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// Copyright 2010 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 (
"io"
"os"
)
// A NodeType is the type of a Node.
type NodeType int
const (
ErrorNode NodeType = iota
TextNode
DocumentNode
ElementNode
CommentNode
)
// A Node consists of a NodeType and some Data (tag name for element nodes,
// content for text) and are part of a tree of Nodes. Element nodes may also
// contain a slice of Attributes. Data is unescaped, so that it looks like
// "a<b" rather than "a&lt;b".
type Node struct {
Parent *Node
Child []*Node
Type NodeType
Data string
Attr []Attribute
}
// A parser implements the HTML5 parsing algorithm:
// http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#tree-construction
type parser struct {
// tokenizer provides the tokens for the parser.
tokenizer *Tokenizer
// tok is the most recently read token.
tok Token
// Self-closing tags like <hr/> are re-interpreted as a two-token sequence:
// <hr> followed by </hr>. hasSelfClosingToken is true if we have just read
// the synthetic start tag and the next one due is the matching end tag.
hasSelfClosingToken bool
// doc is the document root element.
doc *Node
// The stack of open elements (section 10.2.3.2).
stack []*Node
// Element pointers (section 10.2.3.4).
head, form *Node
// Other parsing state flags (section 10.2.3.5).
scripting, framesetOK bool
}
// push pushes onto the stack of open elements.
func (p *parser) push(n *Node) {
p.stack = append(p.stack, n)
}
// top returns the top of the stack of open elements.
// This is also known as the current node.
func (p *parser) top() *Node {
if n := len(p.stack); n > 0 {
return p.stack[n-1]
}
return p.doc
}
// pop pops the top of the stack of open elements.
// It will panic if the stack is empty.
func (p *parser) pop() *Node {
n := len(p.stack)
ret := p.stack[n-1]
p.stack = p.stack[:n-1]
return ret
}
// stopTags for use in popUntil. These come from section 10.2.3.2.
var (
defaultScopeStopTags = []string{"applet", "caption", "html", "table", "td", "th", "marquee", "object"}
listItemScopeStopTags = []string{"applet", "caption", "html", "table", "td", "th", "marquee", "object", "ol", "ul"}
buttonScopeStopTags = []string{"applet", "caption", "html", "table", "td", "th", "marquee", "object", "button"}
tableScopeStopTags = []string{"html", "table"}
)
// popUntil pops the stack of open elements at the highest element whose tag
// is in matchTags, provided there is no higher element in stopTags. It returns
// whether or not there was such an element. If there was not, popUntil leaves
// the stack unchanged.
//
// For example, if the stack was:
// ["html", "body", "font", "table", "b", "i", "u"]
// then popUntil([]string{"html, "table"}, "font") would return false, but
// popUntil([]string{"html, "table"}, "i") would return true and the resultant
// stack would be:
// ["html", "body", "font", "table", "b"]
//
// If an element's tag is in both stopTags and matchTags, then the stack will
// be popped and the function returns true (provided, of course, there was no
// higher element in the stack that was also in stopTags). For example,
// popUntil([]string{"html, "table"}, "table") would return true and leave:
// ["html", "body", "font"]
func (p *parser) popUntil(stopTags []string, matchTags ...string) bool {
for i := len(p.stack) - 1; i >= 0; i-- {
tag := p.stack[i].Data
for _, t := range matchTags {
if t == tag {
p.stack = p.stack[:i]
return true
}
}
for _, t := range stopTags {
if t == tag {
return false
}
}
}
return false
}
// addChild adds a child node n to the top element, and pushes n if it is an
// element node (text nodes are not part of the stack of open elements).
func (p *parser) addChild(n *Node) {
m := p.top()
m.Child = append(m.Child, n)
if n.Type == ElementNode {
p.push(n)
}
}
// addText calls addChild with a text node.
func (p *parser) addText(text string) {
// TODO: merge s with previous text, if the preceding node is a text node.
// TODO: distinguish whitespace text from others.
p.addChild(&Node{
Type: TextNode,
Data: text,
})
}
// addElement calls addChild with an element node.
func (p *parser) addElement(tag string, attr []Attribute) {
p.addChild(&Node{
Type: ElementNode,
Data: tag,
Attr: attr,
})
}
// Section 10.2.3.3.
func (p *parser) addFormattingElement(tag string, attr []Attribute) {
p.addElement(tag, attr)
// TODO.
