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			336 lines
		
	
	
	
		
			8.4 KiB
		
	
	
	
		
			Go
		
	
	
	
	
	
			
		
		
	
	
			336 lines
		
	
	
	
		
			8.4 KiB
		
	
	
	
		
			Go
		
	
	
	
	
	
package md2man
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import (
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	"fmt"
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	"io"
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	"os"
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	"strings"
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	"github.com/russross/blackfriday/v2"
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)
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// roffRenderer implements the blackfriday.Renderer interface for creating
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// roff format (manpages) from markdown text
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type roffRenderer struct {
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	extensions   blackfriday.Extensions
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	listCounters []int
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	firstHeader  bool
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	firstDD      bool
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	listDepth    int
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}
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const (
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	titleHeader      = ".TH "
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	topLevelHeader   = "\n\n.SH "
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	secondLevelHdr   = "\n.SH "
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	otherHeader      = "\n.SS "
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	crTag            = "\n"
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	emphTag          = "\\fI"
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	emphCloseTag     = "\\fP"
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	strongTag        = "\\fB"
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	strongCloseTag   = "\\fP"
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	breakTag         = "\n.br\n"
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	paraTag          = "\n.PP\n"
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	hruleTag         = "\n.ti 0\n\\l'\\n(.lu'\n"
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	linkTag          = "\n\\[la]"
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	linkCloseTag     = "\\[ra]"
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	codespanTag      = "\\fB\\fC"
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	codespanCloseTag = "\\fR"
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	codeTag          = "\n.PP\n.RS\n\n.nf\n"
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	codeCloseTag     = "\n.fi\n.RE\n"
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	quoteTag         = "\n.PP\n.RS\n"
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	quoteCloseTag    = "\n.RE\n"
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	listTag          = "\n.RS\n"
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	listCloseTag     = "\n.RE\n"
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	dtTag            = "\n.TP\n"
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	dd2Tag           = "\n"
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	tableStart       = "\n.TS\nallbox;\n"
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	tableEnd         = ".TE\n"
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	tableCellStart   = "T{\n"
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	tableCellEnd     = "\nT}\n"
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)
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// NewRoffRenderer creates a new blackfriday Renderer for generating roff documents
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// from markdown
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func NewRoffRenderer() *roffRenderer { // nolint: golint
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	var extensions blackfriday.Extensions
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	extensions |= blackfriday.NoIntraEmphasis
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	extensions |= blackfriday.Tables
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	extensions |= blackfriday.FencedCode
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	extensions |= blackfriday.SpaceHeadings
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	extensions |= blackfriday.Footnotes
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	extensions |= blackfriday.Titleblock
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	extensions |= blackfriday.DefinitionLists
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	return &roffRenderer{
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		extensions: extensions,
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	}
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}
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// GetExtensions returns the list of extensions used by this renderer implementation
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func (r *roffRenderer) GetExtensions() blackfriday.Extensions {
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	return r.extensions
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}
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// RenderHeader handles outputting the header at document start
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func (r *roffRenderer) RenderHeader(w io.Writer, ast *blackfriday.Node) {
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	// disable hyphenation
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	out(w, ".nh\n")
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}
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// RenderFooter handles outputting the footer at the document end; the roff
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// renderer has no footer information
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func (r *roffRenderer) RenderFooter(w io.Writer, ast *blackfriday.Node) {
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}
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// RenderNode is called for each node in a markdown document; based on the node
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// type the equivalent roff output is sent to the writer
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func (r *roffRenderer) RenderNode(w io.Writer, node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
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	var walkAction = blackfriday.GoToNext
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	switch node.Type {
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	case blackfriday.Text:
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		escapeSpecialChars(w, node.Literal)
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	case blackfriday.Softbreak:
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		out(w, crTag)
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	case blackfriday.Hardbreak:
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		out(w, breakTag)
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	case blackfriday.Emph:
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		if entering {
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			out(w, emphTag)
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		} else {
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			out(w, emphCloseTag)
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		}
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	case blackfriday.Strong:
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		if entering {
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			out(w, strongTag)
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		} else {
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			out(w, strongCloseTag)
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		}
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	case blackfriday.Link:
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		if !entering {
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			out(w, linkTag+string(node.LinkData.Destination)+linkCloseTag)
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		}
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	case blackfriday.Image:
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		// ignore images
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		walkAction = blackfriday.SkipChildren
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	case blackfriday.Code:
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		out(w, codespanTag)
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		escapeSpecialChars(w, node.Literal)
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		out(w, codespanCloseTag)
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	case blackfriday.Document:
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		break
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	case blackfriday.Paragraph:
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		// roff .PP markers break lists
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		if r.listDepth > 0 {
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			return blackfriday.GoToNext
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		}
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		if entering {
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			out(w, paraTag)
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		} else {
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			out(w, crTag)
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		}
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	case blackfriday.BlockQuote:
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		if entering {
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			out(w, quoteTag)
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		} else {
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			out(w, quoteCloseTag)
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		}
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	case blackfriday.Heading:
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		r.handleHeading(w, node, entering)
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	case blackfriday.HorizontalRule:
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		out(w, hruleTag)
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	case blackfriday.List:
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		r.handleList(w, node, entering)
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	case blackfriday.Item:
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		r.handleItem(w, node, entering)
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	case blackfriday.CodeBlock:
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		out(w, codeTag)
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		escapeSpecialChars(w, node.Literal)
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		out(w, codeCloseTag)
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	case blackfriday.Table:
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		r.handleTable(w, node, entering)
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	case blackfriday.TableHead:
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	case blackfriday.TableBody:
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	case blackfriday.TableRow:
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		// no action as cell entries do all the nroff formatting
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		return blackfriday.GoToNext
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	case blackfriday.TableCell:
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		r.handleTableCell(w, node, entering)
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	case blackfriday.HTMLSpan:
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		// ignore other HTML tags
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	default:
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		fmt.Fprintln(os.Stderr, "WARNING: go-md2man does not handle node type "+node.Type.String())
