// 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<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<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 "<!--" + escapeCommentString(t.Data) + "-->" case DoctypeToken: return "<!DOCTYPE " + EscapeString(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++ { if n, err := r.Read(b); 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 != '/' { z.raw.end-- 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() { // When modifying this function, consider manually increasing the // maxSuffixLen constant in func TestComments, from 6 to e.g. 9 or more. // That increase should only be temporary, not committed, as it // exponentially affects the test running time. 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 } }() var dashCount int beginning := true for { c := z.readByte() if z.err != nil { z.data.end = z.calculateAbruptCommentDataEnd() return } switch c { case '-': dashCount++ continue case '>': if dashCount >= 2 || beginning { z.data.end = z.raw.end - len("-->") return } case '!': if dashCount >= 2 { c = z.readByte() if z.err != nil { z.data.end = z.calculateAbruptCommentDataEnd() return } else if c == '>' { z.data.end = z.raw.end - len("--!>") return } else if c == '-' { dashCount = 1 beginning = false continue } } } dashCount = 0 beginning = false } } func (z *Tokenizer) calculateAbruptCommentDataEnd() int { raw := z.Raw() const prefixLen = len("<!--") if len(raw) >= prefixLen { raw = raw[prefixLen:] if hasSuffix(raw, "--!") { return z.raw.end - 3 } else if hasSuffix(raw, "--") { return z.raw.end - 2 } else if hasSuffix(raw, "-") { return z.raw.end - 1 } } return z.raw.end } func hasSuffix(b []byte, suffix string) bool { if len(b) < len(suffix) { return false } b = b[len(b)-len(suffix):] for i := range b { if b[i] != suffix[i] { return false } } return true } // 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 '=': if z.pendingAttr[0].start+1 == z.raw.end { // WHATWG 13.2.5.32, if we see an equals sign before the attribute name // begins, we treat it as a character in the attribute name and continue. continue } fallthrough case ' ', '\n', '\r', '\t', '\f', '/', '>': // WHATWG 13.2.5.33 Attribute name state // We need to reconsume the char in the after attribute name state to support the / character 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 == '/' { // WHATWG 13.2.5.34 After attribute name state // U+002F SOLIDUS (/) - Switch to the self-closing start tag state. 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. // // The token stream's raw bytes partition the byte stream (up until an // ErrorToken). There are no overlaps or gaps between two consecutive token's // raw bytes. One implication is that the byte offset of the current token is // the sum of the lengths of all previous tokens' raw bytes. 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 }