}
// Section 10.2.3.3.
func (p *parser) reconstructActiveFormattingElements() {
// TODO.
}
// read reads the next token. This is usually from the tokenizer, but it may
// be the synthesized end tag implied by a self-closing tag.
func (p *parser) read() os.Error {
if p.hasSelfClosingToken {
p.hasSelfClosingToken = false
p.tok.Type = EndTagToken
p.tok.Attr = nil
return nil
}
p.tokenizer.Next()
p.tok = p.tokenizer.Token()
switch p.tok.Type {
case ErrorToken:
return p.tokenizer.Error()
case SelfClosingTagToken:
p.hasSelfClosingToken = true
p.tok.Type = StartTagToken
}
return nil
}
// Section 10.2.4.
func (p *parser) acknowledgeSelfClosingTag() {
p.hasSelfClosingToken = false
}
// An insertion mode (section 10.2.3.1) is the state transition function from
// a particular state in the HTML5 parser's state machine. It updates the
// parser's fields depending on parser.token (where ErrorToken means EOF). In
// addition to returning the next insertionMode state, it also returns whether
// the token was consumed.
type insertionMode func(*parser) (insertionMode, bool)
// useTheRulesFor runs the delegate insertionMode over p, returning the actual
// insertionMode unless the delegate caused a state transition.
// Section 10.2.3.1, "using the rules for".
func useTheRulesFor(p *parser, actual, delegate insertionMode) (insertionMode, bool) {
im, consumed := delegate(p)
if im != delegate {
return im, consumed
}
return actual, consumed
}
// Section 10.2.5.4.
func initialIM(p *parser) (insertionMode, bool) {
// TODO: check p.tok for DOCTYPE.
return beforeHTMLIM, false
}
// Section 10.2.5.5.
func beforeHTMLIM(p *parser) (insertionMode, bool) {
var (
add bool
attr []Attribute
implied bool
)
switch p.tok.Type {
case ErrorToken:
implied = true
case TextToken:
// TODO: distinguish whitespace text from others.
implied = true
case StartTagToken:
if p.tok.Data == "html" {
add = true
attr = p.tok.Attr
} else {
implied = true
}
case EndTagToken:
switch p.tok.Data {
case "head", "body", "html", "br":
implied = true
default:
// Ignore the token.
}
}
if add || implied {
p.addElement("html", attr)
}
return beforeHeadIM, !implied
}
// Section 10.2.5.6.
func beforeHeadIM(p *parser) (insertionMode, bool) {
var (
add bool
attr []Attribute
implied bool
)
switch p.tok.Type {
case ErrorToken:
implied = true
case TextToken:
// TODO: distinguish whitespace text from others.
implied = true
case StartTagToken:
switch p.tok.Data {
case "head":
add = true
attr = p.tok.Attr
case "html":
return useTheRulesFor(p, beforeHeadIM, inBodyIM)
default:
implied = true
}
case EndTagToken:
switch p.tok.Data {
case "head", "body", "html", "br":
implied = true
default:
// Ignore the token.
}
}
if add || implied {
p.addElement("head", attr)
}
return inHeadIM, !implied
}
// Section 10.2.5.7.
func inHeadIM(p *parser) (insertionMode, bool) {
var (
pop bool
implied bool
)
switch p.tok.Type {
case ErrorToken, TextToken:
implied = true
case StartTagToken:
switch p.tok.Data {
case "meta":
// TODO.
case "script":
// TODO.
default:
implied = true
}
case EndTagToken:
if p.tok.Data == "head" {
pop = true
}
// TODO.
}
if pop || implied {
n := p.pop()
if n.Data != "head" {
panic("html: bad parser state")
}
return afterHeadIM, !implied
}
return inHeadIM, !implied
}
// Section 10.2.5.9.
func afterHeadIM(p *parser) (insertionMode, bool) {
var (
add bool
attr []Attribute
framesetOK bool
implied bool
)
switch p.tok.Type {
case ErrorToken, TextToken:
implied = true
framesetOK = true
case StartTagToken:
switch p.tok.Data {
case "html":
// TODO.
case "body":
add = true
attr = p.tok.Attr
framesetOK = false
case "frameset":
// TODO.
case "base", "basefont", "bgsound", "link", "meta", "noframes", "script", "style", "title":
// TODO.
case "head":
// TODO.
default:
implied = true
framesetOK = true
}
case EndTagToken:
// TODO.
