1 files changed, 513 insertions, 0 deletions

diff --git a/src/go/doc/comment.go b/src/go/doc/comment.go
new file mode 100644
index 0000000..92131a3
--- /dev/null
+++ b/src/go/doc/comment.go
@@ -0,0 +1,513 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Godoc comment extraction and comment -> HTML formatting.
+
+package doc
+
+import (
+	"bytes"
+	"internal/lazyregexp"
+	"io"
+	"strings"
+	"text/template" // for HTMLEscape
+	"unicode"
+	"unicode/utf8"
+)
+
+const (
+	ldquo = "“"
+	rdquo = "”"
+	ulquo = "“"
+	urquo = "”"
+)
+
+var (
+	htmlQuoteReplacer    = strings.NewReplacer(ulquo, ldquo, urquo, rdquo)
+	unicodeQuoteReplacer = strings.NewReplacer("``", ulquo, "''", urquo)
+)
+
+// Escape comment text for HTML. If nice is set,
+// also turn `` into “ and '' into ”.
+func commentEscape(w io.Writer, text string, nice bool) {
+	if nice {
+		// In the first pass, we convert `` and '' into their unicode equivalents.
+		// This prevents them from being escaped in HTMLEscape.
+		text = convertQuotes(text)
+		var buf bytes.Buffer
+		template.HTMLEscape(&buf, []byte(text))
+		// Now we convert the unicode quotes to their HTML escaped entities to maintain old behavior.
+		// We need to use a temp buffer to read the string back and do the conversion,
+		// otherwise HTMLEscape will escape & to &
+		htmlQuoteReplacer.WriteString(w, buf.String())
+		return
+	}
+	template.HTMLEscape(w, []byte(text))
+}
+
+func convertQuotes(text string) string {
+	return unicodeQuoteReplacer.Replace(text)
+}
+
+const (
+	// Regexp for Go identifiers
+	identRx = `[\pL_][\pL_0-9]*`
+
+	// Regexp for URLs
+	// Match parens, and check later for balance - see #5043, #22285
+	// Match .,:;?! within path, but not at end - see #18139, #16565
+	// This excludes some rare yet valid urls ending in common punctuation
+	// in order to allow sentences ending in URLs.
+
+	// protocol (required) e.g. http
+	protoPart = `(https?|ftp|file|gopher|mailto|nntp)`
+	// host (required) e.g. www.example.com or [::1]:8080
+	hostPart = `([a-zA-Z0-9_@\-.\[\]:]+)`
+	// path+query+fragment (optional) e.g. /path/index.html?q=foo#bar
+	pathPart = `([.,:;?!]*[a-zA-Z0-9$'()*+&#=@~_/\-\[\]%])*`
+
+	urlRx = protoPart + `://` + hostPart + pathPart
+)
+
+var matchRx = lazyregexp.New(`(` + urlRx + `)|(` + identRx + `)`)
+
+var (
+	html_a      = []byte(`<a href="`)
+	html_aq     = []byte(`">`)
+	html_enda   = []byte("</a>")
+	html_i      = []byte("<i>")
+	html_endi   = []byte("</i>")
+	html_p      = []byte("<p>\n")
+	html_endp   = []byte("</p>\n")
+	html_pre    = []byte("<pre>")
+	html_endpre = []byte("</pre>\n")
+	html_h      = []byte(`<h3 id="`)
+	html_hq     = []byte(`">`)
+	html_endh   = []byte("</h3>\n")
+)
+
+// Emphasize and escape a line of text for HTML. URLs are converted into links;
+// if the URL also appears in the words map, the link is taken from the map (if
+// the corresponding map value is the empty string, the URL is not converted
+// into a link). Go identifiers that appear in the words map are italicized; if
+// the corresponding map value is not the empty string, it is considered a URL
+// and the word is converted into a link. If nice is set, the remaining text's
+// appearance is improved where it makes sense (e.g., `` is turned into &ldquo;
+// and '' into &rdquo;).
