Merge sso://github/beevik/etree, add mandatory files

Bug: 158031244
Test: N/A

Change-Id: Idda5b583f92c0d952e1af23dcf90eed94db2f843

14 files changed, 4156 insertions, 0 deletions

diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..e12bb98
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,18 @@
+language: go
+sudo: false
+
+env:
+  - GO111MODULE=on
+
+go:
+  - 1.11.x
+  - 1.12.x
+  - tip
+
+matrix:
+  allow_failures:
+    - go: tip
+
+script:
+  - go vet ./...
+  - go test -v ./...
diff --git a/CONTRIBUTORS b/CONTRIBUTORS
new file mode 100644
index 0000000..03211a8
--- /dev/null
+++ b/CONTRIBUTORS
@@ -0,0 +1,10 @@
+Brett Vickers (beevik)
+Felix Geisendörfer (felixge)
+Kamil Kisiel (kisielk)
+Graham King (grahamking)
+Matt Smith (ma314smith)
+Michal Jemala (michaljemala)
+Nicolas Piganeau (npiganeau)
+Chris Brown (ccbrown)
+Earncef Sequeira (earncef)
+Gabriel de Labachelerie (wuzuf)
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..26f1f77
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,24 @@
+Copyright 2015-2019 Brett Vickers. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+   1. Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+   2. Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY COPYRIGHT HOLDER ``AS IS'' AND ANY
+EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..bcfee03
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,20 @@
+name: "go-etree"
+description:
+    "The etree package is a lightweight, pure go package that expresses XML in "
+    "the form of an element tree. Its design was inspired by the Python "
+    "ElementTree module."
+
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://github.com/beevik/etree"
+  }
+  url {
+    type: GIT
+    value: "https://github.com/beevik/etree.git"
+  }
+  version: "v1.1.0"
+  last_upgrade_date { year: 2020 month: 2 day: 22 }
+  license_type: NOTICE
+}
+
diff --git a/MODULE_LICENSE_BSD b/MODULE_LICENSE_BSD
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_BSD
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..08ec26b
--- /dev/null
+++ b/README.md
@@ -0,0 +1,205 @@
+[![Build Status](https://travis-ci.org/beevik/etree.svg?branch=master)](https://travis-ci.org/beevik/etree)
+[![GoDoc](https://godoc.org/github.com/beevik/etree?status.svg)](https://godoc.org/github.com/beevik/etree)
+
+etree
+=====
+
+The etree package is a lightweight, pure go package that expresses XML in
+the form of an element tree.  Its design was inspired by the Python
+[ElementTree](http://docs.python.org/2/library/xml.etree.elementtree.html)
+module.
+
+Some of the package's capabilities and features:
+
+* Represents XML documents as trees of elements for easy traversal.
+* Imports, serializes, modifies or creates XML documents from scratch.
+* Writes and reads XML to/from files, byte slices, strings and io interfaces.
+* Performs simple or complex searches with lightweight XPath-like query APIs.
+* Auto-indents XML using spaces or tabs for better readability.
+* Implemented in pure go; depends only on standard go libraries.
+* Built on top of the go [encoding/xml](http://golang.org/pkg/encoding/xml)
+  package.
+
+### Creating an XML document
+
+The following example creates an XML document from scratch using the etree
+package and outputs its indented contents to stdout.
+```go
+doc := etree.NewDocument()
+doc.CreateProcInst("xml", `version="1.0" encoding="UTF-8"`)
+doc.CreateProcInst("xml-stylesheet", `type="text/xsl" href="style.xsl"`)
+
+people := doc.CreateElement("People")
+people.CreateComment("These are all known people")
+
+jon := people.CreateElement("Person")
+jon.CreateAttr("name", "Jon")
+
+sally := people.CreateElement("Person")
+sally.CreateAttr("name", "Sally")
+
+doc.Indent(2)
+doc.WriteTo(os.Stdout)
+```
+
+Output:
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<?xml-stylesheet type="text/xsl" href="style.xsl"?>
+<People>
+  <!--These are all known people-->
+  <Person name="Jon"/>
+  <Person name="Sally"/>
+</People>
+```
+
+### Reading an XML file
+
+Suppose you have a file on disk called `bookstore.xml` containing the
+following data:
+
+```xml
+<bookstore xmlns:p="urn:schemas-books-com:prices">
+
+  <book category="COOKING">
+    <title lang="en">Everyday Italian</title>
+    <author>Giada De Laurentiis</author>
+    <year>2005</year>
+    <p:price>30.00</p:price>
+  </book>
+
+  <book category="CHILDREN">
+    <title lang="en">Harry Potter</title>
+    <author>J K. Rowling</author>
+    <year>2005</year>
+    <p:price>29.99</p:price>
+  </book>
+
+  <book category="WEB">
+    <title lang="en">XQuery Kick Start</title>
+    <author>James McGovern</author>
+    <author>Per Bothner</author>
+    <author>Kurt Cagle</author>
+    <author>James Linn</author>
+    <author>Vaidyanathan Nagarajan</author>
+    <year>2003</year>
+    <p:price>49.99</p:price>
+  </book>
+
+  <book category="WEB">
+    <title lang="en">Learning XML</title>
+    <author>Erik T. Ray</author>
+    <year>2003</year>
+    <p:price>39.95</p:price>
+  </book>
+
+</bookstore>
+```
+
+This code reads the file's contents into an etree document.
+```go
+doc := etree.NewDocument()
+if err := doc.ReadFromFile("bookstore.xml"); err != nil {
+    panic(err)
+}
+```
+
+You can also read XML from a string, a byte slice, or an `io.Reader`.
+
+### Processing elements and attributes
+
+This example illustrates several ways to access elements and attributes using
+etree selection queries.
+```go
+root := doc.SelectElement("bookstore")
+fmt.Println("ROOT element:", root.Tag)
+
+for _, book := range root.SelectElements("book") {
+    fmt.Println("CHILD element:", book.Tag)
+    if title := book.SelectElement("title"); title != nil {
+        lang := title.SelectAttrValue("lang", "unknown")
+        fmt.Printf("  TITLE: %s (%s)\n", title.Text(), lang)
+    }
+    for _, attr := range book.Attr {
+        fmt.Printf("  ATTR: %s=%s\n", attr.Key, attr.Value)
+    }
+}
+```
+Output:
+```
+ROOT element: bookstore
+CHILD element: book
+  TITLE: Everyday Italian (en)
+  ATTR: category=COOKING
+CHILD element: book
+  TITLE: Harry Potter (en)
+  ATTR: category=CHILDREN
+CHILD element: book
+  TITLE: XQuery Kick Start (en)
+  ATTR: category=WEB
+CHILD element: book
+  TITLE: Learning XML (en)
+  ATTR: category=WEB
+```
+
+### Path queries
+
+This example uses etree's path functions to select all book titles that fall
+into the category of 'WEB'.  The double-slash prefix in the path causes the
+search for book elements to occur recursively; book elements may appear at any
+level of the XML hierarchy.
+```go
+for _, t := range doc.FindElements("//book[@category='WEB']/title") {
+    fmt.Println("Title:", t.Text())
+}
+```
+
+Output:
+```
+Title: XQuery Kick Start
+Title: Learning XML
+```
+
+This example finds the first book element under the root bookstore element and
+outputs the tag and text of each of its child elements.
+```go
+for _, e := range doc.FindElements("./bookstore/book[1]/*") {
+    fmt.Printf("%s: %s\n", e.Tag, e.Text())
+}
+```
+
+Output:
+```
+title: Everyday Italian
+author: Giada De Laurentiis
+year: 2005
+price: 30.00
+```
+
+This example finds all books with a price of 49.99 and outputs their titles.
+```go
+path := etree.MustCompilePath("./bookstore/book[p:price='49.99']/title")
+for _, e := range doc.FindElementsPath(path) {
+    fmt.Println(e.Text())
+}
+```
+
+Output:
+```
+XQuery Kick Start
+```
+
+Note that this example uses the FindElementsPath function, which takes as an
+argument a pre-compiled path object. Use precompiled paths when you plan to
+search with the same path more than once.
+
+### Other features
+
+These are just a few examples of the things the etree package can do. See the
+[documentation](http://godoc.org/github.com/beevik/etree) for a complete
+description of its capabilities.
+
+### Contributing
+
+This project accepts contributions. Just fork the repo and submit a pull
+request!
diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
new file mode 100644
index 0000000..ee59d7a
--- /dev/null
+++ b/RELEASE_NOTES.md
@@ -0,0 +1,109 @@
+Release v1.1.0
+==============
+
+**New Features**
+
+* New attribute helpers.
+  * Added the `Element.SortAttrs` method, which lexicographically sorts an
+    element's attributes by key.
+* New `ReadSettings` properties.
+  * Added `Entity` for the support of custom entity maps.
+* New `WriteSettings` properties.
+  * Added `UseCRLF` to allow the output of CR-LF newlines instead of the
+    default LF newlines. This is useful on Windows systems.
+* Additional support for text and CDATA sections.
+  * The `Element.Text` method now returns the concatenation of all consecutive
+    character data tokens immediately following an element's opening tag.
+  * Added `Element.SetCData` to replace the character data immediately
+    following an element's opening tag with a CDATA section.
+  * Added `Element.CreateCData` to create and add a CDATA section child
+    `CharData` token to an element.
+  * Added `Element.CreateText` to create and add a child text `CharData` token
+    to an element.
+  * Added `NewCData` to create a parentless CDATA section `CharData` token.
+  * Added `NewText` to create a parentless text `CharData`
+    token.
+  * Added `CharData.IsCData` to detect if the token contains a CDATA section.
+  * Added `CharData.IsWhitespace` to detect if the token contains whitespace
+    inserted by one of the document Indent functions.
+  * Modified `Element.SetText` so that it replaces a run of consecutive
+    character data tokens following the element's opening tag (instead of just
+    the first one).
+* New "tail text" support.
+  * Added the `Element.Tail` method, which returns the text immediately
+    following an element's closing tag.
+  * Added the `Element.SetTail` method, which modifies the text immediately
+    following an element's closing tag.
+* New element child insertion and removal methods.
+  * Added the `Element.InsertChildAt` method, which inserts a new child token
+    before the specified child token index.
+  * Added the `Element.RemoveChildAt` method, which removes the child token at
+    the specified child token index.
+* New element and attribute queries.
+  * Added the `Element.Index` method, which returns the element's index within
+    its parent element's child token list.
+  * Added the `Element.NamespaceURI` method to return the namespace URI
+    associated with an element.
+  * Added the `Attr.NamespaceURI` method to return the namespace URI
+    associated with an element.
+  * Added the `Attr.Element` method to return the element that an attribute
+    belongs to.
+* New Path filter functions.
+  * Added `[local-name()='val']` to keep elements whose unprefixed tag matches
+    the desired value.
+  * Added `[name()='val']` to keep elements whose full tag matches the desired
+    value.
+  * Added `[namespace-prefix()='val']` to keep elements whose namespace prefix
+    matches the desired value.
+  * Added `[namespace-uri()='val']` to keep elements whose namespace URI
+    matches the desired value.
+
+**Bug Fixes**
+
+* A default XML `CharSetReader` is now used to prevent failed parsing of XML
+  documents using certain encodings.
+  ([Issue](https://github.com/beevik/etree/issues/53)).
+* All characters are now properly escaped according to XML parsing rules.
+  ([Issue](https://github.com/beevik/etree/issues/55)).
+* The `Document.Indent` and `Document.IndentTabs` functions no longer insert
+  empty string `CharData` tokens.
+
+**Deprecated**
+
+* `Element`
+    * The `InsertChild` method is deprecated. Use `InsertChildAt` instead.
+    * The `CreateCharData` method is deprecated. Use `CreateText` instead.
+* `CharData`
+    * The `NewCharData` method is deprecated. Use `NewText` instead.
+
+
+Release v1.0.1
+==============
+
+**Changes**
+
+* Added support for absolute etree Path queries. An absolute path begins with
+  `/` or `//` and begins its search from the element's document root.
+* Added [`GetPath`](https://godoc.org/github.com/beevik/etree#Element.GetPath)
+  and [`GetRelativePath`](https://godoc.org/github.com/beevik/etree#Element.GetRelativePath)
+  functions to the [`Element`](https://godoc.org/github.com/beevik/etree#Element)
+  type.
+
+**Breaking changes**
+
+* A path starting with `//` is now interpreted as an absolute path.
+  Previously, it was interpreted as a relative path starting from the element
+  whose
+  [`FindElement`](https://godoc.org/github.com/beevik/etree#Element.FindElement)
+  method was called.  To remain compatible with this release, all paths
+  prefixed with `//` should be prefixed with `.//` when called from any
+  element other than the document's root.
+* [**edit 2/1/2019**]: Minor releases should not contain breaking changes.
+  Even though this breaking change was very minor, it was a mistake to include
+  it in this minor release. In the future, all breaking changes will be
+  limited to major releases (e.g., version 2.0.0).
+
+Release v1.0.0
+==============
+
+Initial release.
diff --git a/etree.go b/etree.go
new file mode 100644
index 0000000..8a8c9bb
--- /dev/null
+++ b/etree.go
@@ -0,0 +1,1505 @@
+// Copyright 2015-2019 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package etree provides XML services through an Element Tree
+// abstraction.
+package etree
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/xml"
+	"errors"
+	"io"
+	"os"
+	"sort"
+	"strings"
+)
+
+const (
+	// NoIndent is used with the Document Indent function to disable all
+	// indenting.
+	NoIndent = -1
+)
+
+// ErrXML is returned when XML parsing fails due to incorrect formatting.
+var ErrXML = errors.New("etree: invalid XML format")
+
+// ReadSettings determine the default behavior of the Document's ReadFrom*
+// methods.
+type ReadSettings struct {
+	// CharsetReader to be passed to standard xml.Decoder. Default: nil.
+	CharsetReader func(charset string, input io.Reader) (io.Reader, error)
+
+	// Permissive allows input containing common mistakes such as missing tags
+	// or attribute values. Default: false.
+	Permissive bool
+
+	// Entity to be passed to standard xml.Decoder. Default: nil.
+	Entity map[string]string
+}
+
+// newReadSettings creates a default ReadSettings record.
+func newReadSettings() ReadSettings {
+	return ReadSettings{
+		CharsetReader: func(label string, input io.Reader) (io.Reader, error) {
+			return input, nil
+		},
+		Permissive: false,
+	}
+}
+
+// dup creates a duplicate of the ReadSettings object.
+func (s *ReadSettings) dup() ReadSettings {
+	var entityCopy map[string]string
+	if s.Entity != nil {
+		entityCopy = make(map[string]string)
+		for k, v := range s.Entity {
+			entityCopy[k] = v
+		}
+	}
+	return ReadSettings{
+		CharsetReader: s.CharsetReader,
+		Permissive:    s.Permissive,
+		Entity:        entityCopy,
+	}
+}
+
+// WriteSettings determine the behavior of the Document's WriteTo* and
+// Indent* methods.
+type WriteSettings struct {
+	// CanonicalEndTags forces the production of XML end tags, even for
+	// elements that have no child elements. Default: false.
+	CanonicalEndTags bool
+
+	// CanonicalText forces the production of XML character references for
+	// text data characters &, <, and >. If false, XML character references
+	// are also produced for " and '. Default: false.
+	CanonicalText bool
+
+	// CanonicalAttrVal forces the production of XML character references for
+	// attribute value characters &, < and ". If false, XML character
+	// references are also produced for > and '. Default: false.
+	CanonicalAttrVal bool
+
+	// UseCRLF causes the document's indentation methods to use a carriage
+	// return followed by a linefeed ("\r\n") when outputting a newline. If
+	// false, only a linefeed is used ("\n"). Default: false.
+	UseCRLF bool
+}
+
+// newWriteSettings creates a default WriteSettings record.
+func newWriteSettings() WriteSettings {
+	return WriteSettings{
+		CanonicalEndTags: false,
+		CanonicalText:    false,
+		CanonicalAttrVal: false,
+		UseCRLF:          false,
+	}
+}
+
+// dup creates a dulicate of the WriteSettings object.
+func (s *WriteSettings) dup() WriteSettings {
+	return *s
+}
+
+// A Token is an interface type used to represent XML elements, character
+// data, CDATA sections, XML comments, XML directives, and XML processing
+// instructions.
+type Token interface {
+	Parent() *Element
+	Index() int
+	dup(parent *Element) Token
+	setParent(parent *Element)
+	setIndex(index int)
+	writeTo(w *bufio.Writer, s *WriteSettings)
+}
+
+// A Document is a container holding a complete XML tree.
