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// Copyright 2009 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 xml implements a simple XML 1.0 parser that
// understands XML name spaces.
package xml

// References:
//    Annotated XML spec: http://www.xml.com/axml/testaxml.htm
//    XML name spaces: http://www.w3.org/TR/REC-xml-names/

// TODO(rsc):
//      Test error handling.

import (
        "bufio"
        "bytes"
        "fmt"
        "io"
        "strconv"
        "strings"
        "unicode"
        "unicode/utf8"
)

// A SyntaxError represents a syntax error in the XML input stream.
type SyntaxError struct {
        Msg  string
        Line int
}

func (e *SyntaxError) Error() string {
        return "XML syntax error on line " + strconv.Itoa(e.Line) + ": " + e.Msg
}

// A Name represents an XML name (Local) annotated
// with a name space identifier (Space).
// In tokens returned by Decoder.Token, the Space identifier
// is given as a canonical URL, not the short prefix used
// in the document being parsed.
type Name struct {
        Space, Local string
}

// An Attr represents an attribute in an XML element (Name=Value).
type Attr struct {
        Name  Name
        Value string
}

// A Token is an interface holding one of the token types:
// StartElement, EndElement, CharData, Comment, ProcInst, or Directive.
type Token interface{}

// A StartElement represents an XML start element.
type StartElement struct {
        Name Name
        Attr []Attr
}

func (e StartElement) Copy() StartElement {
        attrs := make([]Attr, len(e.Attr))
        copy(attrs, e.Attr)
        e.Attr = attrs
        return e
}

// An EndElement represents an XML end element.
type EndElement struct {
        Name Name
}

// A CharData represents XML character data (raw text),
// in which XML escape sequences have been replaced by
// the characters they represent.
type CharData []byte

func makeCopy(b []byte) []byte {
        b1 := make([]byte, len(b))
        copy(b1, b)
        return b1
}

func (c CharData) Copy() CharData { return CharData(makeCopy(c)) }

// A Comment represents an XML comment of the form <!--comment-->.
// The bytes do not include the <!-- and --> comment markers.
type Comment []byte

func (c Comment) Copy() Comment { return Comment(makeCopy(c)) }

// A ProcInst represents an XML processing instruction of the form <?target inst?>
type ProcInst struct {
        Target string
        Inst   []byte
}

func (p ProcInst) Copy() ProcInst {
        p.Inst = makeCopy(p.Inst)
        return p
}

// A Directive represents an XML directive of the form <!text>.
// The bytes do not include the <! and > markers.
type Directive []byte

func (d Directive) Copy() Directive { return Directive(makeCopy(d)) }

// CopyToken returns a copy of a Token.
func CopyToken(t Token) Token {
        switch v := t.(type) {
        case CharData:
                return v.Copy()
        case Comment:
                return v.Copy()
        case Directive:
                return v.Copy()
        case ProcInst:
                return v.Copy()
        case StartElement:
                return v.Copy()
        }
        return t
}

// A Decoder represents an XML parser reading a particular input stream.
// The parser assumes that its input is encoded in UTF-8.
type Decoder struct {
        // Strict defaults to true, enforcing the requirements
        // of the XML specification.
        // If set to false, the parser allows input containing common
        // mistakes:
        //      * If an element is missing an end tag, the parser invents
        //        end tags as necessary to keep the return values from Token
        //        properly balanced.
        //      * In attribute values and character data, unknown or malformed
        //        character entities (sequences beginning with &) are left alone.
        //
        // Setting:
        //
        //      d.Strict = false;
        //      d.AutoClose = HTMLAutoClose;
        //      d.Entity = HTMLEntity
        //
        // creates a parser that can handle typical HTML.
        Strict bool

        // When Strict == false, AutoClose indicates a set of elements to
        // consider closed immediately after they are opened, regardless
        // of whether an end element is present.
        AutoClose []string

        // Entity can be used to map non-standard entity names to string replacements.
        // The parser behaves as if these standard mappings are present in the map,
        // regardless of the actual map content:
        //
        //      "lt": "<",
        //      "gt": ">",
        //      "amp": "&",
        //      "apos": "'",
        //      "quot": `"`,
        Entity map[string]string

        // CharsetReader, if non-nil, defines a function to generate
        // charset-conversion readers, converting from the provided
        // non-UTF-8 charset into UTF-8. If CharsetReader is nil or
        // returns an error, parsing stops with an error. One of the
        // the CharsetReader's result values must be non-nil.
        CharsetReader func(charset string, input io.Reader) (io.Reader, error)

        r         io.ByteReader
        buf       bytes.Buffer
        saved     *bytes.Buffer
        stk       *stack
        free      *stack
        needClose bool
        toClose   Name
        nextToken Token
        nextByte  int
        ns        map[string]string
        err       error
        line      int
        tmp       [32]byte
}

// NewDecoder creates a new XML parser reading from r.
func NewDecoder(r io.Reader) *Decoder {
        d := &Decoder{
                ns:       make(map[string]string),
                nextByte: -1,
                line:     1,
                Strict:   true,
        }
        d.switchToReader(r)
        return d
}

// Token returns the next XML token in the input stream.
// At the end of the input stream, Token returns nil, io.EOF.
//
// Slices of bytes in the returned token data refer to the
// parser's internal buffer and remain valid only until the next
// call to Token.  To acquire a copy of the bytes, call CopyToken
// or the token's Copy method.
//
// Token expands self-closing elements such as <br/>
// into separate start and end elements returned by successive calls.
//
// Token guarantees that the StartElement and EndElement
// tokens it returns are properly nested and matched:
// if Token encounters an unexpected end element,
// it will return an error.
//
// Token implements XML name spaces as described by
// http://www.w3.org/TR/REC-xml-names/.  Each of the
// Name structures contained in the Token has the Space
// set to the URL identifying its name space when known.
// If Token encounters an unrecognized name space prefix,
// it uses the prefix as the Space rather than report an error.
func (d *Decoder) Token() (t Token, err error) {
        if d.nextToken != nil {
                t = d.nextToken
                d.nextToken = nil
        } else if t, err = d.RawToken(); err != nil {
                return
        }

        if !d.Strict {
                if t1, ok := d.autoClose(t); ok {
                        d.nextToken = t
                        t = t1
                }
        }
        switch t1 := t.(type) {
        case StartElement:
                // In XML name spaces, the translations listed in the
                // attributes apply to the element name and
                // to the other attribute names, so process
                // the translations first.
                for _, a := range t1.Attr {
                        if a.Name.Space == "xmlns" {
                                v, ok := d.ns[a.Name.Local]
                                d.pushNs(a.Name.Local, v, ok)
                                d.ns[a.Name.Local] = a.Value
                        }
                        if a.Name.Space == "" && a.Name.Local == "xmlns" {
                                // Default space for untagged names
                                v, ok := d.ns[""]
                                d.pushNs("", v, ok)
                                d.ns[""] = a.Value
                        }
                }

                d.translate(&t1.Name, true)
                for i := range t1.Attr {
                        d.translate(&t1.Attr[i].Name, false)
                }
                d.pushElement(t1.Name)
                t = t1

        case EndElement:
                d.translate(&t1.Name, true)
                if !d.popElement(&t1) {
                        return nil, d.err
                }
                t = t1
        }
        return
}