+func emphasize(w io.Writer, line string, words map[string]string, nice bool) {
+	for {
+		m := matchRx.FindStringSubmatchIndex(line)
+		if m == nil {
+			break
+		}
+		// m >= 6 (two parenthesized sub-regexps in matchRx, 1st one is urlRx)
+
+		// write text before match
+		commentEscape(w, line[0:m[0]], nice)
+
+		// adjust match for URLs
+		match := line[m[0]:m[1]]
+		if strings.Contains(match, "://") {
+			m0, m1 := m[0], m[1]
+			for _, s := range []string{"()", "{}", "[]"} {
+				open, close := s[:1], s[1:] // E.g., "(" and ")"
+				// require opening parentheses before closing parentheses (#22285)
+				if i := strings.Index(match, close); i >= 0 && i < strings.Index(match, open) {
+					m1 = m0 + i
+					match = line[m0:m1]
+				}
+				// require balanced pairs of parentheses (#5043)
+				for i := 0; strings.Count(match, open) != strings.Count(match, close) && i < 10; i++ {
+					m1 = strings.LastIndexAny(line[:m1], s)
+					match = line[m0:m1]
+				}
+			}
+			if m1 != m[1] {
+				// redo matching with shortened line for correct indices
+				m = matchRx.FindStringSubmatchIndex(line[:m[0]+len(match)])
+			}
+		}
+
+		// analyze match
+		url := ""
+		italics := false
+		if words != nil {
+			url, italics = words[match]
+		}
+		if m[2] >= 0 {
+			// match against first parenthesized sub-regexp; must be match against urlRx
+			if !italics {
+				// no alternative URL in words list, use match instead
+				url = match
+			}
+			italics = false // don't italicize URLs
+		}
+
+		// write match
+		if len(url) > 0 {
+			w.Write(html_a)
+			template.HTMLEscape(w, []byte(url))
+			w.Write(html_aq)
+		}
+		if italics {
+			w.Write(html_i)
+		}
+		commentEscape(w, match, nice)
+		if italics {
+			w.Write(html_endi)
+		}
+		if len(url) > 0 {
+			w.Write(html_enda)
+		}
+
+		// advance
+		line = line[m[1]:]
+	}
+	commentEscape(w, line, nice)
+}
+
+func indentLen(s string) int {
+	i := 0
+	for i < len(s) && (s[i] == ' ' || s[i] == '\t') {
+		i++
+	}
+	return i
+}
+
+func isBlank(s string) bool {
+	return len(s) == 0 || (len(s) == 1 && s[0] == '\n')
+}
+
+func commonPrefix(a, b string) string {
+	i := 0
+	for i < len(a) && i < len(b) && a[i] == b[i] {
+		i++
+	}
+	return a[0:i]
+}
+
+func unindent(block []string) {
+	if len(block) == 0 {
+		return
+	}
+
+	// compute maximum common white prefix
+	prefix := block[0][0:indentLen(block[0])]
+	for _, line := range block {
+		if !isBlank(line) {
+			prefix = commonPrefix(prefix, line[0:indentLen(line)])
+		}
+	}
+	n := len(prefix)
+
+	// remove
+	for i, line := range block {
+		if !isBlank(line) {
+			block[i] = line[n:]
+		}
+	}
+}
+
+// heading returns the trimmed line if it passes as a section heading;
+// otherwise it returns the empty string.
+func heading(line string) string {
+	line = strings.TrimSpace(line)
+	if len(line) == 0 {
+		return ""
+	}
+
+	// a heading must start with an uppercase letter
+	r, _ := utf8.DecodeRuneInString(line)
+	if !unicode.IsLetter(r) || !unicode.IsUpper(r) {
+		return ""
+	}
+
+	// it must end in a letter or digit:
+	r, _ = utf8.DecodeLastRuneInString(line)
+	if !unicode.IsLetter(r) && !unicode.IsDigit(r) {
+		return ""
+	}
+
+	// exclude lines with illegal characters. we allow "(),"
+	if strings.ContainsAny(line, ";:!?+*/=[]{}_^°&§~%#@<\">\\") {
+		return ""
+	}
+
+	// allow "'" for possessive "'s" only
+	for b := line; ; {
+		i := strings.IndexRune(b, '\'')
+		if i < 0 {
+			break
+		}
+		if i+1 >= len(b) || b[i+1] != 's' || (i+2 < len(b) && b[i+2] != ' ') {
+			return "" // not followed by "s "
+		}
+		b = b[i+2:]
+	}
+
+	// allow "." when followed by non-space
+	for b := line; ; {
+		i := strings.IndexRune(b, '.')
