golang/mikael/madonctl: comparison vendor/github.com/russross/blackfriday/block.go

equal deleted inserted replaced

-:c040f992052f
+:1c52a0eeb952
+//
+// 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.
+//
+//
+// Functions to parse block-level elements.
+//
+package blackfriday
+import (
+	"bytes"
+	"strings"
+	"unicode"
+)
+// Parse block-level data.
+// Note: this function and many that it calls assume that
+// the input buffer ends with a newline.
+func (p *parser) block(out *bytes.Buffer, data []byte) {
+	if len(data) == 0 || data[len(data)-1] != '\n' {
+		panic("block input is missing terminating newline")
+	}
+	// this is called recursively: enforce a maximum depth
+	if p.nesting >= p.maxNesting {
+		return
+	}
+	p.nesting++
+	// parse out one block-level construct at a time
+	for len(data) > 0 {
+		// prefixed header:
+		//
+		// # Header 1
+		// ## Header 2
+		// ...
+		// ###### Header 6
+		if p.isPrefixHeader(data) {
+			data = data[p.prefixHeader(out, data):]
+			continue
+		}
+		// block of preformatted HTML:
+		//
+		// <div>
+		//     ...
+		// </div>
+		if data[0] == '<' {
+			if i := p.html(out, data, true); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+		// title block
+		//
+		// % stuff
+		// % more stuff
+		// % even more stuff
+		if p.flags&EXTENSION_TITLEBLOCK != 0 {
+			if data[0] == '%' {
+				if i := p.titleBlock(out, data, true); i > 0 {
+					data = data[i:]
+					continue
+				}
+			}
+		}
+		// blank lines.  note: returns the # of bytes to skip
+		if i := p.isEmpty(data); i > 0 {
+			data = data[i:]
+			continue
+		}
+		// indented code block:
+		//
+		//     func max(a, b int) int {
+		//         if a > b {
+		//             return a
+		//         }
+		//         return b
+		//      }
+		if p.codePrefix(data) > 0 {
+			data = data[p.code(out, data):]
+			continue
+		}
+		// fenced code block:
+		//
+		// ``` go info string here
+		// func fact(n int) int {
+		//     if n <= 1 {
+		//         return n
+		//     }
+		//     return n * fact(n-1)
+		// }
+		// ```
+		if p.flags&EXTENSION_FENCED_CODE != 0 {
+			if i := p.fencedCodeBlock(out, data, true); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+		// horizontal rule:
+		//
+		// ------
+		// or
+		// ******
+		// or
+		// ______
+		if p.isHRule(data) {
+			p.r.HRule(out)
+			var i int
+			for i = 0; data[i] != '\n'; i++ {
+			}
+			data = data[i:]
+			continue
+		}
+		// block quote:
+		//
+		// > A big quote I found somewhere
+		// > on the web
+		if p.quotePrefix(data) > 0 {
+			data = data[p.quote(out, data):]
+			continue
+		}
+		// table:
+		//
+		// Name  | Age | Phone
+		// ------|-----|---------
+		// Bob   | 31  | 555-1234
+		// Alice | 27  | 555-4321
+		if p.flags&EXTENSION_TABLES != 0 {
+			if i := p.table(out, data); i > 0 {
+				data = data[i:]
+				continue
+			}
+		}
+		// an itemized/unordered list:
+		//
+		// * Item 1
+		// * Item 2
+		//
+		// also works with + or -
+		if p.uliPrefix(data) > 0 {
+			data = data[p.list(out, data, 0):]
+			continue
+		}
+		// a numbered/ordered list:
+		//
+		// 1. Item 1
+		// 2. Item 2
+		if p.oliPrefix(data) > 0 {
+			data = data[p.list(out, data, LIST_TYPE_ORDERED):]
+			continue
+		}
+		// definition lists:
+		//
+		// Term 1
+		// :   Definition a
+		// :   Definition b
+		//
+		// Term 2
+		// :   Definition c
+		if p.flags&EXTENSION_DEFINITION_LISTS != 0 {
+			if p.dliPrefix(data) > 0 {
+				data = data[p.list(out, data, LIST_TYPE_DEFINITION):]
+				continue
+			}
+		}
+		// anything else must look like a normal paragraph
+		// note: this finds underlined headers, too
+		data = data[p.paragraph(out, data):]
+	}
+	p.nesting--
+}
+func (p *parser) isPrefixHeader(data []byte) bool {
+	if data[0] != '#' {
+		return false
+	}
+	if p.flags&EXTENSION_SPACE_HEADERS != 0 {
+		level := 0
+		for level < 6 && data[level] == '#' {