// Apply name space translation to name n.
// The default name space (for Space=="")
// applies only to element names, not to attribute names.
func (d *Decoder) translate(n *Name, isElementName bool) {
        switch {
        case n.Space == "xmlns":
                return
        case n.Space == "" && !isElementName:
                return
        case n.Space == "" && n.Local == "xmlns":
                return
        }
        if v, ok := d.ns[n.Space]; ok {
                n.Space = v
        }
}

func (d *Decoder) switchToReader(r io.Reader) {
        // Get efficient byte at a time reader.
        // Assume that if reader has its own
        // ReadByte, it's efficient enough.
        // Otherwise, use bufio.
        if rb, ok := r.(io.ByteReader); ok {
                d.r = rb
        } else {
                d.r = bufio.NewReader(r)
        }
}

// Parsing state - stack holds old name space translations
// and the current set of open elements.  The translations to pop when
// ending a given tag are *below* it on the stack, which is
// more work but forced on us by XML.
type stack struct {
        next *stack
        kind int
        name Name
        ok   bool
}

const (
        stkStart = iota
        stkNs
)

func (d *Decoder) push(kind int) *stack {
        s := d.free
        if s != nil {
                d.free = s.next
        } else {
                s = new(stack)
        }
        s.next = d.stk
        s.kind = kind
        d.stk = s
        return s
}

func (d *Decoder) pop() *stack {
        s := d.stk
        if s != nil {
                d.stk = s.next
                s.next = d.free
                d.free = s
        }
        return s
}

// Record that we are starting an element with the given name.
func (d *Decoder) pushElement(name Name) {
        s := d.push(stkStart)
        s.name = name
}

// Record that we are changing the value of ns[local].
// The old value is url, ok.
func (d *Decoder) pushNs(local string, url string, ok bool) {
        s := d.push(stkNs)
        s.name.Local = local
        s.name.Space = url
        s.ok = ok
}

// Creates a SyntaxError with the current line number.
func (d *Decoder) syntaxError(msg string) error {
        return &SyntaxError{Msg: msg, Line: d.line}
}

// Record that we are ending an element with the given name.
// The name must match the record at the top of the stack,
// which must be a pushElement record.
// After popping the element, apply any undo records from
// the stack to restore the name translations that existed
// before we saw this element.
func (d *Decoder) popElement(t *EndElement) bool {
        s := d.pop()
        name := t.Name
        switch {
        case s == nil || s.kind != stkStart:
                d.err = d.syntaxError("unexpected end element </" + name.Local + ">")
                return false
        case s.name.Local != name.Local:
                if !d.Strict {
                        d.needClose = true
                        d.toClose = t.Name
                        t.Name = s.name
                        return true
                }
                d.err = d.syntaxError("element <" + s.name.Local + "> closed by </" + name.Local + ">")
                return false
        case s.name.Space != name.Space:
                d.err = d.syntaxError("element <" + s.name.Local + "> in space " + s.name.Space +
                        "closed by </" + name.Local + "> in space " + name.Space)
                return false
        }

        // Pop stack until a Start is on the top, undoing the
        // translations that were associated with the element we just closed.
        for d.stk != nil && d.stk.kind != stkStart {
                s := d.pop()
                if s.ok {
                        d.ns[s.name.Local] = s.name.Space
                } else {
                        delete(d.ns, s.name.Local)
                }
        }

        return true
}

// If the top element on the stack is autoclosing and
// t is not the end tag, invent the end tag.
func (d *Decoder) autoClose(t Token) (Token, bool) {
        if d.stk == nil || d.stk.kind != stkStart {
                return nil, false
        }
        name := strings.ToLower(d.stk.name.Local)
        for _, s := range d.AutoClose {
                if strings.ToLower(s) == name {
                        // This one should be auto closed if t doesn't close it.
                        et, ok := t.(EndElement)
                        if !ok || et.Name.Local != name {
                                return EndElement{d.stk.name}, true
                        }
                        break
                }
        }
        return nil, false
}

// RawToken is like Token but does not verify that
// start and end elements match and does not translate
// name space prefixes to their corresponding URLs.
func (d *Decoder) RawToken() (Token, error) {
        if d.err != nil {
                return nil, d.err
        }
        if d.needClose {
                // The last element we read was self-closing and
                // we returned just the StartElement half.
                // Return the EndElement half now.
                d.needClose = false
                return EndElement{d.toClose}, nil
        }

        b, ok := d.getc()
        if !ok {
                return nil, d.err
        }

        if b != '<' {
                // Text section.
                d.ungetc(b)
                data := d.text(-1, false)
                if data == nil {
                        return nil, d.err
                }
                return CharData(data), nil
        }

        if b, ok = d.mustgetc(); !ok {
                return nil, d.err
        }
        switch b {
        case '/':
                // </: End element
                var name Name
                if name, ok = d.nsname(); !ok {
                        if d.err == nil {
                                d.err = d.syntaxError("expected element name after </")
                        }
                        return nil, d.err
                }
                d.space()
                if b, ok = d.mustgetc(); !ok {
                        return nil, d.err
                }
                if b != '>' {
                        d.err = d.syntaxError("invalid characters between </" + name.Local + " and >")
                        return nil, d.err
                }
                return EndElement{name}, nil

        case '?':
                // <?: Processing instruction.
                // TODO(rsc): Should parse the <?xml declaration to make sure
                // the version is 1.0 and the encoding is UTF-8.
                var target string
                if target, ok = d.name(); !ok {
                        if d.err == nil {
                                d.err = d.syntaxError("expected target name after <?")
                        }
                        return nil, d.err
                }
                d.space()
                d.buf.Reset()
                var b0 byte
                for {
                        if b, ok = d.mustgetc(); !ok {
                                return nil, d.err
                        }
                        d.buf.WriteByte(b)
                        if b0 == '?' && b == '>' {
                                break
                        }
                        b0 = b
                }
                data := d.buf.Bytes()
                data = data[0 : len(data)-2] // chop ?>

                if target == "xml" {
                        enc := procInstEncoding(string(data))
                        if enc != "" && enc != "utf-8" && enc != "UTF-8" {
                                if d.CharsetReader == nil {
                                        d.err = fmt.Errorf("xml: encoding %q declared but Decoder.CharsetReader is nil", enc)
                                        return nil, d.err
                                }
                                newr, err := d.CharsetReader(enc, d.r.(io.Reader))
                                if err != nil {
                                        d.err = fmt.Errorf("xml: opening charset %q: %v", enc, err)
                                        return nil, d.err
                                }
                                if newr == nil {
                                        panic("CharsetReader returned a nil Reader for charset " + enc)
                                }
                                d.switchToReader(newr)
                        }
                }
                return ProcInst{target, data}, nil

