the ListItem renderer. // Multiple flag values may be ORed together. // These are mostly of interest if you are writing a new output format. const ( ListTypeOrdered ListType = 1 << iota ListTypeDefinition ListTypeTerm ListItemContainsBlock ListItemBeginningOfList ListItemEndOfList ) type TableFlags int // These are the possible flag values for the table cell renderer. // Only a single one of these values will be used; they are not ORed together. // These are mostly of interest if you are writing a new output format. const ( TableAlignmentLeft = 1 << iota TableAlignmentRight TableAlignmentCenter = (TableAlignmentLeft | TableAlignmentRight) ) // The size of a tab stop. const ( TabSizeDefault = 4 TabSizeDouble = 8 ) // blockTags is a set of tags that are recognized as HTML block tags. // Any of these can be included in markdown text without special escaping. var blockTags = map[string]struct{}{ "blockquote": struct{}{}, "del": struct{}{}, "div": struct{}{}, "dl": struct{}{}, "fieldset": struct{}{}, "form": struct{}{}, "h1": struct{}{}, "h2": struct{}{}, "h3": struct{}{}, "h4": struct{}{}, "h5": struct{}{}, "h6": struct{}{}, "iframe": struct{}{}, "ins": struct{}{}, "math": struct{}{}, "noscript": struct{}{}, "ol": struct{}{}, "pre": struct{}{}, "p": struct{}{}, "script": struct{}{}, "style": struct{}{}, "table": struct{}{}, "ul": struct{}{}, // HTML5 "address": struct{}{}, "article": struct{}{}, "aside": struct{}{}, "canvas": struct{}{}, "figcaption": struct{}{}, "figure": struct{}{}, "footer": struct{}{}, "header": struct{}{}, "hgroup": struct{}{}, "main": struct{}{}, "nav": struct{}{}, "output": struct{}{}, "progress": struct{}{}, "section": struct{}{}, "video": struct{}{}, } // Renderer is the rendering interface. // This is mostly of interest if you are implementing a new rendering format. // // When a byte slice is provided, it contains the (rendered) contents of the // element. // // When a callback is provided instead, it will write the contents of the // respective element directly to the output buffer and return true on success. // If the callback returns false, the rendering function should reset the // output buffer as though it had never been called. // // Currently Html and Latex implementations are provided type Renderer interface { // block-level callbacks BlockCode(text []byte, lang string) BlockQuote(text []byte) BlockHtml(text []byte) BeginHeader(level int, id string) EndHeader(level int, id string, header []byte) HRule() BeginList(flags ListType) EndList(flags ListType) ListItem(text []byte, flags ListType) BeginParagraph() EndParagraph() Table(header []byte, body []byte, columnData []int) TableRow(text []byte) TableHeaderCell(out *bytes.Buffer, text []byte, flags int) TableCell(out *bytes.Buffer, text []byte, flags int) BeginFootnotes() EndFootnotes() FootnoteItem(name, text []byte, flags ListType) TitleBlock(text []byte) // Span-level callbacks AutoLink(link []byte, kind LinkType) CodeSpan(text []byte) DoubleEmphasis(text []byte) Emphasis(text []byte) Image(link []byte, title []byte, alt []byte) LineBreak() Link(link []byte, title []byte, content []byte) RawHtmlTag(tag []byte) TripleEmphasis(text []byte) StrikeThrough(text []byte) FootnoteRef(ref []byte, id int) // Low-level callbacks Entity(entity []byte) NormalText(text []byte) // Header and footer DocumentHeader() DocumentFooter() GetFlags() HtmlFlags CaptureWrites(processor func()) []byte CopyWrites(processor func()) []byte Write(b []byte) (int, error) GetResult() []byte } // Callback functions for inline parsing. One such function is defined // for each character that triggers a response when parsing inline data. type inlineParser func(p *parser, data []byte, offset int) int // Parser holds runtime state used by the parser. // This is constructed by the Markdown function. type parser struct { r Renderer refOverride ReferenceOverrideFunc refs map[string]*reference inlineCallback [256]inlineParser flags Extensions nesting int maxNesting int insideLink bool // Footnotes need to be ordered as well as available to quickly check for // presence. If a ref is also a footnote, it's stored both in refs and here // in notes. Slice is nil if footnotes not enabled. notes []*reference doc *Node tip *Node // = doc oldTip *Node lastMatchedContainer *Node // = doc allClosed bool } func (p *parser) getRef(refid string) (ref *reference, found bool) { if p.refOverride != nil { r, overridden := p.refOverride(refid) if overridden { if r == nil { return nil, false } return &reference{ link: []byte(r.Link), title: []byte(r.Title), noteId: 0, hasBlock: false, text: []byte(r.Text)}, true } } // refs are case insensitive ref, found = p.refs[strings.ToLower(refid)] return ref, found } func (p *parser) finalize(block *Node) { above := block.Parent block.open = false p.tip = above } func (p *parser) addChild(node NodeType, offset uint32) *Node { for !p.tip.canContain(node) { p.finalize(p.tip) } newNode := NewNode(node) newNode.content = []byte{} p.tip.appendChild(newNode) p.tip = newNode return newNode } func (p *parser) closeUnmatchedBlocks() { if !p.allClosed { for p.oldTip != p.lastMatchedContainer { parent := p.oldTip.Parent p.finalize(p.oldTip) p.oldTip = parent } p.allClosed = true } } // // // Public interface // // // Reference represents the details of a link. // See the documentation in Options for more details on use-case. type Reference struct { // Link is usually the URL the reference points to. Link string // Title is the alternate text describing the link in more detail. Title string // Text is the optional text to override the ref with if the syntax used was // [refid][] Text string } // ReferenceOverrideFunc is expected to be called with a reference string and // return either a valid Reference type that the reference string maps to or // nil. If overridden is false, the default reference logic will be executed. // See the documentation in Options for more details on use-case. type ReferenceOverrideFunc func(reference string) (ref *Reference, overridden bool) // Options represents configurable overrides and callbacks (in addition to the // extension flag set) for configuring a Markdown parse. type Options struct { // Extensions is a flag set of bit-wise ORed extension bits. See the // Extensions flags defined in this package. Extensions Extensions // ReferenceOverride is an optional function callback that is called every // time a reference is resolved. // // In Markdown, the link reference syntax can be made to resolve a link to // a reference instead of an inline URL, in one of the following ways: // // * [link text][refid] // * [refid][] // // Usually, the refid is defined at the bottom of the Markdown document. If // this override function is provided, the refid is passed to the override // function first, before consulting the defined refids at the bottom. If // the override function indicates an override did not occur, the refids at // the bottom will be used to fill in the link details. ReferenceOverride ReferenceOverrideFunc } // MarkdownBasic is a convenience function for simple rendering. // It processes markdown input with no extensions enabled. func MarkdownBasic(input []byte) []byte { // set up the HTML renderer htmlFlags := UseXHTML renderer := HtmlRenderer(htmlFlags, "", "") // set up the parser return MarkdownOptions(input, renderer, Options{Extensions: 0}) } // Call Markdown with most useful extensions enabled // MarkdownCommon is a convenience function for simple rendering. // It processes markdown input with common extensions enabled, including: // // * Smartypants processing with smart fractions and LaTeX dashes // // * Intra-word emphasis suppression // // * Tables // // * Fenced code blocks // // * Autolinking // // * Strikethrough support // // * Strict header parsing // // * Custom Header IDs func MarkdownCommon(input []byte) []byte { // set up the HTML renderer renderer := HtmlRenderer(commonHtmlFlags, "", "") return MarkdownOptions(input, renderer, Options{ Extensions: commonExtensions}) } // Markdown is the main rendering function. // It parses and renders a block of markdown-encoded text. // The supplied Renderer is used to format the output, and extensions dictates // which non-standard extensions are enabled. // // To use the supplied Html or LaTeX renderers, see HtmlRenderer and // LatexRenderer, respectively. func Markdown(input []byte, renderer Renderer, extensions Extensions) []byte { return MarkdownOptions(input, renderer, Options{ Extensions: extensions}) } // MarkdownOptions is just like Markdown but takes additional options through // the Options struct. func MarkdownOptions(input []byte, renderer Renderer, opts Options) []byte { // no point in parsing if we can't render if renderer == nil { return nil } extensions := opts.Extensions // fill in the render structure p := new(parser) p.r = renderer p.flags = extensions p.refOverride = opts.ReferenceOverride p.refs = make(map[string]*reference) p.maxNesting = 16 p.insideLink = false docNode := NewNode(Document) p.doc = docNode p.tip = docNode p.oldTip = docNode p.lastMatchedContainer = docNode p.allClosed = true // register inline parsers p.inlineCallback['*'] = emphasis p.inlineCallback['_'] = emphasis if extensions&Strikethrough != 0 { p.inlineCallback['~'] = emphasis } p.inlineCallback['`'] = codeSpan p.inlineCallback['\n'] = lineBreak p.inlineCallback['['] = link p.inlineCallback['<'] = leftAngle p.inlineCallback['\\'] = escape p.inlineCallback['&'] = entity p.inlineCallback['!'] = maybeImage p.inlineCallback['^'] = maybeInlineFootnote if extensions&Autolink != 0 { p.inlineCallback['h'] = maybeAutoLink p.inlineCallback['m'] = maybeAutoLink p.inlineCallback['f'] = maybeAutoLink p.inlineCallback['H'] = maybeAutoLink p.inlineCallback['M'] = maybeAutoLink p.inlineCallback['F'] = maybeAutoLink } if extensions&Footnotes != 0 { p.notes = make([]*reference, 0) } first := firstPass(p, input) second := secondPass(p, first) return second } // first pass: // - extract references // - expand tabs // - normalize newlines // - copy everything else func firstPass(p *parser, input []byte) []byte { var out bytes.Buffer tabSize := TabSizeDefault if p.flags&TabSizeEight != 0 { tabSize = TabSizeDouble } beg, end := 0, 0 lastFencedCodeBlockEnd := 0 for beg < len(input) { // iterate over lines if end = isReference(p, input[beg:], tabSize); end > 0 { beg += end } else { // skip to the next line end = beg for end < len(input) && input[end] != '\n' && input[end] != '\r' { end++ } if p.flags&FencedCode != 0 { // track fenced code block boundaries to suppress tab expansion // inside them: if beg >= lastFencedCodeBlockEnd { if i := p.fencedCode(input[beg:], false); i > 0 { lastFencedCodeBlockEnd = beg + i } } } // add the line body if present if end > beg { if end < lastFencedCodeBlockEnd { // Do not expand tabs while inside fenced code blocks. out.Write(input[beg:end]) } else { expandTabs(&out, input[beg:end], tabSize) } } out.WriteByte('\n') if end < len(input) && input[end] == '\r' { end++ } if end < len(input) && input[end] == '\n' { end++ } beg = end } } // empty input? if out.Len() == 0 { out.WriteByte('\n') } return out.Bytes() } // second pass: actual rendering func secondPass(p *parser, input []byte) []byte { p.r.DocumentHeader() p.block(input) if p.flags&Footnotes != 0 && len(p.notes) > 0 { p.r.BeginFootnotes() flags := ListItemBeginningOfList for i := 0; i < len(p.notes); i += 1 { ref := p.notes[i] var buf bytes.Buffer if ref.hasBlock { flags |= ListItemContainsBlock buf.Write(p.r.CaptureWrites(func() { p.block(ref.title) })) } else { buf.Write(p.r.CaptureWrites(func() { p.inline(ref.title) })) } p.r.FootnoteItem(ref.link, buf.Bytes(), flags) flags &^= ListItemBeginningOfList | ListItemContainsBlock } p.r.EndFootnotes() } p.r.DocumentFooter() if p.nesting != 0 { panic("Nesting level did not end at zero") } return p.r.GetResult() } // // Link references // // This section implements support for references that (usually) appear // as footnotes in a document, and can be referenced anywhere in the document. // The basic format is: // // [1]: http://www.google.com/ "Google" // [2]: http://www.github.com/ "Github" // // Anywhere in the document, the reference can be linked by referring to its // label, i.e., 1 and 2 in this example, as in: // // This library is hosted on [Github][2], a git hosting site. // // Actual footnotes as specified in Pandoc and supported by some other Markdown // libraries such as php-markdown are also taken care of. They look like this: // // This sentence needs a bit of further explanation.