1 // Copyright 2010 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 package html
6 7 import (
8 "bytes"
9 "errors"
10 "io"
11 "strconv"
12 "strings"
13 14 "golang.org/x/net/html/atom"
15 )
16 17 // A TokenType is the type of a Token.
18 type TokenType uint32
19 20 const (
21 // ErrorToken means that an error occurred during tokenization.
22 ErrorToken TokenType = iota
23 // TextToken means a text node.
24 TextToken
25 // A StartTagToken looks like <a>.
26 StartTagToken
27 // An EndTagToken looks like </a>.
28 EndTagToken
29 // A SelfClosingTagToken tag looks like <br/>.
30 SelfClosingTagToken
31 // A CommentToken looks like <!--x-->.
32 CommentToken
33 // A DoctypeToken looks like <!DOCTYPE x>
34 DoctypeToken
35 )
36 37 // ErrBufferExceeded means that the buffering limit was exceeded.
38 var ErrBufferExceeded = errors.New("max buffer exceeded")
39 40 // String returns a string representation of the TokenType.
41 func (t TokenType) String() string {
42 switch t {
43 case ErrorToken:
44 return "Error"
45 case TextToken:
46 return "Text"
47 case StartTagToken:
48 return "StartTag"
49 case EndTagToken:
50 return "EndTag"
51 case SelfClosingTagToken:
52 return "SelfClosingTag"
53 case CommentToken:
54 return "Comment"
55 case DoctypeToken:
56 return "Doctype"
57 }
58 return "Invalid(" + strconv.Itoa(int(t)) + ")"
59 }
60 61 // An Attribute is an attribute namespace-key-value triple. Namespace is
62 // non-empty for foreign attributes like xlink, Key is alphabetic (and hence
63 // does not contain escapable characters like '&', '<' or '>'), and Val is
64 // unescaped (it looks like "a<b" rather than "a<b").
65 //
66 // Namespace is only used by the parser, not the tokenizer.
67 type Attribute struct {
68 Namespace, Key, Val string
69 }
70 71 // A Token consists of a TokenType and some Data (tag name for start and end
72 // tags, content for text, comments and doctypes). A tag Token may also contain
73 // a slice of Attributes. Data is unescaped for all Tokens (it looks like "a<b"
74 // rather than "a<b"). For tag Tokens, DataAtom is the atom for Data, or
75 // zero if Data is not a known tag name.
76 type Token struct {
77 Type TokenType
78 DataAtom atom.Atom
79 Data string
80 Attr []Attribute
81 }
82 83 // tagString returns a string representation of a tag Token's Data and Attr.
84 func (t Token) tagString() string {
85 if len(t.Attr) == 0 {
86 return t.Data
87 }
88 buf := bytes.NewBufferString(t.Data)
89 for _, a := range t.Attr {
90 buf.WriteByte(' ')
91 buf.WriteString(a.Key)
92 buf.WriteString(`="`)
93 escape(buf, a.Val)
94 buf.WriteByte('"')
95 }
96 return buf.String()
97 }
98 99 // String returns a string representation of the Token.
100 func (t Token) String() string {
101 switch t.Type {
102 case ErrorToken:
103 return ""
104 case TextToken:
105 return EscapeString(t.Data)
106 case StartTagToken:
107 return "<" + t.tagString() + ">"
108 case EndTagToken:
109 return "</" + t.tagString() + ">"
110 case SelfClosingTagToken:
111 return "<" + t.tagString() + "/>"
112 case CommentToken:
113 return "<!--" + escapeCommentString(t.Data) + "-->"
114 case DoctypeToken:
115 return "<!DOCTYPE " + EscapeString(t.Data) + ">"
116 }
117 return "Invalid(" + strconv.Itoa(int(t.Type)) + ")"
118 }
119 120 // span is a range of bytes in a Tokenizer's buffer. The start is inclusive,
121 // the end is exclusive.
122 type span struct {
123 start, end int
124 }
125 126 // A Tokenizer returns a stream of HTML Tokens.
127 type Tokenizer struct {
128 // r is the source of the HTML text.
129 r io.Reader
130 // tt is the TokenType of the current token.
131 tt TokenType
132 // err is the first error encountered during tokenization. It is possible
133 // for tt != Error && err != nil to hold: this means that Next returned a
134 // valid token but the subsequent Next call will return an error token.
135 // For example, if the HTML text input was just "plain", then the first
136 // Next call would set z.err to io.EOF but return a TextToken, and all
137 // subsequent Next calls would return an ErrorToken.
138 // err is never reset. Once it becomes non-nil, it stays non-nil.
139 err error
140 // readErr is the error returned by the io.Reader r. It is separate from
141 // err because it is valid for an io.Reader to return (n int, err1 error)
142 // such that n > 0 && err1 != nil, and callers should always process the
143 // n > 0 bytes before considering the error err1.
144 readErr error
145 // buf[raw.start:raw.end] holds the raw bytes of the current token.
146 // buf[raw.end:] is buffered input that will yield future tokens.
147 raw span
148 buf []byte
149 // maxBuf limits the data buffered in buf. A value of 0 means unlimited.
150 maxBuf int
151 // buf[data.start:data.end] holds the raw bytes of the current token's data:
152 // a text token's text, a tag token's tag name, etc.
153 data span
154 // pendingAttr is the attribute key and value currently being tokenized.