        case '!':
                // <!: Maybe comment, maybe CDATA.
                if b, ok = d.mustgetc(); !ok {
                        return nil, d.err
                }
                switch b {
                case '-': // <!-
                        // Probably <!-- for a comment.
                        if b, ok = d.mustgetc(); !ok {
                                return nil, d.err
                        }
                        if b != '-' {
                                d.err = d.syntaxError("invalid sequence <!- not part of <!--")
                                return nil, d.err
                        }
                        // Look for terminator.
                        d.buf.Reset()
                        var b0, b1 byte
                        for {
                                if b, ok = d.mustgetc(); !ok {
                                        return nil, d.err
                                }
                                d.buf.WriteByte(b)
                                if b0 == '-' && b1 == '-' && b == '>' {
                                        break
                                }
                                b0, b1 = b1, b
                        }
                        data := d.buf.Bytes()
                        data = data[0 : len(data)-3] // chop -->
                        return Comment(data), nil

                case '[': // <![
                        // Probably <![CDATA[.
                        for i := 0; i < 6; i++ {
                                if b, ok = d.mustgetc(); !ok {
                                        return nil, d.err
                                }
                                if b != "CDATA["[i] {
                                        d.err = d.syntaxError("invalid <![ sequence")
                                        return nil, d.err
                                }
                        }
                        // Have <![CDATA[.  Read text until ]]>.
                        data := d.text(-1, true)
                        if data == nil {
                                return nil, d.err
                        }
                        return CharData(data), nil
                }

                // Probably a directive: <!DOCTYPE ...>, <!ENTITY ...>, etc.
                // We don't care, but accumulate for caller. Quoted angle
                // brackets do not count for nesting.
                d.buf.Reset()
                d.buf.WriteByte(b)
                inquote := uint8(0)
                depth := 0
                for {
                        if b, ok = d.mustgetc(); !ok {
                                return nil, d.err
                        }
                        if inquote == 0 && b == '>' && depth == 0 {
                                break
                        }
                        d.buf.WriteByte(b)
                        switch {
                        case b == inquote:
                                inquote = 0

                        case inquote != 0:
                                // in quotes, no special action

                        case b == '\'' || b == '"':
                                inquote = b

                        case b == '>' && inquote == 0:
                                depth--

                        case b == '<' && inquote == 0:
                                depth++
                        }
                }
                return Directive(d.buf.Bytes()), nil
        }

        // Must be an open element like <a href="foo">
        d.ungetc(b)

        var (
                name  Name
                empty bool
                attr  []Attr
        )
        if name, ok = d.nsname(); !ok {
                if d.err == nil {
                        d.err = d.syntaxError("expected element name after <")
                }
                return nil, d.err
        }

        attr = make([]Attr, 0, 4)
        for {
                d.space()
                if b, ok = d.mustgetc(); !ok {
                        return nil, d.err
                }
                if b == '/' {
                        empty = true
                        if b, ok = d.mustgetc(); !ok {
                                return nil, d.err
                        }
                        if b != '>' {
                                d.err = d.syntaxError("expected /> in element")
                                return nil, d.err
                        }
                        break
                }
                if b == '>' {
                        break
                }
                d.ungetc(b)

                n := len(attr)
                if n >= cap(attr) {
                        nattr := make([]Attr, n, 2*cap(attr))
                        copy(nattr, attr)
                        attr = nattr
                }
                attr = attr[0 : n+1]
                a := &attr[n]
                if a.Name, ok = d.nsname(); !ok {
                        if d.err == nil {
                                d.err = d.syntaxError("expected attribute name in element")
                        }
                        return nil, d.err
                }
                d.space()
                if b, ok = d.mustgetc(); !ok {
                        return nil, d.err
                }
                if b != '=' {
                        if d.Strict {
                                d.err = d.syntaxError("attribute name without = in element")
                                return nil, d.err
                        } else {
                                d.ungetc(b)
                                a.Value = a.Name.Local
                        }
                } else {
                        d.space()
                        data := d.attrval()
                        if data == nil {
                                return nil, d.err
                        }
                        a.Value = string(data)
                }
        }
        if empty {
                d.needClose = true
                d.toClose = name
        }
        return StartElement{name, attr}, nil
}

func (d *Decoder) attrval() []byte {
        b, ok := d.mustgetc()
        if !ok {
                return nil
        }
        // Handle quoted attribute values
        if b == '"' || b == '\'' {
                return d.text(int(b), false)
        }
        // Handle unquoted attribute values for strict parsers
        if d.Strict {
                d.err = d.syntaxError("unquoted or missing attribute value in element")
                return nil
        }
        // Handle unquoted attribute values for unstrict parsers
        d.ungetc(b)
        d.buf.Reset()
        for {
                b, ok = d.mustgetc()
                if !ok {
                        return nil
                }
                // http://www.w3.org/TR/REC-html40/intro/sgmltut.html#h-3.2.2
                if 'a' <= b && b <= 'z' || 'A' <= b && b <= 'Z' ||
                        '0' <= b && b <= '9' || b == '_' || b == ':' || b == '-' {
                        d.buf.WriteByte(b)
                } else {
                        d.ungetc(b)
                        break
                }
        }
        return d.buf.Bytes()
}

// Skip spaces if any
func (d *Decoder) space() {
        for {
                b, ok := d.getc()
                if !ok {
                        return
                }
                switch b {
                case ' ', '\r', '\n', '\t':
                default:
                        d.ungetc(b)
                        return
                }
        }
}

// Read a single byte.
// If there is no byte to read, return ok==false
// and leave the error in d.err.
// Maintain line number.
func (d *Decoder) getc() (b byte, ok bool) {
        if d.err != nil {
                return 0, false
        }
        if d.nextByte >= 0 {
                b = byte(d.nextByte)
                d.nextByte = -1
        } else {
                b, d.err = d.r.ReadByte()
                if d.err != nil {
                        return 0, false
                }
                if d.saved != nil {
                        d.saved.WriteByte(b)
                }
        }
        if b == '\n' {
                d.line++
        }
        return b, true
}

// Return saved offset.
// If we did ungetc (nextByte >= 0), have to back up one.
func (d *Decoder) savedOffset() int {
        n := d.saved.Len()
        if d.nextByte >= 0 {
                n--
        }
        return n
}

