2fd401c8f1
From-SVN: r181964
187 lines
4.9 KiB
Go
187 lines
4.9 KiB
Go
// Copyright 2011 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.
|
|
|
|
package html
|
|
|
|
import (
|
|
"bufio"
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
)
|
|
|
|
type writer interface {
|
|
io.Writer
|
|
WriteByte(byte) error
|
|
WriteString(string) (int, error)
|
|
}
|
|
|
|
// Render renders the parse tree n to the given writer.
|
|
//
|
|
// Rendering is done on a 'best effort' basis: calling Parse on the output of
|
|
// Render will always result in something similar to the original tree, but it
|
|
// is not necessarily an exact clone unless the original tree was 'well-formed'.
|
|
// 'Well-formed' is not easily specified; the HTML5 specification is
|
|
// complicated.
|
|
//
|
|
// Calling Parse on arbitrary input typically results in a 'well-formed' parse
|
|
// tree. However, it is possible for Parse to yield a 'badly-formed' parse tree.
|
|
// For example, in a 'well-formed' parse tree, no <a> element is a child of
|
|
// another <a> element: parsing "<a><a>" results in two sibling elements.
|
|
// Similarly, in a 'well-formed' parse tree, no <a> element is a child of a
|
|
// <table> element: parsing "<p><table><a>" results in a <p> with two sibling
|
|
// children; the <a> is reparented to the <table>'s parent. However, calling
|
|
// Parse on "<a><table><a>" does not return an error, but the result has an <a>
|
|
// element with an <a> child, and is therefore not 'well-formed'.
|
|
//
|
|
// Programmatically constructed trees are typically also 'well-formed', but it
|
|
// is possible to construct a tree that looks innocuous but, when rendered and
|
|
// re-parsed, results in a different tree. A simple example is that a solitary
|
|
// text node would become a tree containing <html>, <head> and <body> elements.
|
|
// Another example is that the programmatic equivalent of "a<head>b</head>c"
|
|
// becomes "<html><head><head/><body>abc</body></html>".
|
|
func Render(w io.Writer, n *Node) error {
|
|
if x, ok := w.(writer); ok {
|
|
return render(x, n)
|
|
}
|
|
buf := bufio.NewWriter(w)
|
|
if err := render(buf, n); err != nil {
|
|
return err
|
|
}
|
|
return buf.Flush()
|
|
}
|
|
|
|
func render(w writer, n *Node) error {
|
|
// Render non-element nodes; these are the easy cases.
|
|
switch n.Type {
|
|
case ErrorNode:
|
|
return errors.New("html: cannot render an ErrorNode node")
|
|
case TextNode:
|
|
return escape(w, n.Data)
|
|
case DocumentNode:
|
|
for _, c := range n.Child {
|
|
if err := render(w, c); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
return nil
|
|
case ElementNode:
|
|
// No-op.
|
|
case CommentNode:
|
|
if _, err := w.WriteString("<!--"); err != nil {
|
|
return err
|
|
}
|
|
if _, err := w.WriteString(n.Data); err != nil {
|
|
return err
|
|
}
|
|
if _, err := w.WriteString("-->"); err != nil {
|
|
return err
|
|
}
|
|
return nil
|
|
case DoctypeNode:
|
|
if _, err := w.WriteString("<!DOCTYPE "); err != nil {
|
|
return err
|
|
}
|
|
if _, err := w.WriteString(n.Data); err != nil {
|
|
return err
|
|
}
|
|
return w.WriteByte('>')
|
|
default:
|
|
return errors.New("html: unknown node type")
|
|
}
|
|
|
|
// Render the <xxx> opening tag.
|
|
if err := w.WriteByte('<'); err != nil {
|
|
return err
|
|
}
|
|
if _, err := w.WriteString(n.Data); err != nil {
|
|
return err
|
|
}
|
|
for _, a := range n.Attr {
|
|
if err := w.WriteByte(' '); err != nil {
|
|
return err
|
|
}
|
|
if _, err := w.WriteString(a.Key); err != nil {
|
|
return err
|
|
}
|
|
if _, err := w.WriteString(`="`); err != nil {
|
|
return err
|
|
}
|
|
if err := escape(w, a.Val); err != nil {
|
|
return err
|
|
}
|
|
if err := w.WriteByte('"'); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
if voidElements[n.Data] {
|
|
if len(n.Child) != 0 {
|
|
return fmt.Errorf("html: void element <%s> has child nodes", n.Data)
|
|
}
|
|
_, err := w.WriteString("/>")
|
|
return err
|
|
}
|
|
if err := w.WriteByte('>'); err != nil {
|
|
return err
|
|
}
|
|
|
|
// Render any child nodes.
|
|
switch n.Data {
|
|
case "noembed", "noframes", "noscript", "script", "style":
|
|
for _, c := range n.Child {
|
|
if c.Type != TextNode {
|
|
return fmt.Errorf("html: raw text element <%s> has non-text child node", n.Data)
|
|
}
|
|
if _, err := w.WriteString(c.Data); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
case "textarea", "title":
|
|
for _, c := range n.Child {
|
|
if c.Type != TextNode {
|
|
return fmt.Errorf("html: RCDATA element <%s> has non-text child node", n.Data)
|
|
}
|
|
if err := render(w, c); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
default:
|
|
for _, c := range n.Child {
|
|
if err := render(w, c); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
}
|
|
|
|
// Render the </xxx> closing tag.
|
|
if _, err := w.WriteString("</"); err != nil {
|
|
return err
|
|
}
|
|
if _, err := w.WriteString(n.Data); err != nil {
|
|
return err
|
|
}
|
|
return w.WriteByte('>')
|
|
}
|
|
|
|
// Section 13.1.2, "Elements", gives this list of void elements. Void elements
|
|
// are those that can't have any contents.
|
|
var voidElements = map[string]bool{
|
|
"area": true,
|
|
"base": true,
|
|
"br": true,
|
|
"col": true,
|
|
"command": true,
|
|
"embed": true,
|
|
"hr": true,
|
|
"img": true,
|
|
"input": true,
|
|
"keygen": true,
|
|
"link": true,
|
|
"meta": true,
|
|
"param": true,
|
|
"source": true,
|
|
"track": true,
|
|
"wbr": true,
|
|
}
|