+			level++
+		}
+		if data[level] != ' ' {
+			return false
+		}
+	}
+	return true
+}
+func (p *parser) prefixHeader(out *bytes.Buffer, data []byte) int {
+	level := 0
+	for level < 6 && data[level] == '#' {
+		level++
+	}
+	i := skipChar(data, level, ' ')
+	end := skipUntilChar(data, i, '\n')
+	skip := end
+	id := ""
+	if p.flags&EXTENSION_HEADER_IDS != 0 {
+		j, k := 0, 0
+		// find start/end of header id
+		for j = i; j < end-1 && (data[j] != '{' || data[j+1] != '#'); j++ {
+		}
+		for k = j + 1; k < end && data[k] != '}'; k++ {
+		}
+		// extract header id iff found
+		if j < end && k < end {
+			id = string(data[j+2 : k])
+			end = j
+			skip = k + 1
+			for end > 0 && data[end-1] == ' ' {
+				end--
+			}
+		}
+	}
+	for end > 0 && data[end-1] == '#' {
+		if isBackslashEscaped(data, end-1) {
+			break
+		}
+		end--
+	}
+	for end > 0 && data[end-1] == ' ' {
+		end--
+	}
+	if end > i {
+		if id == "" && p.flags&EXTENSION_AUTO_HEADER_IDS != 0 {
+			id = SanitizedAnchorName(string(data[i:end]))
+		}
+		work := func() bool {
+			p.inline(out, data[i:end])
+			return true
+		}
+		p.r.Header(out, work, level, id)
+	}
+	return skip
+}
+func (p *parser) isUnderlinedHeader(data []byte) int {
+	// test of level 1 header
+	if data[0] == '=' {
+		i := skipChar(data, 1, '=')
+		i = skipChar(data, i, ' ')
+		if data[i] == '\n' {
+			return 1
+		} else {
+			return 0
+		}
+	}
+	// test of level 2 header
+	if data[0] == '-' {
+		i := skipChar(data, 1, '-')
+		i = skipChar(data, i, ' ')
+		if data[i] == '\n' {
+			return 2
+		} else {
+			return 0
+		}
+	}
+	return 0
+}
+func (p *parser) titleBlock(out *bytes.Buffer, data []byte, doRender bool) int {
+	if data[0] != '%' {
+		return 0
+	}
+	splitData := bytes.Split(data, []byte("\n"))
+	var i int
+	for idx, b := range splitData {
+		if !bytes.HasPrefix(b, []byte("%")) {
+			i = idx // - 1
+			break
+		}
+	}
+	data = bytes.Join(splitData[0:i], []byte("\n"))
+	p.r.TitleBlock(out, data)
+	return len(data)
+}
+func (p *parser) html(out *bytes.Buffer, data []byte, doRender bool) int {
+	var i, j int
+	// identify the opening tag
+	if data[0] != '<' {
+		return 0
+	}
+	curtag, tagfound := p.htmlFindTag(data[1:])
+	// handle special cases
+	if !tagfound {
+		// check for an HTML comment
+		if size := p.htmlComment(out, data, doRender); size > 0 {
+			return size
+		}
+		// check for an <hr> tag
+		if size := p.htmlHr(out, data, doRender); size > 0 {
+			return size
+		}
+		// check for HTML CDATA
+		if size := p.htmlCDATA(out, data, doRender); size > 0 {
+			return size
+		}
+		// no special case recognized
+		return 0
+	}
+	// look for an unindented matching closing tag
+	// followed by a blank line
+	found := false
+	/*
+		closetag := []byte("\n</" + curtag + ">")
+		j = len(curtag) + 1
+		for !found {
+			// scan for a closing tag at the beginning of a line
+			if skip := bytes.Index(data[j:], closetag); skip >= 0 {
+				j += skip + len(closetag)
+			} else {
+				break
+			}
+			// see if it is the only thing on the line
+			if skip := p.isEmpty(data[j:]); skip > 0 {
+				// see if it is followed by a blank line/eof
+				j += skip
+				if j >= len(data) {
+					found = true
+					i = j
+				} else {
+					if skip := p.isEmpty(data[j:]); skip > 0 {
+						j += skip
+						found = true
+						i = j
+					}
+				}
+			}
+		}
+	*/
+	// if not found, try a second pass looking for indented match
+	// but not if tag is "ins" or "del" (following original Markdown.pl)
+	if !found && curtag != "ins" && curtag != "del" {
+		i = 1
+		for i < len(data) {
+			i++
+			for i < len(data) && !(data[i-1] == '<' && data[i] == '/') {
+				i++
+			}
+			if i+2+len(curtag) >= len(data) {
+				break
+			}
+			j = p.htmlFindEnd(curtag, data[i-1:])
+			if j > 0 {
+				i += j - 1
+				found = true
+				break
+			}
+		}
+	}
+	if !found {
+		return 0
+	}
+	// the end of the block has been found