// Must read a single byte.
// If there is no byte to read,
// set d.err to SyntaxError("unexpected EOF")
// and return ok==false
func (d *Decoder) mustgetc() (b byte, ok bool) {
        if b, ok = d.getc(); !ok {
                if d.err == io.EOF {
                        d.err = d.syntaxError("unexpected EOF")
                }
        }
        return
}

// Unread a single byte.
func (d *Decoder) ungetc(b byte) {
        if b == '\n' {
                d.line--
        }
        d.nextByte = int(b)
}

var entity = map[string]int{
        "lt":   '<',
        "gt":   '>',
        "amp":  '&',
        "apos": '\'',
        "quot": '"',
}

// Read plain text section (XML calls it character data).
// If quote >= 0, we are in a quoted string and need to find the matching quote.
// If cdata == true, we are in a <![CDATA[ section and need to find ]]>.
// On failure return nil and leave the error in d.err.
func (d *Decoder) text(quote int, cdata bool) []byte {
        var b0, b1 byte
        var trunc int
        d.buf.Reset()
Input:
        for {
                b, ok := d.getc()
                if !ok {
                        if cdata {
                                if d.err == io.EOF {
                                        d.err = d.syntaxError("unexpected EOF in CDATA section")
                                }
                                return nil
                        }
                        break Input
                }

                // <![CDATA[ section ends with ]]>.
                // It is an error for ]]> to appear in ordinary text.
                if b0 == ']' && b1 == ']' && b == '>' {
                        if cdata {
                                trunc = 2
                                break Input
                        }
                        d.err = d.syntaxError("unescaped ]]> not in CDATA section")
                        return nil
                }

                // Stop reading text if we see a <.
                if b == '<' && !cdata {
                        if quote >= 0 {
                                d.err = d.syntaxError("unescaped < inside quoted string")
                                return nil
                        }
                        d.ungetc('<')
                        break Input
                }
                if quote >= 0 && b == byte(quote) {
                        break Input
                }
                if b == '&' && !cdata {
                        // Read escaped character expression up to semicolon.
                        // XML in all its glory allows a document to define and use
                        // its own character names with <!ENTITY ...> directives.
                        // Parsers are required to recognize lt, gt, amp, apos, and quot
                        // even if they have not been declared.  That's all we allow.
                        var i int
                        for i = 0; i < len(d.tmp); i++ {
                                var ok bool
                                d.tmp[i], ok = d.getc()
                                if !ok {
                                        if d.err == io.EOF {
                                                d.err = d.syntaxError("unexpected EOF")
                                        }
                                        return nil
                                }
                                c := d.tmp[i]
                                if c == ';' {
                                        break
                                }
                                if 'a' <= c && c <= 'z' ||
                                        'A' <= c && c <= 'Z' ||
                                        '0' <= c && c <= '9' ||
                                        c == '_' || c == '#' {
                                        continue
                                }
                                d.ungetc(c)
                                break
                        }
                        s := string(d.tmp[0:i])
                        if i >= len(d.tmp) {
                                if !d.Strict {
                                        b0, b1 = 0, 0
                                        d.buf.WriteByte('&')
                                        d.buf.Write(d.tmp[0:i])
                                        continue Input
                                }
                                d.err = d.syntaxError("character entity expression &" + s + "... too long")
                                return nil
                        }
                        var haveText bool
                        var text string
                        if i >= 2 && s[0] == '#' {
                                var n uint64
                                var err error
                                if i >= 3 && s[1] == 'x' {
                                        n, err = strconv.ParseUint(s[2:], 16, 64)
                                } else {
                                        n, err = strconv.ParseUint(s[1:], 10, 64)
                                }
                                if err == nil && n <= unicode.MaxRune {
                                        text = string(n)
                                        haveText = true
                                }
                        } else {
                                if r, ok := entity[s]; ok {
                                        text = string(r)
                                        haveText = true
                                } else if d.Entity != nil {
                                        text, haveText = d.Entity[s]
                                }
                        }
                        if !haveText {
                                if !d.Strict {
                                        b0, b1 = 0, 0
                                        d.buf.WriteByte('&')
                                        d.buf.Write(d.tmp[0:i])
                                        continue Input
                                }
                                d.err = d.syntaxError("invalid character entity &" + s + ";")
                                return nil
                        }
                        d.buf.Write([]byte(text))
                        b0, b1 = 0, 0
                        continue Input
                }
                d.buf.WriteByte(b)
                b0, b1 = b1, b
        }
        data := d.buf.Bytes()
        data = data[0 : len(data)-trunc]

        // Inspect each rune for being a disallowed character.
        buf := data
        for len(buf) > 0 {
                r, size := utf8.DecodeRune(buf)
                if r == utf8.RuneError && size == 1 {
                        d.err = d.syntaxError("invalid UTF-8")
                        return nil
                }
                buf = buf[size:]
                if !isInCharacterRange(r) {
                        d.err = d.syntaxError(fmt.Sprintf("illegal character code %U", r))
                        return nil
                }
        }

        // Must rewrite \r and \r\n into \n.
        w := 0
        for r := 0; r < len(data); r++ {
                b := data[r]
                if b == '\r' {
                        if r+1 < len(data) && data[r+1] == '\n' {
                                continue
                        }
                        b = '\n'
                }
                data[w] = b
                w++
        }
        return data[0:w]
}

// Decide whether the given rune is in the XML Character Range, per
// the Char production of http://www.xml.com/axml/testaxml.htm,
// Section 2.2 Characters.
func isInCharacterRange(r rune) (inrange bool) {
        return r == 0x09 ||
                r == 0x0A ||
                r == 0x0D ||
                r >= 0x20 && r <= 0xDF77 ||
                r >= 0xE000 && r <= 0xFFFD ||
                r >= 0x10000 && r <= 0x10FFFF
}

// Get name space name: name with a : stuck in the middle.
// The part before the : is the name space identifier.
func (d *Decoder) nsname() (name Name, ok bool) {
        s, ok := d.name()
        if !ok {
                return
        }
        i := strings.Index(s, ":")
        if i < 0 {
                name.Local = s
        } else {
                name.Space = s[0:i]
                name.Local = s[i+1:]
        }
        return name, true
}

// Get name: /first(first|second)*/
// Do not set d.err if the name is missing (unless unexpected EOF is received):
// let the caller provide better context.
func (d *Decoder) name() (s string, ok bool) {
        var b byte
        if b, ok = d.mustgetc(); !ok {
                return
        }

        // As a first approximation, we gather the bytes [A-Za-z_:.-\x80-\xFF]*
        if b < utf8.RuneSelf && !isNameByte(b) {
                d.ungetc(b)
                return "", false
        }
        d.buf.Reset()
        d.buf.WriteByte(b)
        for {
                if b, ok = d.mustgetc(); !ok {
                        return
                }
                if b < utf8.RuneSelf && !isNameByte(b) {
                        d.ungetc(b)
                        break
                }
                d.buf.WriteByte(b)
        }