+//
+// A document has a single embedded element, which contains zero or more child
+// tokens, one of which is usually the root element. The embedded element may
+// include other children such as processing instruction tokens or character
+// data tokens. The document's embedded element is never directly serialized;
+// only its children are.
+//
+// A document also contains read and write settings, which influence the way
+// the document is deserialized, serialized, and indented.
+type Document struct {
+	Element
+	ReadSettings  ReadSettings
+	WriteSettings WriteSettings
+}
+
+// An Element represents an XML element, its attributes, and its child tokens.
+type Element struct {
+	Space, Tag string   // namespace prefix and tag
+	Attr       []Attr   // key-value attribute pairs
+	Child      []Token  // child tokens (elements, comments, etc.)
+	parent     *Element // parent element
+	index      int      // token index in parent's children
+}
+
+// An Attr represents a key-value attribute within an XML element.
+type Attr struct {
+	Space, Key string   // The attribute's namespace prefix and key
+	Value      string   // The attribute value string
+	element    *Element // element containing the attribute
+}
+
+// charDataFlags are used with CharData tokens to store additional settings.
+type charDataFlags uint8
+
+const (
+	// The CharData contains only whitespace.
+	whitespaceFlag charDataFlags = 1 << iota
+
+	// The CharData contains a CDATA section.
+	cdataFlag
+)
+
+// CharData may be used to represent simple text data or a CDATA section
+// within an XML document. The Data property should never be modified
+// directly; use the SetData method instead.
+type CharData struct {
+	Data   string // the simple text or CDATA section content
+	parent *Element
+	index  int
+	flags  charDataFlags
+}
+
+// A Comment represents an XML comment.
+type Comment struct {
+	Data   string // the comment's text
+	parent *Element
+	index  int
+}
+
+// A Directive represents an XML directive.
+type Directive struct {
+	Data   string // the directive string
+	parent *Element
+	index  int
+}
+
+// A ProcInst represents an XML processing instruction.
+type ProcInst struct {
+	Target string // the processing instruction target
+	Inst   string // the processing instruction value
+	parent *Element
+	index  int
+}
+
+// NewDocument creates an XML document without a root element.
+func NewDocument() *Document {
+	return &Document{
+		Element:       Element{Child: make([]Token, 0)},
+		ReadSettings:  newReadSettings(),
+		WriteSettings: newWriteSettings(),
+	}
+}
+
+// NewDocumentWithRoot creates an XML document and sets the element 'e' as its
+// root element. If the element 'e' is already part of another document, it is
+// first removed from its existing document.
+func NewDocumentWithRoot(e *Element) *Document {
+	d := NewDocument()
+	d.SetRoot(e)
+	return d
+}
+
+// Copy returns a recursive, deep copy of the document.
+func (d *Document) Copy() *Document {
+	return &Document{
+		Element:       *(d.Element.dup(nil).(*Element)),
+		ReadSettings:  d.ReadSettings.dup(),
+		WriteSettings: d.WriteSettings.dup(),
+	}
+}
+
+// Root returns the root element of the document. It returns nil if there is
+// no root element.
+func (d *Document) Root() *Element {
+	for _, t := range d.Child {
+		if c, ok := t.(*Element); ok {
+			return c
+		}
+	}
+	return nil
+}
+
+// SetRoot replaces the document's root element with the element 'e'. If the
+// document already has a root element when this function is called, then the
+// existing root element is unbound from the document. If the element 'e' is
+// part of another document, then it is unbound from the other document.
+func (d *Document) SetRoot(e *Element) {
+	if e.parent != nil {
+		e.parent.RemoveChild(e)
+	}
+
+	// If there is already a root element, replace it.
+	p := &d.Element
+	for i, t := range p.Child {
+		if _, ok := t.(*Element); ok {
+			t.setParent(nil)
+			t.setIndex(-1)
+			p.Child[i] = e
+			e.setParent(p)
+			e.setIndex(i)
+			return
+		}
+	}
+
+	// No existing root element, so add it.
+	p.addChild(e)
+}
+
+// ReadFrom reads XML from the reader 'r' into this document. The function
+// returns the number of bytes read and any error encountered.
+func (d *Document) ReadFrom(r io.Reader) (n int64, err error) {
+	return d.Element.readFrom(r, d.ReadSettings)
+}
+
+// ReadFromFile reads XML from a local file at path 'filepath' into this
+// document.
+func (d *Document) ReadFromFile(filepath string) error {
+	f, err := os.Open(filepath)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = d.ReadFrom(f)
+	return err
+}
+
+// ReadFromBytes reads XML from the byte slice 'b' into the this document.
+func (d *Document) ReadFromBytes(b []byte) error {
+	_, err := d.ReadFrom(bytes.NewReader(b))
+	return err
+}
+
+// ReadFromString reads XML from the string 's' into this document.
+func (d *Document) ReadFromString(s string) error {
+	_, err := d.ReadFrom(strings.NewReader(s))
+	return err
+}
+
+// WriteTo serializes the document out to the writer 'w'. The function returns
+// the number of bytes written and any error encountered.
+func (d *Document) WriteTo(w io.Writer) (n int64, err error) {
+	cw := newCountWriter(w)
+	b := bufio.NewWriter(cw)
+	for _, c := range d.Child {
+		c.writeTo(b, &d.WriteSettings)
+	}
+	err, n = b.Flush(), cw.bytes
+	return
+}
+
+// WriteToFile serializes the document out to the file at path 'filepath'.
+func (d *Document) WriteToFile(filepath string) error {
+	f, err := os.Create(filepath)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = d.WriteTo(f)
+	return err
+}
+
+// WriteToBytes serializes this document into a slice of bytes.
+func (d *Document) WriteToBytes() (b []byte, err error) {
+	var buf bytes.Buffer
+	if _, err = d.WriteTo(&buf); err != nil {
+		return
+	}
+	return buf.Bytes(), nil
+}
+
+// WriteToString serializes this document into a string.
+func (d *Document) WriteToString() (s string, err error) {
+	var b []byte
+	if b, err = d.WriteToBytes(); err != nil {
+		return
+	}
+	return string(b), nil
+}
+
+type indentFunc func(depth int) string
+
+// Indent modifies the document's element tree by inserting character data
+// tokens containing newlines and indentation. The amount of indentation per
+// depth level is given by the 'spaces' parameter. Pass etree.NoIndent for
+// 'spaces' if you want no indentation at all.
+func (d *Document) Indent(spaces int) {
+	var indent indentFunc
+	switch {
+	case spaces < 0:
+		indent = func(depth int) string { return "" }
+	case d.WriteSettings.UseCRLF:
+		indent = func(depth int) string { return indentCRLF(depth*spaces, indentSpaces) }
+	default:
+		indent = func(depth int) string { return indentLF(depth*spaces, indentSpaces) }
+	}
+	d.Element.indent(0, indent)
+}
+
+// IndentTabs modifies the document's element tree by inserting CharData
+// tokens containing newlines and tabs for indentation.  One tab is used per
+// indentation level.
+func (d *Document) IndentTabs() {
+	var indent indentFunc
+	switch d.WriteSettings.UseCRLF {
+	case true:
+		indent = func(depth int) string { return indentCRLF(depth, indentTabs) }
+	default:
+		indent = func(depth int) string { return indentLF(depth, indentTabs) }
+	}
+	d.Element.indent(0, indent)
+}
+
+// NewElement creates an unparented element with the specified tag (i.e.,
+// name). The tag may include a namespace prefix followed by a colon.
+func NewElement(tag string) *Element {
+	space, stag := spaceDecompose(tag)
+	return newElement(space, stag, nil)
+}
+
+// newElement is a helper function that creates an element and binds it to
+// a parent element if possible.
+func newElement(space, tag string, parent *Element) *Element {
+	e := &Element{
+		Space:  space,
+		Tag:    tag,
+		Attr:   make([]Attr, 0),
+		Child:  make([]Token, 0),
+		parent: parent,
+		index:  -1,
+	}
+	if parent != nil {
+		parent.addChild(e)
+	}
+	return e
+}
+
+// Copy creates a recursive, deep copy of the element and all its attributes
+// and children. The returned element has no parent but can be parented to a
+// another element using AddChild, or added to a document with SetRoot or
+// NewDocumentWithRoot.
+func (e *Element) Copy() *Element {
+	return e.dup(nil).(*Element)
+}
+
+// FullTag returns the element e's complete tag, including namespace prefix if
+// present.
+func (e *Element) FullTag() string {
+	if e.Space == "" {
+		return e.Tag
+	}
+	return e.Space + ":" + e.Tag
+}
+
+// NamespaceURI returns the XML namespace URI associated with the element. If
+// the element is part of the XML default namespace, NamespaceURI returns the
+// empty string.
+func (e *Element) NamespaceURI() string {
+	if e.Space == "" {
+		return e.findDefaultNamespaceURI()
+	}
+	return e.findLocalNamespaceURI(e.Space)
+}
+
+// findLocalNamespaceURI finds the namespace URI corresponding to the
+// requested prefix.
+func (e *Element) findLocalNamespaceURI(prefix string) string {
+	for _, a := range e.Attr {
+		if a.Space == "xmlns" && a.Key == prefix {
+			return a.Value
+		}
+	}
+
+	if e.parent == nil {
+		return ""
+	}
+
+	return e.parent.findLocalNamespaceURI(prefix)
+}
+
+// findDefaultNamespaceURI finds the default namespace URI of the element.
+func (e *Element) findDefaultNamespaceURI() string {
+	for _, a := range e.Attr {
+		if a.Space == "" && a.Key == "xmlns" {
+			return a.Value
+		}
+	}
+
+	if e.parent == nil {
+		return ""
+	}
+
+	return e.parent.findDefaultNamespaceURI()
+}
+
+// namespacePrefix returns the namespace prefix associated with the element.
+func (e *Element) namespacePrefix() string {
+	return e.Space
+}
+
+// name returns the tag associated with the element.
+func (e *Element) name() string {
+	return e.Tag
+}
+
+// Text returns all character data immediately following the element's opening
+// tag.
+func (e *Element) Text() string {
+	if len(e.Child) == 0 {
+		return ""
+	}
+
+	text := ""
+	for _, ch := range e.Child {
+		if cd, ok := ch.(*CharData); ok {
+			if text == "" {
+				text = cd.Data
+			} else {
+				text += cd.Data
+			}
+		} else {
+			break
+		}
+	}
+	return text
+}
+
+// SetText replaces all character data immediately following an element's
+// opening tag with the requested string.
+func (e *Element) SetText(text string) {
+	e.replaceText(0, text, 0)
+}
+
+// SetCData replaces all character data immediately following an element's
+// opening tag with a CDATA section.
+func (e *Element) SetCData(text string) {
+	e.replaceText(0, text, cdataFlag)
+}
+
+// Tail returns all character data immediately following the element's end
+// tag.
+func (e *Element) Tail() string {
+	if e.Parent() == nil {
+		return ""
+	}
+
+	p := e.Parent()
+	i := e.Index()
+
+	text := ""
+	for _, ch := range p.Child[i+1:] {
+		if cd, ok := ch.(*CharData); ok {
+			if text == "" {
+				text = cd.Data
+			} else {
+				text += cd.Data
+			}
+		} else {
+			break
+		}
+	}
+	return text
+}
+
+// SetTail replaces all character data immediately following the element's end
+// tag with the requested string.
+func (e *Element) SetTail(text string) {
+	if e.Parent() == nil {
+		return
+	}
+
+	p := e.Parent()
+	p.replaceText(e.Index()+1, text, 0)
+}
+
+// replaceText is a helper function that replaces a series of chardata tokens
+// starting at index i with the requested text.
+func (e *Element) replaceText(i int, text string, flags charDataFlags) {
+	end := e.findTermCharDataIndex(i)
+
+	switch {
+	case end == i:
+		if text != "" {
+			// insert a new chardata token at index i
+			cd := newCharData(text, flags, nil)
+			e.InsertChildAt(i, cd)
+		}
+
+	case end == i+1:
+		if text == "" {
+			// remove the chardata token at index i
+			e.RemoveChildAt(i)
+		} else {
+			// replace the first and only character token at index i
+			cd := e.Child[i].(*CharData)
+			cd.Data, cd.flags = text, flags
+		}
+
+	default:
+		if text == "" {
+			// remove all chardata tokens starting from index i
+			copy(e.Child[i:], e.Child[end:])
+			removed := end - i
+			e.Child = e.Child[:len(e.Child)-removed]
+			for j := i; j < len(e.Child); j++ {
+				e.Child[j].setIndex(j)
+			}
+		} else {
+			// replace the first chardata token at index i and remove all
+			// subsequent chardata tokens
+			cd := e.Child[i].(*CharData)
+			cd.Data, cd.flags = text, flags
+			copy(e.Child[i+1:], e.Child[end:])
+			removed := end - (i + 1)
+			e.Child = e.Child[:len(e.Child)-removed]
+			for j := i + 1; j < len(e.Child); j++ {
+				e.Child[j].setIndex(j)
+			}
+		}
+	}
+}
+
+// findTermCharDataIndex finds the index of the first child token that isn't
+// a CharData token. It starts from the requested start index.
+func (e *Element) findTermCharDataIndex(start int) int {
+	for i := start; i < len(e.Child); i++ {
+		if _, ok := e.Child[i].(*CharData); !ok {
+			return i
+		}
+	}
+	return len(e.Child)
+}
+
+// CreateElement creates a new element with the specified tag (i.e., name) and
+// adds it as the last child token of this element. The tag may include a
+// prefix followed by a colon.
+func (e *Element) CreateElement(tag string) *Element {
+	space, stag := spaceDecompose(tag)
+	return newElement(space, stag, e)
+}
+
+// AddChild adds the token 't' as the last child of the element. If token 't'
+// was already the child of another element, it is first removed from its
+// parent element.
+func (e *Element) AddChild(t Token) {
+	if t.Parent() != nil {
+		t.Parent().RemoveChild(t)
+	}
+	e.addChild(t)
+}
+
+// InsertChild inserts the token 't' into this element's list of children just
+// before the element's existing child token 'ex'. If the existing element
+// 'ex' does not appear in this element's list of child tokens, then 't' is
+// added to the end of this element's list of child tokens. If token 't' is
+// already the child of another element, it is first removed from the other
+// element's list of child tokens.
+//
+// Deprecated: InsertChild is deprecated. Use InsertChildAt instead.
+func (e *Element) InsertChild(ex Token, t Token) {
+	if ex == nil || ex.Parent() != e {
+		e.AddChild(t)
+		return
+	}
+
+	if t.Parent() != nil {
+		t.Parent().RemoveChild(t)
+	}
+
+	t.setParent(e)
+
+	i := ex.Index()
+	e.Child = append(e.Child, nil)
+	copy(e.Child[i+1:], e.Child[i:])
+	e.Child[i] = t
+
+	for j := i; j < len(e.Child); j++ {
+		e.Child[j].setIndex(j)
+	}
+}
+
+// InsertChildAt inserts the token 't' into this element's list of child
+// tokens just before the requested 'index'. If the index is greater than or
+// equal to the length of the list of child tokens, then the token 't' is
+// added to the end of the list of child tokens.
+func (e *Element) InsertChildAt(index int, t Token) {
+	if index >= len(e.Child) {
+		e.AddChild(t)
+		return
+	}
+
+	if t.Parent() != nil {
+		if t.Parent() == e && t.Index() > index {
+			index--
+		}
+		t.Parent().RemoveChild(t)
+	}
+
+	t.setParent(e)
+
+	e.Child = append(e.Child, nil)
+	copy(e.Child[index+1:], e.Child[index:])
+	e.Child[index] = t
+
+	for j := index; j < len(e.Child); j++ {
+		e.Child[j].setIndex(j)
+	}
+}
+
+// RemoveChild attempts to remove the token 't' from this element's list of
+// child tokens. If the token 't' was a child of this element, then it is
+// removed and returned. Otherwise, nil is returned.
+func (e *Element) RemoveChild(t Token) Token {
+	if t.Parent() != e {
+		return nil
+	}
+	return e.RemoveChildAt(t.Index())
+}
+
+// RemoveChildAt removes the child token appearing in slot 'index' of this
+// element's list of child tokens. The removed child token is then returned.
+// If the index is out of bounds, no child is removed and nil is returned.
+func (e *Element) RemoveChildAt(index int) Token {
+	if index >= len(e.Child) {
+		return nil
+	}
+
+	t := e.Child[index]
+	for j := index + 1; j < len(e.Child); j++ {
+		e.Child[j].setIndex(j - 1)
+	}
+	e.Child = append(e.Child[:index], e.Child[index+1:]...)
+	t.setIndex(-1)
+	t.setParent(nil)
+	return t
+}
+
+// ReadFrom reads XML from the reader ;ri' and stores the result as a new
+// child of this element.