+	if doRender {
+		// trim newlines
+		end := i
+		for end > 0 && data[end-1] == '\n' {
+			end--
+		}
+		p.r.BlockHtml(out, data[:end])
+	}
+	return i
+}
+func (p *parser) renderHTMLBlock(out *bytes.Buffer, data []byte, start int, doRender bool) int {
+	// html block needs to end with a blank line
+	if i := p.isEmpty(data[start:]); i > 0 {
+		size := start + i
+		if doRender {
+			// trim trailing newlines
+			end := size
+			for end > 0 && data[end-1] == '\n' {
+				end--
+			}
+			p.r.BlockHtml(out, data[:end])
+		}
+		return size
+	}
+	return 0
+}
+// HTML comment, lax form
+func (p *parser) htmlComment(out *bytes.Buffer, data []byte, doRender bool) int {
+	i := p.inlineHTMLComment(out, data)
+	return p.renderHTMLBlock(out, data, i, doRender)
+}
+// HTML CDATA section
+func (p *parser) htmlCDATA(out *bytes.Buffer, data []byte, doRender bool) int {
+	const cdataTag = "<![cdata["
+	const cdataTagLen = len(cdataTag)
+	if len(data) < cdataTagLen+1 {
+		return 0
+	}
+	if !bytes.Equal(bytes.ToLower(data[:cdataTagLen]), []byte(cdataTag)) {
+		return 0
+	}
+	i := cdataTagLen
+	// scan for an end-of-comment marker, across lines if necessary
+	for i < len(data) && !(data[i-2] == ']' && data[i-1] == ']' && data[i] == '>') {
+		i++
+	}
+	i++
+	// no end-of-comment marker
+	if i >= len(data) {
+		return 0
+	}
+	return p.renderHTMLBlock(out, data, i, doRender)
+}
+// HR, which is the only self-closing block tag considered
+func (p *parser) htmlHr(out *bytes.Buffer, data []byte, doRender bool) int {
+	if data[0] != '<' || (data[1] != 'h' && data[1] != 'H') || (data[2] != 'r' && data[2] != 'R') {
+		return 0
+	}
+	if data[3] != ' ' && data[3] != '/' && data[3] != '>' {
+		// not an <hr> tag after all; at least not a valid one
+		return 0
+	}
+	i := 3
+	for data[i] != '>' && data[i] != '\n' {
+		i++
+	}
+	if data[i] == '>' {
+		return p.renderHTMLBlock(out, data, i+1, doRender)
+	}
+	return 0
+}
+func (p *parser) htmlFindTag(data []byte) (string, bool) {
+	i := 0
+	for isalnum(data[i]) {
+		i++
+	}
+	key := string(data[:i])
+	if _, ok := blockTags[key]; ok {
+		return key, true
+	}
+	return "", false
+}
+func (p *parser) htmlFindEnd(tag string, data []byte) int {
+	// assume data[0] == '<' && data[1] == '/' already tested
+	// check if tag is a match
+	closetag := []byte("</" + tag + ">")
+	if !bytes.HasPrefix(data, closetag) {
+		return 0
+	}
+	i := len(closetag)
+	// check that the rest of the line is blank
+	skip := 0
+	if skip = p.isEmpty(data[i:]); skip == 0 {
+		return 0
+	}
+	i += skip
+	skip = 0
+	if i >= len(data) {
+		return i
+	}
+	if p.flags&EXTENSION_LAX_HTML_BLOCKS != 0 {
+		return i
+	}
+	if skip = p.isEmpty(data[i:]); skip == 0 {
+		// following line must be blank
+		return 0
+	}
+	return i + skip
+}
+func (*parser) isEmpty(data []byte) int {
+	// it is okay to call isEmpty on an empty buffer
+	if len(data) == 0 {
+		return 0
+	}
+	var i int
+	for i = 0; i < len(data) && data[i] != '\n'; i++ {
+		if data[i] != ' ' && data[i] != '\t' {
+			return 0
+		}
+	}
+	return i + 1
+}
+func (*parser) isHRule(data []byte) bool {
+	i := 0
+	// skip up to three spaces
+	for i < 3 && data[i] == ' ' {
+		i++
+	}
+	// look at the hrule char
+	if data[i] != '*' && data[i] != '-' && data[i] != '_' {
+		return false
+	}
+	c := data[i]
+	// the whole line must be the char or whitespace
+	n := 0
+	for data[i] != '\n' {
+		switch {
+		case data[i] == c:
+			n++
+		case data[i] != ' ':
+			return false
+		}
+		i++
+	}
+	return n >= 3
+}
+// isFenceLine checks if there's a fence line (e.g., ``` or ``` go) at the beginning of data,
+// and returns the end index if so, or 0 otherwise. It also returns the marker found.
+// If syntax is not nil, it gets set to the syntax specified in the fence line.
+// A final newline is mandatory to recognize the fence line, unless newlineOptional is true.