[^note] // // [^note]: This is the explanation. // // Footnotes should be placed at the end of the document in an ordered list. // Inline footnotes such as: // // Inline footnotes^[Not supported.] also exist. // // are not yet supported. // References are parsed and stored in this struct. type reference struct { link []byte title []byte noteId int // 0 if not a footnote ref hasBlock bool text []byte } func (r *reference) String() string { return fmt.Sprintf("{link: %q, title: %q, text: %q, noteId: %d, hasBlock: %v}", r.link, r.title, r.text, r.noteId, r.hasBlock) } // Check whether or not data starts with a reference link. // If so, it is parsed and stored in the list of references // (in the render struct). // Returns the number of bytes to skip to move past it, // or zero if the first line is not a reference. func isReference(p *parser, data []byte, tabSize int) int { // up to 3 optional leading spaces if len(data) < 4 { return 0 } i := 0 for i < 3 && data[i] == ' ' { i++ } noteId := 0 // id part: anything but a newline between brackets if data[i] != '[' { return 0 } i++ if p.flags&Footnotes != 0 { if i < len(data) && data[i] == '^' { // we can set it to anything here because the proper noteIds will // be assigned later during the second pass. It just has to be != 0 noteId = 1 i++ } } idOffset := i for i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != ']' { i++ } if i >= len(data) || data[i] != ']' { return 0 } idEnd := i // spacer: colon (space | tab)* newline? (space | tab)* i++ if i >= len(data) || data[i] != ':' { return 0 } i++ for i < len(data) && (data[i] == ' ' || data[i] == '\t') { i++ } if i < len(data) && (data[i] == '\n' || data[i] == '\r') { i++ if i < len(data) && data[i] == '\n' && data[i-1] == '\r' { i++ } } for i < len(data) && (data[i] == ' ' || data[i] == '\t') { i++ } if i >= len(data) { return 0 } var ( linkOffset, linkEnd int titleOffset, titleEnd int lineEnd int raw []byte hasBlock bool ) if p.flags&Footnotes != 0 && noteId != 0 { linkOffset, linkEnd, raw, hasBlock = scanFootnote(p, data, i, tabSize) lineEnd = linkEnd } else { linkOffset, linkEnd, titleOffset, titleEnd, lineEnd = scanLinkRef(p, data, i) } if lineEnd == 0 { return 0 } // a valid ref has been found ref := &reference{ noteId: noteId, hasBlock: hasBlock, } if noteId > 0 { // reusing the link field for the id since footnotes don't have links ref.link = data[idOffset:idEnd] // if footnote, it's not really a title, it's the contained text ref.title = raw } else { ref.link = data[linkOffset:linkEnd] ref.title = data[titleOffset:titleEnd] } // id matches are case-insensitive id := string(bytes.ToLower(data[idOffset:idEnd])) p.refs[id] = ref return lineEnd } func scanLinkRef(p *parser, data []byte, i int) (linkOffset, linkEnd, titleOffset, titleEnd, lineEnd int) { // link: whitespace-free sequence, optionally between angle brackets if data[i] == '<' { i++ } linkOffset = i for i < len(data) && data[i] != ' ' && data[i] != '\t' && data[i] != '\n' && data[i] != '\r' { i++ } if i == len(data) { return } linkEnd = i if data[linkOffset] == '<' && data[linkEnd-1] == '>' { linkOffset++ linkEnd-- } // optional spacer: (space | tab)* (newline | '\'' | '"' | '(' ) for i < len(data) && (data[i] == ' ' || data[i] == '\t') { i++ } if i < len(data) && data[i] != '\n' && data[i] != '\r' && data[i] != '\'' && data[i] != '"' && data[i] != '(' { return } // compute end-of-line if i >= len(data) || data[i] == '\r' || data[i] == '\n' { lineEnd = i } if i+1 < len(data) && data[i] == '\r' && data[i+1] == '\n' { lineEnd++ } // optional (space|tab)* spacer after a newline if lineEnd > 0 { i = lineEnd + 1 for i < len(data) && (data[i] == ' ' || data[i] == '\t') { i++ } } // optional title: any non-newline sequence enclosed in '"() alone on its line if i+1 < len(data) && (data[i] == '\'' || data[i] == '"' || data[i] == '(') { i++ titleOffset = i // look for EOL for i < len(data) && data[i] != '\n' && data[i] != '\r' { i++ } if i+1 < len(data) && data[i] == '\n' && data[i+1] == '\r' { titleEnd = i + 1 } else { titleEnd = i } // step back i-- for i > titleOffset && (data[i] == ' ' || data[i] == '\t') { i-- } if i > titleOffset && (data[i] == '\'' || data[i] == '"' || data[i] == ')') { lineEnd = titleEnd titleEnd = i } } return } // The first bit of this logic is the same as (*parser).listItem, but the rest // is much simpler. This