155 // When complete, pendingAttr is pushed onto attr. nAttrReturned is
156 // incremented on each call to TagAttr.
157 pendingAttr [2]span
158 attr [][2]span
159 nAttrReturned int
160 // rawTag is the "script" in "</script>" that closes the next token. If
161 // non-empty, the subsequent call to Next will return a raw or RCDATA text
162 // token: one that treats "<p>" as text instead of an element.
163 // rawTag's contents are lower-cased.
164 rawTag string
165 // textIsRaw is whether the current text token's data is not escaped.
166 textIsRaw bool
167 // convertNUL is whether NUL bytes in the current token's data should
168 // be converted into \ufffd replacement characters.
169 convertNUL bool
170 // allowCDATA is whether CDATA sections are allowed in the current context.
171 allowCDATA bool
172 }
173 174 // AllowCDATA sets whether or not the tokenizer recognizes <![CDATA[foo]]> as
175 // the text "foo". The default value is false, which means to recognize it as
176 // a bogus comment "<!-- [CDATA[foo]] -->" instead.
177 //
178 // Strictly speaking, an HTML5 compliant tokenizer should allow CDATA if and
179 // only if tokenizing foreign content, such as MathML and SVG. However,
180 // tracking foreign-contentness is difficult to do purely in the tokenizer,
181 // as opposed to the parser, due to HTML integration points: an <svg> element
182 // can contain a <foreignObject> that is foreign-to-SVG but not foreign-to-
183 // HTML. For strict compliance with the HTML5 tokenization algorithm, it is the
184 // responsibility of the user of a tokenizer to call AllowCDATA as appropriate.
185 // In practice, if using the tokenizer without caring whether MathML or SVG
186 // CDATA is text or comments, such as tokenizing HTML to find all the anchor
187 // text, it is acceptable to ignore this responsibility.
188 func (z *Tokenizer) AllowCDATA(allowCDATA bool) {
189 z.allowCDATA = allowCDATA
190 }
191 192 // NextIsNotRawText instructs the tokenizer that the next token should not be
193 // considered as 'raw text'. Some elements, such as script and title elements,
194 // normally require the next token after the opening tag to be 'raw text' that
195 // has no child elements. For example, tokenizing "<title>a<b>c</b>d</title>"
196 // yields a start tag token for "<title>", a text token for "a<b>c</b>d", and
197 // an end tag token for "</title>". There are no distinct start tag or end tag
198 // tokens for the "<b>" and "</b>".
199 //
200 // This tokenizer implementation will generally look for raw text at the right
201 // times. Strictly speaking, an HTML5 compliant tokenizer should not look for
202 // raw text if in foreign content: <title> generally needs raw text, but a
203 // <title> inside an <svg> does not. Another example is that a <textarea>
204 // generally needs raw text, but a <textarea> is not allowed as an immediate
205 // child of a <select>; in normal parsing, a <textarea> implies </select>, but
206 // one cannot close the implicit element when parsing a <select>'s InnerHTML.
207 // Similarly to AllowCDATA, tracking the correct moment to override raw-text-
208 // ness is difficult to do purely in the tokenizer, as opposed to the parser.
209 // For strict compliance with the HTML5 tokenization algorithm, it is the
210 // responsibility of the user of a tokenizer to call NextIsNotRawText as
211 // appropriate. In practice, like AllowCDATA, it is acceptable to ignore this
212 // responsibility for basic usage.
213 //
214 // Note that this 'raw text' concept is different from the one offered by the
215 // Tokenizer.Raw method.
216 func (z *Tokenizer) NextIsNotRawText() {
217 z.rawTag = ""
218 }
219 220 // Err returns the error associated with the most recent ErrorToken token.
221 // This is typically io.EOF, meaning the end of tokenization.
222 func (z *Tokenizer) Err() error {
223 if z.tt != ErrorToken {
224 return nil
225 }
226 return z.err
227 }
228 229 // readByte returns the next byte from the input stream, doing a buffered read
230 // from z.r into z.buf if necessary. z.buf[z.raw.start:z.raw.end] remains a contiguous byte
231 // slice that holds all the bytes read so far for the current token.
232 // It sets z.err if the underlying reader returns an error.
233 // Pre-condition: z.err == nil.
234 func (z *Tokenizer) readByte() byte {
235 if z.raw.end >= len(z.buf) {
236 // Our buffer is exhausted and we have to read from z.r. Check if the
237 // previous read resulted in an error.
238 if z.readErr != nil {
239 z.err = z.readErr
240 return 0
241 }
242 // We copy z.buf[z.raw.start:z.raw.end] to the beginning of z.buf. If the length
243 // z.raw.end - z.raw.start is more than half the capacity of z.buf, then we
244 // allocate a new buffer before the copy.
245 c := cap(z.buf)
246 d := z.raw.end - z.raw.start
247 var buf1 []byte
248 if 2*d > c {
249 buf1 = make([]byte, d, 2*c)
250 } else {
251 buf1 = z.buf[:d]
252 }
253 copy(buf1, z.buf[z.raw.start:z.raw.end])
254 if x := z.raw.start; x != 0 {
255 // Adjust the data/attr spans to refer to the same contents after the copy.