+func isFenceLine(data []byte, info *string, oldmarker string, newlineOptional bool) (end int, marker string) {
+	i, size := 0, 0
+	// skip up to three spaces
+	for i < len(data) && i < 3 && data[i] == ' ' {
+		i++
+	}
+	// check for the marker characters: ~ or `
+	if i >= len(data) {
+		return 0, ""
+	}
+	if data[i] != '~' && data[i] != '`' {
+		return 0, ""
+	}
+	c := data[i]
+	// the whole line must be the same char or whitespace
+	for i < len(data) && data[i] == c {
+		size++
+		i++
+	}
+	// the marker char must occur at least 3 times
+	if size < 3 {
+		return 0, ""
+	}
+	marker = string(data[i-size : i])
+	// if this is the end marker, it must match the beginning marker
+	if oldmarker != "" && marker != oldmarker {
+		return 0, ""
+	}
+	// TODO(shurcooL): It's probably a good idea to simplify the 2 code paths here
+	// into one, always get the info string, and discard it if the caller doesn't care.
+	if info != nil {
+		infoLength := 0
+		i = skipChar(data, i, ' ')
+		if i >= len(data) {
+			if newlineOptional && i == len(data) {
+				return i, marker
+			}
+			return 0, ""
+		}
+		infoStart := i
+		if data[i] == '{' {
+			i++
+			infoStart++
+			for i < len(data) && data[i] != '}' && data[i] != '\n' {
+				infoLength++
+				i++
+			}
+			if i >= len(data) || data[i] != '}' {
+				return 0, ""
+			}
+			// strip all whitespace at the beginning and the end
+			// of the {} block
+			for infoLength > 0 && isspace(data[infoStart]) {
+				infoStart++
+				infoLength--
+			}
+			for infoLength > 0 && isspace(data[infoStart+infoLength-1]) {
+				infoLength--
+			}
+			i++
+		} else {
+			for i < len(data) && !isverticalspace(data[i]) {
+				infoLength++
+				i++
+			}
+		}
+		*info = strings.TrimSpace(string(data[infoStart : infoStart+infoLength]))
+	}
+	i = skipChar(data, i, ' ')
+	if i >= len(data) || data[i] != '\n' {
+		if newlineOptional && i == len(data) {
+			return i, marker
+		}
+		return 0, ""
+	}
+	return i + 1, marker // Take newline into account.
+}
+// fencedCodeBlock returns the end index if data contains a fenced code block at the beginning,
+// or 0 otherwise. It writes to out if doRender is true, otherwise it has no side effects.
+// If doRender is true, a final newline is mandatory to recognize the fenced code block.
+func (p *parser) fencedCodeBlock(out *bytes.Buffer, data []byte, doRender bool) int {
+	var infoString string
+	beg, marker := isFenceLine(data, &infoString, "", false)
+	if beg == 0 || beg >= len(data) {
+		return 0
+	}
+	var work bytes.Buffer
+	for {
+		// safe to assume beg < len(data)
+		// check for the end of the code block
+		newlineOptional := !doRender
+		fenceEnd, _ := isFenceLine(data[beg:], nil, marker, newlineOptional)
+		if fenceEnd != 0 {
+			beg += fenceEnd
+			break
+		}
+		// copy the current line
+		end := skipUntilChar(data, beg, '\n') + 1
+		// did we reach the end of the buffer without a closing marker?
+		if end >= len(data) {
+			return 0
+		}
+		// verbatim copy to the working buffer
+		if doRender {
+			work.Write(data[beg:end])
+		}
+		beg = end
+	}
+	if doRender {
+		p.r.BlockCode(out, work.Bytes(), infoString)
+	}
+	return beg
+}
+func (p *parser) table(out *bytes.Buffer, data []byte) int {
+	var header bytes.Buffer
+	i, columns := p.tableHeader(&header, data)
+	if i == 0 {
+		return 0
+	}
+	var body bytes.Buffer
+	for i < len(data) {
+		pipes, rowStart := 0, i
+		for ; data[i] != '\n'; i++ {
+			if data[i] == '|' {
+				pipes++
+			}
+		}
+		if pipes == 0 {
+			i = rowStart
+			break
+		}
+		// include the newline in data sent to tableRow
+		i++
+		p.tableRow(&body, data[rowStart:i], columns, false)
+	}
+	p.r.Table(out, header.Bytes(), body.Bytes(), columns)
+	return i
+}
+// check if the specified position is preceded by an odd number of backslashes
+func isBackslashEscaped(data []byte, i int) bool {
+	backslashes := 0
+	for i-backslashes-1 >= 0 && data[i-backslashes-1] == '\\' {
+		backslashes++
+	}
+	return backslashes&1 == 1
+}
+func (p *parser) tableHeader(out *bytes.Buffer, data []byte) (size int, columns []int) {
+	i := 0
+	colCount := 1
+	for i = 0; data[i] != '\n'; i++ {
+		if data[i] == '|' && !isBackslashEscaped(data, i) {
+			colCount++
+		}
+	}
+	// doesn't look like a table header
+	if colCount == 1 {
+		return
+	}
+	// include the newline in the data sent to tableRow
