1 files changed, 397 insertions, 0 deletions
diff --git a/libgo/go/html/token.go b/libgo/go/html/token.go
new file mode 100644
index 00000000000..0d4de254308
--- /dev/null
+++ b/libgo/go/html/token.go
@@ -0,0 +1,397 @@
+// 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"
+	"io"
+	"os"
+	"strconv"
+)
+
+// A TokenType is the type of a Token.
+type TokenType int
+
+const (
+	// Error means that an error occurred during tokenization.
+	Error TokenType = iota
+	// Text means a text node.
+	Text
+	// A StartTag looks like <a>.
+	StartTag
+	// An EndTag looks like </a>.
+	EndTag
+	// A SelfClosingTag tag looks like <br/>.
+	SelfClosingTag
+)
+
+// String returns a string representation of the TokenType.
+func (t TokenType) String() string {
+	switch t {
+	case Error:
+		return "Error"
+	case Text:
+		return "Text"
+	case StartTag:
+		return "StartTag"
+	case EndTag:
+		return "EndTag"
+	case SelfClosingTag:
+		return "SelfClosingTag"
+	}
+	return "Invalid(" + strconv.Itoa(int(t)) + ")"
+}
+
+// An Attribute is an attribute key-value pair. 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").
+type Attribute struct {
+	Key, Val string
+}
+
+// A Token consists of a TokenType and some Data (tag name for start and end
+// tags, content for text). A tag Token may also contain a slice of Attributes.
+// Data is unescaped for both tag and text Tokens (it looks like "a<b" rather
+// than "a&lt;b").
+type Token struct {
+	Type TokenType
+	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.NewBuffer(nil)
+	buf.WriteString(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 Error:
+		return ""
+	case Text:
+		return EscapeString(t.Data)
+	case StartTag:
+		return "<" + t.tagString() + ">"
+	case EndTag:
+		return "</" + t.tagString() + ">"
+	case SelfClosingTag:
+		return "<" + t.tagString() + "/>"
+	}
+	return "Invalid(" + strconv.Itoa(int(t.Type)) + ")"
+}
+
+// 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 most recently read token. If tt == Error
+	// then err is the error associated with trying to read that token.
+	tt  TokenType
+	err os.Error
+	// buf[p0:p1] holds the raw data of the most recent token.
+	// buf[p1:] is buffered input that will yield future tokens.
+	p0, p1 int
+	buf    []byte
+}
+
+// Error returns the error associated with the most recent Error token. This is
+// typically os.EOF, meaning the end of tokenization.
+func (z *Tokenizer) Error() os.Error {
+	if z.tt != Error {
+		return nil
+	}
+	return z.err
+}
+
+// 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.p0:z.p1]
+}
+
+// readByte returns the next byte from the input stream, doing a buffered read
+// from z.r into z.buf if necessary. z.buf[z.p0:z.p1] remains a contiguous byte
+// slice that holds all the bytes read so far for the current token.
+func (z *Tokenizer) readByte() (byte, os.Error) {
+	if z.p1 >= len(z.buf) {
+		// Our buffer is exhausted and we have to read from z.r.
+		// We copy z.buf[z.p0:z.p1] to the beginning of z.buf. If the length
+		// z.p1 - z.p0 is more than half the capacity of z.buf, then we
+		// allocate a new buffer before the copy.
+		c := cap(z.buf)
+		d := z.p1 - z.p0
+		var buf1 []byte
+		if 2*d > c {
+			buf1 = make([]byte, d, 2*c)
+		} else {
+			buf1 = z.buf[0:d]
+		}
+		copy(buf1, z.buf[z.p0:z.p1])
+		z.p0, z.p1, z.buf = 0, d, buf1[0:d]
+		// Now that we have copied the live bytes to the start of the buffer,
+		// we read from z.r into the remainder.
+		n, err := z.r.Read(buf1[d:cap(buf1)])
+		if err != nil {
+			return 0, err
+		}
+		z.buf = buf1[0 : d+n]
+	}
+	x := z.buf[z.p1]
+	z.p1++
+	return x, nil
+}
+
+// readTo keeps reading bytes until x is found.
+func (z *Tokenizer) readTo(x uint8) os.Error {
+	for {
+		c, err := z.readByte()
+		if err != nil {
+			return err
+		}
+		switch c {
+		case x:
+			return nil
+		case '\\':
+			_, err = z.readByte()
+			if err != nil {
+				return err
+			}
+		}
+	}
+	panic("unreachable")
+}
+
+// nextTag returns the next TokenType starting from the tag open state.
+func (z *Tokenizer) nextTag() (tt TokenType, err os.Error) {
+	c, err := z.readByte()
+	if err != nil {
+		return Error, err
+	}
+	switch {
+	case c == '/':
+		tt = EndTag
+	// Lower-cased characters are more common in tag names, so we check for them first.