256 z.data.start -= x
257 z.data.end -= x
258 z.pendingAttr[0].start -= x
259 z.pendingAttr[0].end -= x
260 z.pendingAttr[1].start -= x
261 z.pendingAttr[1].end -= x
262 for i := range z.attr {
263 z.attr[i][0].start -= x
264 z.attr[i][0].end -= x
265 z.attr[i][1].start -= x
266 z.attr[i][1].end -= x
267 }
268 }
269 z.raw.start, z.raw.end, z.buf = 0, d, buf1[:d]
270 // Now that we have copied the live bytes to the start of the buffer,
271 // we read from z.r into the remainder.
272 var n int
273 n, z.readErr = readAtLeastOneByte(z.r, buf1[d:cap(buf1)])
274 if n == 0 {
275 z.err = z.readErr
276 return 0
277 }
278 z.buf = buf1[:d+n]
279 }
280 x := z.buf[z.raw.end]
281 z.raw.end++
282 if z.maxBuf > 0 && z.raw.end-z.raw.start >= z.maxBuf {
283 z.err = ErrBufferExceeded
284 return 0
285 }
286 return x
287 }
288 289 // Buffered returns a slice containing data buffered but not yet tokenized.
290 func (z *Tokenizer) Buffered() []byte {
291 return z.buf[z.raw.end:]
292 }
293 294 // readAtLeastOneByte wraps an io.Reader so that reading cannot return (0, nil).
295 // It returns io.ErrNoProgress if the underlying r.Read method returns (0, nil)
296 // too many times in succession.
297 func readAtLeastOneByte(r io.Reader, b []byte) (int, error) {
298 for i := 0; i < 100; i++ {
299 if n, err := r.Read(b); n != 0 || err != nil {
300 return n, err
301 }
302 }
303 return 0, io.ErrNoProgress
304 }
305 306 // skipWhiteSpace skips past any white space.
307 func (z *Tokenizer) skipWhiteSpace() {
308 if z.err != nil {
309 return
310 }
311 for {
312 c := z.readByte()
313 if z.err != nil {
314 return
315 }
316 switch c {
317 case ' ', '\n', '\r', '\t', '\f':
318 // No-op.
319 default:
320 z.raw.end--
321 return
322 }
323 }
324 }
325 326 // readRawOrRCDATA reads until the next "</foo>", where "foo" is z.rawTag and
327 // is typically something like "script" or "textarea".
328 func (z *Tokenizer) readRawOrRCDATA() {
329 if z.rawTag == "script" {
330 z.readScript()
331 z.textIsRaw = true
332 z.rawTag = ""
333 return
334 }
335 loop:
336 for {
337 c := z.readByte()
338 if z.err != nil {
339 break loop
340 }
341 if c != '<' {
342 continue loop
343 }
344 c = z.readByte()
345 if z.err != nil {
346 break loop
347 }
348 if c != '/' {
349 z.raw.end--
350 continue loop
351 }
352 if z.readRawEndTag() || z.err != nil {
353 break loop
354 }
355 }
356 z.data.end = z.raw.end
357 // A textarea's or title's RCDATA can contain escaped entities.
358 z.textIsRaw = z.rawTag != "textarea" && z.rawTag != "title"
359 z.rawTag = ""
360 }
361 362 // readRawEndTag attempts to read a tag like "</foo>", where "foo" is z.rawTag.
363 // If it succeeds, it backs up the input position to reconsume the tag and
364 // returns true. Otherwise it returns false. The opening "</" has already been
365 // consumed.
366 func (z *Tokenizer) readRawEndTag() bool {
367 for i := 0; i < len(z.rawTag); i++ {
368 c := z.readByte()
369 if z.err != nil {
370 return false
371 }
372 if c != z.rawTag[i] && c != z.rawTag[i]-('a'-'A') {
373 z.raw.end--
374 return false
375 }
376 }
377 c := z.readByte()
378 if z.err != nil {
379 return false
380 }
381 switch c {
382 case ' ', '\n', '\r', '\t', '\f', '/', '>':
383 // The 3 is 2 for the leading "</" plus 1 for the trailing character c.
384 z.raw.end -= 3 + len(z.rawTag)
385 return true
386 }
387 z.raw.end--
388 return false
389 }
390 391 // readScript reads until the next </script> tag, following the byzantine
392 // rules for escaping/hiding the closing tag.