+	header := data[:i+1]
+	// column count ignores pipes at beginning or end of line
+	if data[0] == '|' {
+		colCount--
+	}
+	if i > 2 && data[i-1] == '|' && !isBackslashEscaped(data, i-1) {
+		colCount--
+	}
+	columns = make([]int, colCount)
+	// move on to the header underline
+	i++
+	if i >= len(data) {
+		return
+	}
+	if data[i] == '|' && !isBackslashEscaped(data, i) {
+		i++
+	}
+	i = skipChar(data, i, ' ')
+	// each column header is of form: / *:?-+:? *|/ with # dashes + # colons >= 3
+	// and trailing | optional on last column
+	col := 0
+	for data[i] != '\n' {
+		dashes := 0
+		if data[i] == ':' {
+			i++
+			columns[col] |= TABLE_ALIGNMENT_LEFT
+			dashes++
+		}
+		for data[i] == '-' {
+			i++
+			dashes++
+		}
+		if data[i] == ':' {
+			i++
+			columns[col] |= TABLE_ALIGNMENT_RIGHT
+			dashes++
+		}
+		for data[i] == ' ' {
+			i++
+		}
+		// end of column test is messy
+		switch {
+		case dashes < 3:
+			// not a valid column
+			return
+		case data[i] == '|' && !isBackslashEscaped(data, i):
+			// marker found, now skip past trailing whitespace
+			col++
+			i++
+			for data[i] == ' ' {
+				i++
+			}
+			// trailing junk found after last column
+			if col >= colCount && data[i] != '\n' {
+				return
+			}
+		case (data[i] != '|' || isBackslashEscaped(data, i)) && col+1 < colCount:
+			// something else found where marker was required
+			return
+		case data[i] == '\n':
+			// marker is optional for the last column
+			col++
+		default:
+			// trailing junk found after last column
+			return
+		}
+	}
+	if col != colCount {
+		return
+	}
+	p.tableRow(out, header, columns, true)
+	size = i + 1
+	return
+}
+func (p *parser) tableRow(out *bytes.Buffer, data []byte, columns []int, header bool) {
+	i, col := 0, 0
+	var rowWork bytes.Buffer
+	if data[i] == '|' && !isBackslashEscaped(data, i) {
+		i++
+	}
+	for col = 0; col < len(columns) && i < len(data); col++ {
+		for data[i] == ' ' {
+			i++
+		}
+		cellStart := i
+		for (data[i] != '|' || isBackslashEscaped(data, i)) && data[i] != '\n' {
+			i++
+		}
+		cellEnd := i
+		// skip the end-of-cell marker, possibly taking us past end of buffer
+		i++
+		for cellEnd > cellStart && data[cellEnd-1] == ' ' {
+			cellEnd--
+		}
+		var cellWork bytes.Buffer
+		p.inline(&cellWork, data[cellStart:cellEnd])
+		if header {
+			p.r.TableHeaderCell(&rowWork, cellWork.Bytes(), columns[col])
+		} else {
+			p.r.TableCell(&rowWork, cellWork.Bytes(), columns[col])
+		}
+	}
+	// pad it out with empty columns to get the right number
+	for ; col < len(columns); col++ {
+		if header {
+			p.r.TableHeaderCell(&rowWork, nil, columns[col])
+		} else {
+			p.r.TableCell(&rowWork, nil, columns[col])
+		}
+	}
+	// silently ignore rows with too many cells
+	p.r.TableRow(out, rowWork.Bytes())
+}
+// returns blockquote prefix length
+func (p *parser) quotePrefix(data []byte) int {
+	i := 0
+	for i < 3 && data[i] == ' ' {
+		i++
+	}
+	if data[i] == '>' {
+		if data[i+1] == ' ' {
+			return i + 2
+		}
+		return i + 1
+	}
+	return 0
+}
+// blockquote ends with at least one blank line
+// followed by something without a blockquote prefix
+func (p *parser) terminateBlockquote(data []byte, beg, end int) bool {
+	if p.isEmpty(data[beg:]) <= 0 {
+		return false
+	}
+	if end >= len(data) {
+		return true
+	}
+	return p.quotePrefix(data[end:]) == 0 && p.isEmpty(data[end:]) == 0
+}
+// parse a blockquote fragment
+func (p *parser) quote(out *bytes.Buffer, data []byte) int {
+	var raw bytes.Buffer
+	beg, end := 0, 0
+	for beg < len(data) {
+		end = beg
+		// Step over whole lines, collecting them. While doing that, check for
+		// fenced code and if one's found, incorporate it altogether,
+		// irregardless of any contents inside it
+		for data[end] != '\n' {
+			if p.flags&EXTENSION_FENCED_CODE != 0 {
+				if i := p.fencedCodeBlock(out, data[end:], false); i > 0 {
+					// -1 to compensate for the extra end++ after the loop:
+					end += i - 1
+					break
+				}
+			}
+			end++
+		}
+		end++
+		if pre := p.quotePrefix(data[beg:]); pre > 0 {
+			// skip the prefix
+			beg += pre
+		} else if p.terminateBlockquote(data, beg, end) {
+			break
+		}
+		// this line is part of the blockquote
+		raw.Write(data[beg:end])
+		beg = end
+	}
+	var cooked bytes.Buffer
+	p.block(&cooked, raw.Bytes())