function simply finds the entire block and shifts it // over by one tab if it is indeed a block (just returns the line if it's not). // blockEnd is the end of the section in the input buffer, and contents is the // extracted text that was shifted over one tab. It will need to be rendered at // the end of the document. func scanFootnote(p *parser, data []byte, i, indentSize int) (blockStart, blockEnd int, contents []byte, hasBlock bool) { if i == 0 || len(data) == 0 { return } // skip leading whitespace on first line for i < len(data) && data[i] == ' ' { i++ } blockStart = i // find the end of the line blockEnd = i for i < len(data) && data[i-1] != '\n' { i++ } // get working buffer var raw bytes.Buffer // put the first line into the working buffer raw.Write(data[blockEnd:i]) blockEnd = i // process the following lines containsBlankLine := false gatherLines: for blockEnd < len(data) { i++ // find the end of this line for i < len(data) && data[i-1] != '\n' { i++ } // if it is an empty line, guess that it is part of this item // and move on to the next line if p.isEmpty(data[blockEnd:i]) > 0 { containsBlankLine = true blockEnd = i continue } n := 0 if n = isIndented(data[blockEnd:i], indentSize); n == 0 { // this is the end of the block. // we don't want to include this last line in the index. break gatherLines } // if there were blank lines before this one, insert a new one now if containsBlankLine { raw.WriteByte('\n') containsBlankLine = false } // get rid of that first tab, write to buffer raw.Write(data[blockEnd+n : i]) hasBlock = true blockEnd = i } if data[blockEnd-1] != '\n' { raw.WriteByte('\n') } contents = raw.Bytes() return } // // // Miscellaneous helper functions // // // Test if a character is a punctuation symbol. // Taken from a private function in regexp in the stdlib. func ispunct(c byte) bool { for _, r := range []byte("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~") { if c == r { return true } } return false } // Test if a character is a whitespace character. func isspace(c byte) bool { return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\f' || c == '\v' } // Test if a character is letter. func isletter(c byte) bool { return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') } // Test if a character is a letter or a digit. // TODO: check when this is looking for ASCII alnum and when it should use unicode func isalnum(c byte) bool { return (c >= '0' && c <= '9') || isletter(c) } // Replace tab characters with spaces, aligning to the next TAB_SIZE column. // always ends output with a newline func expandTabs(out *bytes.Buffer, line []byte, tabSize int) { // first, check for common cases: no tabs, or only tabs at beginning of line i, prefix := 0, 0 slowcase := false for i = 0; i < len(line); i++ { if line[i] == '\t' { if prefix == i { prefix++ } else { slowcase = true break } } } // no need to decode runes if all tabs are at the beginning of the line if !slowcase { for i = 0; i < prefix*tabSize; i++ { out.WriteByte(' ') } out.Write(line[prefix:]) return } // the slow case: we need to count runes to figure out how // many spaces to insert for each tab column := 0 i = 0 for i < len(line) { start := i for i < len(line) && line[i] != '\t' { _, size := utf8.DecodeRune(line[i:]) i += size column++ } if i > start { out.Write(line[start:i]) } if i >= len(line) { break } for { out.WriteByte(' ') column++ if column%tabSize == 0 { break } } i++ } } // Find if a line counts as indented or not. // Returns number of characters the indent is (0 = not indented). func isIndented(data []byte, indentSize int) int { if len(data) == 0 { return 0 } if data[0] == '\t' { return 1 } if len(data) < indentSize { return 0 } for i := 0; i < indentSize; i++ { if data[i] != ' ' { return 0 } } return indentSize } // Create a url-safe slug for fragments func slugify(in []byte) []byte { if len(in) == 0 { return in } out := make([]byte, 0, len(in)) sym := false for _, ch := range in { if isalnum(ch) { sym = false out = append(out, ch) } else if sym { continue } else { out = append(out, '-') sym = true } } var a, b int var ch byte for a, ch = range out { if ch != '-' { break } } for b = len(out) - 1; b > 0; b-- { if out[b] != '-' { break } } return out[a : b+1] } |