+		if i < 0 {
+			break
+		}
+		if i+1 >= len(b) || b[i+1] == ' ' {
+			return "" // not followed by non-space
+		}
+		b = b[i+1:]
+	}
+
+	return line
+}
+
+type op int
+
+const (
+	opPara op = iota
+	opHead
+	opPre
+)
+
+type block struct {
+	op    op
+	lines []string
+}
+
+var nonAlphaNumRx = lazyregexp.New(`[^a-zA-Z0-9]`)
+
+func anchorID(line string) string {
+	// Add a "hdr-" prefix to avoid conflicting with IDs used for package symbols.
+	return "hdr-" + nonAlphaNumRx.ReplaceAllString(line, "_")
+}
+
+// ToHTML converts comment text to formatted HTML.
+// The comment was prepared by DocReader,
+// so it is known not to have leading, trailing blank lines
+// nor to have trailing spaces at the end of lines.
+// The comment markers have already been removed.
+//
+// Each span of unindented non-blank lines is converted into
+// a single paragraph. There is one exception to the rule: a span that
+// consists of a single line, is followed by another paragraph span,
+// begins with a capital letter, and contains no punctuation
+// other than parentheses and commas is formatted as a heading.
+//
+// A span of indented lines is converted into a <pre> block,
+// with the common indent prefix removed.
+//
+// URLs in the comment text are converted into links; if the URL also appears
+// in the words map, the link is taken from the map (if the corresponding map
+// value is the empty string, the URL is not converted into a link).
+//
+// A pair of (consecutive) backticks (`) is converted to a unicode left quote (“), and a pair of (consecutive)
+// single quotes (') is converted to a unicode right quote (”).
+//
+// Go identifiers that appear in the words map are italicized; if the corresponding
+// map value is not the empty string, it is considered a URL and the word is converted
+// into a link.
+func ToHTML(w io.Writer, text string, words map[string]string) {
+	for _, b := range blocks(text) {
+		switch b.op {
+		case opPara:
+			w.Write(html_p)
+			for _, line := range b.lines {
+				emphasize(w, line, words, true)
+			}
+			w.Write(html_endp)
+		case opHead:
+			w.Write(html_h)
+			id := ""
+			for _, line := range b.lines {
+				if id == "" {
+					id = anchorID(line)
+					w.Write([]byte(id))
+					w.Write(html_hq)
+				}
+				commentEscape(w, line, true)
+			}
+			if id == "" {
+				w.Write(html_hq)
+			}
+			w.Write(html_endh)
+		case opPre:
+			w.Write(html_pre)
+			for _, line := range b.lines {
+				emphasize(w, line, nil, false)
+			}
+			w.Write(html_endpre)
+		}
+	}
+}
+
+func blocks(text string) []block {
+	var (
+		out  []block
+		para []string
+
+		lastWasBlank   = false
+		lastWasHeading = false
+	)
+
+	close := func() {
+		if para != nil {
+			out = append(out, block{opPara, para})
+			para = nil
+		}
+	}
+
+	lines := strings.SplitAfter(text, "\n")
+	unindent(lines)
+	for i := 0; i < len(lines); {
+		line := lines[i]
+		if isBlank(line) {
+			// close paragraph
+			close()
+			i++
+			lastWasBlank = true
+			continue
+		}
+		if indentLen(line) > 0 {
+			// close paragraph
+			close()
+
+			// count indented or blank lines
+			j := i + 1
+			for j < len(lines) && (isBlank(lines[j]) || indentLen(lines[j]) > 0) {
+				j++
+			}
+			// but not trailing blank lines
+			for j > i && isBlank(lines[j-1]) {
+				j--
+			}
+			pre := lines[i:j]
+			i = j
+
+			unindent(pre)
+
+			// put those lines in a pre block
+			out = append(out, block{opPre, pre})
+			lastWasHeading = false
+			continue
+		}
+
+		if lastWasBlank && !lastWasHeading && i+2 < len(lines) &&
+			isBlank(lines[i+1]) && !isBlank(lines[i+2]) && indentLen(lines[i+2]) == 0 {
+			// current line is non-blank, surrounded by blank lines
+			// and the next non-blank line is not indented: this
+			// might be a heading.