+	p.r.BlockQuote(out, cooked.Bytes())
+	return end
+}
+// returns prefix length for block code
+func (p *parser) codePrefix(data []byte) int {
+	if data[0] == ' ' && data[1] == ' ' && data[2] == ' ' && data[3] == ' ' {
+		return 4
+	}
+	return 0
+}
+func (p *parser) code(out *bytes.Buffer, data []byte) int {
+	var work bytes.Buffer
+	i := 0
+	for i < len(data) {
+		beg := i
+		for data[i] != '\n' {
+			i++
+		}
+		i++
+		blankline := p.isEmpty(data[beg:i]) > 0
+		if pre := p.codePrefix(data[beg:i]); pre > 0 {
+			beg += pre
+		} else if !blankline {
+			// non-empty, non-prefixed line breaks the pre
+			i = beg
+			break
+		}
+		// verbatim copy to the working buffeu
+		if blankline {
+			work.WriteByte('\n')
+		} else {
+			work.Write(data[beg:i])
+		}
+	}
+	// trim all the \n off the end of work
+	workbytes := work.Bytes()
+	eol := len(workbytes)
+	for eol > 0 && workbytes[eol-1] == '\n' {
+		eol--
+	}
+	if eol != len(workbytes) {
+		work.Truncate(eol)
+	}
+	work.WriteByte('\n')
+	p.r.BlockCode(out, work.Bytes(), "")
+	return i
+}
+// returns unordered list item prefix
+func (p *parser) uliPrefix(data []byte) int {
+	i := 0
+	// start with up to 3 spaces
+	for i < 3 && data[i] == ' ' {
+		i++
+	}
+	// need a *, +, or - followed by a space
+	if (data[i] != '*' && data[i] != '+' && data[i] != '-') ||
+		data[i+1] != ' ' {
+		return 0
+	}
+	return i + 2
+}
+// returns ordered list item prefix
+func (p *parser) oliPrefix(data []byte) int {
+	i := 0
+	// start with up to 3 spaces
+	for i < 3 && data[i] == ' ' {
+		i++
+	}
+	// count the digits
+	start := i
+	for data[i] >= '0' && data[i] <= '9' {
+		i++
+	}
+	// we need >= 1 digits followed by a dot and a space
+	if start == i || data[i] != '.' || data[i+1] != ' ' {
+		return 0
+	}
+	return i + 2
+}
+// returns definition list item prefix
+func (p *parser) dliPrefix(data []byte) int {
+	i := 0
+	// need a : followed by a spaces
+	if data[i] != ':' || data[i+1] != ' ' {
+		return 0
+	}
+	for data[i] == ' ' {
+		i++
+	}
+	return i + 2
+}
+// parse ordered or unordered list block
+func (p *parser) list(out *bytes.Buffer, data []byte, flags int) int {
+	i := 0
+	flags |= LIST_ITEM_BEGINNING_OF_LIST
+	work := func() bool {
+		for i < len(data) {
+			skip := p.listItem(out, data[i:], &flags)
+			i += skip
+			if skip == 0 || flags&LIST_ITEM_END_OF_LIST != 0 {
+				break
+			}
+			flags &= ^LIST_ITEM_BEGINNING_OF_LIST
+		}
+		return true
+	}
+	p.r.List(out, work, flags)
+	return i
+}
+// Parse a single list item.
+// Assumes initial prefix is already removed if this is a sublist.
+func (p *parser) listItem(out *bytes.Buffer, data []byte, flags *int) int {
+	// keep track of the indentation of the first line
+	itemIndent := 0
+	for itemIndent < 3 && data[itemIndent] == ' ' {
+		itemIndent++
+	}
+	i := p.uliPrefix(data)
+	if i == 0 {
+		i = p.oliPrefix(data)
+	}
+	if i == 0 {
+		i = p.dliPrefix(data)
+		// reset definition term flag
+		if i > 0 {
+			*flags &= ^LIST_TYPE_TERM
+		}
+	}
+	if i == 0 {
+		// if in defnition list, set term flag and continue
+		if *flags&LIST_TYPE_DEFINITION != 0 {
+			*flags |= LIST_TYPE_TERM
+		} else {
+			return 0
+		}
+	}
+	// skip leading whitespace on first line
+	for data[i] == ' ' {
+		i++
+	}
+	// find the end of the line
+	line := i
+	for i > 0 && data[i-1] != '\n' {
+		i++
+	}
+	// get working buffer
+	var raw bytes.Buffer
+	// put the first line into the working buffer
+	raw.Write(data[line:i])
+	line = i
+	// process the following lines
+	containsBlankLine := false
+	sublist := 0
+	codeBlockMarker := ""
+gatherlines:
+	for line < len(data) {
+		i++
+		// find the end of this line
+		for 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[line:i]) > 0 {
+			containsBlankLine = true
+			raw.Write(data[line:i])
+			line = i
+			continue
+		}
+		// calculate the indentation
+		indent := 0
+		for indent < 4 && line+indent < i && data[line+indent] == ' ' {
+			indent++
+		}
+		chunk := data[line+indent : i]
+		if p.flags&EXTENSION_FENCED_CODE != 0 {
+			// determine if in or out of codeblock
+			// if in codeblock, ignore normal list processing
+			_, marker := isFenceLine(chunk, nil, codeBlockMarker, false)
+			if marker != "" {
+				if codeBlockMarker == "" {
+					// start of codeblock
+					codeBlockMarker = marker
+				} else {
+					// end of codeblock.