+func (e *Element) readFrom(ri io.Reader, settings ReadSettings) (n int64, err error) {
+	r := newCountReader(ri)
+	dec := xml.NewDecoder(r)
+	dec.CharsetReader = settings.CharsetReader
+	dec.Strict = !settings.Permissive
+	dec.Entity = settings.Entity
+	var stack stack
+	stack.push(e)
+	for {
+		t, err := dec.RawToken()
+		switch {
+		case err == io.EOF:
+			return r.bytes, nil
+		case err != nil:
+			return r.bytes, err
+		case stack.empty():
+			return r.bytes, ErrXML
+		}
+
+		top := stack.peek().(*Element)
+
+		switch t := t.(type) {
+		case xml.StartElement:
+			e := newElement(t.Name.Space, t.Name.Local, top)
+			for _, a := range t.Attr {
+				e.createAttr(a.Name.Space, a.Name.Local, a.Value, e)
+			}
+			stack.push(e)
+		case xml.EndElement:
+			stack.pop()
+		case xml.CharData:
+			data := string(t)
+			var flags charDataFlags
+			if isWhitespace(data) {
+				flags = whitespaceFlag
+			}
+			newCharData(data, flags, top)
+		case xml.Comment:
+			newComment(string(t), top)
+		case xml.Directive:
+			newDirective(string(t), top)
+		case xml.ProcInst:
+			newProcInst(t.Target, string(t.Inst), top)
+		}
+	}
+}
+
+// SelectAttr finds an element attribute matching the requested 'key' and, if
+// found, returns a pointer to the matching attribute. The function returns
+// nil if no matching attribute is found. The key may include a namespace
+// prefix followed by a colon.
+func (e *Element) SelectAttr(key string) *Attr {
+	space, skey := spaceDecompose(key)
+	for i, a := range e.Attr {
+		if spaceMatch(space, a.Space) && skey == a.Key {
+			return &e.Attr[i]
+		}
+	}
+	return nil
+}
+
+// SelectAttrValue finds an element attribute matching the requested 'key' and
+// returns its value if found. If no matching attribute is found, the function
+// returns the 'dflt' value instead. The key may include a namespace prefix
+// followed by a colon.
+func (e *Element) SelectAttrValue(key, dflt string) string {
+	space, skey := spaceDecompose(key)
+	for _, a := range e.Attr {
+		if spaceMatch(space, a.Space) && skey == a.Key {
+			return a.Value
+		}
+	}
+	return dflt
+}
+
+// ChildElements returns all elements that are children of this element.
+func (e *Element) ChildElements() []*Element {
+	var elements []*Element
+	for _, t := range e.Child {
+		if c, ok := t.(*Element); ok {
+			elements = append(elements, c)
+		}
+	}
+	return elements
+}
+
+// SelectElement returns the first child element with the given 'tag' (i.e.,
+// name). The function returns nil if no child element matching the tag is
+// found. The tag may include a namespace prefix followed by a colon.
+func (e *Element) SelectElement(tag string) *Element {
+	space, stag := spaceDecompose(tag)
+	for _, t := range e.Child {
+		if c, ok := t.(*Element); ok && spaceMatch(space, c.Space) && stag == c.Tag {
+			return c
+		}
+	}
+	return nil
+}
+
+// SelectElements returns a slice of all child elements with the given 'tag'
+// (i.e., name). The tag may include a namespace prefix followed by a colon.
+func (e *Element) SelectElements(tag string) []*Element {
+	space, stag := spaceDecompose(tag)
+	var elements []*Element
+	for _, t := range e.Child {
+		if c, ok := t.(*Element); ok && spaceMatch(space, c.Space) && stag == c.Tag {
+			elements = append(elements, c)
+		}
+	}
+	return elements
+}
+
+// FindElement returns the first element matched by the XPath-like 'path'
+// string. The function returns nil if no child element is found using the
+// path. It panics if an invalid path string is supplied.
+func (e *Element) FindElement(path string) *Element {
+	return e.FindElementPath(MustCompilePath(path))
+}
+
+// FindElementPath returns the first element matched by the 'path' object. The
+// function returns nil if no element is found using the path.
+func (e *Element) FindElementPath(path Path) *Element {
+	p := newPather()
+	elements := p.traverse(e, path)
+	if len(elements) > 0 {
+		return elements[0]
+	}
+	return nil
+}
+
+// FindElements returns a slice of elements matched by the XPath-like 'path'
+// string. The function returns nil if no child element is found using the
+// path. It panics if an invalid path string is supplied.
+func (e *Element) FindElements(path string) []*Element {
+	return e.FindElementsPath(MustCompilePath(path))
+}
+
+// FindElementsPath returns a slice of elements matched by the 'path' object.
+func (e *Element) FindElementsPath(path Path) []*Element {
+	p := newPather()
+	return p.traverse(e, path)
+}
+
+// GetPath returns the absolute path of the element. The absolute path is the
+// full path from the document's root.
+func (e *Element) GetPath() string {
+	path := []string{}
+	for seg := e; seg != nil; seg = seg.Parent() {
+		if seg.Tag != "" {
+			path = append(path, seg.Tag)
+		}
+	}
+
+	// Reverse the path.
+	for i, j := 0, len(path)-1; i < j; i, j = i+1, j-1 {
+		path[i], path[j] = path[j], path[i]
+	}
+
+	return "/" + strings.Join(path, "/")
+}
+
+// GetRelativePath returns the path of this element relative to the 'source'
+// element. If the two elements are not part of the same element tree, then
+// the function returns the empty string.
+func (e *Element) GetRelativePath(source *Element) string {
+	var path []*Element
+
+	if source == nil {
+		return ""
+	}
+
+	// Build a reverse path from the element toward the root. Stop if the
+	// source element is encountered.
+	var seg *Element
+	for seg = e; seg != nil && seg != source; seg = seg.Parent() {
+		path = append(path, seg)
+	}
+
+	// If we found the source element, reverse the path and compose the
+	// string.
+	if seg == source {
+		if len(path) == 0 {
+			return "."
+		}
+		parts := []string{}
+		for i := len(path) - 1; i >= 0; i-- {
+			parts = append(parts, path[i].Tag)
+		}
+		return "./" + strings.Join(parts, "/")
+	}
+
+	// The source wasn't encountered, so climb from the source element toward
+	// the root of the tree until an element in the reversed path is
+	// encountered.
+
+	findPathIndex := func(e *Element, path []*Element) int {
+		for i, ee := range path {
+			if e == ee {
+				return i
+			}
+		}
+		return -1
+	}
+
+	climb := 0
+	for seg = source; seg != nil; seg = seg.Parent() {
+		i := findPathIndex(seg, path)
+		if i >= 0 {
+			path = path[:i] // truncate at found segment
+			break
+		}
+		climb++
+	}
+
+	// No element in the reversed path was encountered, so the two elements
+	// must not be part of the same tree.
+	if seg == nil {
+		return ""
+	}
+
+	// Reverse the (possibly truncated) path and prepend ".." segments to
+	// climb.
+	parts := []string{}
+	for i := 0; i < climb; i++ {
+		parts = append(parts, "..")
+	}
+	for i := len(path) - 1; i >= 0; i-- {
+		parts = append(parts, path[i].Tag)
+	}
+	return strings.Join(parts, "/")
+}
+
+// indent recursively inserts proper indentation between an XML element's
+// child tokens.
+func (e *Element) indent(depth int, indent indentFunc) {
+	e.stripIndent()
+	n := len(e.Child)
+	if n == 0 {
+		return
+	}
+
+	oldChild := e.Child
+	e.Child = make([]Token, 0, n*2+1)
+	isCharData, firstNonCharData := false, true
+	for _, c := range oldChild {
+		// Insert NL+indent before child if it's not character data.
+		// Exceptions: when it's the first non-character-data child, or when
+		// the child is at root depth.
+		_, isCharData = c.(*CharData)
+		if !isCharData {
+			if !firstNonCharData || depth > 0 {
+				s := indent(depth)
+				if s != "" {
+					newCharData(s, whitespaceFlag, e)
+				}
+			}
+			firstNonCharData = false
+		}
+
+		e.addChild(c)
+
+		// Recursively process child elements.
+		if ce, ok := c.(*Element); ok {
+			ce.indent(depth+1, indent)
+		}
+	}
+
+	// Insert NL+indent before the last child.
+	if !isCharData {
+		if !firstNonCharData || depth > 0 {
+			s := indent(depth - 1)
+			if s != "" {
+				newCharData(s, whitespaceFlag, e)
+			}
+		}
+	}
+}
+
+// stripIndent removes any previously inserted indentation.
+func (e *Element) stripIndent() {
+	// Count the number of non-indent child tokens
+	n := len(e.Child)
+	for _, c := range e.Child {
+		if cd, ok := c.(*CharData); ok && cd.IsWhitespace() {
+			n--
+		}
+	}
+	if n == len(e.Child) {
+		return
+	}
+
+	// Strip out indent CharData
+	newChild := make([]Token, n)
+	j := 0
+	for _, c := range e.Child {
+		if cd, ok := c.(*CharData); ok && cd.IsWhitespace() {
+			continue
+		}
+		newChild[j] = c
+		newChild[j].setIndex(j)
+		j++
+	}
+	e.Child = newChild
+}
+
+// dup duplicates the element.
+func (e *Element) dup(parent *Element) Token {
+	ne := &Element{
+		Space:  e.Space,
+		Tag:    e.Tag,
+		Attr:   make([]Attr, len(e.Attr)),
+		Child:  make([]Token, len(e.Child)),
+		parent: parent,
+		index:  e.index,
+	}
+	for i, t := range e.Child {
+		ne.Child[i] = t.dup(ne)
+	}
+	copy(ne.Attr, e.Attr)
+	return ne
+}
+
+// Parent returns this element's parent element. It returns nil if this
+// element has no parent.
+func (e *Element) Parent() *Element {
+	return e.parent
+}
+
+// Index returns the index of this element within its parent element's
+// list of child tokens. If this element has no parent, then the function
+// returns -1.
+func (e *Element) Index() int {
+	return e.index
+}
+
+// setParent replaces this element token's parent.
+func (e *Element) setParent(parent *Element) {
+	e.parent = parent
+}
+
+// setIndex sets this element token's index within its parent's Child slice.
+func (e *Element) setIndex(index int) {
+	e.index = index
+}
+
+// writeTo serializes the element to the writer w.
+func (e *Element) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteByte('<')
+	w.WriteString(e.FullTag())
+	for _, a := range e.Attr {
+		w.WriteByte(' ')
+		a.writeTo(w, s)
+	}
+	if len(e.Child) > 0 {
+		w.WriteByte('>')
+		for _, c := range e.Child {
+			c.writeTo(w, s)
+		}
+		w.Write([]byte{'<', '/'})
+		w.WriteString(e.FullTag())
+		w.WriteByte('>')
+	} else {
+		if s.CanonicalEndTags {
+			w.Write([]byte{'>', '<', '/'})
+			w.WriteString(e.FullTag())
+			w.WriteByte('>')
+		} else {
+			w.Write([]byte{'/', '>'})
+		}
+	}
+}
+
+// addChild adds a child token to the element e.
+func (e *Element) addChild(t Token) {
+	t.setParent(e)
+	t.setIndex(len(e.Child))
+	e.Child = append(e.Child, t)
+}
+
+// CreateAttr creates an attribute with the specified 'key' and 'value' and
+// adds it to this element. If an attribute with same key already exists on
+// this element, then its value is replaced. The key may include a namespace
+// prefix followed by a colon.
+func (e *Element) CreateAttr(key, value string) *Attr {
+	space, skey := spaceDecompose(key)
+	return e.createAttr(space, skey, value, e)
+}
+
+// createAttr is a helper function that creates attributes.
+func (e *Element) createAttr(space, key, value string, parent *Element) *Attr {
+	for i, a := range e.Attr {
+		if space == a.Space && key == a.Key {
+			e.Attr[i].Value = value
+			return &e.Attr[i]
+		}
+	}
+	a := Attr{
+		Space:   space,
+		Key:     key,
+		Value:   value,
+		element: parent,
+	}
+	e.Attr = append(e.Attr, a)
+	return &e.Attr[len(e.Attr)-1]
+}
+
+// RemoveAttr removes the first attribute of this element whose key matches
+// 'key'. It returns a copy of the removed attribute if a match is found. If
+// no match is found, it returns nil. The key may include a namespace prefix
+// followed by a colon.
+func (e *Element) RemoveAttr(key string) *Attr {
+	space, skey := spaceDecompose(key)
+	for i, a := range e.Attr {
+		if space == a.Space && skey == a.Key {
+			e.Attr = append(e.Attr[0:i], e.Attr[i+1:]...)
+			return &Attr{
+				Space:   a.Space,
+				Key:     a.Key,
+				Value:   a.Value,
+				element: nil,
+			}
+		}
+	}
+	return nil
+}
+
+// SortAttrs sorts this element's attributes lexicographically by key.
+func (e *Element) SortAttrs() {
+	sort.Sort(byAttr(e.Attr))
+}
+
+type byAttr []Attr
+
+func (a byAttr) Len() int {
+	return len(a)
+}
+
+func (a byAttr) Swap(i, j int) {
+	a[i], a[j] = a[j], a[i]
+}
+
+func (a byAttr) Less(i, j int) bool {
+	sp := strings.Compare(a[i].Space, a[j].Space)
+	if sp == 0 {
+		return strings.Compare(a[i].Key, a[j].Key) < 0
+	}
+	return sp < 0
+}
+
+// FullKey returns this attribute's complete key, including namespace prefix
+// if present.
+func (a *Attr) FullKey() string {
+	if a.Space == "" {
+		return a.Key
+	}
+	return a.Space + ":" + a.Key
+}
+
+// Element returns a pointer to the element containing this attribute.
+func (a *Attr) Element() *Element {
+	return a.element
+}
+
+// NamespaceURI returns the XML namespace URI associated with this attribute.
+// The function returns the empty string if the attribute is unprefixed or
+// if the attribute is part of the XML default namespace.
+func (a *Attr) NamespaceURI() string {
+	if a.Space == "" {
+		return ""
+	}
+	return a.element.findLocalNamespaceURI(a.Space)
+}
+
+// writeTo serializes the attribute to the writer.
+func (a *Attr) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteString(a.FullKey())
+	w.WriteString(`="`)
+	var m escapeMode
+	if s.CanonicalAttrVal {
+		m = escapeCanonicalAttr
+	} else {
+		m = escapeNormal
+	}
+	escapeString(w, a.Value, m)
+	w.WriteByte('"')
+}
+
+// NewText creates an unparented CharData token containing simple text data.
+func NewText(text string) *CharData {
+	return newCharData(text, 0, nil)
+}
+
+// NewCData creates an unparented XML character CDATA section with 'data' as
+// its content.
+func NewCData(data string) *CharData {
+	return newCharData(data, cdataFlag, nil)
+}
+
+// NewCharData creates an unparented CharData token containing simple text
+// data.
+//
+// Deprecated: NewCharData is deprecated. Instead, use NewText, which does the
+// same thing.
+func NewCharData(data string) *CharData {
+	return newCharData(data, 0, nil)
+}
+
+// newCharData creates a character data token and binds it to a parent
+// element. If parent is nil, the CharData token remains unbound.
+func newCharData(data string, flags charDataFlags, parent *Element) *CharData {
+	c := &CharData{
+		Data:   data,
+		parent: nil,
+		index:  -1,
+		flags:  flags,
+	}
+	if parent != nil {
+		parent.addChild(c)
+	}
+	return c
+}
+
+// CreateText creates a CharData token simple text data and adds it to the
+// end of this element's list of child tokens.
+func (e *Element) CreateText(text string) *CharData {
+	return newCharData(text, 0, e)
+}
+
+// CreateCData creates a CharData token containing a CDATA section with 'data'
+// as its content and adds it to the end of this element's list of child
+// tokens.
+func (e *Element) CreateCData(data string) *CharData {
+	return newCharData(data, cdataFlag, e)
+}
+
+// CreateCharData creates a CharData token simple text data and adds it to the
+// end of this element's list of child tokens.
+//
+// Deprecated: CreateCharData is deprecated. Instead, use CreateText, which
+// does the same thing.
+func (e *Element) CreateCharData(data string) *CharData {
+	return newCharData(data, 0, e)
+}
+
+// SetData modifies the content of the CharData token. In the case of a
+// CharData token containing simple text, the simple text is modified. In the
+// case of a CharData token containing a CDATA section, the CDATA section's
+// content is modified.
