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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 (
"bytes"
"errors"
"io"
"strconv"
"strings"
"golang.org/x/net/html/atom"
)
// A TokenType is the type of a Token.
type TokenType uint32
const (
// ErrorToken means that an error occurred during tokenization.
ErrorToken TokenType = iota
// TextToken means a text node.
TextToken
// A StartTagToken looks like <a>.
StartTagToken
// An EndTagToken looks like </a>.
EndTagToken
// A SelfClosingTagToken tag looks like <br/>.
SelfClosingTagToken
// A CommentToken looks like <!--x-->.
CommentToken
// A DoctypeToken looks like <!DOCTYPE x>
DoctypeToken
)
// ErrBufferExceeded means that the buffering limit was exceeded.
var ErrBufferExceeded = errors.New("max buffer exceeded")
// String returns a string representation of the TokenType.
func (t TokenType) String() string {
switch t {
case ErrorToken:
return "Error"
case TextToken:
return "Text"
case StartTagToken:
return "StartTag"
case EndTagToken:
return "EndTag"
case SelfClosingTagToken:
return "SelfClosingTag"
case CommentToken:
return "Comment"
case DoctypeToken:
return "Doctype"
}
return "Invalid(" + strconv.Itoa(int(t)) + ")"
}
// An Attribute is an attribute namespace-key-value triple. Namespace is
// non-empty for foreign attributes like xlink, Key is alphabetic (and hence
// does not contain escapable characters like '&', '<' or '>'), and Val is
// unescaped (it looks like "a<b" rather than "a&lt;b").
//
// Namespace is only used by the parser, not the tokenizer.
type Attribute struct {
Namespace, Key, Val string
}
// A Token consists of a TokenType and some Data (tag name for start and end
// tags, content for text, comments and doctypes). A tag Token may also contain
// a slice of Attributes. Data is unescaped for all Tokens (it looks like "a<b"
// rather than "a&lt;b"). For tag Tokens, DataAtom is the atom for Data, or
// zero if Data is not a known tag name.
type Token struct {
Type TokenType
DataAtom atom.Atom
Data string
Attr []Attribute
}
// tagString returns a string representation of a tag Token's Data and Attr.
func (t Token) tagString() string {
if len(t.Attr) == 0 {
return t.Data
}
buf := bytes.NewBufferString(t.Data)
for _, a := range t.Attr {
buf.WriteByte(' ')
buf.WriteString(a.Key)
buf.WriteString(`="`)
escape(buf, a.Val)
buf.WriteByte('"')
}
return buf.String()
}
// String returns a string representation of the Token.
func (t Token) String() string {
switch t.Type {
case ErrorToken:
return ""
case TextToken:
return EscapeString(t.Data)
case StartTagToken:
return "<" + t.tagString() + ">"
case EndTagToken:
return "</" + t.tagString() + ">"
case SelfClosingTagToken:
return "<" + t.tagString() + "/>"
case CommentToken:
return "<!--" + t.Data + "-->"
case DoctypeToken:
return "<!DOCTYPE " + t.Data + ">"
}
return "Invalid(" + strconv.Itoa(int(t.Type)) + ")"
}
// span is a range of bytes in a Tokenizer's buffer. The start is inclusive,
// the end is exclusive.
type span struct {
start, end int
}
// A Tokenizer returns a stream of HTML Tokens.
type Tokenizer struct {
// r is the source of the HTML text.
r io.Reader
// tt is the TokenType of the current token.
tt TokenType
// err is the first error encountered during tokenization. It is possible
// for tt != Error && err != nil to hold: this means that Next returned a
// valid token but the subsequent Next call will return an error token.
// For example, if the HTML text input was just "plain", then the first
// Next call would set z.err to io.EOF but return a TextToken, and all
// subsequent Next calls would return an ErrorToken.
// err is never reset. Once it becomes non-nil, it stays non-nil.
err error
// readErr is the error returned by the io.Reader r. It is separate from
// err because it is valid for an io.Reader to return (n int, err1 error)
// such that n > 0 && err1 != nil, and callers should always process the
// n > 0 bytes before considering the error err1.
readErr error
// buf[raw.start:raw.end] holds the raw bytes of the current token.