+					*flags |= LIST_ITEM_CONTAINS_BLOCK
+					codeBlockMarker = ""
+				}
+			}
+			// we are in a codeblock, write line, and continue
+			if codeBlockMarker != "" || marker != "" {
+				raw.Write(data[line+indent : i])
+				line = i
+				continue gatherlines
+			}
+		}
+		// evaluate how this line fits in
+		switch {
+		// is this a nested list item?
+		case (p.uliPrefix(chunk) > 0 && !p.isHRule(chunk)) ||
+			p.oliPrefix(chunk) > 0 ||
+			p.dliPrefix(chunk) > 0:
+			if containsBlankLine {
+				// end the list if the type changed after a blank line
+				if indent <= itemIndent &&
+					((*flags&LIST_TYPE_ORDERED != 0 && p.uliPrefix(chunk) > 0) ||
+						(*flags&LIST_TYPE_ORDERED == 0 && p.oliPrefix(chunk) > 0)) {
+					*flags |= LIST_ITEM_END_OF_LIST
+					break gatherlines
+				}
+				*flags |= LIST_ITEM_CONTAINS_BLOCK
+			}
+			// to be a nested list, it must be indented more
+			// if not, it is the next item in the same list
+			if indent <= itemIndent {
+				break gatherlines
+			}
+			// is this the first item in the nested list?
+			if sublist == 0 {
+				sublist = raw.Len()
+			}
+		// is this a nested prefix header?
+		case p.isPrefixHeader(chunk):
+			// if the header is not indented, it is not nested in the list
+			// and thus ends the list
+			if containsBlankLine && indent < 4 {
+				*flags |= LIST_ITEM_END_OF_LIST
+				break gatherlines
+			}
+			*flags |= LIST_ITEM_CONTAINS_BLOCK
+		// anything following an empty line is only part
+		// of this item if it is indented 4 spaces
+		// (regardless of the indentation of the beginning of the item)
+		case containsBlankLine && indent < 4:
+			if *flags&LIST_TYPE_DEFINITION != 0 && i < len(data)-1 {
+				// is the next item still a part of this list?
+				next := i
+				for data[next] != '\n' {
+					next++
+				}
+				for next < len(data)-1 && data[next] == '\n' {
+					next++
+				}
+				if i < len(data)-1 && data[i] != ':' && data[next] != ':' {
+					*flags |= LIST_ITEM_END_OF_LIST
+				}
+			} else {
+				*flags |= LIST_ITEM_END_OF_LIST
+			}
+			break gatherlines
+		// a blank line means this should be parsed as a block
+		case containsBlankLine:
+			*flags |= LIST_ITEM_CONTAINS_BLOCK
+		}
+		containsBlankLine = false
+		// add the line into the working buffer without prefix
+		raw.Write(data[line+indent : i])
+		line = i
+	}
+	// If reached end of data, the Renderer.ListItem call we're going to make below
+	// is definitely the last in the list.
+	if line >= len(data) {
+		*flags |= LIST_ITEM_END_OF_LIST
+	}
+	rawBytes := raw.Bytes()
+	// render the contents of the list item
+	var cooked bytes.Buffer
+	if *flags&LIST_ITEM_CONTAINS_BLOCK != 0 && *flags&LIST_TYPE_TERM == 0 {
+		// intermediate render of block item, except for definition term
+		if sublist > 0 {
+			p.block(&cooked, rawBytes[:sublist])
+			p.block(&cooked, rawBytes[sublist:])
+		} else {
+			p.block(&cooked, rawBytes)
+		}
+	} else {
+		// intermediate render of inline item
+		if sublist > 0 {
+			p.inline(&cooked, rawBytes[:sublist])
+			p.block(&cooked, rawBytes[sublist:])
+		} else {
+			p.inline(&cooked, rawBytes)
+		}
+	}
+	// render the actual list item
+	cookedBytes := cooked.Bytes()
+	parsedEnd := len(cookedBytes)
+	// strip trailing newlines
+	for parsedEnd > 0 && cookedBytes[parsedEnd-1] == '\n' {
+		parsedEnd--
+	}
+	p.r.ListItem(out, cookedBytes[:parsedEnd], *flags)
+	return line
+}
+// render a single paragraph that has already been parsed out
+func (p *parser) renderParagraph(out *bytes.Buffer, data []byte) {
+	if len(data) == 0 {
+		return
+	}
+	// trim leading spaces
+	beg := 0
+	for data[beg] == ' ' {
+		beg++
+	}
+	// trim trailing newline
+	end := len(data) - 1
+	// trim trailing spaces
+	for end > beg && data[end-1] == ' ' {
+		end--
+	}
+	work := func() bool {
+		p.inline(out, data[beg:end])
+		return true
+	}
+	p.r.Paragraph(out, work)
+}
+func (p *parser) paragraph(out *bytes.Buffer, data []byte) int {
+	// prev: index of 1st char of previous line
+	// line: index of 1st char of current line
+	// i: index of cursor/end of current line
+	var prev, line, i int
+	// keep going until we find something to mark the end of the paragraph
+	for i < len(data) {
+		// mark the beginning of the current line
+		prev = line
+		current := data[i:]
+		line = i
+		// did we find a blank line marking the end of the paragraph?