+	case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
+		tt = StartTag
+	case c == '!':
+		return Error, os.NewError("html: TODO(nigeltao): implement comments")
+	case c == '?':
+		return Error, os.NewError("html: TODO(nigeltao): implement XML processing instructions")
+	default:
+		return Error, os.NewError("html: TODO(nigeltao): handle malformed tags")
+	}
+	for {
+		c, err := z.readByte()
+		if err != nil {
+			return Text, err
+		}
+		switch c {
+		case '"':
+			err = z.readTo('"')
+			if err != nil {
+				return Text, err
+			}
+		case '\'':
+			err = z.readTo('\'')
+			if err != nil {
+				return Text, err
+			}
+		case '>':
+			if z.buf[z.p1-2] == '/' && tt == StartTag {
+				return SelfClosingTag, nil
+			}
+			return tt, nil
+		}
+	}
+	panic("unreachable")
+}
+
+// Next scans the next token and returns its type.
+func (z *Tokenizer) Next() TokenType {
+	if z.err != nil {
+		z.tt = Error
+		return z.tt
+	}
+	z.p0 = z.p1
+	c, err := z.readByte()
+	if err != nil {
+		z.tt, z.err = Error, err
+		return z.tt
+	}
+	if c == '<' {
+		z.tt, z.err = z.nextTag()
+		return z.tt
+	}
+	for {
+		c, err := z.readByte()
+		if err != nil {
+			z.tt, z.err = Error, err
+			if err == os.EOF {
+				z.tt = Text
+			}
+			return z.tt
+		}
+		if c == '<' {
+			z.p1--
+			z.tt = Text
+			return z.tt
+		}
+	}
+	panic("unreachable")
+}
+
+// trim returns the largest j such that z.buf[i:j] contains only white space,
+// or only white space plus the final ">" or "/>" of the raw data.
+func (z *Tokenizer) trim(i int) int {
+	k := z.p1
+	for ; i < k; i++ {
+		switch z.buf[i] {
+		case ' ', '\n', '\t', '\f':
+			continue
+		case '>':
+			if i == k-1 {
+				return k
+			}
+		case '/':
+			if i == k-2 {
+				return k
+			}
+		}
+		return i
+	}
+	return k
+}
+
+// lower finds the largest alphabetic [a-zA-Z]* word at the start of z.buf[i:]
+// and returns that word lower-cased, as well as the trimmed cursor location
+// after that word.
+func (z *Tokenizer) lower(i int) ([]byte, int) {
+	i0 := i
+loop:
+	for ; i < z.p1; i++ {
+		c := z.buf[i]
+		// TODO(nigeltao): Check what '0' <= c && c <= '9' should do.
+		switch {
+		case 'A' <= c && c <= 'Z':
+			z.buf[i] = c + 'a' - 'A'
+		case 'a' <= c && c <= 'z':
+			// No-op.
+		default:
+			break loop
+		}
+	}
+	return z.buf[i0:i], z.trim(i)
+}
+
+// Text returns the raw data after unescaping.
+// The contents of the returned slice may change on the next call to Next.
+func (z *Tokenizer) Text() []byte {
+	s := unescape(z.Raw())
+	z.p0 = z.p1
+	return s
+}
+
+// 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, remaining bool) {
+	i := z.p0 + 1
+	if i >= z.p1 {
+		z.p0 = z.p1
+		return nil, false
+	}
+	if z.buf[i] == '/' {
+		i++
+	}
+	name, z.p0 = z.lower(i)
+	remaining = z.p0 != z.p1
+	return
+}
+
+// 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, remaining bool) {
+	key, i := z.lower(z.p0)
+	// Get past the "=\"".
+	if i == z.p1 || z.buf[i] != '=' {
+		return
+	}
+	i = z.trim(i + 1)
+	if i == z.p1 || z.buf[i] != '"' {
+		return
+	}
+	i = z.trim(i + 1)
+	// Copy and unescape everything up to the closing '"'.
+	dst, src := i, i
+loop:
+	for src < z.p1 {
+		c := z.buf[src]
+		switch c {
+		case '"':
+			src++
+			break loop
+		case '&':
+			dst, src = unescapeEntity(z.buf, dst, src)
+		case '\\':
+			if src == z.p1 {
+				z.buf[dst] = '\\'
+				dst++
+			} else {
+				z.buf[dst] = z.buf[src+1]
+				dst, src = dst+1, src+2
+			}
+		default:
+			z.buf[dst] = c
+			dst, src = dst+1, src+1
+		}
+	}
+	val, z.p0 = z.buf[i:dst], z.trim(src)
+	remaining = z.p0 != z.p1
+	return
+}
+
+// Token returns the next 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 Text:
+		t.Data = string(z.Text())
+	case StartTag, EndTag, SelfClosingTag:
+		var attr []Attribute
+		name, remaining := z.TagName()
+		for remaining {
+			var key, val []byte
+			key, val, remaining = z.TagAttr()
+			attr = append(attr, Attribute{string(key), string(val)})
+		}
+		t.Data = string(name)
+		t.Attr = attr
+	}
+	return t
+}
+
+// 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 &Tokenizer{
+		r:   r,
+		buf: make([]byte, 0, 4096),
+	}
+}