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// 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 (
"go/ast"
"io"
"regexp"
"strings"
"text/template" // for HTMLEscape
)
func isWhitespace(ch byte) bool { return ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r' }
func stripTrailingWhitespace(s string) string {
i := len(s)
for i > 0 && isWhitespace(s[i-1]) {
i--
}
return s[0:i]
}
// CommentText returns the text of comment,
// with the comment markers - //, /*, and */ - removed.
func CommentText(comment *ast.CommentGroup) string {
if comment == nil {
return ""
}
comments := make([]string, len(comment.List))
for i, c := range comment.List {
comments[i] = string(c.Text)
}
lines := make([]string, 0, 10) // most comments are less than 10 lines
for _, c := range comments {
// Remove comment markers.
// The parser has given us exactly the comment text.
switch c[1] {
case '/':
//-style comment
c = c[2:]
// Remove leading space after //, if there is one.
// TODO(gri) This appears to be necessary in isolated
// cases (bignum.RatFromString) - why?
if len(c) > 0 && c[0] == ' ' {
c = c[1:]
}
case '*':
/*-style comment */
c = c[2 : len(c)-2]
}
// Split on newlines.
cl := strings.Split(c, "\n")
// Walk lines, stripping trailing white space and adding to list.
for _, l := range cl {
lines = append(lines, stripTrailingWhitespace(l))
}
}
// Remove leading blank lines; convert runs of
// interior blank lines to a single blank line.
n := 0
for _, line := range lines {
if line != "" || n > 0 && lines[n-1] != "" {
lines[n] = line
n++
}
}
lines = lines[0:n]
// Add final "" entry to get trailing newline from Join.
if n > 0 && lines[n-1] != "" {
lines = append(lines, "")
}
return strings.Join(lines, "\n")
}
// Split bytes into lines.
func split(text []byte) [][]byte {
// count lines
n := 0
last := 0
for i, c := range text {
if c == '\n' {
last = i + 1
n++
}
}
if last < len(text) {
n++
}
// split
out := make([][]byte, n)
last = 0
n = 0
for i, c := range text {
if c == '\n' {
out[n] = text[last : i+1]
last = i + 1
n++
}
}
if last < len(text) {
out[n] = text[last:]
}
return out
}
var (
ldquo = []byte("“")
rdquo = []byte("”")
)
// Escape comment text for HTML. If nice is set,
// also turn `` into “ and '' into ”.
func commentEscape(w io.Writer, s []byte, nice bool) {
last := 0
if nice {
for i := 0; i < len(s)-1; i++ {
ch := s[i]
if ch == s[i+1] && (ch == '`' || ch == '\'') {
template.HTMLEscape(w, s[last:i])
last = i + 2
switch ch {
case '`':
w.Write(ldquo)
case '\'':
w.Write(rdquo)
}
i++ // loop will add one more
}
}
}
template.HTMLEscape(w, s[last:])
}
const (
// Regexp for Go identifiers
identRx = `[a-zA-Z_][a-zA-Z_0-9]*` // TODO(gri) ASCII only for now - fix this
// Regexp for URLs
protocol = `(https?|ftp|file|gopher|mailto|news|nntp|telnet|wais|prospero):`
hostPart = `[a-zA-Z0-9_@\-]+`
filePart = `[a-zA-Z0-9_?%#~&/\-+=]+`
urlRx = protocol + `//` + // http://
hostPart + `([.:]` + hostPart + `)*/?` + // //www.google.com:8080/
filePart + `([:.,]` + filePart + `)*`
)
var matchRx = regexp.MustCompile(`(` + identRx + `)|(` + urlRx + `)`)
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")
)
// 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 “
// and '' into ”).
func emphasize(w io.Writer, line []byte, words map[string]string, nice bool) {
for {
m := matchRx.FindSubmatchIndex(line)
if m == nil {
break
}
// m >= 6 (two parenthesized sub-regexps in matchRx, 1st one is identRx)
// write text before match
commentEscape(w, line[0:m[0]], nice)
// analyze match
match := line[m[0]:m[1]]
url := ""
italics := false
if words != nil {
url, italics = words[string(match)]
}
if m[2] < 0 {
// didn't match against first parenthesized sub-regexp; must be match against urlRx
if !italics {
// no alternative URL in words list, use match instead
url = string(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 []byte) int {
i := 0
for i < len(s) && (s[i] == ' ' || s[i] == '\t') {
i++
}
return i
}
func isBlank(s []byte) bool { return len(s) == 0 || (len(s) == 1 && s[0] == '\n') }
func commonPrefix(a, b []byte) []byte {
i := 0
for i < len(a) && i < len(b) && a[i] == b[i] {
i++
}
return a[0:i]
}
func unindent(block [][]byte) {
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:]
}
}
}
// Convert 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.
//
// Turn each run of multiple \n into </p><p>.
// Turn each run of indented lines into a <pre> block without indent.
//
// 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).
//
// 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, s []byte, words map[string]string) {
inpara := false
close := func() {
if inpara {
w.Write(html_endp)
inpara = false
}
}
open := func() {
if !inpara {
w.Write(html_p)
inpara = true
}
}
lines := split(s)
unindent(lines)
for i := 0; i < len(lines); {
line := lines[i]
if isBlank(line) {
// close paragraph
close()
i++
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--
}
block := lines[i:j]
i = j
unindent(block)
// put those lines in a pre block
w.Write(html_pre)
for _, line := range block {
emphasize(w, line, nil, false) // no nice text formatting
}
w.Write(html_endpre)
continue
}
// open paragraph
open()
emphasize(w, lines[i], words, true) // nice text formatting
i++
}
close()
}
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