Teach doc.go about // comments.

This is in preparation for changing all the comments.

Change-Id: Id7ff24331a3b9d108402238c63eeeb462c7cd809
Reviewed-on: https://boringssl-review.googlesource.com/18945
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

util/doc.go

@@ -74,8 +74,13 @@ const (
 	cppGuard     = "#if defined(__cplusplus)"
 	commentStart = "/* "
 	commentEnd   = " */"
+	lineComment  = "// "
 )
 
+func isComment(line string) bool {
+	return strings.HasPrefix(line, commentStart) || strings.HasPrefix(line, lineComment)
+}
+
 func extractComment(lines []string, lineNo int) (comment []string, rest []string, restLineNo int, err error) {
 	if len(lines) == 0 {
 		return nil, lines, lineNo, nil
@@ -84,7 +89,10 @@ func extractComment(lines []string, lineNo int) (comment []string, rest []string
 	restLineNo = lineNo
 	rest = lines
 
-	if !strings.HasPrefix(rest[0], commentStart) {
+	var isBlock bool
+	if strings.HasPrefix(rest[0], commentStart) {
+		isBlock = true
+	} else if !strings.HasPrefix(rest[0], lineComment) {
 		panic("extractComment called on non-comment")
 	}
 	commentParagraph := rest[0][len(commentStart):]
@@ -92,25 +100,34 @@ func extractComment(lines []string, lineNo int) (comment []string, rest []string
 	restLineNo++
 
 	for len(rest) > 0 {
-		i := strings.Index(commentParagraph, commentEnd)
-		if i >= 0 {
-			if i != len(commentParagraph)-len(commentEnd) {
-				err = fmt.Errorf("garbage after comment end on line %d", restLineNo)
+		if isBlock {
+			i := strings.Index(commentParagraph, commentEnd)
+			if i >= 0 {
+				if i != len(commentParagraph)-len(commentEnd) {
+					err = fmt.Errorf("garbage after comment end on line %d", restLineNo)
+					return
+				}
+				commentParagraph = commentParagraph[:i]
+				if len(commentParagraph) > 0 {
+					comment = append(comment, commentParagraph)
+				}
 				return
 			}
-			commentParagraph = commentParagraph[:i]
-			if len(commentParagraph) > 0 {
-				comment = append(comment, commentParagraph)
-			}
-			return
 		}
 
 		line := rest[0]
-		if !strings.HasPrefix(line, " *") {
-			err = fmt.Errorf("comment doesn't start with block prefix on line %d: %s", restLineNo, line)
+		if isBlock {
+			if !strings.HasPrefix(line, " *") {
+				err = fmt.Errorf("comment doesn't start with block prefix on line %d: %s", restLineNo, line)
+				return
+			}
+		} else if !strings.HasPrefix(line, "//") {
+			if len(commentParagraph) > 0 {
+				comment = append(comment, commentParagraph)
+			}
 			return
 		}
-		if len(line) == 2 || line[2] != '/' {
+		if len(line) == 2 || !isBlock || line[2] != '/' {
 			line = line[2:]
 		}
 		if strings.HasPrefix(line, "   ") {
@@ -309,7 +326,7 @@ func (config *Config) parseHeader(path string) (*HeaderFile, error) {
 	}
 
 	oldLines = lines
-	if len(lines) > 0 && strings.HasPrefix(lines[0], commentStart) {
+	if len(lines) > 0 && isComment(lines[0]) {
 		comment, rest, restLineNo, err := extractComment(lines, lineNo)
 		if err != nil {
 			return nil, err
@@ -345,7 +362,7 @@ func (config *Config) parseHeader(path string) (*HeaderFile, error) {
 
 		var section HeaderSection
 
-		if strings.HasPrefix(line, commentStart) {
+		if isComment(line) {
 			comment, rest, restLineNo, err := extractComment(lines, lineNo)
 			if err != nil {
 				return nil, err
@@ -380,7 +397,7 @@ func (config *Config) parseHeader(path string) (*HeaderFile, error) {
 
 			var comment []string
 			var decl string
-			if strings.HasPrefix(line, commentStart) {
+			if isComment(line) {
 				comment, lines, lineNo, err = extractComment(lines, lineNo)
 				if err != nil {
 					return nil, err