+			if head := heading(line); head != "" {
+				close()
+				out = append(out, block{opHead, []string{head}})
+				i += 2
+				lastWasHeading = true
+				continue
+			}
+		}
+
+		// open paragraph
+		lastWasBlank = false
+		lastWasHeading = false
+		para = append(para, lines[i])
+		i++
+	}
+	close()
+
+	return out
+}
+
+// ToText prepares comment text for presentation in textual output.
+// It wraps paragraphs of text to width or fewer Unicode code points
+// and then prefixes each line with the indent. In preformatted sections
+// (such as program text), it prefixes each non-blank line with preIndent.
+//
+// A pair of (consecutive) backticks (`) is converted to a unicode left quote (“), and a pair of (consecutive)
+// single quotes (') is converted to a unicode right quote (”).
+func ToText(w io.Writer, text string, indent, preIndent string, width int) {
+	l := lineWrapper{
+		out:    w,
+		width:  width,
+		indent: indent,
+	}
+	for _, b := range blocks(text) {
+		switch b.op {
+		case opPara:
+			// l.write will add leading newline if required
+			for _, line := range b.lines {
+				line = convertQuotes(line)
+				l.write(line)
+			}
+			l.flush()
+		case opHead:
+			w.Write(nl)
+			for _, line := range b.lines {
+				line = convertQuotes(line)
+				l.write(line + "\n")
+			}
+			l.flush()
+		case opPre:
+			w.Write(nl)
+			for _, line := range b.lines {
+				if isBlank(line) {
+					w.Write([]byte("\n"))
+				} else {
+					w.Write([]byte(preIndent))
+					w.Write([]byte(line))
+				}
+			}
+		}
+	}
+}
+
+type lineWrapper struct {
+	out       io.Writer
+	printed   bool
+	width     int
+	indent    string
+	n         int
+	pendSpace int
+}
+
+var nl = []byte("\n")
+var space = []byte(" ")
+var prefix = []byte("// ")
+
+func (l *lineWrapper) write(text string) {
+	if l.n == 0 && l.printed {
+		l.out.Write(nl) // blank line before new paragraph
+	}
+	l.printed = true
+
+	needsPrefix := false
+	isComment := strings.HasPrefix(text, "//")
+	for _, f := range strings.Fields(text) {
+		w := utf8.RuneCountInString(f)
+		// wrap if line is too long
+		if l.n > 0 && l.n+l.pendSpace+w > l.width {
+			l.out.Write(nl)
+			l.n = 0
+			l.pendSpace = 0
+			needsPrefix = isComment && !strings.HasPrefix(f, "//")
+		}
+		if l.n == 0 {
+			l.out.Write([]byte(l.indent))
+		}
+		if needsPrefix {
+			l.out.Write(prefix)
+			needsPrefix = false
+		}
+		l.out.Write(space[:l.pendSpace])
+		l.out.Write([]byte(f))
+		l.n += l.pendSpace + w
+		l.pendSpace = 1
+	}
+}
+
+func (l *lineWrapper) flush() {
+	if l.n == 0 {
+		return
+	}
+	l.out.Write(nl)
+	l.pendSpace = 0
+	l.n = 0
+}