        // Then we check the characters.
        s = d.buf.String()
        for i, c := range s {
                if !unicode.Is(first, c) && (i == 0 || !unicode.Is(second, c)) {
                        d.err = d.syntaxError("invalid XML name: " + s)
                        return "", false
                }
        }
        return s, true
}

func isNameByte(c byte) bool {
        return 'A' <= c && c <= 'Z' ||
                'a' <= c && c <= 'z' ||
                '0' <= c && c <= '9' ||
                c == '_' || c == ':' || c == '.' || c == '-'
}

// These tables were generated by cut and paste from Appendix B of
// the XML spec at http://www.xml.com/axml/testaxml.htm
// and then reformatting.  First corresponds to (Letter | '_' | ':')
// and second corresponds to NameChar.

var first = &unicode.RangeTable{
        R16: []unicode.Range16{
                {0x003A, 0x003A, 1},
                {0x0041, 0x005A, 1},
                {0x005F, 0x005F, 1},
                {0x0061, 0x007A, 1},
                {0x00C0, 0x00D6, 1},
                {0x00D8, 0x00F6, 1},
                {0x00F8, 0x00FF, 1},
                {0x0100, 0x0131, 1},
                {0x0134, 0x013E, 1},
                {0x0141, 0x0148, 1},
                {0x014A, 0x017E, 1},
                {0x0180, 0x01C3, 1},
                {0x01CD, 0x01F0, 1},
                {0x01F4, 0x01F5, 1},
                {0x01FA, 0x0217, 1},
                {0x0250, 0x02A8, 1},
                {0x02BB, 0x02C1, 1},
                {0x0386, 0x0386, 1},
                {0x0388, 0x038A, 1},
                {0x038C, 0x038C, 1},
                {0x038E, 0x03A1, 1},
                {0x03A3, 0x03CE, 1},
                {0x03D0, 0x03D6, 1},
                {0x03DA, 0x03E0, 2},
                {0x03E2, 0x03F3, 1},
                {0x0401, 0x040C, 1},
                {0x040E, 0x044F, 1},
                {0x0451, 0x045C, 1},
                {0x045E, 0x0481, 1},
                {0x0490, 0x04C4, 1},
                {0x04C7, 0x04C8, 1},
                {0x04CB, 0x04CC, 1},
                {0x04D0, 0x04EB, 1},
                {0x04EE, 0x04F5, 1},
                {0x04F8, 0x04F9, 1},
                {0x0531, 0x0556, 1},
                {0x0559, 0x0559, 1},
                {0x0561, 0x0586, 1},
                {0x05D0, 0x05EA, 1},
                {0x05F0, 0x05F2, 1},
                {0x0621, 0x063A, 1},
                {0x0641, 0x064A, 1},
                {0x0671, 0x06B7, 1},
                {0x06BA, 0x06BE, 1},
                {0x06C0, 0x06CE, 1},
                {0x06D0, 0x06D3, 1},
                {0x06D5, 0x06D5, 1},
                {0x06E5, 0x06E6, 1},
                {0x0905, 0x0939, 1},
                {0x093D, 0x093D, 1},
                {0x0958, 0x0961, 1},
                {0x0985, 0x098C, 1},
                {0x098F, 0x0990, 1},
                {0x0993, 0x09A8, 1},
                {0x09AA, 0x09B0, 1},
                {0x09B2, 0x09B2, 1},
                {0x09B6, 0x09B9, 1},
                {0x09DC, 0x09DD, 1},
                {0x09DF, 0x09E1, 1},
                {0x09F0, 0x09F1, 1},
                {0x0A05, 0x0A0A, 1},
                {0x0A0F, 0x0A10, 1},
                {0x0A13, 0x0A28, 1},
                {0x0A2A, 0x0A30, 1},
                {0x0A32, 0x0A33, 1},
                {0x0A35, 0x0A36, 1},
                {0x0A38, 0x0A39, 1},
                {0x0A59, 0x0A5C, 1},
                {0x0A5E, 0x0A5E, 1},
                {0x0A72, 0x0A74, 1},
                {0x0A85, 0x0A8B, 1},
                {0x0A8D, 0x0A8D, 1},
                {0x0A8F, 0x0A91, 1},
                {0x0A93, 0x0AA8, 1},
                {0x0AAA, 0x0AB0, 1},
                {0x0AB2, 0x0AB3, 1},
                {0x0AB5, 0x0AB9, 1},
                {0x0ABD, 0x0AE0, 0x23},
                {0x0B05, 0x0B0C, 1},
                {0x0B0F, 0x0B10, 1},
                {0x0B13, 0x0B28, 1},
                {0x0B2A, 0x0B30, 1},
                {0x0B32, 0x0B33, 1},
                {0x0B36, 0x0B39, 1},
                {0x0B3D, 0x0B3D, 1},
                {0x0B5C, 0x0B5D, 1},
                {0x0B5F, 0x0B61, 1},
                {0x0B85, 0x0B8A, 1},
                {0x0B8E, 0x0B90, 1},
                {0x0B92, 0x0B95, 1},
                {0x0B99, 0x0B9A, 1},
                {0x0B9C, 0x0B9C, 1},
                {0x0B9E, 0x0B9F, 1},
                {0x0BA3, 0x0BA4, 1},
                {0x0BA8, 0x0BAA, 1},
                {0x0BAE, 0x0BB5, 1},
                {0x0BB7, 0x0BB9, 1},
                {0x0C05, 0x0C0C, 1},
                {0x0C0E, 0x0C10, 1},
                {0x0C12, 0x0C28, 1},
                {0x0C2A, 0x0C33, 1},
                {0x0C35, 0x0C39, 1},
                {0x0C60, 0x0C61, 1},
                {0x0C85, 0x0C8C, 1},
                {0x0C8E, 0x0C90, 1},
                {0x0C92, 0x0CA8, 1},
                {0x0CAA, 0x0CB3, 1},
                {0x0CB5, 0x0CB9, 1},
                {0x0CDE, 0x0CDE, 1},
                {0x0CE0, 0x0CE1, 1},
                {0x0D05, 0x0D0C, 1},
                {0x0D0E, 0x0D10, 1},
                {0x0D12, 0x0D28, 1},
                {0x0D2A, 0x0D39, 1},
                {0x0D60, 0x0D61, 1},
                {0x0E01, 0x0E2E, 1},
                {0x0E30, 0x0E30, 1},
                {0x0E32, 0x0E33, 1},
                {0x0E40, 0x0E45, 1},
                {0x0E81, 0x0E82, 1},
                {0x0E84, 0x0E84, 1},
                {0x0E87, 0x0E88, 1},
                {0x0E8A, 0x0E8D, 3},
                {0x0E94, 0x0E97, 1},
                {0x0E99, 0x0E9F, 1},
                {0x0EA1, 0x0EA3, 1},
                {0x0EA5, 0x0EA7, 2},
                {0x0EAA, 0x0EAB, 1},
                {0x0EAD, 0x0EAE, 1},
                {0x0EB0, 0x0EB0, 1},
                {0x0EB2, 0x0EB3, 1},
                {0x0EBD, 0x0EBD, 1},
                {0x0EC0, 0x0EC4, 1},
                {0x0F40, 0x0F47, 1},
                {0x0F49, 0x0F69, 1},
                {0x10A0, 0x10C5, 1},
                {0x10D0, 0x10F6, 1},
                {0x1100, 0x1100, 1},
                {0x1102, 0x1103, 1},
                {0x1105, 0x1107, 1},
                {0x1109, 0x1109, 1},
                {0x110B, 0x110C, 1},
                {0x110E, 0x1112, 1},
                {0x113C, 0x1140, 2},
                {0x114C, 0x1150, 2},
                {0x1154, 0x1155, 1},
                {0x1159, 0x1159, 1},
                {0x115F, 0x1161, 1},
                {0x1163, 0x1169, 2},
                {0x116D, 0x116E, 1},
                {0x1172, 0x1173, 1},
                {0x1175, 0x119E, 0x119E - 0x1175},
                {0x11A8, 0x11AB, 0x11AB - 0x11A8},
                {0x11AE, 0x11AF, 1},
                {0x11B7, 0x11B8, 1},
                {0x11BA, 0x11BA, 1},
                {0x11BC, 0x11C2, 1},
                {0x11EB, 0x11F0, 0x11F0 - 0x11EB},
                {0x11F9, 0x11F9, 1},
                {0x1E00, 0x1E9B, 1},
                {0x1EA0, 0x1EF9, 1},
                {0x1F00, 0x1F15, 1},
                {0x1F18, 0x1F1D, 1},
                {0x1F20, 0x1F45, 1},
                {0x1F48, 0x1F4D, 1},
                {0x1F50, 0x1F57, 1},
                {0x1F59, 0x1F5B, 0x1F5B - 0x1F59},
                {0x1F5D, 0x1F5D, 1},
                {0x1F5F, 0x1F7D, 1},
                {0x1F80, 0x1FB4, 1},
                {0x1FB6, 0x1FBC, 1},
                {0x1FBE, 0x1FBE, 1},
                {0x1FC2, 0x1FC4, 1},
                {0x1FC6, 0x1FCC, 1},
                {0x1FD0, 0x1FD3, 1},
                {0x1FD6, 0x1FDB, 1},
                {0x1FE0, 0x1FEC, 1},
                {0x1FF2, 0x1FF4, 1},
                {0x1FF6, 0x1FFC, 1},
                {0x2126, 0x2126, 1},
                {0x212A, 0x212B, 1},
                {0x212E, 0x212E, 1},
                {0x2180, 0x2182, 1},
                {0x3007, 0x3007, 1},
                {0x3021, 0x3029, 1},
                {0x3041, 0x3094, 1},
                {0x30A1, 0x30FA, 1},
                {0x3105, 0x312C, 1},
                {0x4E00, 0x9FA5, 1},
                {0xAC00, 0xD7A3, 1},
        },
}