}
if add || implied {
p.addElement("body", attr)
p.framesetOK = framesetOK
}
return inBodyIM, !implied
}
// Section 10.2.5.10.
func inBodyIM(p *parser) (insertionMode, bool) {
var endP bool
switch p.tok.Type {
case TextToken:
p.addText(p.tok.Data)
p.framesetOK = false
case StartTagToken:
switch p.tok.Data {
case "address", "article", "aside", "blockquote", "center", "details", "dir", "div", "dl", "fieldset", "figcaption", "figure", "footer", "header", "hgroup", "menu", "nav", "ol", "p", "section", "summary", "ul":
// TODO: Do the proper "does the stack of open elements has a p element in button scope" algorithm in section 10.2.3.2.
n := p.top()
if n.Type == ElementNode && n.Data == "p" {
endP = true
} else {
p.addElement(p.tok.Data, p.tok.Attr)
}
case "h1", "h2", "h3", "h4", "h5", "h6":
// TODO: auto-insert </p> if necessary.
switch n := p.top(); n.Data {
case "h1", "h2", "h3", "h4", "h5", "h6":
p.pop()
}
p.addElement(p.tok.Data, p.tok.Attr)
case "b", "big", "code", "em", "font", "i", "s", "small", "strike", "strong", "tt", "u":
p.reconstructActiveFormattingElements()
p.addFormattingElement(p.tok.Data, p.tok.Attr)
case "area", "br", "embed", "img", "input", "keygen", "wbr":
p.reconstructActiveFormattingElements()
p.addElement(p.tok.Data, p.tok.Attr)
p.pop()
p.acknowledgeSelfClosingTag()
p.framesetOK = false
case "table":
// TODO: auto-insert </p> if necessary, depending on quirks mode.
p.addElement(p.tok.Data, p.tok.Attr)
p.framesetOK = false
return inTableIM, true
case "hr":
// TODO: auto-insert </p> if necessary.
p.addElement(p.tok.Data, p.tok.Attr)
p.pop()
p.acknowledgeSelfClosingTag()
p.framesetOK = false
default:
// TODO.
}
case EndTagToken:
switch p.tok.Data {
case "body":
// TODO: autoclose the stack of open elements.
return afterBodyIM, true
case "a", "b", "big", "code", "em", "font", "i", "nobr", "s", "small", "strike", "strong", "tt", "u":
// TODO: implement the "adoption agency" algorithm:
// http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#adoptionAgency
if p.tok.Data == p.top().Data {
p.pop()
}
default:
// TODO.
}
}
if endP {
// TODO: do the proper algorithm.
n := p.pop()
if n.Type != ElementNode || n.Data != "p" {
panic("unreachable")
}
}
return inBodyIM, !endP
}
// Section 10.2.5.12.
func inTableIM(p *parser) (insertionMode, bool) {
var (
add bool
data string
attr []Attribute
consumed bool
)
switch p.tok.Type {
case ErrorToken:
// Stop parsing.
return nil, true
case TextToken:
// TODO.
case StartTagToken:
switch p.tok.Data {
case "tbody", "tfoot", "thead":
add = true
data = p.tok.Data
attr = p.tok.Attr
consumed = true
case "td", "th", "tr":
add = true
data = "tbody"
default:
// TODO.
}
case EndTagToken:
switch p.tok.Data {
case "table":
if p.popUntil(tableScopeStopTags, "table") {
// TODO: "reset the insertion mode appropriately" as per 10.2.3.1.
return inBodyIM, false
}
// Ignore the token.
return inTableIM, true
case "body", "caption", "col", "colgroup", "html", "tbody", "td", "tfoot", "th", "thead", "tr":
// Ignore the token.
return inTableIM, true
}
}
if add {
// TODO: clear the stack back to a table context.
p.addElement(data, attr)
return inTableBodyIM, consumed
}
// TODO: return useTheRulesFor(inTableIM, inBodyIM, p) unless etc. etc. foster parenting.
return inTableIM, true
}
// Section 10.2.5.16.
func inTableBodyIM(p *parser) (insertionMode, bool) {
var (
add bool
data string
attr []Attribute
consumed bool
)
switch p.tok.Type {
case ErrorToken:
// TODO.
case TextToken:
// TODO.
case StartTagToken:
switch p.tok.Data {
case "tr":
add = true
data = p.tok.Data
attr = p.tok.Attr
consumed = true
case "td", "th":
add = true
data = "tr"
consumed = false
default:
// TODO.