// buf[raw.end:] is buffered input that will yield future tokens.
raw span
buf []byte
// maxBuf limits the data buffered in buf. A value of 0 means unlimited.
maxBuf int
// buf[data.start:data.end] holds the raw bytes of the current token's data:
// a text token's text, a tag token's tag name, etc.
data span
// pendingAttr is the attribute key and value currently being tokenized.
// When complete, pendingAttr is pushed onto attr. nAttrReturned is
// incremented on each call to TagAttr.
pendingAttr [2]span
attr [][2]span
nAttrReturned int
// rawTag is the "script" in "</script>" that closes the next token. If
// non-empty, the subsequent call to Next will return a raw or RCDATA text
// token: one that treats "<p>" as text instead of an element.
// rawTag's contents are lower-cased.
rawTag string
// textIsRaw is whether the current text token's data is not escaped.
textIsRaw bool
// convertNUL is whether NUL bytes in the current token's data should
// be converted into \ufffd replacement characters.
convertNUL bool
// allowCDATA is whether CDATA sections are allowed in the current context.
allowCDATA bool
}
// AllowCDATA sets whether or not the tokenizer recognizes <![CDATA[foo]]> as
// the text "foo". The default value is false, which means to recognize it as
// a bogus comment "<!-- [CDATA[foo]] -->" instead.
//
// Strictly speaking, an HTML5 compliant tokenizer should allow CDATA if and
// only if tokenizing foreign content, such as MathML and SVG. However,
// tracking foreign-contentness is difficult to do purely in the tokenizer,
// as opposed to the parser, due to HTML integration points: an <svg> element
// can contain a <foreignObject> that is foreign-to-SVG but not foreign-to-
// HTML. For strict compliance with the HTML5 tokenization algorithm, it is the
// responsibility of the user of a tokenizer to call AllowCDATA as appropriate.
// In practice, if using the tokenizer without caring whether MathML or SVG
// CDATA is text or comments, such as tokenizing HTML to find all the anchor
// text, it is acceptable to ignore this responsibility.
func (z *Tokenizer) AllowCDATA(allowCDATA bool) {
z.allowCDATA = allowCDATA
}
// NextIsNotRawText instructs the tokenizer that the next token should not be
// considered as 'raw text'. Some elements, such as script and title elements,
// normally require the next token after the opening tag to be 'raw text' that
// has no child elements. For example, tokenizing "<title>a<b>c</b>d</title>"
// yields a start tag token for "<title>", a text token for "a<b>c</b>d", and
// an end tag token for "</title>". There are no distinct start tag or end tag
// tokens for the "<b>" and "</b>".
//
// This tokenizer implementation will generally look for raw text at the right
// times. Strictly speaking, an HTML5 compliant tokenizer should not look for
// raw text if in foreign content: <title> generally needs raw text, but a
// <title> inside an <svg> does not. Another example is that a <textarea>
// generally needs raw text, but a <textarea> is not allowed as an immediate
// child of a <select>; in normal parsing, a <textarea> implies </select>, but
// one cannot close the implicit element when parsing a <select>'s InnerHTML.
// Similarly to AllowCDATA, tracking the correct moment to override raw-text-
// ness is difficult to do purely in the tokenizer, as opposed to the parser.
// For strict compliance with the HTML5 tokenization algorithm, it is the
// responsibility of the user of a tokenizer to call NextIsNotRawText as
// appropriate. In practice, like AllowCDATA, it is acceptable to ignore this
// responsibility for basic usage.
//
// Note that this 'raw text' concept is different from the one offered by the
// Tokenizer.Raw method.
func (z *Tokenizer) NextIsNotRawText() {
z.rawTag = ""
}
// Err returns the error associated with the most recent ErrorToken token.
// This is typically io.EOF, meaning the end of tokenization.
func (z *Tokenizer) Err() error {
if z.tt != ErrorToken {
return nil
}
return z.err
}
// readByte returns the next byte from the input stream, doing a buffered read
// from z.r into z.buf if necessary. z.buf[z.raw.start:z.raw.end] remains a contiguous byte
// slice that holds all the bytes read so far for the current token.