var second = &unicode.RangeTable{
        R16: []unicode.Range16{
                {0x002D, 0x002E, 1},
                {0x0030, 0x0039, 1},
                {0x00B7, 0x00B7, 1},
                {0x02D0, 0x02D1, 1},
                {0x0300, 0x0345, 1},
                {0x0360, 0x0361, 1},
                {0x0387, 0x0387, 1},
                {0x0483, 0x0486, 1},
                {0x0591, 0x05A1, 1},
                {0x05A3, 0x05B9, 1},
                {0x05BB, 0x05BD, 1},
                {0x05BF, 0x05BF, 1},
                {0x05C1, 0x05C2, 1},
                {0x05C4, 0x0640, 0x0640 - 0x05C4},
                {0x064B, 0x0652, 1},
                {0x0660, 0x0669, 1},
                {0x0670, 0x0670, 1},
                {0x06D6, 0x06DC, 1},
                {0x06DD, 0x06DF, 1},
                {0x06E0, 0x06E4, 1},
                {0x06E7, 0x06E8, 1},
                {0x06EA, 0x06ED, 1},
                {0x06F0, 0x06F9, 1},
                {0x0901, 0x0903, 1},
                {0x093C, 0x093C, 1},
                {0x093E, 0x094C, 1},
                {0x094D, 0x094D, 1},
                {0x0951, 0x0954, 1},
                {0x0962, 0x0963, 1},
                {0x0966, 0x096F, 1},
                {0x0981, 0x0983, 1},
                {0x09BC, 0x09BC, 1},
                {0x09BE, 0x09BF, 1},
                {0x09C0, 0x09C4, 1},
                {0x09C7, 0x09C8, 1},
                {0x09CB, 0x09CD, 1},
                {0x09D7, 0x09D7, 1},
                {0x09E2, 0x09E3, 1},
                {0x09E6, 0x09EF, 1},
                {0x0A02, 0x0A3C, 0x3A},
                {0x0A3E, 0x0A3F, 1},
                {0x0A40, 0x0A42, 1},
                {0x0A47, 0x0A48, 1},
                {0x0A4B, 0x0A4D, 1},
                {0x0A66, 0x0A6F, 1},
                {0x0A70, 0x0A71, 1},
                {0x0A81, 0x0A83, 1},
                {0x0ABC, 0x0ABC, 1},
                {0x0ABE, 0x0AC5, 1},
                {0x0AC7, 0x0AC9, 1},
                {0x0ACB, 0x0ACD, 1},
                {0x0AE6, 0x0AEF, 1},
                {0x0B01, 0x0B03, 1},
                {0x0B3C, 0x0B3C, 1},
                {0x0B3E, 0x0B43, 1},
                {0x0B47, 0x0B48, 1},
                {0x0B4B, 0x0B4D, 1},
                {0x0B56, 0x0B57, 1},
                {0x0B66, 0x0B6F, 1},
                {0x0B82, 0x0B83, 1},
                {0x0BBE, 0x0BC2, 1},
                {0x0BC6, 0x0BC8, 1},
                {0x0BCA, 0x0BCD, 1},
                {0x0BD7, 0x0BD7, 1},
                {0x0BE7, 0x0BEF, 1},
                {0x0C01, 0x0C03, 1},
                {0x0C3E, 0x0C44, 1},
                {0x0C46, 0x0C48, 1},
                {0x0C4A, 0x0C4D, 1},
                {0x0C55, 0x0C56, 1},
                {0x0C66, 0x0C6F, 1},
                {0x0C82, 0x0C83, 1},
                {0x0CBE, 0x0CC4, 1},
                {0x0CC6, 0x0CC8, 1},
                {0x0CCA, 0x0CCD, 1},
                {0x0CD5, 0x0CD6, 1},
                {0x0CE6, 0x0CEF, 1},
                {0x0D02, 0x0D03, 1},
                {0x0D3E, 0x0D43, 1},
                {0x0D46, 0x0D48, 1},
                {0x0D4A, 0x0D4D, 1},
                {0x0D57, 0x0D57, 1},
                {0x0D66, 0x0D6F, 1},
                {0x0E31, 0x0E31, 1},
                {0x0E34, 0x0E3A, 1},
                {0x0E46, 0x0E46, 1},
                {0x0E47, 0x0E4E, 1},
                {0x0E50, 0x0E59, 1},
                {0x0EB1, 0x0EB1, 1},
                {0x0EB4, 0x0EB9, 1},
                {0x0EBB, 0x0EBC, 1},
                {0x0EC6, 0x0EC6, 1},
                {0x0EC8, 0x0ECD, 1},
                {0x0ED0, 0x0ED9, 1},
                {0x0F18, 0x0F19, 1},
                {0x0F20, 0x0F29, 1},
                {0x0F35, 0x0F39, 2},
                {0x0F3E, 0x0F3F, 1},
                {0x0F71, 0x0F84, 1},
                {0x0F86, 0x0F8B, 1},
                {0x0F90, 0x0F95, 1},
                {0x0F97, 0x0F97, 1},
                {0x0F99, 0x0FAD, 1},
                {0x0FB1, 0x0FB7, 1},
                {0x0FB9, 0x0FB9, 1},
                {0x20D0, 0x20DC, 1},
                {0x20E1, 0x3005, 0x3005 - 0x20E1},
                {0x302A, 0x302F, 1},
                {0x3031, 0x3035, 1},
                {0x3099, 0x309A, 1},
                {0x309D, 0x309E, 1},
                {0x30FC, 0x30FE, 1},
        },
}