393 func (z *Tokenizer) readScript() {
394 defer func() {
395 z.data.end = z.raw.end
396 }()
397 var c byte
398 399 scriptData:
400 c = z.readByte()
401 if z.err != nil {
402 return
403 }
404 if c == '<' {
405 goto scriptDataLessThanSign
406 }
407 goto scriptData
408 409 scriptDataLessThanSign:
410 c = z.readByte()
411 if z.err != nil {
412 return
413 }
414 switch c {
415 case '/':
416 goto scriptDataEndTagOpen
417 case '!':
418 goto scriptDataEscapeStart
419 }
420 z.raw.end--
421 goto scriptData
422 423 scriptDataEndTagOpen:
424 if z.readRawEndTag() || z.err != nil {
425 return
426 }
427 goto scriptData
428 429 scriptDataEscapeStart:
430 c = z.readByte()
431 if z.err != nil {
432 return
433 }
434 if c == '-' {
435 goto scriptDataEscapeStartDash
436 }
437 z.raw.end--
438 goto scriptData
439 440 scriptDataEscapeStartDash:
441 c = z.readByte()
442 if z.err != nil {
443 return
444 }
445 if c == '-' {
446 goto scriptDataEscapedDashDash
447 }
448 z.raw.end--
449 goto scriptData
450 451 scriptDataEscaped:
452 c = z.readByte()
453 if z.err != nil {
454 return
455 }
456 switch c {
457 case '-':
458 goto scriptDataEscapedDash
459 case '<':
460 goto scriptDataEscapedLessThanSign
461 }
462 goto scriptDataEscaped
463 464 scriptDataEscapedDash:
465 c = z.readByte()
466 if z.err != nil {
467 return
468 }
469 switch c {
470 case '-':
471 goto scriptDataEscapedDashDash
472 case '<':
473 goto scriptDataEscapedLessThanSign
474 }
475 goto scriptDataEscaped
476 477 scriptDataEscapedDashDash:
478 c = z.readByte()
479 if z.err != nil {
480 return
481 }
482 switch c {
483 case '-':
484 goto scriptDataEscapedDashDash
485 case '<':
486 goto scriptDataEscapedLessThanSign
487 case '>':
488 goto scriptData
489 }
490 goto scriptDataEscaped
491 492 scriptDataEscapedLessThanSign:
493 c = z.readByte()
494 if z.err != nil {
495 return
496 }
497 if c == '/' {
498 goto scriptDataEscapedEndTagOpen
499 }
500 if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' {
501 goto scriptDataDoubleEscapeStart
502 }
503 z.raw.end--
504 goto scriptData
505 506 scriptDataEscapedEndTagOpen:
507 if z.readRawEndTag() || z.err != nil {
508 return
509 }
510 goto scriptDataEscaped
511 512 scriptDataDoubleEscapeStart:
513 z.raw.end--
514 for i := 0; i < len("script"); i++ {
515 c = z.readByte()
516 if z.err != nil {
517 return
518 }
519 if c != "script"[i] && c != "SCRIPT"[i] {
520 z.raw.end--
521 goto scriptDataEscaped
522 }
523 }
524 c = z.readByte()
525 if z.err != nil {
526 return
527 }
528 switch c {
529 case ' ', '\n', '\r', '\t', '\f', '/', '>':
530 goto scriptDataDoubleEscaped
531 }
532 z.raw.end--
533 goto scriptDataEscaped
534 535 scriptDataDoubleEscaped:
536 c = z.readByte()
537 if z.err != nil {
538 return
539 }
540 switch c {
541 case '-':
542 goto scriptDataDoubleEscapedDash
543 case '<':
544 goto scriptDataDoubleEscapedLessThanSign
545 }
546 goto scriptDataDoubleEscaped
547 548 scriptDataDoubleEscapedDash:
549 c = z.readByte()
550 if z.err != nil {
551 return
552 }
553 switch c {
554 case '-':
555 goto scriptDataDoubleEscapedDashDash
556 case '<':
557 goto scriptDataDoubleEscapedLessThanSign
558 }
559 goto scriptDataDoubleEscaped
560 561 scriptDataDoubleEscapedDashDash:
562 c = z.readByte()
563 if z.err != nil {
564 return
565 }
566 switch c {
567 case '-':
568 goto scriptDataDoubleEscapedDashDash
569 case '<':
570 goto scriptDataDoubleEscapedLessThanSign
571 case '>':
572 goto scriptData
573 }
574 goto scriptDataDoubleEscaped
575 576 scriptDataDoubleEscapedLessThanSign:
577 c = z.readByte()
578 if z.err != nil {
579 return
580 }
581 if c == '/' {
582 goto scriptDataDoubleEscapeEnd
583 }
584 z.raw.end--
585 goto scriptDataDoubleEscaped
586 587 scriptDataDoubleEscapeEnd:
588 if z.readRawEndTag() {
589 z.raw.end += len("</script>")
590 goto scriptDataEscaped
591 }
592 if z.err != nil {
593 return
594 }
595 goto scriptDataDoubleEscaped
596 }
597 598 // readComment reads the next comment token starting with "<!--". The opening
599 // "<!--" has already been consumed.
600 func (z *Tokenizer) readComment() {
601 // When modifying this function, consider manually increasing the
602 // maxSuffixLen constant in func TestComments, from 6 to e.g. 9 or more.
603 // That increase should only be temporary, not committed, as it
604 // exponentially affects the test running time.
605 606 z.data.start = z.raw.end
607 defer func() {
608 if z.data.end < z.data.start {
609 // It's a comment with no data, like <!-->.