// It sets z.err if the underlying reader returns an error.
// Pre-condition: z.err == nil.
func (z *Tokenizer) readByte() byte {
if z.raw.end >= len(z.buf) {
// Our buffer is exhausted and we have to read from z.r. Check if the
// previous read resulted in an error.
if z.readErr != nil {
z.err = z.readErr
return 0
}
// We copy z.buf[z.raw.start:z.raw.end] to the beginning of z.buf. If the length
// z.raw.end - z.raw.start is more than half the capacity of z.buf, then we
// allocate a new buffer before the copy.
c := cap(z.buf)
d := z.raw.end - z.raw.start
var buf1 []byte
if 2*d > c {
buf1 = make([]byte, d, 2*c)
} else {
buf1 = z.buf[:d]
}
copy(buf1, z.buf[z.raw.start:z.raw.end])
if x := z.raw.start; x != 0 {
// Adjust the data/attr spans to refer to the same contents after the copy.
z.data.start -= x
z.data.end -= x
z.pendingAttr[0].start -= x
z.pendingAttr[0].end -= x
z.pendingAttr[1].start -= x
z.pendingAttr[1].end -= x
for i := range z.attr {
z.attr[i][0].start -= x
z.attr[i][0].end -= x
z.attr[i][1].start -= x
z.attr[i][1].end -= x
}
}
z.raw.start, z.raw.end, z.buf = 0, d, buf1[:d]
// Now that we have copied the live bytes to the start of the buffer,
// we read from z.r into the remainder.
var n int
n, z.readErr = readAtLeastOneByte(z.r, buf1[d:cap(buf1)])
if n == 0 {
z.err = z.readErr
return 0
}
z.buf = buf1[:d+n]
}
x := z.buf[z.raw.end]
z.raw.end++
if z.maxBuf > 0 && z.raw.end-z.raw.start >= z.maxBuf {
z.err = ErrBufferExceeded
return 0
}
return x
}
// Buffered returns a slice containing data buffered but not yet tokenized.
func (z *Tokenizer) Buffered() []byte {
return z.buf[z.raw.end:]
}
// readAtLeastOneByte wraps an io.Reader so that reading cannot return (0, nil).
// It returns io.ErrNoProgress if the underlying r.Read method returns (0, nil)
// too many times in succession.
func readAtLeastOneByte(r io.Reader, b []byte) (int, error) {
for i := 0; i < 100; i++ {
n, err := r.Read(b)
if n != 0 || err != nil {
return n, err
}
}
return 0, io.ErrNoProgress
}
// skipWhiteSpace skips past any white space.
func (z *Tokenizer) skipWhiteSpace() {
if z.err != nil {
return
}
for {
c := z.readByte()
if z.err != nil {
return
}
switch c {
case ' ', '\n', '\r', '\t', '\f':
// No-op.
default:
z.raw.end--
return
}
}
}
// readRawOrRCDATA reads until the next "</foo>", where "foo" is z.rawTag and
// is typically something like "script" or "textarea".
func (z *Tokenizer) readRawOrRCDATA() {
if z.rawTag == "script" {
z.readScript()
z.textIsRaw = true
z.rawTag = ""
return
}
loop:
for {
c := z.readByte()
if z.err != nil {
break loop
}
if c != '<' {
continue loop
}
c = z.readByte()
if z.err != nil {
break loop
}
if c != '/' {
continue loop
}
if z.readRawEndTag() || z.err != nil {
break loop
}
}
z.data.end = z.raw.end
// A textarea's or title's RCDATA can contain escaped entities.
z.textIsRaw = z.rawTag != "textarea" && z.rawTag != "title"
z.rawTag = ""
}
// readRawEndTag attempts to read a tag like "</foo>", where "foo" is z.rawTag.