+func (c *CharData) SetData(text string) {
+	c.Data = text
+	if isWhitespace(text) {
+		c.flags |= whitespaceFlag
+	} else {
+		c.flags &= ^whitespaceFlag
+	}
+}
+
+// IsCData returns true if this CharData token is contains a CDATA section. It
+// returns false if the CharData token contains simple text.
+func (c *CharData) IsCData() bool {
+	return (c.flags & cdataFlag) != 0
+}
+
+// IsWhitespace returns true if this CharData token contains only whitespace.
+func (c *CharData) IsWhitespace() bool {
+	return (c.flags & whitespaceFlag) != 0
+}
+
+// Parent returns this CharData token's parent element, or nil if it has no
+// parent.
+func (c *CharData) Parent() *Element {
+	return c.parent
+}
+
+// Index returns the index of this CharData token within its parent element's
+// list of child tokens. If this CharData token has no parent, then the
+// function returns -1.
+func (c *CharData) Index() int {
+	return c.index
+}
+
+// dup duplicates the character data.
+func (c *CharData) dup(parent *Element) Token {
+	return &CharData{
+		Data:   c.Data,
+		flags:  c.flags,
+		parent: parent,
+		index:  c.index,
+	}
+}
+
+// setParent replaces the character data token's parent.
+func (c *CharData) setParent(parent *Element) {
+	c.parent = parent
+}
+
+// setIndex sets the CharData token's index within its parent element's Child
+// slice.
+func (c *CharData) setIndex(index int) {
+	c.index = index
+}
+
+// writeTo serializes character data to the writer.
+func (c *CharData) writeTo(w *bufio.Writer, s *WriteSettings) {
+	if c.IsCData() {
+		w.WriteString(`<![CDATA[`)
+		w.WriteString(c.Data)
+		w.WriteString(`]]>`)
+	} else {
+		var m escapeMode
+		if s.CanonicalText {
+			m = escapeCanonicalText
+		} else {
+			m = escapeNormal
+		}
+		escapeString(w, c.Data, m)
+	}
+}
+
+// NewComment creates an unparented comment token.
+func NewComment(comment string) *Comment {
+	return newComment(comment, nil)
+}
+
+// NewComment creates a comment token and sets its parent element to 'parent'.
+func newComment(comment string, parent *Element) *Comment {
+	c := &Comment{
+		Data:   comment,
+		parent: nil,
+		index:  -1,
+	}
+	if parent != nil {
+		parent.addChild(c)
+	}
+	return c
+}
+
+// CreateComment creates a comment token using the specified 'comment' string
+// and adds it as the last child token of this element.
+func (e *Element) CreateComment(comment string) *Comment {
+	return newComment(comment, e)
+}
+
+// dup duplicates the comment.
+func (c *Comment) dup(parent *Element) Token {
+	return &Comment{
+		Data:   c.Data,
+		parent: parent,
+		index:  c.index,
+	}
+}
+
+// Parent returns comment token's parent element, or nil if it has no parent.
+func (c *Comment) Parent() *Element {
+	return c.parent
+}
+
+// Index returns the index of this Comment token within its parent element's
+// list of child tokens. If this Comment token has no parent, then the
+// function returns -1.
+func (c *Comment) Index() int {
+	return c.index
+}
+
+// setParent replaces the comment token's parent.
+func (c *Comment) setParent(parent *Element) {
+	c.parent = parent
+}
+
+// setIndex sets the Comment token's index within its parent element's Child
+// slice.
+func (c *Comment) setIndex(index int) {
+	c.index = index
+}
+
+// writeTo serialies the comment to the writer.
+func (c *Comment) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteString("<!--")
+	w.WriteString(c.Data)
+	w.WriteString("-->")
+}
+
+// NewDirective creates an unparented XML directive token.
+func NewDirective(data string) *Directive {
+	return newDirective(data, nil)
+}
+
+// newDirective creates an XML directive and binds it to a parent element. If
+// parent is nil, the Directive remains unbound.
+func newDirective(data string, parent *Element) *Directive {
+	d := &Directive{
+		Data:   data,
+		parent: nil,
+		index:  -1,
+	}
+	if parent != nil {
+		parent.addChild(d)
+	}
+	return d
+}
+
+// CreateDirective creates an XML directive token with the specified 'data'
+// value and adds it as the last child token of this element.
+func (e *Element) CreateDirective(data string) *Directive {
+	return newDirective(data, e)
+}
+
+// dup duplicates the directive.
+func (d *Directive) dup(parent *Element) Token {
+	return &Directive{
+		Data:   d.Data,
+		parent: parent,
+		index:  d.index,
+	}
+}
+
+// Parent returns directive token's parent element, or nil if it has no
+// parent.
+func (d *Directive) Parent() *Element {
+	return d.parent
+}
+
+// Index returns the index of this Directive token within its parent element's
+// list of child tokens. If this Directive token has no parent, then the
+// function returns -1.
+func (d *Directive) Index() int {
+	return d.index
+}
+
+// setParent replaces the directive token's parent.
+func (d *Directive) setParent(parent *Element) {
+	d.parent = parent
+}
+
+// setIndex sets the Directive token's index within its parent element's Child
+// slice.
+func (d *Directive) setIndex(index int) {
+	d.index = index
+}
+
+// writeTo serializes the XML directive to the writer.
+func (d *Directive) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteString("<!")
+	w.WriteString(d.Data)
+	w.WriteString(">")
+}
+
+// NewProcInst creates an unparented XML processing instruction.
+func NewProcInst(target, inst string) *ProcInst {
+	return newProcInst(target, inst, nil)
+}
+
+// newProcInst creates an XML processing instruction and binds it to a parent
+// element. If parent is nil, the ProcInst remains unbound.
+func newProcInst(target, inst string, parent *Element) *ProcInst {
+	p := &ProcInst{
+		Target: target,
+		Inst:   inst,
+		parent: nil,
+		index:  -1,
+	}
+	if parent != nil {
+		parent.addChild(p)
+	}
+	return p
+}
+
+// CreateProcInst creates an XML processing instruction token with the
+// sepcified 'target' and instruction 'inst'. It is then added as the last
+// child token of this element.
+func (e *Element) CreateProcInst(target, inst string) *ProcInst {
+	return newProcInst(target, inst, e)
+}
+
+// dup duplicates the procinst.
+func (p *ProcInst) dup(parent *Element) Token {
+	return &ProcInst{
+		Target: p.Target,
+		Inst:   p.Inst,
+		parent: parent,
+		index:  p.index,
+	}
+}
+
+// Parent returns processing instruction token's parent element, or nil if it
+// has no parent.
+func (p *ProcInst) Parent() *Element {
+	return p.parent
+}
+
+// Index returns the index of this ProcInst token within its parent element's
+// list of child tokens. If this ProcInst token has no parent, then the
+// function returns -1.
+func (p *ProcInst) Index() int {
+	return p.index
+}
+
+// setParent replaces the processing instruction token's parent.
+func (p *ProcInst) setParent(parent *Element) {
+	p.parent = parent
+}
+
+// setIndex sets the processing instruction token's index within its parent
+// element's Child slice.
+func (p *ProcInst) setIndex(index int) {
+	p.index = index
+}
+
+// writeTo serializes the processing instruction to the writer.
+func (p *ProcInst) writeTo(w *bufio.Writer, s *WriteSettings) {
+	w.WriteString("<?")
+	w.WriteString(p.Target)
+	if p.Inst != "" {
+		w.WriteByte(' ')
+		w.WriteString(p.Inst)
+	}
+	w.WriteString("?>")
+}
diff --git a/etree_test.go b/etree_test.go
new file mode 100644
index 0000000..501f4ad
--- /dev/null
+++ b/etree_test.go
@@ -0,0 +1,1115 @@
+// Copyright 2015-2019 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package etree
+
+import (
+	"encoding/xml"
+	"io"
+	"strings"
+	"testing"
+)
+
+func newDocumentFromString(t *testing.T, s string) *Document {
+	t.Helper()
+	doc := NewDocument()
+	err := doc.ReadFromString(s)
+	if err != nil {
+		t.Error("etree: failed to parse document")
+	}
+	return doc
+}
+
+func checkStrEq(t *testing.T, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("etree: unexpected result.\nGot:\n%s\nWanted:\n%s\n", got, want)
+	}
+}
+
+func checkStrBinaryEq(t *testing.T, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("etree: unexpected result.\nGot:\n%v\nWanted:\n%v\n", []byte(got), []byte(want))
+	}
+}
+
+func checkIntEq(t *testing.T, got, want int) {
+	t.Helper()
+	if got != want {
+		t.Errorf("etree: unexpected integer. Got: %d. Wanted: %d\n", got, want)
+	}
+}
+
+func checkBoolEq(t *testing.T, got, want bool) {
+	t.Helper()
+	if got != want {
+		t.Errorf("etree: unexpected boolean. Got: %v. Wanted: %v\n", got, want)
+	}
+}
+
+func checkElementEq(t *testing.T, got, want *Element) {
+	t.Helper()
+	if got != want {
+		t.Errorf("etree: unexpected element. Got: %v. Wanted: %v.\n", got, want)
+	}
+}
+
+func checkDocEq(t *testing.T, doc *Document, expected string) {
+	t.Helper()
+	doc.Indent(NoIndent)
+	s, err := doc.WriteToString()
+	if err != nil {
+		t.Error("etree: failed to serialize document")
+	}
+	if s != expected {
+		t.Errorf("etree: unexpected document.\nGot:\n%s\nWanted:\n%s\n", s, expected)
+	}
+}
+
+func checkIndexes(t *testing.T, e *Element) {
+	t.Helper()
+	for i := 0; i < len(e.Child); i++ {
+		c := e.Child[i]
+		if c.Index() != i {
+			t.Errorf("Child index mismatch. Got %d, expected %d.", c.Index(), i)
+		}
+		if ce, ok := c.(*Element); ok {
+			checkIndexes(t, ce)
+		}
+	}
+}
+
+func TestDocument(t *testing.T) {
+	// Create a document
+	doc := NewDocument()
+	doc.CreateProcInst("xml", `version="1.0" encoding="UTF-8"`)
+	doc.CreateProcInst("xml-stylesheet", `type="text/xsl" href="style.xsl"`)
+	store := doc.CreateElement("store")
+	store.CreateAttr("xmlns:t", "urn:books-com:titles")
+	store.CreateDirective("Directive")
+	store.CreateComment("This is a comment")
+	book := store.CreateElement("book")
+	book.CreateAttr("lang", "fr")
+	book.CreateAttr("lang", "en")
+	title := book.CreateElement("t:title")
+	title.SetText("Nicholas Nickleby")
+	title.SetText("Great Expectations")
+	author := book.CreateElement("author")
+	author.CreateCharData("Charles Dickens")
+	review := book.CreateElement("review")
+	review.CreateCData("<<< Will be replaced")
+	review.SetCData(">>> Excellent book")
+	doc.IndentTabs()
+
+	checkIndexes(t, &doc.Element)
+
+	// Serialize the document to a string
+	s, err := doc.WriteToString()
+	if err != nil {
+		t.Error("etree: failed to serialize document")
+	}
+
+	// Make sure the serialized XML matches expectation.
+	expected := `<?xml version="1.0" encoding="UTF-8"?>
+<?xml-stylesheet type="text/xsl" href="style.xsl"?>
+<store xmlns:t="urn:books-com:titles">
+	<!Directive>
+	<!--This is a comment-->
+	<book lang="en">
+		<t:title>Great Expectations</t:title>
+		<author>Charles Dickens</author>
+		<review><![CDATA[>>> Excellent book]]></review>
+	</book>
+</store>
+`
+	checkStrEq(t, s, expected)
+
+	// Test the structure of the XML
+	if doc.Root() != store {
+		t.Error("etree: root mismatch")
+	}
+	if len(store.ChildElements()) != 1 || len(store.Child) != 7 {
+		t.Error("etree: incorrect tree structure")
+	}
+	if len(book.ChildElements()) != 3 || len(book.Attr) != 1 || len(book.Child) != 7 {
+		t.Error("etree: incorrect tree structure")
+	}
+	if len(title.ChildElements()) != 0 || len(title.Child) != 1 || len(title.Attr) != 0 {
+		t.Error("etree: incorrect tree structure")
+	}
+	if len(author.ChildElements()) != 0 || len(author.Child) != 1 || len(author.Attr) != 0 {
+		t.Error("etree: incorrect tree structure")
+	}
+	if len(review.ChildElements()) != 0 || len(review.Child) != 1 || len(review.Attr) != 0 {
+		t.Error("etree: incorrect tree structure")
+	}
+	if book.parent != store || store.parent != &doc.Element || doc.parent != nil {
+		t.Error("etree: incorrect tree structure")
+	}
+	if title.parent != book || author.parent != book {
+		t.Error("etree: incorrect tree structure")
+	}
+
+	// Perform some basic queries on the document
+	elements := doc.SelectElements("store")
+	if len(elements) != 1 || elements[0] != store {
+		t.Error("etree: incorrect SelectElements result")
+	}
+	element := doc.SelectElement("store")
+	if element != store {
+		t.Error("etree: incorrect SelectElement result")
+	}
+	elements = store.SelectElements("book")
+	if len(elements) != 1 || elements[0] != book {
+		t.Error("etree: incorrect SelectElements result")
+	}
+	element = store.SelectElement("book")
+	if element != book {
+		t.Error("etree: incorrect SelectElement result")
+	}
+	attr := book.SelectAttr("lang")
+	if attr == nil || attr.Key != "lang" || attr.Value != "en" {
+		t.Error("etree: incorrect SelectAttr result")
+	}
+	if book.SelectAttrValue("lang", "unknown") != "en" {
+		t.Error("etree: incorrect SelectAttrValue result")
+	}
+	if book.SelectAttrValue("t:missing", "unknown") != "unknown" {
+		t.Error("etree: incorrect SelectAttrValue result")
+	}
+	attr = book.RemoveAttr("lang")
+	if attr.Value != "en" {
+		t.Error("etree: incorrect RemoveAttr result")
+	}
+	book.CreateAttr("lang", "de")
+	attr = book.RemoveAttr("lang")
+	if attr.Value != "de" {
+		t.Error("etree: incorrect RemoveAttr result")
+	}
+	element = book.SelectElement("t:title")
+	if element != title || element.Text() != "Great Expectations" || len(element.Attr) != 0 {
+		t.Error("etree: incorrect SelectElement result")
+	}
+	element = book.SelectElement("title")
+	if element != title {
+		t.Error("etree: incorrect SelectElement result")
+	}
+	element = book.SelectElement("p:title")
+	if element != nil {
+		t.Error("etree: incorrect SelectElement result")
+	}
+	element = book.RemoveChildAt(title.Index()).(*Element)
+	if element != title {
+		t.Error("etree: incorrect RemoveElement result")
+	}
+	element = book.SelectElement("title")
+	if element != nil {
+		t.Error("etree: incorrect SelectElement result")
+	}
+	element = book.SelectElement("review")
+	if element != review || element.Text() != ">>> Excellent book" || len(element.Attr) != 0 {
+		t.Error("etree: incorrect SelectElement result")
+	}
+}
+
+func TestDocumentReadNonUTF8Encodings(t *testing.T) {
+	s := `<?xml version="1.0" encoding="ISO-8859-1"?>
+	<store>
+	<book lang="en">
+		<title>Great Expectations</title>
+		<author>Charles Dickens</author>
+	</book>
+</store>`
+
+	doc := NewDocument()
+	doc.ReadSettings.CharsetReader = func(label string, input io.Reader) (io.Reader, error) {
+		return input, nil
+	}
+	err := doc.ReadFromString(s)
+	if err != nil {
+		t.Fatal("etree: incorrect ReadFromString result")
+	}
+}
+
+func TestDocumentReadPermissive(t *testing.T) {
+	s := "<select disabled></select>"
+
+	doc := NewDocument()
+	err := doc.ReadFromString(s)
+	if err == nil {
+		t.Fatal("etree: incorrect ReadFromString result")
+	}
+
+	doc.ReadSettings.Permissive = true
+	err = doc.ReadFromString(s)
+	if err != nil {
+		t.Fatal("etree: incorrect ReadFromString result")
+	}
+}
+
+func TestDocumentReadHTMLEntities(t *testing.T) {
+	s := `<store>
+	<book lang="en">
+		<title>&rarr;&nbsp;Great Expectations</title>
+		<author>Charles Dickens</author>
+	</book>
+</store>`
+
+	doc := NewDocument()
+	err := doc.ReadFromString(s)
+	if err == nil {
+		t.Fatal("etree: incorrect ReadFromString result")
+	}
+
+	doc.ReadSettings.Entity = xml.HTMLEntity
+	err = doc.ReadFromString(s)
+	if err != nil {
+		t.Fatal("etree: incorrect ReadFromString result")
+	}
+}
+
+func TestEscapeCodes(t *testing.T) {
+	cases := []struct {
+		input         string
+		normal        string
+		attrCanonical string
+		textCanonical string
+	}{
+		{
+			"&<>'\"\t\n\r",
+			"<e a=\"&amp;&lt;&gt;&apos;&quot;\t\n\r\">&amp;&lt;&gt;&apos;&quot;\t\n\r</e>",
+			"<e a=\"&amp;&lt;>'&quot;&#x9;&#xA;&#xD;\">&amp;&lt;&gt;&apos;&quot;\t\n\r</e>",
+			"<e a=\"&amp;&lt;&gt;&apos;&quot;\t\n\r\">&amp;&lt;&gt;'\"\t\n&#xD;</e>",
+		},
+		{
+			"\x00\x1f\x08\x09\x0a\x0d",
+			"<e a=\"���\t\n\r\">���\t\n\r</e>",
+			"<e a=\"���&#x9;&#xA;&#xD;\">���\t\n\r</e>",
+			"<e a=\"���\t\n\r\">���\t\n&#xD;</e>",
+		},
+	}
+	for _, c := range cases {
+		doc := NewDocument()
+
+		e := doc.CreateElement("e")
+		e.SetText(c.input)
+		e.CreateAttr("a", c.input)
+
+		doc.WriteSettings.CanonicalText = false
+		doc.WriteSettings.CanonicalAttrVal = false
+		s, err := doc.WriteToString()
+		if err != nil {
+			t.Error("etree: Escape test produced inocrrect result.")