+		if n := p.isEmpty(current); n > 0 {
+			// did this blank line followed by a definition list item?
+			if p.flags&EXTENSION_DEFINITION_LISTS != 0 {
+				if i < len(data)-1 && data[i+1] == ':' {
+					return p.list(out, data[prev:], LIST_TYPE_DEFINITION)
+				}
+			}
+			p.renderParagraph(out, data[:i])
+			return i + n
+		}
+		// an underline under some text marks a header, so our paragraph ended on prev line
+		if i > 0 {
+			if level := p.isUnderlinedHeader(current); level > 0 {
+				// render the paragraph
+				p.renderParagraph(out, data[:prev])
+				// ignore leading and trailing whitespace
+				eol := i - 1
+				for prev < eol && data[prev] == ' ' {
+					prev++
+				}
+				for eol > prev && data[eol-1] == ' ' {
+					eol--
+				}
+				// render the header
+				// this ugly double closure avoids forcing variables onto the heap
+				work := func(o *bytes.Buffer, pp *parser, d []byte) func() bool {
+					return func() bool {
+						pp.inline(o, d)
+						return true
+					}
+				}(out, p, data[prev:eol])
+				id := ""
+				if p.flags&EXTENSION_AUTO_HEADER_IDS != 0 {
+					id = SanitizedAnchorName(string(data[prev:eol]))
+				}
+				p.r.Header(out, work, level, id)
+				// find the end of the underline
+				for data[i] != '\n' {
+					i++
+				}
+				return i
+			}
+		}
+		// if the next line starts a block of HTML, then the paragraph ends here
+		if p.flags&EXTENSION_LAX_HTML_BLOCKS != 0 {
+			if data[i] == '<' && p.html(out, current, false) > 0 {
+				// rewind to before the HTML block
+				p.renderParagraph(out, data[:i])
+				return i
+			}
+		}
+		// if there's a prefixed header or a horizontal rule after this, paragraph is over
+		if p.isPrefixHeader(current) || p.isHRule(current) {
+			p.renderParagraph(out, data[:i])
+			return i
+		}
+		// if there's a fenced code block, paragraph is over
+		if p.flags&EXTENSION_FENCED_CODE != 0 {
+			if p.fencedCodeBlock(out, current, false) > 0 {
+				p.renderParagraph(out, data[:i])
+				return i
+			}
+		}
+		// if there's a definition list item, prev line is a definition term
+		if p.flags&EXTENSION_DEFINITION_LISTS != 0 {
+			if p.dliPrefix(current) != 0 {
+				return p.list(out, data[prev:], LIST_TYPE_DEFINITION)
+			}
+		}
+		// if there's a list after this, paragraph is over
+		if p.flags&EXTENSION_NO_EMPTY_LINE_BEFORE_BLOCK != 0 {
+			if p.uliPrefix(current) != 0 ||
+				p.oliPrefix(current) != 0 ||
+				p.quotePrefix(current) != 0 ||
+				p.codePrefix(current) != 0 {
+				p.renderParagraph(out, data[:i])
+				return i
+			}
+		}
+		// otherwise, scan to the beginning of the next line
+		for data[i] != '\n' {
+			i++
+		}
+		i++
+	}
+	p.renderParagraph(out, data[:i])
+	return i
+}
+// SanitizedAnchorName returns a sanitized anchor name for the given text.
+//
+// It implements the algorithm specified in the package comment.
+func SanitizedAnchorName(text string) string {
+	var anchorName []rune
+	futureDash := false
+	for _, r := range text {
+		switch {
+		case unicode.IsLetter(r) || unicode.IsNumber(r):
+			if futureDash && len(anchorName) > 0 {
+				anchorName = append(anchorName, '-')
+			}
+			futureDash = false
+			anchorName = append(anchorName, unicode.ToLower(r))
+		default:
+			futureDash = true
+		}
+	}
+	return string(anchorName)
+}