// If it succeeds, it backs up the input position to reconsume the tag and
// returns true. Otherwise it returns false. The opening "</" has already been
// consumed.
func (z *Tokenizer) readRawEndTag() bool {
for i := 0; i < len(z.rawTag); i++ {
c := z.readByte()
if z.err != nil {
return false
}
if c != z.rawTag[i] && c != z.rawTag[i]-('a'-'A') {
z.raw.end--
return false
}
}
c := z.readByte()
if z.err != nil {
return false
}
switch c {
case ' ', '\n', '\r', '\t', '\f', '/', '>':
// The 3 is 2 for the leading "</" plus 1 for the trailing character c.
z.raw.end -= 3 + len(z.rawTag)
return true
}
z.raw.end--
return false
}
// readScript reads until the next </script> tag, following the byzantine
// rules for escaping/hiding the closing tag.
func (z *Tokenizer) readScript() {
defer func() {
z.data.end = z.raw.end
}()
var c byte
scriptData:
c = z.readByte()
if z.err != nil {
return
}
if c == '<' {
goto scriptDataLessThanSign
}
goto scriptData
scriptDataLessThanSign:
c = z.readByte()
if z.err != nil {
return
}
switch c {
case '/':
goto scriptDataEndTagOpen
case '!':
goto scriptDataEscapeStart
}
z.raw.end--
goto scriptData
scriptDataEndTagOpen:
if z.readRawEndTag() || z.err != nil {
return
}
goto scriptData
scriptDataEscapeStart:
c = z.readByte()
if z.err != nil {
return
}
if c == '-' {
goto scriptDataEscapeStartDash
}
z.raw.end--
goto scriptData
scriptDataEscapeStartDash:
c = z.readByte()
if z.err != nil {
return
}
if c == '-' {
goto scriptDataEscapedDashDash
}
z.raw.end--
goto scriptData
scriptDataEscaped:
c = z.readByte()
if z.err != nil {
return
}
switch c {
case '-':
goto scriptDataEscapedDash
case '<':
goto scriptDataEscapedLessThanSign
}
goto scriptDataEscaped
scriptDataEscapedDash:
c = z.readByte()
if z.err != nil {
return
}
switch c {
case '-':
goto scriptDataEscapedDashDash
case '<':
goto scriptDataEscapedLessThanSign
}
goto scriptDataEscaped
scriptDataEscapedDashDash:
c = z.readByte()
if z.err != nil {
return
}
switch c {
case '-':
goto scriptDataEscapedDashDash
case '<':
goto scriptDataEscapedLessThanSign
case '>':
goto scriptData
}
goto scriptDataEscaped
scriptDataEscapedLessThanSign:
c = z.readByte()
if z.err != nil {
return
}
if c == '/' {
goto scriptDataEscapedEndTagOpen
}
if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' {
goto scriptDataDoubleEscapeStart
}
z.raw.end--
goto scriptData
scriptDataEscapedEndTagOpen:
if z.readRawEndTag() || z.err != nil {
return
}
goto scriptDataEscaped
scriptDataDoubleEscapeStart:
z.raw.end--
for i := 0; i < len("script"); i++ {
c = z.readByte()
if z.err != nil {
return
}
if c != "script"[i] && c != "SCRIPT"[i] {
z.raw.end--
goto scriptDataEscaped
}
}
c = z.readByte()
if z.err != nil {
return
}
switch c {
case ' ', '\n', '\r', '\t', '\f', '/', '>':
goto scriptDataDoubleEscaped
}
z.raw.end--
goto scriptDataEscaped
scriptDataDoubleEscaped:
c = z.readByte()
if z.err != nil {
return
}
switch c {
case '-':
goto scriptDataDoubleEscapedDash
case '<':
goto scriptDataDoubleEscapedLessThanSign
}
goto scriptDataDoubleEscaped
scriptDataDoubleEscapedDash:
c = z.readByte()
if z.err != nil {
return
}
switch c {
case '-':
goto scriptDataDoubleEscapedDashDash
case '<':
goto scriptDataDoubleEscapedLessThanSign
}
goto scriptDataDoubleEscaped
scriptDataDoubleEscapedDashDash:
c = z.readByte()
if z.err != nil {
return
}
switch c {
case '-':
goto scriptDataDoubleEscapedDashDash
case '<':
goto scriptDataDoubleEscapedLessThanSign
case '>':
goto scriptData
}
goto scriptDataDoubleEscaped
scriptDataDoubleEscapedLessThanSign:
c = z.readByte()
if z.err != nil {
return
}
if c == '/' {
goto scriptDataDoubleEscapeEnd
}
z.raw.end--
goto scriptDataDoubleEscaped
scriptDataDoubleEscapeEnd:
if z.readRawEndTag() {
z.raw.end += len("</script>")
goto scriptDataEscaped
}
if z.err != nil {
return
}
goto scriptDataDoubleEscaped
}
// readComment reads the next comment token starting with "<!--". The opening
// "<!--" has already been consumed.