+		}
+		checkStrEq(t, s, c.normal)
+
+		doc.WriteSettings.CanonicalText = false
+		doc.WriteSettings.CanonicalAttrVal = true
+		s, err = doc.WriteToString()
+		if err != nil {
+			t.Error("etree: Escape test produced inocrrect result.")
+		}
+		checkStrEq(t, s, c.attrCanonical)
+
+		doc.WriteSettings.CanonicalText = true
+		doc.WriteSettings.CanonicalAttrVal = false
+		s, err = doc.WriteToString()
+		if err != nil {
+			t.Error("etree: Escape test produced inocrrect result.")
+		}
+		checkStrEq(t, s, c.textCanonical)
+	}
+}
+
+func TestCanonical(t *testing.T) {
+	BOM := "\xef\xbb\xbf"
+
+	doc := NewDocument()
+	doc.WriteSettings.CanonicalEndTags = true
+	doc.WriteSettings.CanonicalText = true
+	doc.WriteSettings.CanonicalAttrVal = true
+	doc.CreateCharData(BOM)
+	doc.CreateProcInst("xml-stylesheet", `type="text/xsl" href="style.xsl"`)
+
+	people := doc.CreateElement("People")
+	people.CreateComment("These are all known people")
+
+	jon := people.CreateElement("Person")
+	jon.CreateAttr("name", "Jon O'Reilly")
+	jon.SetText("\r<'\">&\u0004\u0005\u001f�")
+
+	sally := people.CreateElement("Person")
+	sally.CreateAttr("name", "Sally")
+	sally.CreateAttr("escape", "\r\n\t<'\">&")
+
+	doc.Indent(2)
+	s, err := doc.WriteToString()
+	if err != nil {
+		t.Error("etree: WriteSettings WriteTo produced incorrect result.")
+	}
+
+	expected := BOM + `<?xml-stylesheet type="text/xsl" href="style.xsl"?>
+<People>
+  <!--These are all known people-->
+  <Person name="Jon O'Reilly">&#xD;&lt;'"&gt;&amp;����</Person>
+  <Person name="Sally" escape="&#xD;&#xA;&#x9;&lt;'&quot;>&amp;"></Person>
+</People>
+`
+	checkStrEq(t, s, expected)
+}
+
+func TestCopy(t *testing.T) {
+	s := `<store>
+	<book lang="en">
+		<title>Great Expectations</title>
+		<author>Charles Dickens</author>
+	</book>
+</store>`
+
+	doc := newDocumentFromString(t, s)
+
+	s1, err := doc.WriteToString()
+	if err != nil {
+		t.Error("etree: incorrect WriteToString result")
+	}
+
+	doc2 := doc.Copy()
+	checkIndexes(t, &doc2.Element)
+	s2, err := doc2.WriteToString()
+	if err != nil {
+		t.Error("etree: incorrect Copy result")
+	}
+
+	if s1 != s2 {
+		t.Error("etree: mismatched Copy result")
+		t.Error("wanted:\n" + s1)
+		t.Error("got:\n" + s2)
+	}
+
+	e1 := doc.FindElement("./store/book/title")
+	e2 := doc2.FindElement("./store/book/title")
+	if e1 == nil || e2 == nil {
+		t.Error("etree: incorrect FindElement result")
+	}
+	if e1 == e2 {
+		t.Error("etree: incorrect FindElement result")
+	}
+
+	e1.parent.RemoveChildAt(e1.Index())
+	s1, _ = doc.WriteToString()
+	s2, _ = doc2.WriteToString()
+	if s1 == s2 {
+		t.Error("etree: incorrect result after RemoveElement")
+	}
+}
+
+func TestGetPath(t *testing.T) {
+	s := `<a>
+ <b1>
+  <c1>
+   <d1/>
+   <d1a/>
+  </c1>
+ </b1>
+ <b2>
+  <c2>
+   <d2/>
+  </c2>
+ </b2>
+</a>`
+
+	doc := newDocumentFromString(t, s)
+
+	cases := []struct {
+		from    string
+		to      string
+		relpath string
+		topath  string
+	}{
+		{"a", ".", "..", "/"},
+		{".", "a", "./a", "/a"},
+		{"a/b1/c1/d1", ".", "../../../..", "/"},
+		{".", "a/b1/c1/d1", "./a/b1/c1/d1", "/a/b1/c1/d1"},
+		{"a", "a", ".", "/a"},
+		{"a/b1", "a/b1/c1", "./c1", "/a/b1/c1"},
+		{"a/b1/c1", "a/b1", "..", "/a/b1"},
+		{"a/b1/c1", "a/b1/c1", ".", "/a/b1/c1"},
+		{"a", "a/b1", "./b1", "/a/b1"},
+		{"a/b1", "a", "..", "/a"},
+		{"a", "a/b1/c1", "./b1/c1", "/a/b1/c1"},
+		{"a/b1/c1", "a", "../..", "/a"},
+		{"a/b1/c1/d1", "a", "../../..", "/a"},
+		{"a", "a/b1/c1/d1", "./b1/c1/d1", "/a/b1/c1/d1"},
+		{"a/b1", "a/b2", "../b2", "/a/b2"},
+		{"a/b2", "a/b1", "../b1", "/a/b1"},
+		{"a/b1/c1/d1", "a/b2/c2/d2", "../../../b2/c2/d2", "/a/b2/c2/d2"},
+		{"a/b2/c2/d2", "a/b1/c1/d1", "../../../b1/c1/d1", "/a/b1/c1/d1"},
+		{"a/b1/c1/d1", "a/b1/c1/d1a", "../d1a", "/a/b1/c1/d1a"},
+	}
+
+	for _, c := range cases {
+		fe := doc.FindElement(c.from)
+		te := doc.FindElement(c.to)
+
+		rp := te.GetRelativePath(fe)
+		if rp != c.relpath {
+			t.Errorf("GetRelativePath from '%s' to '%s'. Expected '%s', got '%s'.\n", c.from, c.to, c.relpath, rp)
+		}
+
+		p := te.GetPath()
+		if p != c.topath {
+			t.Errorf("GetPath for '%s'. Expected '%s', got '%s'.\n", c.to, c.topath, p)
+		}
+	}
+}
+
+func TestInsertChild(t *testing.T) {
+	s := `<book lang="en">
+  <t:title>Great Expectations</t:title>
+  <author>Charles Dickens</author>
+</book>
+`
+
+	doc := newDocumentFromString(t, s)
+
+	year := NewElement("year")
+	year.SetText("1861")
+
+	book := doc.FindElement("//book")
+	book.InsertChildAt(book.SelectElement("t:title").Index(), year)
+
+	expected1 := `<book lang="en">
+  <year>1861</year>
+  <t:title>Great Expectations</t:title>
+  <author>Charles Dickens</author>
+</book>
+`
+	doc.Indent(2)
+	s1, _ := doc.WriteToString()
+	checkStrEq(t, s1, expected1)
+
+	book.RemoveChildAt(year.Index())
+	book.InsertChildAt(book.SelectElement("author").Index(), year)
+
+	expected2 := `<book lang="en">
+  <t:title>Great Expectations</t:title>
+  <year>1861</year>
+  <author>Charles Dickens</author>
+</book>
+`
+	doc.Indent(2)
+	s2, _ := doc.WriteToString()
+	checkStrEq(t, s2, expected2)
+
+	book.RemoveChildAt(year.Index())
+	book.InsertChildAt(len(book.Child), year)
+
+	expected3 := `<book lang="en">
+  <t:title>Great Expectations</t:title>
+  <author>Charles Dickens</author>
+  <year>1861</year>
+</book>
+`
+	doc.Indent(2)
+	s3, _ := doc.WriteToString()
+	checkStrEq(t, s3, expected3)
+
+	book.RemoveChildAt(year.Index())
+	book.InsertChildAt(999, year)
+
+	expected4 := `<book lang="en">
+  <t:title>Great Expectations</t:title>
+  <author>Charles Dickens</author>
+  <year>1861</year>
+</book>
+`
+	doc.Indent(2)
+	s4, _ := doc.WriteToString()
+	checkStrEq(t, s4, expected4)
+}
+
+func TestCdata(t *testing.T) {
+	var tests = []struct {
+		in, out string
+	}{
+		{`<tag>1234567</tag>`, "1234567"},
+		{`<tag><![CDATA[1234567]]></tag>`, "1234567"},
+		{`<tag>1<![CDATA[2]]>3<![CDATA[4]]>5<![CDATA[6]]>7</tag>`, "1234567"},
+		{`<tag>1<![CDATA[2]]>3<inner>4</inner>5<![CDATA[6]]>7</tag>`, "123"},
+		{`<tag>1<inner>4</inner>5<![CDATA[6]]>7</tag>`, "1"},
+		{`<tag><![CDATA[1]]><inner>4</inner>5<![CDATA[6]]>7</tag>`, "1"},
+	}
+
+	for _, test := range tests {
+		doc := NewDocument()
+		err := doc.ReadFromString(test.in)
+		if err != nil {
+			t.Fatal("etree ReadFromString: " + err.Error())
+		}
+
+		tag := doc.FindElement("tag")
+		if tag.Text() != test.out {
+			t.Fatalf("etree invalid cdata. Expected: %v. Got: %v\n", test.out, tag.Text())
+		}
+	}
+}
+
+func TestAddChild(t *testing.T) {
+	s := `<book lang="en">
+  <t:title>Great Expectations</t:title>
+  <author>Charles Dickens</author>
+</book>
+`
+	doc1 := newDocumentFromString(t, s)
+
+	doc2 := NewDocument()
+	root := doc2.CreateElement("root")
+
+	for _, e := range doc1.FindElements("//book/*") {
+		root.AddChild(e)
+	}
+
+	expected1 := `<book lang="en"/>
+`
+	doc1.Indent(2)
+	s1, _ := doc1.WriteToString()
+	checkStrEq(t, s1, expected1)
+
+	expected2 := `<root>
+  <t:title>Great Expectations</t:title>
+  <author>Charles Dickens</author>
+</root>
+`
+	doc2.Indent(2)
+	s2, _ := doc2.WriteToString()
+	checkStrEq(t, s2, expected2)
+}
+
+func TestSetRoot(t *testing.T) {
+	s := `<?test a="wow"?>
+<book>
+  <title>Great Expectations</title>
+  <author>Charles Dickens</author>
+</book>
+`
+	doc := newDocumentFromString(t, s)
+
+	origroot := doc.Root()
+	if origroot.Parent() != &doc.Element {
+		t.Error("Root incorrect")
+	}
+
+	newroot := NewElement("root")
+	doc.SetRoot(newroot)
+
+	if doc.Root() != newroot {
+		t.Error("doc.Root() != newroot")
+	}
+	if origroot.Parent() != nil {
+		t.Error("origroot.Parent() != nil")
+	}
+
+	expected1 := `<?test a="wow"?>
+<root/>
+`
+	doc.Indent(2)
+	s1, _ := doc.WriteToString()
+	checkStrEq(t, s1, expected1)
+
+	doc.SetRoot(origroot)
+	doc.Indent(2)
+	expected2 := s
+	s2, _ := doc.WriteToString()
+	checkStrEq(t, s2, expected2)
+
+	doc2 := NewDocument()
+	doc2.CreateProcInst("test", `a="wow"`)
+	doc2.SetRoot(NewElement("root"))
+	doc2.Indent(2)
+	expected3 := expected1
+	s3, _ := doc2.WriteToString()
+	checkStrEq(t, s3, expected3)
+
+	doc2.SetRoot(doc.Root())
+	doc2.Indent(2)
+	expected4 := s
+	s4, _ := doc2.WriteToString()
+	checkStrEq(t, s4, expected4)
+
+	expected5 := `<?test a="wow"?>
+`
+	doc.Indent(2)
+	s5, _ := doc.WriteToString()
+	checkStrEq(t, s5, expected5)
+}
+
+func TestSortAttrs(t *testing.T) {
+	s := `<el foo='5' Foo='2' aaa='4' สวัสดี='7' AAA='1' a01='3' z='6' a:ZZZ='9' a:AAA='8'/>`
+	doc := newDocumentFromString(t, s)
+	doc.Root().SortAttrs()
+	doc.Indent(2)
+	out, _ := doc.WriteToString()
+	checkStrEq(t, out, `<el AAA="1" Foo="2" a01="3" aaa="4" foo="5" z="6" สวัสดี="7" a:AAA="8" a:ZZZ="9"/>`+"\n")
+}
+
+func TestCharsetReaderEncoding(t *testing.T) {
+	cases := []string{
+		`<?xml version="1.0" encoding="ISO-8859-1"?><foo></foo>`,
+		`<?xml version="1.0" encoding="UTF-8"?><foo></foo>`,
+		`<?xml version="1.0" encoding="US-ASCII"?><foo></foo>`,
+	}
+
+	for _, c := range cases {
+		doc := NewDocument()
+		if err := doc.ReadFromBytes([]byte(c)); err != nil {
+			t.Error(err)
+		}
+	}
+}
+
+func TestCharData(t *testing.T) {
+	doc := NewDocument()
+	root := doc.CreateElement("root")
+	root.CreateCharData("This ")
+	root.CreateCData("is ")
+	e1 := NewText("a ")
+	e2 := NewCData("text ")
+	root.AddChild(e1)
+	root.AddChild(e2)
+	root.CreateCharData("Element!!")
+
+	s, err := doc.WriteToString()
+	if err != nil {
+		t.Error("etree: failed to serialize document")
+	}
+
+	checkStrEq(t, s, `<root>This <![CDATA[is ]]>a <![CDATA[text ]]>Element!!</root>`)
+
+	// Check we can parse the output
+	err = doc.ReadFromString(s)
+	if err != nil {
+		t.Fatal("etree: incorrect ReadFromString result")
+	}
+	if doc.Root().Text() != "This is a text Element!!" {
+		t.Error("etree: invalid text")
+	}
+}
+
+func TestIndentSettings(t *testing.T) {
+	doc := NewDocument()
+	root := doc.CreateElement("root")
+	ch1 := root.CreateElement("child1")
+	ch1.CreateElement("child2")
+
+	// First test with NoIndent.
+	doc.Indent(NoIndent)
+	s, err := doc.WriteToString()
+	if err != nil {
+		t.Error("etree: failed to serialize document")
+	}
+	expected := "<root><child1><child2/></child1></root>"
+	checkStrEq(t, s, expected)
+
+	// Run all indent test cases.
