346 lines
8.4 KiB
Go
346 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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defineTerm 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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arglistTag = "\n.TP\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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r.handleText(w, node, entering)
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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.TableCell:
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r.handleTableCell(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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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) handleText(w io.Writer, node *blackfriday.Node, entering bool) {
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var (
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start, end string
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)
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// handle special roff table cell text encapsulation
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if node.Parent.Type == blackfriday.TableCell {
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if len(node.Literal) > 30 {
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start = tableCellStart
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end = tableCellEnd
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} else {
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// end rows that aren't terminated by "tableCellEnd" with a cr if end of row
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if node.Parent.Next == nil && !node.Parent.IsHeader {
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end = crTag
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}
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}
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}
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out(w, start)
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escapeSpecialChars(w, node.Literal)
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out(w, end)
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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.ListTypeDefinition != 0 {
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// state machine for handling terms and following definitions
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// since blackfriday does not distinguish them properly, nor
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// does it seperate them into separate lists as it should
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if !r.defineTerm {
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out(w, arglistTag)
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r.defineTerm = true
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} else {
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r.defineTerm = false
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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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var (
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start, end string
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)
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if node.IsHeader {
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start = codespanTag
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end = codespanCloseTag
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}
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if entering {
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if node.Prev != nil && node.Prev.Type == blackfriday.TableCell {
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out(w, "\t"+start)
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} else {
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out(w, start)
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}
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} else {
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// need to carriage return if we are at the end of the header row
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if node.IsHeader && node.Next == nil {
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end = 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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// 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 needsBackslash(c byte) bool {
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for _, r := range []byte("-_&\\~") {
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if c == r {
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return true
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}
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}
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return false
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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) && !needsBackslash(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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