func (z *Tokenizer) readComment() {
z.data.start = z.raw.end
defer func() {
if z.data.end < z.data.start {
// It's a comment with no data, like <!-->.
z.data.end = z.data.start
}
}()
for dashCount := 2; ; {
c := z.readByte()
if z.err != nil {
// Ignore up to two dashes at EOF.
if dashCount > 2 {
dashCount = 2
}
z.data.end = z.raw.end - dashCount
return
}
switch c {
case '-':
dashCount++
continue
case '>':
if dashCount >= 2 {
z.data.end = z.raw.end - len("-->")
return
}
case '!':
if dashCount >= 2 {
c = z.readByte()
if z.err != nil {
z.data.end = z.raw.end
return
}
if c == '>' {
z.data.end = z.raw.end - len("--!>")
return
}
}
}
dashCount = 0
}
}
// readUntilCloseAngle reads until the next ">".
func (z *Tokenizer) readUntilCloseAngle() {
z.data.start = z.raw.end
for {
c := z.readByte()
if z.err != nil {
z.data.end = z.raw.end
return
}
if c == '>' {
z.data.end = z.raw.end - len(">")
return
}
}
}
// readMarkupDeclaration reads the next token starting with "<!". It might be
// a "<!--comment-->", a "<!DOCTYPE foo>", a "<![CDATA[section]]>" or
// "<!a bogus comment". The opening "<!" has already been consumed.
func (z *Tokenizer) readMarkupDeclaration() TokenType {
z.data.start = z.raw.end
var c [2]byte
for i := 0; i < 2; i++ {
c[i] = z.readByte()
if z.err != nil {
z.data.end = z.raw.end
return CommentToken
}
}
if c[0] == '-' && c[1] == '-' {
z.readComment()
return CommentToken
}
z.raw.end -= 2
if z.readDoctype() {
return DoctypeToken
}
if z.allowCDATA && z.readCDATA() {
z.convertNUL = true
return TextToken
}
// It's a bogus comment.
z.readUntilCloseAngle()
return CommentToken
}
// readDoctype attempts to read a doctype declaration and returns true if
// successful. The opening "<!" has already been consumed.
func (z *Tokenizer) readDoctype() bool {
const s = "DOCTYPE"
for i := 0; i < len(s); i++ {
c := z.readByte()
if z.err != nil {
z.data.end = z.raw.end
return false
}
if c != s[i] && c != s[i]+('a'-'A') {
// Back up to read the fragment of "DOCTYPE" again.
z.raw.end = z.data.start
return false
}
}
if z.skipWhiteSpace(); z.err != nil {
z.data.start = z.raw.end
z.data.end = z.raw.end
return true
}
z.readUntilCloseAngle()
return true
}
// readCDATA attempts to read a CDATA section and returns true if
// successful. The opening "<!" has already been consumed.
func (z *Tokenizer) readCDATA() bool {
const s = "[CDATA["
for i := 0; i < len(s); i++ {
c := z.readByte()
if z.err != nil {
z.data.end = z.raw.end
return false
}
if c != s[i] {
// Back up to read the fragment of "[CDATA[" again.
z.raw.end = z.data.start
return false
}
}
z.data.start = z.raw.end
brackets := 0
for {
c := z.readByte()
if z.err != nil {
z.data.end = z.raw.end
return true
}
switch c {
case ']':
brackets++
case '>':
if brackets >= 2 {
z.data.end = z.raw.end - len("]]>")
return true
}
brackets = 0
default:
brackets = 0
}
}
}
// startTagIn returns whether the start tag in z.buf[z.data.start:z.data.end]
// case-insensitively matches any element of ss.
