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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [exp/] [html/] [render.go] - Rev 747
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// 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 htmlimport ("bufio""errors""fmt""io""strings")type writer interface {io.WriterWriteByte(byte) errorWriteString(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()}// plaintextAbort is returned from render1 when a <plaintext> element// has been rendered. No more end tags should be rendered after that.var plaintextAbort = errors.New("html: internal error (plaintext abort)")func render(w writer, n *Node) error {err := render1(w, n)if err == plaintextAbort {err = nil}return err}func render1(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 := render1(w, c); err != nil {return err}}return nilcase 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 nilcase DoctypeNode:if _, err := w.WriteString("<!DOCTYPE "); err != nil {return err}if _, err := w.WriteString(n.Data); err != nil {return err}if n.Attr != nil {var p, s stringfor _, a := range n.Attr {switch a.Key {case "public":p = a.Valcase "system":s = a.Val}}if p != "" {if _, err := w.WriteString(" PUBLIC "); err != nil {return err}if err := writeQuoted(w, p); err != nil {return err}if s != "" {if err := w.WriteByte(' '); err != nil {return err}if err := writeQuoted(w, s); err != nil {return err}}} else if s != "" {if _, err := w.WriteString(" SYSTEM "); err != nil {return err}if err := writeQuoted(w, s); 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 a.Namespace != "" {if _, err := w.WriteString(a.Namespace); err != nil {return err}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}// Add initial newline where there is danger of a newline beging ignored.if len(n.Child) > 0 && n.Child[0].Type == TextNode && strings.HasPrefix(n.Child[0].Data, "\n") {switch n.Data {case "pre", "listing", "textarea":if err := w.WriteByte('\n'); err != nil {return err}}}// Render any child nodes.switch n.Data {case "iframe", "noembed", "noframes", "noscript", "plaintext", "script", "style", "xmp":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}}if n.Data == "plaintext" {// Don't render anything else. <plaintext> must be the// last element in the file, with no closing tag.return plaintextAbort}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 := render1(w, c); err != nil {return err}}default:for _, c := range n.Child {if err := render1(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('>')}// writeQuoted writes s to w surrounded by quotes. Normally it will use double// quotes, but if s contains a double quote, it will use single quotes.// It is used for writing the identifiers in a doctype declaration.// In valid HTML, they can't contain both types of quotes.func writeQuoted(w writer, s string) error {var q byte = '"'if strings.Contains(s, `"`) {q = '\''}if err := w.WriteByte(q); err != nil {return err}if _, err := w.WriteString(s); err != nil {return err}if err := w.WriteByte(q); err != nil {return err}return nil}// Section 12.1.2, "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,}