+	tests := []struct {
+		useTabs, useCRLF bool
+		ws, nl           string
+	}{
+		{false, false, " ", "\n"},
+		{false, true, " ", "\r\n"},
+		{true, false, "\t", "\n"},
+		{true, true, "\t", "\r\n"},
+	}
+
+	for _, test := range tests {
+		doc.WriteSettings.UseCRLF = test.useCRLF
+		if test.useTabs {
+			doc.IndentTabs()
+			s, err := doc.WriteToString()
+			if err != nil {
+				t.Error("etree: failed to serialize document")
+			}
+			tab := test.ws
+			expected := "<root>" + test.nl + tab + "<child1>" + test.nl +
+				tab + tab + "<child2/>" + test.nl + tab +
+				"</child1>" + test.nl + "</root>" + test.nl
+			checkStrEq(t, s, expected)
+		} else {
+			for i := 0; i < 256; i++ {
+				doc.Indent(i)
+				s, err := doc.WriteToString()
+				if err != nil {
+					t.Error("etree: failed to serialize document")
+				}
+				tab := strings.Repeat(test.ws, i)
+				expected := "<root>" + test.nl + tab + "<child1>" + test.nl +
+					tab + tab + "<child2/>" + test.nl + tab +
+					"</child1>" + test.nl + "</root>" + test.nl
+				checkStrEq(t, s, expected)
+			}
+		}
+	}
+}
+
+func TestTokenIndexing(t *testing.T) {
+	s := `<?xml version="1.0" encoding="UTF-8"?>
+<?xml-stylesheet type="text/xsl" href="style.xsl"?>
+<store xmlns:t="urn:books-com:titles">
+	<!Directive>
+	<!--This is a comment-->
+	<book lang="en">
+		<t:title>Great Expectations</t:title>
+		<author>Charles Dickens</author>
+		<review/>
+	</book>
+</store>`
+
+	doc := newDocumentFromString(t, s)
+	review := doc.FindElement("/store/book/review")
+	review.SetText("Excellent")
+
+	checkIndexes(t, &doc.Element)
+
+	doc.Indent(4)
+	checkIndexes(t, &doc.Element)
+
+	doc.Indent(NoIndent)
+	checkIndexes(t, &doc.Element)
+
+	e := NewElement("foo")
+	store := doc.SelectElement("store")
+	store.InsertChildAt(0, e)
+	checkIndexes(t, &doc.Element)
+
+	store.RemoveChildAt(0)
+	checkIndexes(t, &doc.Element)
+}
+
+func TestSetText(t *testing.T) {
+	doc := NewDocument()
+	root := doc.CreateElement("root")
+
+	checkDocEq(t, doc, `<root/>`)
+	checkStrEq(t, root.Text(), "")
+	checkIntEq(t, len(root.Child), 0)
+
+	root.SetText("foo")
+	checkDocEq(t, doc, `<root>foo</root>`)
+	checkStrEq(t, root.Text(), "foo")
+	checkIntEq(t, len(root.Child), 1)
+
+	root.SetText("bar")
+	checkDocEq(t, doc, `<root>bar</root>`)
+	checkStrEq(t, root.Text(), "bar")
+	checkIntEq(t, len(root.Child), 1)
+
+	root.CreateCData("cdata")
+	checkDocEq(t, doc, `<root>bar<![CDATA[cdata]]></root>`)
+	checkStrEq(t, root.Text(), "barcdata")
+	checkIntEq(t, len(root.Child), 2)
+
+	root.SetText("qux")
+	checkDocEq(t, doc, `<root>qux</root>`)
+	checkStrEq(t, root.Text(), "qux")
+	checkIntEq(t, len(root.Child), 1)
+
+	root.CreateCData("cdata")
+	checkDocEq(t, doc, `<root>qux<![CDATA[cdata]]></root>`)
+	checkStrEq(t, root.Text(), "quxcdata")
+	checkIntEq(t, len(root.Child), 2)
+
+	root.SetCData("baz")
+	checkDocEq(t, doc, `<root><![CDATA[baz]]></root>`)
+	checkStrEq(t, root.Text(), "baz")
+	checkIntEq(t, len(root.Child), 1)
+
+	root.CreateText("corge")
+	root.CreateCData("grault")
+	root.CreateText("waldo")
+	root.CreateCData("fred")
+	root.CreateElement("child")
+	checkDocEq(t, doc, `<root><![CDATA[baz]]>corge<![CDATA[grault]]>waldo<![CDATA[fred]]><child/></root>`)
+	checkStrEq(t, root.Text(), "bazcorgegraultwaldofred")
+	checkIntEq(t, len(root.Child), 6)
+
+	root.SetText("plugh")
+	checkDocEq(t, doc, `<root>plugh<child/></root>`)
+	checkStrEq(t, root.Text(), "plugh")
+	checkIntEq(t, len(root.Child), 2)
+
+	root.SetText("")
+	checkDocEq(t, doc, `<root><child/></root>`)
+	checkStrEq(t, root.Text(), "")
+	checkIntEq(t, len(root.Child), 1)
+
+	root.SetText("")
+	checkDocEq(t, doc, `<root><child/></root>`)
+	checkStrEq(t, root.Text(), "")
+	checkIntEq(t, len(root.Child), 1)
+
+	root.RemoveChildAt(0)
+	root.CreateText("corge")
+	root.CreateCData("grault")
+	root.CreateText("waldo")
+	root.CreateCData("fred")
+	root.CreateElement("child")
+	checkDocEq(t, doc, `<root>corge<![CDATA[grault]]>waldo<![CDATA[fred]]><child/></root>`)
+	checkStrEq(t, root.Text(), "corgegraultwaldofred")
+	checkIntEq(t, len(root.Child), 5)
+
+	root.SetText("")
+	checkDocEq(t, doc, `<root><child/></root>`)
+	checkStrEq(t, root.Text(), "")
+	checkIntEq(t, len(root.Child), 1)
+}
+
+func TestSetTail(t *testing.T) {
+	doc := NewDocument()
+	root := doc.CreateElement("root")
+	child := root.CreateElement("child")
+	root.CreateText("\n\t")
+	child.SetText("foo")
+	checkDocEq(t, doc, "<root><child>foo</child>\n\t</root>")
+	checkStrEq(t, child.Tail(), "\n\t")
+	checkIntEq(t, len(root.Child), 2)
+	checkIntEq(t, len(child.Child), 1)
+
+	root.CreateCData("    ")
+	checkDocEq(t, doc, "<root><child>foo</child>\n\t<![CDATA[    ]]></root>")
+	checkStrEq(t, child.Tail(), "\n\t    ")
+	checkIntEq(t, len(root.Child), 3)
+	checkIntEq(t, len(child.Child), 1)
+
+	child.SetTail("")
+	checkDocEq(t, doc, "<root><child>foo</child></root>")
+	checkStrEq(t, child.Tail(), "")
+	checkIntEq(t, len(root.Child), 1)
+	checkIntEq(t, len(child.Child), 1)
+
+	child.SetTail("\t\t\t")
+	checkDocEq(t, doc, "<root><child>foo</child>\t\t\t</root>")
+	checkStrEq(t, child.Tail(), "\t\t\t")
+	checkIntEq(t, len(root.Child), 2)
+	checkIntEq(t, len(child.Child), 1)
+
+	child.SetTail("\t\n\n\t")
+	checkDocEq(t, doc, "<root><child>foo</child>\t\n\n\t</root>")
+	checkStrEq(t, child.Tail(), "\t\n\n\t")
+	checkIntEq(t, len(root.Child), 2)
+	checkIntEq(t, len(child.Child), 1)
+
+	child.SetTail("")
+	checkDocEq(t, doc, "<root><child>foo</child></root>")
+	checkStrEq(t, child.Tail(), "")
+	checkIntEq(t, len(root.Child), 1)
+	checkIntEq(t, len(child.Child), 1)
+}
+
+func TestAttrParent(t *testing.T) {
+	doc := NewDocument()
+	root := doc.CreateElement("root")
+	attr1 := root.CreateAttr("bar", "1")
+	attr2 := root.CreateAttr("qux", "2")
+
+	checkIntEq(t, len(root.Attr), 2)
+	checkElementEq(t, attr1.Element(), root)
+	checkElementEq(t, attr2.Element(), root)
+
+	attr1 = root.RemoveAttr("bar")
+	attr2 = root.RemoveAttr("qux")
+	checkElementEq(t, attr1.Element(), nil)
+	checkElementEq(t, attr2.Element(), nil)
+
+	s := `<root a="1" b="2" c="3" d="4"/>`
+	err := doc.ReadFromString(s)
+	if err != nil {
+		t.Error("etree: failed to parse document")
+	}
+
+	root = doc.SelectElement("root")
+	for i := range root.Attr {
+		checkElementEq(t, root.Attr[i].Element(), root)
+	}
+}
+
+func TestDefaultNamespaceURI(t *testing.T) {
+	s := `
+<root xmlns="https://root.example.com" xmlns:attrib="https://attrib.example.com" attrib:a="foo" b="bar">
+	<child1 xmlns="https://child.example.com" attrib:a="foo">
+		<grandchild1 xmlns="https://grandchild.example.com" a="foo">
+		</grandchild1>
+		<grandchild2 a="foo">
+			<greatgrandchild1 attrib:a="foo"/>
+		</grandchild2>
+	</child1>
+	<child2 a="foo"/>
+</root>`
+
+	doc := newDocumentFromString(t, s)
+	root := doc.SelectElement("root")
+	child1 := root.SelectElement("child1")
+	child2 := root.SelectElement("child2")
+	grandchild1 := child1.SelectElement("grandchild1")
+	grandchild2 := child1.SelectElement("grandchild2")
+	greatgrandchild1 := grandchild2.SelectElement("greatgrandchild1")
+
+	checkStrEq(t, doc.NamespaceURI(), "")
+	checkStrEq(t, root.NamespaceURI(), "https://root.example.com")
+	checkStrEq(t, child1.NamespaceURI(), "https://child.example.com")
+	checkStrEq(t, child2.NamespaceURI(), "https://root.example.com")
+	checkStrEq(t, grandchild1.NamespaceURI(), "https://grandchild.example.com")
+	checkStrEq(t, grandchild2.NamespaceURI(), "https://child.example.com")
+	checkStrEq(t, greatgrandchild1.NamespaceURI(), "https://child.example.com")
+
+	checkStrEq(t, root.Attr[0].NamespaceURI(), "")
+	checkStrEq(t, root.Attr[1].NamespaceURI(), "")
+	checkStrEq(t, root.Attr[2].NamespaceURI(), "https://attrib.example.com")
+	checkStrEq(t, root.Attr[3].NamespaceURI(), "")
+	checkStrEq(t, child1.Attr[0].NamespaceURI(), "")
+	checkStrEq(t, child1.Attr[1].NamespaceURI(), "https://attrib.example.com")
+	checkStrEq(t, child2.Attr[0].NamespaceURI(), "")
+	checkStrEq(t, grandchild1.Attr[0].NamespaceURI(), "")
+	checkStrEq(t, grandchild1.Attr[1].NamespaceURI(), "")
+	checkStrEq(t, grandchild2.Attr[0].NamespaceURI(), "")
+	checkStrEq(t, greatgrandchild1.Attr[0].NamespaceURI(), "https://attrib.example.com")
+
+	f := doc.FindElements("//*[namespace-uri()='https://root.example.com']")
+	if len(f) != 2 || f[0] != root || f[1] != child2 {
+		t.Error("etree: failed namespace-uri test")
+	}
+
+	f = doc.FindElements("//*[namespace-uri()='https://child.example.com']")
+	if len(f) != 3 || f[0] != child1 || f[1] != grandchild2 || f[2] != greatgrandchild1 {
+		t.Error("etree: failed namespace-uri test")
+	}
+
+	f = doc.FindElements("//*[namespace-uri()='https://grandchild.example.com']")
+	if len(f) != 1 || f[0] != grandchild1 {
+		t.Error("etree: failed namespace-uri test")
+	}
+
+	f = doc.FindElements("//*[namespace-uri()='']")
+	if len(f) != 0 {
+		t.Error("etree: failed namespace-uri test")
+	}
+
+	f = doc.FindElements("//*[namespace-uri()='foo']")
+	if len(f) != 0 {
+		t.Error("etree: failed namespace-uri test")
+	}
+}
+
+func TestLocalNamespaceURI(t *testing.T) {
+	s := `
+<a:root xmlns:a="https://root.example.com">
+	<b:child1 xmlns:b="https://child.example.com">
+		<c:grandchild1 xmlns:c="https://grandchild.example.com"/>
+		<b:grandchild2>
+			<a:greatgrandchild1/>
+		</b:grandchild2>
+		<a:grandchild3/>
+		<grandchild4/>
+	</b:child1>
+	<a:child2>
+	</a:child2>
+	<child3>
+	</child3>
+</a:root>`
+
+	doc := newDocumentFromString(t, s)
+	root := doc.SelectElement("root")
+	child1 := root.SelectElement("child1")
+	child2 := root.SelectElement("child2")
+	child3 := root.SelectElement("child3")
+	grandchild1 := child1.SelectElement("grandchild1")
+	grandchild2 := child1.SelectElement("grandchild2")
+	grandchild3 := child1.SelectElement("grandchild3")
+	grandchild4 := child1.SelectElement("grandchild4")
+	greatgrandchild1 := grandchild2.SelectElement("greatgrandchild1")
+
+	checkStrEq(t, doc.NamespaceURI(), "")
+	checkStrEq(t, root.NamespaceURI(), "https://root.example.com")
+	checkStrEq(t, child1.NamespaceURI(), "https://child.example.com")
+	checkStrEq(t, child2.NamespaceURI(), "https://root.example.com")
+	checkStrEq(t, child3.NamespaceURI(), "")
+	checkStrEq(t, grandchild1.NamespaceURI(), "https://grandchild.example.com")
+	checkStrEq(t, grandchild2.NamespaceURI(), "https://child.example.com")
+	checkStrEq(t, grandchild3.NamespaceURI(), "https://root.example.com")
+	checkStrEq(t, grandchild4.NamespaceURI(), "")
+	checkStrEq(t, greatgrandchild1.NamespaceURI(), "https://root.example.com")
+
+	f := doc.FindElements("//*[namespace-uri()='https://root.example.com']")
+	if len(f) != 4 || f[0] != root || f[1] != child2 || f[2] != grandchild3 || f[3] != greatgrandchild1 {
+		t.Error("etree: failed namespace-uri test")
+	}
+
+	f = doc.FindElements("//*[namespace-uri()='https://child.example.com']")
+	if len(f) != 2 || f[0] != child1 || f[1] != grandchild2 {
+		t.Error("etree: failed namespace-uri test")
+	}
+
+	f = doc.FindElements("//*[namespace-uri()='https://grandchild.example.com']")
+	if len(f) != 1 || f[0] != grandchild1 {
+		t.Error("etree: failed namespace-uri test")
+	}
+
+	f = doc.FindElements("//*[namespace-uri()='']")
+	if len(f) != 2 || f[0] != child3 || f[1] != grandchild4 {
+		t.Error("etree: failed namespace-uri test")
+	}
+
+	f = doc.FindElements("//*[namespace-uri()='foo']")
+	if len(f) != 0 {
+		t.Error("etree: failed namespace-uri test")
+	}
+}
+
+func TestWhitespace(t *testing.T) {
+	s := "<root>\n\t<child>\n\t\t<grandchild> x</grandchild>\n    </child>\n</root>"
+
+	doc := newDocumentFromString(t, s)
+	root := doc.Root()
+	checkIntEq(t, len(root.Child), 3)
+
+	cd := root.Child[0].(*CharData)
+	checkBoolEq(t, cd.IsWhitespace(), true)
+	checkStrBinaryEq(t, cd.Data, "\n\t")
+
+	cd = root.Child[2].(*CharData)
+	checkBoolEq(t, cd.IsWhitespace(), true)
+	checkStrBinaryEq(t, cd.Data, "\n")
+
+	child := root.SelectElement("child")
+	checkIntEq(t, len(child.Child), 3)
+
+	cd = child.Child[0].(*CharData)
+	checkBoolEq(t, cd.IsWhitespace(), true)
+	checkStrBinaryEq(t, cd.Data, "\n\t\t")
+
+	cd = child.Child[2].(*CharData)
+	checkBoolEq(t, cd.IsWhitespace(), true)
+	checkStrBinaryEq(t, cd.Data, "\n    ")
+
+	grandchild := child.SelectElement("grandchild")
+	checkIntEq(t, len(grandchild.Child), 1)
+
+	cd = grandchild.Child[0].(*CharData)
+	checkBoolEq(t, cd.IsWhitespace(), false)
+
+	cd.SetData(" ")
+	checkBoolEq(t, cd.IsWhitespace(), true)
+
+	cd.SetData("        x")
+	checkBoolEq(t, cd.IsWhitespace(), false)
+
+	cd.SetData("\t\n\r    ")
+	checkBoolEq(t, cd.IsWhitespace(), true)
+
+	cd.SetData("\uFFFD")
+	checkBoolEq(t, cd.IsWhitespace(), false)
+
+	cd.SetData("")
+	checkBoolEq(t, cd.IsWhitespace(), true)
+}
diff --git a/example_test.go b/example_test.go
new file mode 100644
index 0000000..45fc4ca
--- /dev/null
+++ b/example_test.go
@@ -0,0 +1,69 @@
+// Copyright 2015-2019 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package etree
+
+import "os"
+
+// Create an etree Document, add XML entities to it, and serialize it
+// to stdout.