func (z *Tokenizer) startTagIn(ss ...string) bool {
loop:
for _, s := range ss {
if z.data.end-z.data.start != len(s) {
continue loop
}
for i := 0; i < len(s); i++ {
c := z.buf[z.data.start+i]
if 'A' <= c && c <= 'Z' {
c += 'a' - 'A'
}
if c != s[i] {
continue loop
}
}
return true
}
return false
}
// readStartTag reads the next start tag token. The opening "<a" has already
// been consumed, where 'a' means anything in [A-Za-z].
func (z *Tokenizer) readStartTag() TokenType {
z.readTag(true)
if z.err != nil {
return ErrorToken
}
// Several tags flag the tokenizer's next token as raw.
c, raw := z.buf[z.data.start], false
if 'A' <= c && c <= 'Z' {
c += 'a' - 'A'
}
switch c {
case 'i':
raw = z.startTagIn("iframe")
case 'n':
raw = z.startTagIn("noembed", "noframes", "noscript")
case 'p':
raw = z.startTagIn("plaintext")
case 's':
raw = z.startTagIn("script", "style")
case 't':
raw = z.startTagIn("textarea", "title")
case 'x':
raw = z.startTagIn("xmp")
}
if raw {
z.rawTag = strings.ToLower(string(z.buf[z.data.start:z.data.end]))
}
// Look for a self-closing token like "<br/>".
if z.err == nil && z.buf[z.raw.end-2] == '/' {
return SelfClosingTagToken
}
return StartTagToken
}
// readTag reads the next tag token and its attributes. If saveAttr, those
// attributes are saved in z.attr, otherwise z.attr is set to an empty slice.
// The opening "<a" or "</a" has already been consumed, where 'a' means anything
// in [A-Za-z].
func (z *Tokenizer) readTag(saveAttr bool) {
z.attr = z.attr[:0]
z.nAttrReturned = 0
// Read the tag name and attribute key/value pairs.
z.readTagName()
if z.skipWhiteSpace(); z.err != nil {
return
}
for {
c := z.readByte()
if z.err != nil || c == '>' {
break
}
z.raw.end--
z.readTagAttrKey()
z.readTagAttrVal()
// Save pendingAttr if saveAttr and that attribute has a non-empty key.
if saveAttr && z.pendingAttr[0].start != z.pendingAttr[0].end {
z.attr = append(z.attr, z.pendingAttr)
}
if z.skipWhiteSpace(); z.err != nil {
break
}
}
}
// readTagName sets z.data to the "div" in "<div k=v>". The reader (z.raw.end)
// is positioned such that the first byte of the tag name (the "d" in "<div")
// has already been consumed.
func (z *Tokenizer) readTagName() {
z.data.start = z.raw.end - 1
for {
c := z.readByte()
if z.err != nil {
z.data.end = z.raw.end
return
}
switch c {
case ' ', '\n', '\r', '\t', '\f':
z.data.end = z.raw.end - 1
return
case '/', '>':
z.raw.end--
z.data.end = z.raw.end
return
}
}
}
// readTagAttrKey sets z.pendingAttr[0] to the "k" in "<div k=v>".
// Precondition: z.err == nil.
func (z *Tokenizer) readTagAttrKey() {
z.pendingAttr[0].start = z.raw.end
for {
c := z.readByte()
if z.err != nil {
z.pendingAttr[0].end = z.raw.end
return
}
switch c {
case ' ', '\n', '\r', '\t', '\f', '/':
z.pendingAttr[0].end = z.raw.end - 1
return
case '=', '>':
z.raw.end--
z.pendingAttr[0].end = z.raw.end
return
}
}
}
// readTagAttrVal sets z.pendingAttr[1] to the "v" in "<div k=v>".