// HTMLEntity is an entity map containing translations for the
// standard HTML entity characters.
var HTMLEntity = htmlEntity

var htmlEntity = map[string]string{
        /*
                hget http://www.w3.org/TR/html4/sgml/entities.html |
                ssam '
                        ,y /\&gt;/ x/\&lt;(.|\n)+/ s/\n/ /g
                        ,x v/^\&lt;!ENTITY/d
                        ,s/\&lt;!ENTITY ([^ ]+) .*U\+([0-9A-F][0-9A-F][0-9A-F][0-9A-F]) .+/     "\1": "\\u\2",/g
                '
        */
        "nbsp":     "\u00A0",
        "iexcl":    "\u00A1",
        "cent":     "\u00A2",
        "pound":    "\u00A3",
        "curren":   "\u00A4",
        "yen":      "\u00A5",
        "brvbar":   "\u00A6",
        "sect":     "\u00A7",
        "uml":      "\u00A8",
        "copy":     "\u00A9",
        "ordf":     "\u00AA",
        "laquo":    "\u00AB",
        "not":      "\u00AC",
        "shy":      "\u00AD",
        "reg":      "\u00AE",
        "macr":     "\u00AF",
        "deg":      "\u00B0",
        "plusmn":   "\u00B1",
        "sup2":     "\u00B2",
        "sup3":     "\u00B3",
        "acute":    "\u00B4",
        "micro":    "\u00B5",
        "para":     "\u00B6",
        "middot":   "\u00B7",
        "cedil":    "\u00B8",
        "sup1":     "\u00B9",
        "ordm":     "\u00BA",
        "raquo":    "\u00BB",
        "frac14":   "\u00BC",
        "frac12":   "\u00BD",
        "frac34":   "\u00BE",
        "iquest":   "\u00BF",
        "Agrave":   "\u00C0",
        "Aacute":   "\u00C1",
        "Acirc":    "\u00C2",
        "Atilde":   "\u00C3",
        "Auml":     "\u00C4",
        "Aring":    "\u00C5",
        "AElig":    "\u00C6",
        "Ccedil":   "\u00C7",
        "Egrave":   "\u00C8",
        "Eacute":   "\u00C9",
        "Ecirc":    "\u00CA",
        "Euml":     "\u00CB",
        "Igrave":   "\u00CC",
        "Iacute":   "\u00CD",
        "Icirc":    "\u00CE",
        "Iuml":     "\u00CF",
        "ETH":      "\u00D0",
        "Ntilde":   "\u00D1",
        "Ograve":   "\u00D2",
        "Oacute":   "\u00D3",
        "Ocirc":    "\u00D4",
        "Otilde":   "\u00D5",
        "Ouml":     "\u00D6",
        "times":    "\u00D7",
        "Oslash":   "\u00D8",
        "Ugrave":   "\u00D9",
        "Uacute":   "\u00DA",
        "Ucirc":    "\u00DB",
        "Uuml":     "\u00DC",
        "Yacute":   "\u00DD",
        "THORN":    "\u00DE",
        "szlig":    "\u00DF",
        "agrave":   "\u00E0",
        "aacute":   "\u00E1",
        "acirc":    "\u00E2",
        "atilde":   "\u00E3",
        "auml":     "\u00E4",
        "aring":    "\u00E5",
        "aelig":    "\u00E6",
        "ccedil":   "\u00E7",
        "egrave":   "\u00E8",
        "eacute":   "\u00E9",
        "ecirc":    "\u00EA",
        "euml":     "\u00EB",
        "igrave":   "\u00EC",
        "iacute":   "\u00ED",
        "icirc":    "\u00EE",
        "iuml":     "\u00EF",
        "eth":      "\u00F0",
        "ntilde":   "\u00F1",
        "ograve":   "\u00F2",
        "oacute":   "\u00F3",
        "ocirc":    "\u00F4",
        "otilde":   "\u00F5",
        "ouml":     "\u00F6",
        "divide":   "\u00F7",
        "oslash":   "\u00F8",
        "ugrave":   "\u00F9",
        "uacute":   "\u00FA",
        "ucirc":    "\u00FB",
        "uuml":     "\u00FC",
        "yacute":   "\u00FD",
        "thorn":    "\u00FE",
        "yuml":     "\u00FF",
        "fnof":     "\u0192",
        "Alpha":    "\u0391",
        "Beta":     "\u0392",
        "Gamma":    "\u0393",
        "Delta":    "\u0394",
        "Epsilon":  "\u0395",
        "Zeta":     "\u0396",
        "Eta":      "\u0397",
        "Theta":    "\u0398",
        "Iota":     "\u0399",
        "Kappa":    "\u039A",
        "Lambda":   "\u039B",
        "Mu":       "\u039C",
        "Nu":       "\u039D",
        "Xi":       "\u039E",
        "Omicron":  "\u039F",
        "Pi":       "\u03A0",
        "Rho":      "\u03A1",
        "Sigma":    "\u03A3",
        "Tau":      "\u03A4",
        "Upsilon":  "\u03A5",
        "Phi":      "\u03A6",
        "Chi":      "\u03A7",
        "Psi":      "\u03A8",
        "Omega":    "\u03A9",
        "alpha":    "\u03B1",
        "beta":     "\u03B2",
        "gamma":    "\u03B3",
        "delta":    "\u03B4",
        "epsilon":  "\u03B5",
        "zeta":     "\u03B6",
        "eta":      "\u03B7",
        "theta":    "\u03B8",
        "iota":     "\u03B9",
        "kappa":    "\u03BA",
        "lambda":   "\u03BB",
        "mu":       "\u03BC",
        "nu":       "\u03BD",
        "xi":       "\u03BE",
        "omicron":  "\u03BF",
        "pi":       "\u03C0",
        "rho":      "\u03C1",
        "sigmaf":   "\u03C2",
        "sigma":    "\u03C3",
        "tau":      "\u03C4",
        "upsilon":  "\u03C5",
        "phi":      "\u03C6",
        "chi":      "\u03C7",
        "psi":      "\u03C8",
        "omega":    "\u03C9",
        "thetasym": "\u03D1",
        "upsih":    "\u03D2",
        "piv":      "\u03D6",
        "bull":     "\u2022",
        "hellip":   "\u2026",
        "prime":    "\u2032",
        "Prime":    "\u2033",
        "oline":    "\u203E",
        "frasl":    "\u2044",
        "weierp":   "\u2118",
        "image":    "\u2111",
        "real":     "\u211C",
        "trade":    "\u2122",
        "alefsym":  "\u2135",
        "larr":     "\u2190",
        "uarr":     "\u2191",
        "rarr":     "\u2192",
        "darr":     "\u2193",
        "harr":     "\u2194",
        "crarr":    "\u21B5",
        "lArr":     "\u21D0",
        "uArr":     "\u21D1",
        "rArr":     "\u21D2",
        "dArr":     "\u21D3",
        "hArr":     "\u21D4",
        "forall":   "\u2200",
        "part":     "\u2202",
        "exist":    "\u2203",
        "empty":    "\u2205",
        "nabla":    "\u2207",
        "isin":     "\u2208",
        "notin":    "\u2209",
        "ni":       "\u220B",
        "prod":     "\u220F",
        "sum":      "\u2211",
        "minus":    "\u2212",
        "lowast":   "\u2217",
        "radic":    "\u221A",
        "prop":     "\u221D",
        "infin":    "\u221E",
        "ang":      "\u2220",
        "and":      "\u2227",
        "or":       "\u2228",
        "cap":      "\u2229",
        "cup":      "\u222A",
        "int":      "\u222B",
        "there4":   "\u2234",
        "sim":      "\u223C",
        "cong":     "\u2245",
        "asymp":    "\u2248",
        "ne":       "\u2260",
        "equiv":    "\u2261",
        "le":       "\u2264",
        "ge":       "\u2265",
        "sub":      "\u2282",
        "sup":      "\u2283",
        "nsub":     "\u2284",
        "sube":     "\u2286",
        "supe":     "\u2287",
        "oplus":    "\u2295",
        "otimes":   "\u2297",
        "perp":     "\u22A5",
        "sdot":     "\u22C5",
        "lceil":    "\u2308",
        "rceil":    "\u2309",
        "lfloor":   "\u230A",
        "rfloor":   "\u230B",
        "lang":     "\u2329",
        "rang":     "\u232A",
        "loz":      "\u25CA",
        "spades":   "\u2660",
        "clubs":    "\u2663",
        "hearts":   "\u2665",
        "diams":    "\u2666",
        "quot":     "\u0022",
        "amp":      "\u0026",
        "lt":       "\u003C",
        "gt":       "\u003E",
        "OElig":    "\u0152",
        "oelig":    "\u0153",
        "Scaron":   "\u0160",
        "scaron":   "\u0161",
        "Yuml":     "\u0178",
        "circ":     "\u02C6",
        "tilde":    "\u02DC",
        "ensp":     "\u2002",
        "emsp":     "\u2003",
        "thinsp":   "\u2009",
        "zwnj":     "\u200C",
        "zwj":      "\u200D",
        "lrm":      "\u200E",
        "rlm":      "\u200F",
        "ndash":    "\u2013",
        "mdash":    "\u2014",
        "lsquo":    "\u2018",
        "rsquo":    "\u2019",
        "sbquo":    "\u201A",
        "ldquo":    "\u201C",
        "rdquo":    "\u201D",
        "bdquo":    "\u201E",
        "dagger":   "\u2020",
        "Dagger":   "\u2021",
        "permil":   "\u2030",
        "lsaquo":   "\u2039",
        "rsaquo":   "\u203A",
        "euro":     "\u20AC",
}