}
case EndTagToken:
switch p.tok.Data {
case "table":
if p.popUntil(tableScopeStopTags, "tbody", "thead", "tfoot") {
return inTableIM, false
}
// Ignore the token.
return inTableBodyIM, true
case "body", "caption", "col", "colgroup", "html", "td", "th", "tr":
// Ignore the token.
return inTableBodyIM, true
}
}
if add {
// TODO: clear the stack back to a table body context.
p.addElement(data, attr)
return inRowIM, consumed
}
return useTheRulesFor(p, inTableBodyIM, inTableIM)
}
// Section 10.2.5.17.
func inRowIM(p *parser) (insertionMode, bool) {
switch p.tok.Type {
case ErrorToken:
// TODO.
case TextToken:
// TODO.
case StartTagToken:
switch p.tok.Data {
case "td", "th":
// TODO: clear the stack back to a table row context.
p.addElement(p.tok.Data, p.tok.Attr)
// TODO: insert a marker at the end of the list of active formatting elements.
return inCellIM, true
default:
// TODO.
}
case EndTagToken:
switch p.tok.Data {
case "tr":
// TODO.
case "table":
if p.popUntil(tableScopeStopTags, "tr") {
return inTableBodyIM, false
}
// Ignore the token.
return inRowIM, true
case "tbody", "tfoot", "thead":
// TODO.
case "body", "caption", "col", "colgroup", "html", "td", "th":
// Ignore the token.
return inRowIM, true
default:
// TODO.
}
}
return useTheRulesFor(p, inRowIM, inTableIM)
}
// Section 10.2.5.18.
func inCellIM(p *parser) (insertionMode, bool) {
var (
closeTheCellAndReprocess bool
)
switch p.tok.Type {
case StartTagToken:
switch p.tok.Data {
case "caption", "col", "colgroup", "tbody", "td", "tfoot", "th", "thead", "tr":
// TODO: check for "td" or "th" in table scope.
closeTheCellAndReprocess = true
}
case EndTagToken:
switch p.tok.Data {
case "td", "th":
// TODO.
case "body", "caption", "col", "colgroup", "html":
// TODO.
case "table", "tbody", "tfoot", "thead", "tr":
// TODO: check for matching element in table scope.
closeTheCellAndReprocess = true
}
}
if closeTheCellAndReprocess {
if p.popUntil(tableScopeStopTags, "td") || p.popUntil(tableScopeStopTags, "th") {
// TODO: clear the list of active formatting elements up to the last marker.
return inRowIM, false
}
}
return useTheRulesFor(p, inCellIM, inBodyIM)
}
// Section 10.2.5.22.
func afterBodyIM(p *parser) (insertionMode, bool) {
switch p.tok.Type {
case ErrorToken:
// TODO.
case TextToken:
// TODO.
case StartTagToken:
// TODO.
case EndTagToken:
switch p.tok.Data {
case "html":
// TODO: autoclose the stack of open elements.
return afterAfterBodyIM, true
default:
// TODO.
}
}
return afterBodyIM, true
}
// Section 10.2.5.25.
func afterAfterBodyIM(p *parser) (insertionMode, bool) {
switch p.tok.Type {
case ErrorToken:
// Stop parsing.
return nil, true
case TextToken:
// TODO.
case StartTagToken:
if p.tok.Data == "html" {
return useTheRulesFor(p, afterAfterBodyIM, inBodyIM)
}
}
return inBodyIM, false
}
// Parse returns the parse tree for the HTML from the given Reader.
// The input is assumed to be UTF-8 encoded.
func Parse(r io.Reader) (*Node, os.Error) {
p := &parser{
tokenizer: NewTokenizer(r),
doc: &Node{
Type: DocumentNode,
},
scripting: true,
framesetOK: true,
}
// Iterate until EOF. Any other error will cause an early return.
im, consumed := initialIM, true
for {
if consumed {
if err := p.read(); err != nil {
if err == os.EOF {
break
}
return nil, err
}
}
im, consumed = im(p)
}
// Loop until the final token (the ErrorToken signifying EOF) is consumed.
for {
if im, consumed = im(p); consumed {
break
}
}
return p.doc, nil
}