func (z *Tokenizer) readTagAttrVal() {
z.pendingAttr[1].start = z.raw.end
z.pendingAttr[1].end = z.raw.end
if z.skipWhiteSpace(); z.err != nil {
return
}
c := z.readByte()
if z.err != nil {
return
}
if c != '=' {
z.raw.end--
return
}
if z.skipWhiteSpace(); z.err != nil {
return
}
quote := z.readByte()
if z.err != nil {
return
}
switch quote {
case '>':
z.raw.end--
return
case '\'', '"':
z.pendingAttr[1].start = z.raw.end
for {
c := z.readByte()
if z.err != nil {
z.pendingAttr[1].end = z.raw.end
return
}
if c == quote {
z.pendingAttr[1].end = z.raw.end - 1
return
}
}
default:
z.pendingAttr[1].start = z.raw.end - 1
for {
c := z.readByte()
if z.err != nil {
z.pendingAttr[1].end = z.raw.end
return
}
switch c {
case ' ', '\n', '\r', '\t', '\f':
z.pendingAttr[1].end = z.raw.end - 1
return
case '>':
z.raw.end--
z.pendingAttr[1].end = z.raw.end
return
}
}
}
}
// Next scans the next token and returns its type.
func (z *Tokenizer) Next() TokenType {
z.raw.start = z.raw.end
z.data.start = z.raw.end
z.data.end = z.raw.end
if z.err != nil {
z.tt = ErrorToken
return z.tt
}
if z.rawTag != "" {
if z.rawTag == "plaintext" {
// Read everything up to EOF.
for z.err == nil {
z.readByte()
}
z.data.end = z.raw.end
z.textIsRaw = true
} else {
z.readRawOrRCDATA()
}
if z.data.end > z.data.start {
z.tt = TextToken
z.convertNUL = true
return z.tt
}
}
z.textIsRaw = false
z.convertNUL = false
loop:
for {
c := z.readByte()
if z.err != nil {
break loop
}
if c != '<' {
continue loop
}
// Check if the '<' we have just read is part of a tag, comment
// or doctype. If not, it's part of the accumulated text token.
c = z.readByte()
if z.err != nil {
break loop
}
var tokenType TokenType
switch {
case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
tokenType = StartTagToken
case c == '/':
tokenType = EndTagToken
case c == '!' || c == '?':
// We use CommentToken to mean any of "<!--actual comments-->",
// "<!DOCTYPE declarations>" and "<?xml processing instructions?>".
tokenType = CommentToken
default:
// Reconsume the current character.
z.raw.end--
continue
}
// We have a non-text token, but we might have accumulated some text
// before that. If so, we return the text first, and return the non-
// text token on the subsequent call to Next.
if x := z.raw.end - len("<a"); z.raw.start < x {
z.raw.end = x
z.data.end = x
z.tt = TextToken
return z.tt
}
switch tokenType {
case StartTagToken:
z.tt = z.readStartTag()
return z.tt
case EndTagToken:
c = z.readByte()
if z.err != nil {
break loop
}
if c == '>' {
// "</>" does not generate a token at all. Generate an empty comment
// to allow passthrough clients to pick up the data using Raw.
// Reset the tokenizer state and start again.
z.tt = CommentToken
return z.tt
}
if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' {
z.readTag(false)
if z.err != nil {
z.tt = ErrorToken
} else {
z.tt = EndTagToken
}
return z.tt
}
z.raw.end--
z.readUntilCloseAngle()
z.tt = CommentToken
return z.tt
case CommentToken:
if c == '!' {
z.tt = z.readMarkupDeclaration()
return z.tt
}
z.raw.end--
z.readUntilCloseAngle()
z.tt = CommentToken
return z.tt
}
}
if z.raw.start < z.raw.end {
z.data.end = z.raw.end
z.tt = TextToken
return z.tt
}
z.tt = ErrorToken
return z.tt
}
// Raw returns the unmodified text of the current token. Calling Next, Token,
// Text, TagName or TagAttr may change the contents of the returned slice.
func (z *Tokenizer) Raw() []byte {
return z.buf[z.raw.start:z.raw.end]
}
// convertNewlines converts "\r" and "\r\n" in s to "\n".