610 z.data.end = z.data.start
611 }
612 }()
613 614 var dashCount int
615 beginning := true
616 for {
617 c := z.readByte()
618 if z.err != nil {
619 z.data.end = z.calculateAbruptCommentDataEnd()
620 return
621 }
622 switch c {
623 case '-':
624 dashCount++
625 continue
626 case '>':
627 if dashCount >= 2 || beginning {
628 z.data.end = z.raw.end - len("-->")
629 return
630 }
631 case '!':
632 if dashCount >= 2 {
633 c = z.readByte()
634 if z.err != nil {
635 z.data.end = z.calculateAbruptCommentDataEnd()
636 return
637 } else if c == '>' {
638 z.data.end = z.raw.end - len("--!>")
639 return
640 } else if c == '-' {
641 dashCount = 1
642 beginning = false
643 continue
644 }
645 }
646 }
647 dashCount = 0
648 beginning = false
649 }
650 }
651 652 func (z *Tokenizer) calculateAbruptCommentDataEnd() int {
653 raw := z.Raw()
654 const prefixLen = len("<!--")
655 if len(raw) >= prefixLen {
656 raw = raw[prefixLen:]
657 if hasSuffix(raw, "--!") {
658 return z.raw.end - 3
659 } else if hasSuffix(raw, "--") {
660 return z.raw.end - 2
661 } else if hasSuffix(raw, "-") {
662 return z.raw.end - 1
663 }
664 }
665 return z.raw.end
666 }
667 668 func hasSuffix(b []byte, suffix string) bool {
669 if len(b) < len(suffix) {
670 return false
671 }
672 b = b[len(b)-len(suffix):]
673 for i := range b {
674 if b[i] != suffix[i] {
675 return false
676 }
677 }
678 return true
679 }
680 681 // readUntilCloseAngle reads until the next ">".
682 func (z *Tokenizer) readUntilCloseAngle() {
683 z.data.start = z.raw.end
684 for {
685 c := z.readByte()
686 if z.err != nil {
687 z.data.end = z.raw.end
688 return
689 }
690 if c == '>' {
691 z.data.end = z.raw.end - len(">")
692 return
693 }
694 }
695 }
696 697 // readMarkupDeclaration reads the next token starting with "<!". It might be
698 // a "<!--comment-->", a "<!DOCTYPE foo>", a "<![CDATA[section]]>" or
699 // "<!a bogus comment". The opening "<!" has already been consumed.
700 func (z *Tokenizer) readMarkupDeclaration() TokenType {
701 z.data.start = z.raw.end
702 var c [2]byte
703 for i := 0; i < 2; i++ {
704 c[i] = z.readByte()
705 if z.err != nil {
706 z.data.end = z.raw.end
707 return CommentToken
708 }
709 }
710 if c[0] == '-' && c[1] == '-' {
711 z.readComment()
712 return CommentToken
713 }
714 z.raw.end -= 2
715 if z.readDoctype() {
716 return DoctypeToken
717 }
718 if z.allowCDATA && z.readCDATA() {
719 z.convertNUL = true
720 return TextToken
721 }
722 // It's a bogus comment.
723 z.readUntilCloseAngle()
724 return CommentToken
725 }
726 727 // readDoctype attempts to read a doctype declaration and returns true if
728 // successful. The opening "<!" has already been consumed.
729 func (z *Tokenizer) readDoctype() bool {
730 const s = "DOCTYPE"
731 for i := 0; i < len(s); i++ {
732 c := z.readByte()
733 if z.err != nil {
734 z.data.end = z.raw.end
735 return false
736 }
737 if c != s[i] && c != s[i]+('a'-'A') {
738 // Back up to read the fragment of "DOCTYPE" again.
739 z.raw.end = z.data.start
740 return false
741 }
742 }
743 if z.skipWhiteSpace(); z.err != nil {
744 z.data.start = z.raw.end
745 z.data.end = z.raw.end
746 return true
747 }
748 z.readUntilCloseAngle()
749 return true
750 }
751 752 // readCDATA attempts to read a CDATA section and returns true if
753 // successful. The opening "<!" has already been consumed.
754 func (z *Tokenizer) readCDATA() bool {
755 const s = "[CDATA["
756 for i := 0; i < len(s); i++ {
757 c := z.readByte()
758 if z.err != nil {
759 z.data.end = z.raw.end
760 return false
761 }
762 if c != s[i] {
763 // Back up to read the fragment of "[CDATA[" again.
764 z.raw.end = z.data.start
765 return false
766 }
767 }
768 z.data.start = z.raw.end
769 brackets := 0
770 for {
771 c := z.readByte()
772 if z.err != nil {
773 z.data.end = z.raw.end
774 return true
775 }
776 switch c {
777 case ']':
778 brackets++
779 case '>':
780 if brackets >= 2 {
781 z.data.end = z.raw.end - len("]]>")
782 return true
783 }
784 brackets = 0
785 default:
786 brackets = 0
787 }
788 }
789 }
790 791 // startTagIn returns whether the start tag in z.buf[z.data.start:z.data.end]
792 // case-insensitively matches any element of ss.
793 func (z *Tokenizer) startTagIn(ss ...string) bool {
794 loop:
795 for _, s := range ss {
796 if z.data.end-z.data.start != len(s) {
797 continue loop
798 }
799 for i := 0; i < len(s); i++ {
800 c := z.buf[z.data.start+i]
801 if 'A' <= c && c <= 'Z' {
802 c += 'a' - 'A'
803 }
804 if c != s[i] {
805 continue loop
806 }
807 }
808 return true
809 }
810 return false
811 }
812 813 // readStartTag reads the next start tag token. The opening "<a" has already
814 // been consumed, where 'a' means anything in [A-Za-z].
815 func (z *Tokenizer) readStartTag() TokenType {
816 z.readTag(true)
817 if z.err != nil {
818 return ErrorToken
819 }
820 // Several tags flag the tokenizer's next token as raw.