// HTMLAutoClose is the set of HTML elements that
// should be considered to close automatically.
var HTMLAutoClose = htmlAutoClose

var htmlAutoClose = []string{
        /*
                hget http://www.w3.org/TR/html4/loose.dtd |
                9 sed -n 's/<!ELEMENT (.*) - O EMPTY.+/ "\1",/p' | tr A-Z a-z
        */
        "basefont",
        "br",
        "area",
        "link",
        "img",
        "param",
        "hr",
        "input",
        "col     ",
        "frame",
        "isindex",
        "base",
        "meta",
}

var (
        esc_quot = []byte("&#34;") // shorter than "&quot;"
        esc_apos = []byte("&#39;") // shorter than "&apos;"
        esc_amp  = []byte("&amp;")
        esc_lt   = []byte("&lt;")
        esc_gt   = []byte("&gt;")
)

// Escape writes to w the properly escaped XML equivalent
// of the plain text data s.
func Escape(w io.Writer, s []byte) {
        var esc []byte
        last := 0
        for i, c := range s {
                switch c {
                case '"':
                        esc = esc_quot
                case '\'':
                        esc = esc_apos
                case '&':
                        esc = esc_amp
                case '<':
                        esc = esc_lt
                case '>':
                        esc = esc_gt
                default:
                        continue
                }
                w.Write(s[last:i])
                w.Write(esc)
                last = i + 1
        }
        w.Write(s[last:])
}

// procInstEncoding parses the `encoding="..."` or `encoding='...'`
// value out of the provided string, returning "" if not found.
func procInstEncoding(s string) string {
        // TODO: this parsing is somewhat lame and not exact.
        // It works for all actual cases, though.
        idx := strings.Index(s, "encoding=")
        if idx == -1 {
                return ""
        }
        v := s[idx+len("encoding="):]
        if v == "" {
                return ""
        }
        if v[0] != '\'' && v[0] != '"' {
                return ""
        }
        idx = strings.IndexRune(v[1:], rune(v[0]))
        if idx == -1 {
                return ""
        }
        return v[1 : idx+1]
}