// The conversion happens in place, but the resulting slice may be shorter.
func convertNewlines(s []byte) []byte {
for i, c := range s {
if c != '\r' {
continue
}
src := i + 1
if src >= len(s) || s[src] != '\n' {
s[i] = '\n'
continue
}
dst := i
for src < len(s) {
if s[src] == '\r' {
if src+1 < len(s) && s[src+1] == '\n' {
src++
}
s[dst] = '\n'
} else {
s[dst] = s[src]
}
src++
dst++
}
return s[:dst]
}
return s
}
var (
nul = []byte("\x00")
replacement = []byte("\ufffd")
)
// Text returns the unescaped text of a text, comment or doctype token. The
// contents of the returned slice may change on the next call to Next.
func (z *Tokenizer) Text() []byte {
switch z.tt {
case TextToken, CommentToken, DoctypeToken:
s := z.buf[z.data.start:z.data.end]
z.data.start = z.raw.end
z.data.end = z.raw.end
s = convertNewlines(s)
if (z.convertNUL || z.tt == CommentToken) && bytes.Contains(s, nul) {
s = bytes.Replace(s, nul, replacement, -1)
}
if !z.textIsRaw {
s = unescape(s, false)
}
return s
}
return nil
}
// TagName returns the lower-cased name of a tag token (the `img` out of
// `<IMG SRC="foo">`) and whether the tag has attributes.
// The contents of the returned slice may change on the next call to Next.
func (z *Tokenizer) TagName() (name []byte, hasAttr bool) {
if z.data.start < z.data.end {
switch z.tt {
case StartTagToken, EndTagToken, SelfClosingTagToken:
s := z.buf[z.data.start:z.data.end]
z.data.start = z.raw.end
z.data.end = z.raw.end
return lower(s), z.nAttrReturned < len(z.attr)
}
}
return nil, false
}
// TagAttr returns the lower-cased key and unescaped value of the next unparsed
// attribute for the current tag token and whether there are more attributes.
// The contents of the returned slices may change on the next call to Next.
func (z *Tokenizer) TagAttr() (key, val []byte, moreAttr bool) {
if z.nAttrReturned < len(z.attr) {
switch z.tt {
case StartTagToken, SelfClosingTagToken:
x := z.attr[z.nAttrReturned]
z.nAttrReturned++
key = z.buf[x[0].start:x[0].end]
val = z.buf[x[1].start:x[1].end]
return lower(key), unescape(convertNewlines(val), true), z.nAttrReturned < len(z.attr)
}
}
return nil, nil, false
}
// Token returns the current Token. The result's Data and Attr values remain
// valid after subsequent Next calls.
func (z *Tokenizer) Token() Token {
t := Token{Type: z.tt}
switch z.tt {
case TextToken, CommentToken, DoctypeToken:
t.Data = string(z.Text())
case StartTagToken, SelfClosingTagToken, EndTagToken:
name, moreAttr := z.TagName()
for moreAttr {
var key, val []byte
key, val, moreAttr = z.TagAttr()
t.Attr = append(t.Attr, Attribute{"", atom.String(key), string(val)})
}
if a := atom.Lookup(name); a != 0 {
t.DataAtom, t.Data = a, a.String()
} else {
t.DataAtom, t.Data = 0, string(name)
}
}
return t
}
// SetMaxBuf sets a limit on the amount of data buffered during tokenization.
// A value of 0 means unlimited.
func (z *Tokenizer) SetMaxBuf(n int) {
z.maxBuf = n
}
// NewTokenizer returns a new HTML Tokenizer for the given Reader.
// The input is assumed to be UTF-8 encoded.
func NewTokenizer(r io.Reader) *Tokenizer {
return NewTokenizerFragment(r, "")
}
// NewTokenizerFragment returns a new HTML Tokenizer for the given Reader, for
// tokenizing an existing element's InnerHTML fragment. contextTag is that
// element's tag, such as "div" or "iframe".
//
// For example, how the InnerHTML "a<b" is tokenized depends on whether it is
// for a <p> tag or a <script> tag.
//
// The input is assumed to be UTF-8 encoded.
func NewTokenizerFragment(r io.Reader, contextTag string) *Tokenizer {
z := &Tokenizer{
r: r,
buf: make([]byte, 0, 4096),
}
if contextTag != "" {
switch s := strings.ToLower(contextTag); s {
case "iframe", "noembed", "noframes", "noscript", "plaintext", "script", "style", "title", "textarea", "xmp":
z.rawTag = s
}
}
return z
}