821 c, raw := z.buf[z.data.start], false
822 if 'A' <= c && c <= 'Z' {
823 c += 'a' - 'A'
824 }
825 switch c {
826 case 'i':
827 raw = z.startTagIn("iframe")
828 case 'n':
829 raw = z.startTagIn("noembed", "noframes", "noscript")
830 case 'p':
831 raw = z.startTagIn("plaintext")
832 case 's':
833 raw = z.startTagIn("script", "style")
834 case 't':
835 raw = z.startTagIn("textarea", "title")
836 case 'x':
837 raw = z.startTagIn("xmp")
838 }
839 if raw {
840 z.rawTag = strings.ToLower(string(z.buf[z.data.start:z.data.end]))
841 }
842 // Look for a self-closing token (e.g. <br/>).
843 //
844 // Originally, we did this by just checking that the last character of the
845 // tag (ignoring the closing bracket) was a solidus (/) character, but this
846 // is not always accurate.
847 //
848 // We need to be careful that we don't misinterpret a non-self-closing tag
849 // as self-closing, as can happen if the tag contains unquoted attribute
850 // values (i.e. <p a=/>).
851 //
852 // To avoid this, we check that the last non-bracket character of the tag
853 // (z.raw.end-2) isn't the same character as the last non-quote character of
854 // the last attribute of the tag (z.pendingAttr[1].end-1), if the tag has
855 // attributes.
856 nAttrs := len(z.attr)
857 if z.err == nil && z.buf[z.raw.end-2] == '/' && (nAttrs == 0 || z.raw.end-2 != z.attr[nAttrs-1][1].end-1) {
858 return SelfClosingTagToken
859 }
860 return StartTagToken
861 }
862 863 // readTag reads the next tag token and its attributes. If saveAttr, those
864 // attributes are saved in z.attr, otherwise z.attr is set to an empty slice.
865 // The opening "<a" or "</a" has already been consumed, where 'a' means anything
866 // in [A-Za-z].
867 func (z *Tokenizer) readTag(saveAttr bool) {
868 z.attr = z.attr[:0]
869 z.nAttrReturned = 0
870 // Read the tag name and attribute key/value pairs.
871 z.readTagName()
872 if z.skipWhiteSpace(); z.err != nil {
873 return
874 }
875 for {
876 c := z.readByte()
877 if z.err != nil || c == '>' {
878 break
879 }
880 z.raw.end--
881 z.readTagAttrKey()
882 z.readTagAttrVal()
883 // Save pendingAttr if saveAttr and that attribute has a non-empty key.
884 if saveAttr && z.pendingAttr[0].start != z.pendingAttr[0].end {
885 z.attr = append(z.attr, z.pendingAttr)
886 }
887 if z.skipWhiteSpace(); z.err != nil {
888 break
889 }
890 }
891 }
892 893 // readTagName sets z.data to the "div" in "<div k=v>". The reader (z.raw.end)
894 // is positioned such that the first byte of the tag name (the "d" in "<div")
895 // has already been consumed.
896 func (z *Tokenizer) readTagName() {
897 z.data.start = z.raw.end - 1
898 for {
899 c := z.readByte()
900 if z.err != nil {
901 z.data.end = z.raw.end
902 return
903 }
904 switch c {
905 case ' ', '\n', '\r', '\t', '\f':
906 z.data.end = z.raw.end - 1
907 return
908 case '/', '>':
909 z.raw.end--
910 z.data.end = z.raw.end
911 return
912 }
913 }
914 }
915 916 // readTagAttrKey sets z.pendingAttr[0] to the "k" in "<div k=v>".
917 // Precondition: z.err == nil.
918 func (z *Tokenizer) readTagAttrKey() {
919 z.pendingAttr[0].start = z.raw.end
920 for {
921 c := z.readByte()
922 if z.err != nil {
923 z.pendingAttr[0].end = z.raw.end
924 return
925 }
926 switch c {
927 case '=':
928 if z.pendingAttr[0].start+1 == z.raw.end {
929 // WHATWG 13.2.5.32, if we see an equals sign before the attribute name
930 // begins, we treat it as a character in the attribute name and continue.
931 continue
932 }
933 fallthrough
934 case ' ', '\n', '\r', '\t', '\f', '/', '>':
935 // WHATWG 13.2.5.33 Attribute name state
936 // We need to reconsume the char in the after attribute name state to support the / character
937 z.raw.end--
938 z.pendingAttr[0].end = z.raw.end
939 return
940 }
941 }
942 }
943 944 // readTagAttrVal sets z.pendingAttr[1] to the "v" in "<div k=v>".
945 func (z *Tokenizer) readTagAttrVal() {
946 z.pendingAttr[1].start = z.raw.end
947 z.pendingAttr[1].end = z.raw.end
948 if z.skipWhiteSpace(); z.err != nil {
949 return
950 }
951 c := z.readByte()
952 if z.err != nil {
953 return
954 }
955 if c == '/' {
956 // WHATWG 13.2.5.34 After attribute name state
957 // U+002F SOLIDUS (/) - Switch to the self-closing start tag state.