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	}
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	return walkAction
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}
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func (r *roffRenderer) handleHeading(w io.Writer, node *blackfriday.Node, entering bool) {
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	if entering {
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		switch node.Level {
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		case 1:
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			if !r.firstHeader {
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				out(w, titleHeader)
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				r.firstHeader = true
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				break
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			}
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			out(w, topLevelHeader)
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		case 2:
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			out(w, secondLevelHdr)
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		default:
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			out(w, otherHeader)
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		}
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	}
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}
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func (r *roffRenderer) handleList(w io.Writer, node *blackfriday.Node, entering bool) {
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	openTag := listTag
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	closeTag := listCloseTag
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	if node.ListFlags&blackfriday.ListTypeDefinition != 0 {
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		// tags for definition lists handled within Item node
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		openTag = ""
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		closeTag = ""
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	}
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	if entering {
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		r.listDepth++
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		if node.ListFlags&blackfriday.ListTypeOrdered != 0 {
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			r.listCounters = append(r.listCounters, 1)
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		}
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		out(w, openTag)
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	} else {
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		if node.ListFlags&blackfriday.ListTypeOrdered != 0 {
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			r.listCounters = r.listCounters[:len(r.listCounters)-1]
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		}
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		out(w, closeTag)
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		r.listDepth--
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	}
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}
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func (r *roffRenderer) handleItem(w io.Writer, node *blackfriday.Node, entering bool) {
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	if entering {
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		if node.ListFlags&blackfriday.ListTypeOrdered != 0 {
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			out(w, fmt.Sprintf(".IP \"%3d.\" 5\n", r.listCounters[len(r.listCounters)-1]))
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			r.listCounters[len(r.listCounters)-1]++
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		} else if node.ListFlags&blackfriday.ListTypeTerm != 0 {
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			// DT (definition term): line just before DD (see below).
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			out(w, dtTag)
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			r.firstDD = true
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		} else if node.ListFlags&blackfriday.ListTypeDefinition != 0 {
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			// DD (definition description): line that starts with ": ".
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			//
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			// We have to distinguish between the first DD and the
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			// subsequent ones, as there should be no vertical
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			// whitespace between the DT and the first DD.
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			if r.firstDD {
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				r.firstDD = false
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			} else {
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				out(w, dd2Tag)
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			}
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		} else {
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			out(w, ".IP \\(bu 2\n")
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		}
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	} else {
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		out(w, "\n")
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	}
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}
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func (r *roffRenderer) handleTable(w io.Writer, node *blackfriday.Node, entering bool) {
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	if entering {
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		out(w, tableStart)
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		// call walker to count cells (and rows?) so format section can be produced
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		columns := countColumns(node)
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		out(w, strings.Repeat("l ", columns)+"\n")
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		out(w, strings.Repeat("l ", columns)+".\n")
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	} else {
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		out(w, tableEnd)
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	}
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}
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func (r *roffRenderer) handleTableCell(w io.Writer, node *blackfriday.Node, entering bool) {
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	if entering {
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		var start string
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		if node.Prev != nil && node.Prev.Type == blackfriday.TableCell {
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			start = "\t"
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		}
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		if node.IsHeader {
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			start += codespanTag
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		} else if nodeLiteralSize(node) > 30 {
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			start += tableCellStart
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		}
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		out(w, start)
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	} else {
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		var end string
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		if node.IsHeader {
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			end = codespanCloseTag
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		} else if nodeLiteralSize(node) > 30 {
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			end = tableCellEnd
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		}
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		if node.Next == nil && end != tableCellEnd {
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			// Last cell: need to carriage return if we are at the end of the
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			// header row and content isn't wrapped in a "tablecell"
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			end += crTag
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		}
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		out(w, end)
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	}
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}
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func nodeLiteralSize(node *blackfriday.Node) int {
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	total := 0
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	for n := node.FirstChild; n != nil; n = n.FirstChild {
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		total += len(n.Literal)
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	}
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	return total
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}
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// because roff format requires knowing the column count before outputting any table
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// data we need to walk a table tree and count the columns
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func countColumns(node *blackfriday.Node) int {
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	var columns int
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	node.Walk(func(node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
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		switch node.Type {
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		case blackfriday.TableRow:
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			if !entering {
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				return blackfriday.Terminate
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			}
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		case blackfriday.TableCell:
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			if entering {
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				columns++
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			}
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		default:
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		}
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		return blackfriday.GoToNext
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	})
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	return columns
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}
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func out(w io.Writer, output string) {
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	io.WriteString(w, output) // nolint: errcheck
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}
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func escapeSpecialChars(w io.Writer, text []byte) {
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	for i := 0; i < len(text); i++ {
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		// escape initial apostrophe or period
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		if len(text) >= 1 && (text[0] == '\'' || text[0] == '.') {
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			out(w, "\\&")
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		}
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		// directly copy normal characters
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		org := i
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		for i < len(text) && text[i] != '\\' {
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			i++
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		}
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		if i > org {
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			w.Write(text[org:i]) // nolint: errcheck
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		}
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		// escape a character
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		if i >= len(text) {
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			break
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		}
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		w.Write([]byte{'\\', text[i]}) // nolint: errcheck
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	}
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}
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