+func ExampleDocument_creating() {
+	doc := NewDocument()
+	doc.CreateProcInst("xml", `version="1.0" encoding="UTF-8"`)
+	doc.CreateProcInst("xml-stylesheet", `type="text/xsl" href="style.xsl"`)
+
+	people := doc.CreateElement("People")
+	people.CreateComment("These are all known people")
+
+	jon := people.CreateElement("Person")
+	jon.CreateAttr("name", "Jon O'Reilly")
+
+	sally := people.CreateElement("Person")
+	sally.CreateAttr("name", "Sally")
+
+	doc.Indent(2)
+	doc.WriteTo(os.Stdout)
+	// Output:
+	// <?xml version="1.0" encoding="UTF-8"?>
+	// <?xml-stylesheet type="text/xsl" href="style.xsl"?>
+	// <People>
+	//   <!--These are all known people-->
+	//   <Person name="Jon O&apos;Reilly"/>
+	//   <Person name="Sally"/>
+	// </People>
+}
+
+func ExampleDocument_reading() {
+	doc := NewDocument()
+	if err := doc.ReadFromFile("document.xml"); err != nil {
+		panic(err)
+	}
+}
+
+func ExamplePath() {
+	xml := `
+<bookstore>
+	<book>
+		<title>Great Expectations</title>
+		<author>Charles Dickens</author>
+	</book>
+	<book>
+		<title>Ulysses</title>
+		<author>James Joyce</author>
+	</book>
+</bookstore>`
+
+	doc := NewDocument()
+	doc.ReadFromString(xml)
+	for _, e := range doc.FindElements(".//book[author='Charles Dickens']") {
+		doc := NewDocumentWithRoot(e.Copy())
+		doc.Indent(2)
+		doc.WriteTo(os.Stdout)
+	}
+	// Output:
+	// <book>
+	//   <title>Great Expectations</title>
+	//   <author>Charles Dickens</author>
+	// </book>
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..2a269fa
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/beevik/etree
+
+go 1.12
diff --git a/helpers.go b/helpers.go
new file mode 100644
index 0000000..825e14e
--- /dev/null
+++ b/helpers.go
@@ -0,0 +1,276 @@
+// Copyright 2015-2019 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package etree
+
+import (
+	"bufio"
+	"io"
+	"strings"
+	"unicode/utf8"
+)
+
+// A simple stack
+type stack struct {
+	data []interface{}
+}
+
+func (s *stack) empty() bool {
+	return len(s.data) == 0
+}
+
+func (s *stack) push(value interface{}) {
+	s.data = append(s.data, value)
+}
+
+func (s *stack) pop() interface{} {
+	value := s.data[len(s.data)-1]
+	s.data[len(s.data)-1] = nil
+	s.data = s.data[:len(s.data)-1]
+	return value
+}
+
+func (s *stack) peek() interface{} {
+	return s.data[len(s.data)-1]
+}
+
+// A fifo is a simple first-in-first-out queue.
+type fifo struct {
+	data       []interface{}
+	head, tail int
+}
+
+func (f *fifo) add(value interface{}) {
+	if f.len()+1 >= len(f.data) {
+		f.grow()
+	}
+	f.data[f.tail] = value
+	if f.tail++; f.tail == len(f.data) {
+		f.tail = 0
+	}
+}
+
+func (f *fifo) remove() interface{} {
+	value := f.data[f.head]
+	f.data[f.head] = nil
+	if f.head++; f.head == len(f.data) {
+		f.head = 0
+	}
+	return value
+}
+
+func (f *fifo) len() int {
+	if f.tail >= f.head {
+		return f.tail - f.head
+	}
+	return len(f.data) - f.head + f.tail
+}
+
+func (f *fifo) grow() {
+	c := len(f.data) * 2
+	if c == 0 {
+		c = 4
+	}
+	buf, count := make([]interface{}, c), f.len()
+	if f.tail >= f.head {
+		copy(buf[0:count], f.data[f.head:f.tail])
+	} else {
+		hindex := len(f.data) - f.head
+		copy(buf[0:hindex], f.data[f.head:])
+		copy(buf[hindex:count], f.data[:f.tail])
+	}
+	f.data, f.head, f.tail = buf, 0, count
+}
+
+// countReader implements a proxy reader that counts the number of
+// bytes read from its encapsulated reader.
+type countReader struct {
+	r     io.Reader
+	bytes int64
+}
+
+func newCountReader(r io.Reader) *countReader {
+	return &countReader{r: r}
+}
+
+func (cr *countReader) Read(p []byte) (n int, err error) {
+	b, err := cr.r.Read(p)
+	cr.bytes += int64(b)
+	return b, err
+}
+
+// countWriter implements a proxy writer that counts the number of
+// bytes written by its encapsulated writer.
+type countWriter struct {
+	w     io.Writer
+	bytes int64
+}
+
+func newCountWriter(w io.Writer) *countWriter {
+	return &countWriter{w: w}
+}
+
+func (cw *countWriter) Write(p []byte) (n int, err error) {
+	b, err := cw.w.Write(p)
+	cw.bytes += int64(b)
+	return b, err
+}
+
+// isWhitespace returns true if the byte slice contains only
+// whitespace characters.
+func isWhitespace(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if c := s[i]; c != ' ' && c != '\t' && c != '\n' && c != '\r' {
+			return false
+		}
+	}
+	return true
+}
+
+// spaceMatch returns true if namespace a is the empty string
+// or if namespace a equals namespace b.
+func spaceMatch(a, b string) bool {
+	switch {
+	case a == "":
+		return true
+	default:
+		return a == b
+	}
+}
+
+// spaceDecompose breaks a namespace:tag identifier at the ':'
+// and returns the two parts.
+func spaceDecompose(str string) (space, key string) {
+	colon := strings.IndexByte(str, ':')
+	if colon == -1 {
+		return "", str
+	}
+	return str[:colon], str[colon+1:]
+}
+
+// Strings used by indentCRLF and indentLF
+const (
+	indentSpaces = "\r\n                                                                "
+	indentTabs   = "\r\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"
+)
+
+// indentCRLF returns a CRLF newline followed by n copies of the first
+// non-CRLF character in the source string.
+func indentCRLF(n int, source string) string {
+	switch {
+	case n < 0:
+		return source[:2]
+	case n < len(source)-1:
+		return source[:n+2]
+	default:
+		return source + strings.Repeat(source[2:3], n-len(source)+2)
+	}
+}
+
+// indentLF returns a LF newline followed by n copies of the first non-LF
+// character in the source string.
+func indentLF(n int, source string) string {
+	switch {
+	case n < 0:
+		return source[1:2]
+	case n < len(source)-1:
+		return source[1 : n+2]
+	default:
+		return source[1:] + strings.Repeat(source[2:3], n-len(source)+2)
+	}
+}
+
+// nextIndex returns the index of the next occurrence of sep in s,
+// starting from offset.  It returns -1 if the sep string is not found.
+func nextIndex(s, sep string, offset int) int {
+	switch i := strings.Index(s[offset:], sep); i {
+	case -1:
+		return -1
+	default:
+		return offset + i
+	}
+}
+
+// isInteger returns true if the string s contains an integer.
+func isInteger(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if (s[i] < '0' || s[i] > '9') && !(i == 0 && s[i] == '-') {
+			return false
+		}
+	}
+	return true
+}
+
+type escapeMode byte
+
+const (
+	escapeNormal escapeMode = iota
+	escapeCanonicalText
+	escapeCanonicalAttr
+)
+
+// escapeString writes an escaped version of a string to the writer.
+func escapeString(w *bufio.Writer, s string, m escapeMode) {
+	var esc []byte
+	last := 0
+	for i := 0; i < len(s); {
+		r, width := utf8.DecodeRuneInString(s[i:])
+		i += width
+		switch r {
+		case '&':
+			esc = []byte("&amp;")
+		case '<':
+			esc = []byte("&lt;")
+		case '>':
+			if m == escapeCanonicalAttr {
+				continue
+			}
+			esc = []byte("&gt;")
+		case '\'':
+			if m != escapeNormal {
+				continue
+			}
+			esc = []byte("&apos;")
+		case '"':
+			if m == escapeCanonicalText {
+				continue
+			}
+			esc = []byte("&quot;")
+		case '\t':
+			if m != escapeCanonicalAttr {
+				continue
+			}
+			esc = []byte("&#x9;")
+		case '\n':
+			if m != escapeCanonicalAttr {
+				continue
+			}
+			esc = []byte("&#xA;")
+		case '\r':
+			if m == escapeNormal {
+				continue
+			}
+			esc = []byte("&#xD;")
+		default:
+			if !isInCharacterRange(r) || (r == 0xFFFD && width == 1) {
+				esc = []byte("\uFFFD")
+				break
+			}
+			continue
+		}
+		w.WriteString(s[last : i-width])
+		w.Write(esc)
+		last = i
+	}
+	w.WriteString(s[last:])
+}
+
+func isInCharacterRange(r rune) bool {
+	return r == 0x09 ||
+		r == 0x0A ||
+		r == 0x0D ||
+		r >= 0x20 && r <= 0xD7FF ||
+		r >= 0xE000 && r <= 0xFFFD ||
+		r >= 0x10000 && r <= 0x10FFFF
+}
diff --git a/path.go b/path.go
new file mode 100644
index 0000000..d183c89
--- /dev/null
+++ b/path.go
@@ -0,0 +1,580 @@
+// Copyright 2015-2019 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package etree
+
+import (
+	"strconv"
+	"strings"
+)
+
+/*
+A Path is a string that represents a search path through an etree starting
+from the document root or an arbitrary element. Paths are used with the
+Element object's Find* methods to locate and return desired elements.
+
+A Path consists of a series of slash-separated "selectors", each of which may
+be modified by one or more bracket-enclosed "filters". Selectors are used to
+traverse the etree from element to element, while filters are used to narrow
+the list of candidate elements at each node.
+
+Although etree Path strings are structurally and behaviorally similar to XPath
+strings (https://www.w3.org/TR/1999/REC-xpath-19991116/), they have a more
+limited set of selectors and filtering options.
+
+The following selectors are supported by etree paths:
+
+    .               Select the current element.
+    ..              Select the parent of the current element.
+    *               Select all child elements of the current element.
+    /               Select the root element when used at the start of a path.
+    //              Select all descendants of the current element.
+    tag             Select all child elements with a name matching the tag.
+
+The following basic filters are supported:
+
+    [@attrib]       Keep elements with an attribute named attrib.
+    [@attrib='val'] Keep elements with an attribute named attrib and value matching val.
+    [tag]           Keep elements with a child element named tag.
+    [tag='val']     Keep elements with a child element named tag and text matching val.
+    [n]             Keep the n-th element, where n is a numeric index starting from 1.
+
+The following function-based filters are supported:
+
+    [text()]                    Keep elements with non-empty text.
+    [text()='val']              Keep elements whose text matches val.
+    [local-name()='val']        Keep elements whose un-prefixed tag matches val.
+    [name()='val']              Keep elements whose full tag exactly matches val.
+    [namespace-prefix()]        Keep elements with non-empty namespace prefixes.
+    [namespace-prefix()='val']  Keep elements whose namespace prefix matches val.
+    [namespace-uri()]           Keep elements with non-empty namespace URIs.
+    [namespace-uri()='val']     Keep elements whose namespace URI matches val.
+
+Below are some examples of etree path strings.
+
+Select the bookstore child element of the root element:
+    /bookstore
+
+Beginning from the root element, select the title elements of all descendant
+book elements having a 'category' attribute of 'WEB':
+    //book[@category='WEB']/title
+
+Beginning from the current element, select the first descendant book element
+with a title child element containing the text 'Great Expectations':
+    .//book[title='Great Expectations'][1]
+
+Beginning from the current element, select all child elements of book elements
+with an attribute 'language' set to 'english':
+    ./book/*[@language='english']
+
+Beginning from the current element, select all child elements of book elements
+containing the text 'special':
+    ./book/*[text()='special']
+
+Beginning from the current element, select all descendant book elements whose
+title child element has a 'language' attribute of 'french':
+    .//book/title[@language='french']/..
+
+Beginning from the current element, select all descendant book elements
+belonging to the http://www.w3.org/TR/html4/ namespace:
+    .//book[namespace-uri()='http://www.w3.org/TR/html4/']
+
+*/
+type Path struct {
+	segments []segment
+}
+
+// ErrPath is returned by path functions when an invalid etree path is provided.
+type ErrPath string
+
+// Error returns the string describing a path error.
+func (err ErrPath) Error() string {
+	return "etree: " + string(err)
+}
+
+// CompilePath creates an optimized version of an XPath-like string that
+// can be used to query elements in an element tree.
+func CompilePath(path string) (Path, error) {
+	var comp compiler
+	segments := comp.parsePath(path)
+	if comp.err != ErrPath("") {
+		return Path{nil}, comp.err
+	}
+	return Path{segments}, nil
+}
+
+// MustCompilePath creates an optimized version of an XPath-like string that
+// can be used to query elements in an element tree.  Panics if an error
+// occurs.  Use this function to create Paths when you know the path is
+// valid (i.e., if it's hard-coded).
+func MustCompilePath(path string) Path {
+	p, err := CompilePath(path)
+	if err != nil {
+		panic(err)
+	}
+	return p
+}
+
+// A segment is a portion of a path between "/" characters.
+// It contains one selector and zero or more [filters].
+type segment struct {
+	sel     selector
+	filters []filter
+}
+
+func (seg *segment) apply(e *Element, p *pather) {
+	seg.sel.apply(e, p)
+	for _, f := range seg.filters {
+		f.apply(p)
+	}
+}
+
+// A selector selects XML elements for consideration by the
+// path traversal.
+type selector interface {
+	apply(e *Element, p *pather)
+}
+
+// A filter pares down a list of candidate XML elements based
+// on a path filter in [brackets].
+type filter interface {
+	apply(p *pather)
+}
+
+// A pather is helper object that traverses an element tree using
+// a Path object.  It collects and deduplicates all elements matching
+// the path query.
+type pather struct {
+	queue      fifo
+	results    []*Element
+	inResults  map[*Element]bool
+	candidates []*Element
+	scratch    []*Element // used by filters
+}
+
+// A node represents an element and the remaining path segments that
+// should be applied against it by the pather.
+type node struct {
+	e        *Element
+	segments []segment
+}
+
+func newPather() *pather {
+	return &pather{
+		results:    make([]*Element, 0),
+		inResults:  make(map[*Element]bool),
+		candidates: make([]*Element, 0),
+		scratch:    make([]*Element, 0),
+	}
+}
+
+// traverse follows the path from the element e, collecting
+// and then returning all elements that match the path's selectors
+// and filters.
+func (p *pather) traverse(e *Element, path Path) []*Element {
+	for p.queue.add(node{e, path.segments}); p.queue.len() > 0; {
+		p.eval(p.queue.remove().(node))
+	}
+	return p.results
+}
+
+// eval evalutes the current path node by applying the remaining
+// path's selector rules against the node's element.
+func (p *pather) eval(n node) {
+	p.candidates = p.candidates[0:0]
+	seg, remain := n.segments[0], n.segments[1:]
+	seg.apply(n.e, p)
+
+	if len(remain) == 0 {
+		for _, c := range p.candidates {
+			if in := p.inResults[c]; !in {
+				p.inResults[c] = true
+				p.results = append(p.results, c)
+			}
+		}
+	} else {
+		for _, c := range p.candidates {
+			p.queue.add(node{c, remain})
+		}
+	}
+}
+
+// A compiler generates a compiled path from a path string.
+type compiler struct {
+	err ErrPath
+}
+
+// parsePath parses an XPath-like string describing a path
+// through an element tree and returns a slice of segment
+// descriptors.
+func (c *compiler) parsePath(path string) []segment {
+	// If path ends with //, fix it
+	if strings.HasSuffix(path, "//") {
+		path += "*"
+	}
+
+	var segments []segment
+
+	// Check for an absolute path
+	if strings.HasPrefix(path, "/") {
+		segments = append(segments, segment{new(selectRoot), []filter{}})
+		path = path[1:]
+	}
+
+	// Split path into segments
+	for _, s := range splitPath(path) {
+		segments = append(segments, c.parseSegment(s))
+		if c.err != ErrPath("") {
+			break
+		}
+	}
+	return segments
+}
+
+func splitPath(path string) []string {
+	var pieces []string
+	start := 0
+	inquote := false
+	for i := 0; i+1 <= len(path); i++ {
+		if path[i] == '\'' {
+			inquote = !inquote
+		} else if path[i] == '/' && !inquote {
+			pieces = append(pieces, path[start:i])
+			start = i + 1
+		}
+	}
+	return append(pieces, path[start:])
+}
+
+// parseSegment parses a path segment between / characters.