958 return
959 }
960 if c != '=' {
961 z.raw.end--
962 return
963 }
964 if z.skipWhiteSpace(); z.err != nil {
965 return
966 }
967 quote := z.readByte()
968 if z.err != nil {
969 return
970 }
971 switch quote {
972 case '>':
973 z.raw.end--
974 return
975 976 case '\'', '"':
977 z.pendingAttr[1].start = z.raw.end
978 for {
979 c := z.readByte()
980 if z.err != nil {
981 z.pendingAttr[1].end = z.raw.end
982 return
983 }
984 if c == quote {
985 z.pendingAttr[1].end = z.raw.end - 1
986 return
987 }
988 }
989 990 default:
991 z.pendingAttr[1].start = z.raw.end - 1
992 for {
993 c := z.readByte()
994 if z.err != nil {
995 z.pendingAttr[1].end = z.raw.end
996 return
997 }
998 switch c {
999 case ' ', '\n', '\r', '\t', '\f':
1000 z.pendingAttr[1].end = z.raw.end - 1
1001 return
1002 case '>':
1003 z.raw.end--
1004 z.pendingAttr[1].end = z.raw.end
1005 return
1006 }
1007 }
1008 }
1009 }
1010 1011 // Next scans the next token and returns its type.
1012 func (z *Tokenizer) Next() TokenType {
1013 z.raw.start = z.raw.end
1014 z.data.start = z.raw.end
1015 z.data.end = z.raw.end
1016 if z.err != nil {
1017 z.tt = ErrorToken
1018 return z.tt
1019 }
1020 if z.rawTag != "" {
1021 if z.rawTag == "plaintext" {
1022 // Read everything up to EOF.
1023 for z.err == nil {
1024 z.readByte()
1025 }
1026 z.data.end = z.raw.end
1027 z.textIsRaw = true
1028 } else {
1029 z.readRawOrRCDATA()
1030 }
1031 if z.data.end > z.data.start {
1032 z.tt = TextToken
1033 z.convertNUL = true
1034 return z.tt
1035 }
1036 }
1037 z.textIsRaw = false
1038 z.convertNUL = false
1039 1040 loop:
1041 for {
1042 c := z.readByte()
1043 if z.err != nil {
1044 break loop
1045 }
1046 if c != '<' {
1047 continue loop
1048 }
1049 1050 // Check if the '<' we have just read is part of a tag, comment
1051 // or doctype. If not, it's part of the accumulated text token.
1052 c = z.readByte()
1053 if z.err != nil {
1054 break loop
1055 }
1056 var tokenType TokenType
1057 switch {
1058 case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
1059 tokenType = StartTagToken
1060 case c == '/':
1061 tokenType = EndTagToken
1062 case c == '!' || c == '?':
1063 // We use CommentToken to mean any of "<!--actual comments-->",
1064 // "<!DOCTYPE declarations>" and "<?xml processing instructions?>".
1065 tokenType = CommentToken
1066 default:
1067 // Reconsume the current character.
1068 z.raw.end--
1069 continue
1070 }
1071 1072 // We have a non-text token, but we might have accumulated some text
1073 // before that. If so, we return the text first, and return the non-
1074 // text token on the subsequent call to Next.
1075 if x := z.raw.end - len("<a"); z.raw.start < x {
1076 z.raw.end = x
1077 z.data.end = x
1078 z.tt = TextToken
1079 return z.tt
1080 }
1081 switch tokenType {
1082 case StartTagToken:
1083 z.tt = z.readStartTag()
1084 return z.tt
1085 case EndTagToken:
1086 c = z.readByte()
1087 if z.err != nil {
1088 break loop
1089 }
1090 if c == '>' {
1091 // "</>" does not generate a token at all. Generate an empty comment
1092 // to allow passthrough clients to pick up the data using Raw.
1093 // Reset the tokenizer state and start again.
1094 z.tt = CommentToken
1095 return z.tt
1096 }
1097 if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' {
1098 z.readTag(false)
1099 if z.err != nil {
1100 z.tt = ErrorToken
1101 } else {
1102 z.tt = EndTagToken
1103 }
1104 return z.tt
1105 }
1106 z.raw.end--
1107 z.readUntilCloseAngle()
1108 z.tt = CommentToken
1109 return z.tt
1110 case CommentToken:
1111 if c == '!' {
1112 z.tt = z.readMarkupDeclaration()
1113 return z.tt
1114 }
1115 z.raw.end--
1116 z.readUntilCloseAngle()
1117 z.tt = CommentToken
1118 return z.tt
1119 }
1120 }
1121 if z.raw.start < z.raw.end {
1122 z.data.end = z.raw.end
1123 z.tt = TextToken
1124 return z.tt
1125 }
1126 z.tt = ErrorToken
1127 return z.tt
1128 }
1129 1130 // Raw returns the unmodified text of the current token. Calling Next, Token,
1131 // Text, TagName or TagAttr may change the contents of the returned slice.
1132 //
1133 // The token stream's raw bytes partition the byte stream (up until an
1134 // ErrorToken). There are no overlaps or gaps between two consecutive token's
1135 // raw bytes. One implication is that the byte offset of the current token is
1136 // the sum of the lengths of all previous tokens' raw bytes.
1137 func (z *Tokenizer) Raw() []byte {
1138 return z.buf[z.raw.start:z.raw.end]
1139 }
1140 1141 // convertNewlines converts "\r" and "\r\n" in s to "\n".
1142 // The conversion happens in place, but the resulting slice may be shorter.
1143 func convertNewlines(s []byte) []byte {
1144 for i, c := range s {
1145 if c != '\r' {
1146 continue
1147 }
1148 1149 src := i + 1
1150 if src >= len(s) || s[src] != '\n' {
1151 s[i] = '\n'
1152 continue
1153 }
1154 1155 dst := i
1156 for src < len(s) {
1157 if s[src] == '\r' {
1158 if src+1 < len(s) && s[src+1] == '\n' {
1159 src++
1160 }
1161 s[dst] = '\n'
1162 } else {
1163 s[dst] = s[src]
1164 }
1165 src++
1166 dst++
1167 }
1168 return s[:dst]
1169 }
1170 return s
1171 }
1172 1173 var (
1174 nul = []byte("\x00")
1175 replacement = []byte("\ufffd")
1176 )
1177 1178 // Text returns the unescaped text of a text, comment or doctype token. The
1179 // contents of the returned slice may change on the next call to Next.
1180 func (z *Tokenizer) Text() []byte {
1181 switch z.tt {
1182 case TextToken, CommentToken, DoctypeToken:
1183 s := z.buf[z.data.start:z.data.end]
1184 z.data.start = z.raw.end
1185 z.data.end = z.raw.end
1186 s = convertNewlines(s)
1187 if (z.convertNUL || z.tt == CommentToken) && bytes.Contains(s, nul) {
1188 s = bytes.Replace(s, nul, replacement, -1)
1189 }
1190 if !z.textIsRaw {
1191 s = unescape(s, false)
1192 }
1193 return s
1194 }
1195 return nil
1196 }
1197 1198 // TagName returns the lower-cased name of a tag token (the `img` out of
1199 // `<IMG SRC="foo">`) and whether the tag has attributes.
1200 // The contents of the returned slice may change on the next call to Next.
1201 func (z *Tokenizer) TagName() (name []byte, hasAttr bool) {
1202 if z.data.start < z.data.end {
1203 switch z.tt {
1204 case StartTagToken, EndTagToken, SelfClosingTagToken:
1205 s := z.buf[z.data.start:z.data.end]
1206 z.data.start = z.raw.end
1207 z.data.end = z.raw.end
1208 return lower(s), z.nAttrReturned < len(z.attr)
1209 }
1210 }
1211 return nil, false
1212 }
1213 1214 // TagAttr returns the lower-cased key and unescaped value of the next unparsed
1215 // attribute for the current tag token and whether there are more attributes.
1216 // The contents of the returned slices may change on the next call to Next.
1217 func (z *Tokenizer) TagAttr() (key, val []byte, moreAttr bool) {
1218 if z.nAttrReturned < len(z.attr) {
1219 switch z.tt {
1220 case StartTagToken, SelfClosingTagToken:
1221 x := z.attr[z.nAttrReturned]
1222 z.nAttrReturned++
1223 key = z.buf[x[0].start:x[0].end]
1224 val = z.buf[x[1].start:x[1].end]
1225 return lower(key), unescape(convertNewlines(val), true), z.nAttrReturned < len(z.attr)
1226 }
1227 }
1228 return nil, nil, false
1229 }
1230 1231 // Token returns the current Token. The result's Data and Attr values remain
1232 // valid after subsequent Next calls.
1233 func (z *Tokenizer) Token() Token {
1234 t := Token{Type: z.tt}
1235 switch z.tt {
1236 case TextToken, CommentToken, DoctypeToken:
1237 t.Data = string(z.Text())
1238 case StartTagToken, SelfClosingTagToken, EndTagToken:
1239 name, moreAttr := z.TagName()
1240 for moreAttr {
1241 var key, val []byte
1242 key, val, moreAttr = z.TagAttr()
1243 t.Attr = append(t.Attr, Attribute{"", atom.String(key), string(val)})
1244 }
1245 if a := atom.Lookup(name); a != 0 {
1246 t.DataAtom, t.Data = a, a.String()
1247 } else {
1248 t.DataAtom, t.Data = 0, string(name)
1249 }
1250 }
1251 return t
1252 }
1253 1254 // SetMaxBuf sets a limit on the amount of data buffered during tokenization.
1255 // A value of 0 means unlimited.
1256 func (z *Tokenizer) SetMaxBuf(n int) {
1257 z.maxBuf = n
1258 }
1259 1260 // NewTokenizer returns a new HTML Tokenizer for the given Reader.
1261 // The input is assumed to be UTF-8 encoded.
1262 func NewTokenizer(r io.Reader) *Tokenizer {
1263 return NewTokenizerFragment(r, "")
1264 }
1265 1266 // NewTokenizerFragment returns a new HTML Tokenizer for the given Reader, for
1267 // tokenizing an existing element's InnerHTML fragment. contextTag is that
1268 // element's tag, such as "div" or "iframe".
1269 //
1270 // For example, how the InnerHTML "a<b" is tokenized depends on whether it is
1271 // for a <p> tag or a <script> tag.
1272 //
1273 // The input is assumed to be UTF-8 encoded.
1274 func NewTokenizerFragment(r io.Reader, contextTag string) *Tokenizer {
1275 z := &Tokenizer{
1276 r: r,
1277 buf: make([]byte, 0, 4096),
1278 }
1279 if contextTag != "" {
1280 switch s := strings.ToLower(contextTag); s {
1281 case "iframe", "noembed", "noframes", "noscript", "plaintext", "script", "style", "title", "textarea", "xmp":
1282 z.rawTag = s
1283 }
1284 }
1285 return z
1286 }
1287