+func (c *compiler) parseSegment(path string) segment {
+	pieces := strings.Split(path, "[")
+	seg := segment{
+		sel:     c.parseSelector(pieces[0]),
+		filters: []filter{},
+	}
+	for i := 1; i < len(pieces); i++ {
+		fpath := pieces[i]
+		if fpath[len(fpath)-1] != ']' {
+			c.err = ErrPath("path has invalid filter [brackets].")
+			break
+		}
+		seg.filters = append(seg.filters, c.parseFilter(fpath[:len(fpath)-1]))
+	}
+	return seg
+}
+
+// parseSelector parses a selector at the start of a path segment.
+func (c *compiler) parseSelector(path string) selector {
+	switch path {
+	case ".":
+		return new(selectSelf)
+	case "..":
+		return new(selectParent)
+	case "*":
+		return new(selectChildren)
+	case "":
+		return new(selectDescendants)
+	default:
+		return newSelectChildrenByTag(path)
+	}
+}
+
+var fnTable = map[string]func(e *Element) string{
+	"local-name":       (*Element).name,
+	"name":             (*Element).FullTag,
+	"namespace-prefix": (*Element).namespacePrefix,
+	"namespace-uri":    (*Element).NamespaceURI,
+	"text":             (*Element).Text,
+}
+
+// parseFilter parses a path filter contained within [brackets].
+func (c *compiler) parseFilter(path string) filter {
+	if len(path) == 0 {
+		c.err = ErrPath("path contains an empty filter expression.")
+		return nil
+	}
+
+	// Filter contains [@attr='val'], [fn()='val'], or [tag='val']?
+	eqindex := strings.Index(path, "='")
+	if eqindex >= 0 {
+		rindex := nextIndex(path, "'", eqindex+2)
+		if rindex != len(path)-1 {
+			c.err = ErrPath("path has mismatched filter quotes.")
+			return nil
+		}
+
+		key := path[:eqindex]
+		value := path[eqindex+2 : rindex]
+
+		switch {
+		case key[0] == '@':
+			return newFilterAttrVal(key[1:], value)
+		case strings.HasSuffix(key, "()"):
+			name := key[:len(key)-2]
+			if fn, ok := fnTable[name]; ok {
+				return newFilterFuncVal(fn, value)
+			}
+			c.err = ErrPath("path has unknown function " + name)
+			return nil
+		default:
+			return newFilterChildText(key, value)
+		}
+	}
+
+	// Filter contains [@attr], [N], [tag] or [fn()]
+	switch {
+	case path[0] == '@':
+		return newFilterAttr(path[1:])
+	case strings.HasSuffix(path, "()"):
+		name := path[:len(path)-2]
+		if fn, ok := fnTable[name]; ok {
+			return newFilterFunc(fn)
+		}
+		c.err = ErrPath("path has unknown function " + name)
+		return nil
+	case isInteger(path):
+		pos, _ := strconv.Atoi(path)
+		switch {
+		case pos > 0:
+			return newFilterPos(pos - 1)
+		default:
+			return newFilterPos(pos)
+		}
+	default:
+		return newFilterChild(path)
+	}
+}
+
+// selectSelf selects the current element into the candidate list.
+type selectSelf struct{}
+
+func (s *selectSelf) apply(e *Element, p *pather) {
+	p.candidates = append(p.candidates, e)
+}
+
+// selectRoot selects the element's root node.
+type selectRoot struct{}
+
+func (s *selectRoot) apply(e *Element, p *pather) {
+	root := e
+	for root.parent != nil {
+		root = root.parent
+	}
+	p.candidates = append(p.candidates, root)
+}
+
+// selectParent selects the element's parent into the candidate list.
+type selectParent struct{}
+
+func (s *selectParent) apply(e *Element, p *pather) {
+	if e.parent != nil {
+		p.candidates = append(p.candidates, e.parent)
+	}
+}
+
+// selectChildren selects the element's child elements into the
+// candidate list.
+type selectChildren struct{}
+
+func (s *selectChildren) apply(e *Element, p *pather) {
+	for _, c := range e.Child {
+		if c, ok := c.(*Element); ok {
+			p.candidates = append(p.candidates, c)
+		}
+	}
+}
+
+// selectDescendants selects all descendant child elements
+// of the element into the candidate list.
+type selectDescendants struct{}
+
+func (s *selectDescendants) apply(e *Element, p *pather) {
+	var queue fifo
+	for queue.add(e); queue.len() > 0; {
+		e := queue.remove().(*Element)
+		p.candidates = append(p.candidates, e)
+		for _, c := range e.Child {
+			if c, ok := c.(*Element); ok {
+				queue.add(c)
+			}
+		}
+	}
+}
+
+// selectChildrenByTag selects into the candidate list all child
+// elements of the element having the specified tag.
+type selectChildrenByTag struct {
+	space, tag string
+}
+
+func newSelectChildrenByTag(path string) *selectChildrenByTag {
+	s, l := spaceDecompose(path)
+	return &selectChildrenByTag{s, l}
+}
+
+func (s *selectChildrenByTag) apply(e *Element, p *pather) {
+	for _, c := range e.Child {
+		if c, ok := c.(*Element); ok && spaceMatch(s.space, c.Space) && s.tag == c.Tag {
+			p.candidates = append(p.candidates, c)
+		}
+	}
+}
+
+// filterPos filters the candidate list, keeping only the
+// candidate at the specified index.
+type filterPos struct {
+	index int
+}
+
+func newFilterPos(pos int) *filterPos {
+	return &filterPos{pos}
+}
+
+func (f *filterPos) apply(p *pather) {
+	if f.index >= 0 {
+		if f.index < len(p.candidates) {
+			p.scratch = append(p.scratch, p.candidates[f.index])
+		}
+	} else {
+		if -f.index <= len(p.candidates) {
+			p.scratch = append(p.scratch, p.candidates[len(p.candidates)+f.index])
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterAttr filters the candidate list for elements having
+// the specified attribute.
+type filterAttr struct {
+	space, key string
+}
+
+func newFilterAttr(str string) *filterAttr {
+	s, l := spaceDecompose(str)
+	return &filterAttr{s, l}
+}
+
+func (f *filterAttr) apply(p *pather) {
+	for _, c := range p.candidates {
+		for _, a := range c.Attr {
+			if spaceMatch(f.space, a.Space) && f.key == a.Key {
+				p.scratch = append(p.scratch, c)
+				break
+			}
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterAttrVal filters the candidate list for elements having
+// the specified attribute with the specified value.
+type filterAttrVal struct {
+	space, key, val string
+}
+
+func newFilterAttrVal(str, value string) *filterAttrVal {
+	s, l := spaceDecompose(str)
+	return &filterAttrVal{s, l, value}
+}
+
+func (f *filterAttrVal) apply(p *pather) {
+	for _, c := range p.candidates {
+		for _, a := range c.Attr {
+			if spaceMatch(f.space, a.Space) && f.key == a.Key && f.val == a.Value {
+				p.scratch = append(p.scratch, c)
+				break
+			}
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterFunc filters the candidate list for elements satisfying a custom
+// boolean function.
+type filterFunc struct {
+	fn func(e *Element) string
+}
+
+func newFilterFunc(fn func(e *Element) string) *filterFunc {
+	return &filterFunc{fn}
+}
+
+func (f *filterFunc) apply(p *pather) {
+	for _, c := range p.candidates {
+		if f.fn(c) != "" {
+			p.scratch = append(p.scratch, c)
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterFuncVal filters the candidate list for elements containing a value
+// matching the result of a custom function.
+type filterFuncVal struct {
+	fn  func(e *Element) string
+	val string
+}
+
+func newFilterFuncVal(fn func(e *Element) string, value string) *filterFuncVal {
+	return &filterFuncVal{fn, value}
+}
+
+func (f *filterFuncVal) apply(p *pather) {
+	for _, c := range p.candidates {
+		if f.fn(c) == f.val {
+			p.scratch = append(p.scratch, c)
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterChild filters the candidate list for elements having
+// a child element with the specified tag.
+type filterChild struct {
+	space, tag string
+}
+
+func newFilterChild(str string) *filterChild {
+	s, l := spaceDecompose(str)
+	return &filterChild{s, l}
+}
+
+func (f *filterChild) apply(p *pather) {
+	for _, c := range p.candidates {
+		for _, cc := range c.Child {
+			if cc, ok := cc.(*Element); ok &&
+				spaceMatch(f.space, cc.Space) &&
+				f.tag == cc.Tag {
+				p.scratch = append(p.scratch, c)
+			}
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterChildText filters the candidate list for elements having
+// a child element with the specified tag and text.
+type filterChildText struct {
+	space, tag, text string
+}
+
+func newFilterChildText(str, text string) *filterChildText {
+	s, l := spaceDecompose(str)
+	return &filterChildText{s, l, text}
+}
+
+func (f *filterChildText) apply(p *pather) {
+	for _, c := range p.candidates {
+		for _, cc := range c.Child {
+			if cc, ok := cc.(*Element); ok &&
+				spaceMatch(f.space, cc.Space) &&
+				f.tag == cc.Tag &&
+				f.text == cc.Text() {
+				p.scratch = append(p.scratch, c)
+			}
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
diff --git a/path_test.go b/path_test.go
new file mode 100644
index 0000000..ed0b570
--- /dev/null
+++ b/path_test.go
@@ -0,0 +1,222 @@
+// Copyright 2015-2019 Brett Vickers.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package etree
+
+import "testing"
+
+var testXML = `
+<?xml version="1.0" encoding="UTF-8"?>
+<bookstore xmlns:p="urn:books-com:prices">
+
+	<!Directive>
+
+	<book category="COOKING">
+		<title lang="en">Everyday Italian</title>
+		<author>Giada De Laurentiis</author>
+		<year>2005</year>
+		<p:price>30.00</p:price>
+		<editor>Clarkson Potter</editor>
+	</book>
+
+	<book category="CHILDREN">
+		<title lang="en" sku="150">Harry Potter</title>
+		<author>J K. Rowling</author>
+		<year>2005</year>
+		<p:price p:tax="1.99">29.99</p:price>
+		<editor></editor>
+		<editor/>
+	</book>
+
+	<book category="WEB">
+		<title lang="en">XQuery Kick Start</title>
+		<author>James McGovern</author>
+		<author>Per Bothner</author>
+		<author>Kurt Cagle</author>
+		<author>James Linn</author>
+		<author>Vaidyanathan Nagarajan</author>
+		<year>2003</year>
+		<price>49.99</p:price>
+		<editor>
+		</editor>
+	</book>
+
+	<!-- Final book -->
+	<book category="WEB" path="/books/xml">
+		<title lang="en">Learning XML</title>
+		<author>Erik T. Ray</author>
+		<year>2003</year>
+		<p:price>39.95</p:price>
+	</book>
+
+</bookstore>
+`
+
+type test struct {
+	path   string
+	result interface{}
+}
+
+type errorResult string
+
+var tests = []test{
+	// basic queries
+	{"./bookstore/book/title", []string{"Everyday Italian", "Harry Potter", "XQuery Kick Start", "Learning XML"}},
+	{"./bookstore/book/author", []string{"Giada De Laurentiis", "J K. Rowling", "James McGovern", "Per Bothner", "Kurt Cagle", "James Linn", "Vaidyanathan Nagarajan", "Erik T. Ray"}},
+	{"./bookstore/book/year", []string{"2005", "2005", "2003", "2003"}},
+	{"./bookstore/book/p:price", []string{"30.00", "29.99", "39.95"}},
+	{"./bookstore/book/isbn", nil},
+
+	// descendant queries
+	{"//title", []string{"Everyday Italian", "Harry Potter", "XQuery Kick Start", "Learning XML"}},
+	{"//book/title", []string{"Everyday Italian", "Harry Potter", "XQuery Kick Start", "Learning XML"}},
+	{".//title", []string{"Everyday Italian", "Harry Potter", "XQuery Kick Start", "Learning XML"}},
+	{".//bookstore//title", []string{"Everyday Italian", "Harry Potter", "XQuery Kick Start", "Learning XML"}},
+	{".//book/title", []string{"Everyday Italian", "Harry Potter", "XQuery Kick Start", "Learning XML"}},
+	{".//p:price/.", []string{"30.00", "29.99", "39.95"}},
+	{".//price", []string{"30.00", "29.99", "49.99", "39.95"}},
+
+	// positional queries
+	{"./bookstore/book[1]/title", "Everyday Italian"},
+	{"./bookstore/book[4]/title", "Learning XML"},
+	{"./bookstore/book[5]/title", nil},
+	{"./bookstore/book[3]/author[0]", "James McGovern"},
+	{"./bookstore/book[3]/author[1]", "James McGovern"},
+	{"./bookstore/book[3]/author[3]/./.", "Kurt Cagle"},
+	{"./bookstore/book[3]/author[6]", nil},
+	{"./bookstore/book[-1]/title", "Learning XML"},
+	{"./bookstore/book[-4]/title", "Everyday Italian"},
+	{"./bookstore/book[-5]/title", nil},
+
+	// text function queries
+	{"./bookstore/book[author='James McGovern']/title", "XQuery Kick Start"},
+	{"./bookstore/book[author='Per Bothner']/title", "XQuery Kick Start"},
+	{"./bookstore/book[author='Kurt Cagle']/title", "XQuery Kick Start"},
+	{"./bookstore/book[author='James Linn']/title", "XQuery Kick Start"},
+	{"./bookstore/book[author='Vaidyanathan Nagarajan']/title", "XQuery Kick Start"},
+	{"//book[p:price='29.99']/title", "Harry Potter"},
+	{"//book[price='29.99']/title", "Harry Potter"},
+	{"//book/price[text()='29.99']", "29.99"},
+	{"//book/author[text()='Kurt Cagle']", "Kurt Cagle"},
+	{"//book/editor[text()]", []string{"Clarkson Potter", "\n\t\t"}},
+
+	// namespace function queries
+	{"//*[namespace-uri()]", []string{"30.00", "29.99", "39.95"}},
+	{"//*[namespace-uri()='urn:books-com:prices']", []string{"30.00", "29.99", "39.95"}},
+	{"//*[namespace-uri()='foo']", nil},
+	{"//*[namespace-prefix()]", []string{"30.00", "29.99", "39.95"}},
+	{"//*[namespace-prefix()='p']", []string{"30.00", "29.99", "39.95"}},
+	{"//*[name()='p:price']", []string{"30.00", "29.99", "39.95"}},
+	{"//*[local-name()='price']", []string{"30.00", "29.99", "49.99", "39.95"}},
+	{"//price[namespace-uri()='']", []string{"49.99"}},
+	{"//price[namespace-prefix()='']", []string{"49.99"}},
+	{"//price[name()='price']", []string{"49.99"}},
+	{"//price[local-name()='price']", []string{"30.00", "29.99", "49.99", "39.95"}},
+
+	// attribute queries
+	{"./bookstore/book[@category='WEB']/title", []string{"XQuery Kick Start", "Learning XML"}},
+	{"./bookstore/book[@path='/books/xml']/title", []string{"Learning XML"}},
+	{"./bookstore/book[@category='COOKING']/title[@lang='en']", "Everyday Italian"},
+	{"./bookstore/book/title[@lang='en'][@sku='150']", "Harry Potter"},
+	{"./bookstore/book/title[@lang='fr']", nil},
+	{"//p:price[@p:tax='1.99']", []string{"29.99"}},
+	{"//p:price[@tax='1.99']", []string{"29.99"}},
+	{"//p:price[@p:tax]", []string{"29.99"}},
+	{"//p:price[@tax]", []string{"29.99"}},
+
+	// parent queries
+	{"./bookstore/book[@category='COOKING']/title/../../book[4]/title", "Learning XML"},
+
+	// root queries
+	{"/bookstore/book[1]/title", "Everyday Italian"},
+	{"/bookstore/book[4]/title", "Learning XML"},
+	{"/bookstore/book[5]/title", nil},
+	{"/bookstore/book[3]/author[0]", "James McGovern"},
+	{"/bookstore/book[3]/author[1]", "James McGovern"},
+	{"/bookstore/book[3]/author[3]/./.", "Kurt Cagle"},
+	{"/bookstore/book[3]/author[6]", nil},
+	{"/bookstore/book[-1]/title", "Learning XML"},
+	{"/bookstore/book[-4]/title", "Everyday Italian"},
+	{"/bookstore/book[-5]/title", nil},
+
+	// bad paths
+	{"./bookstore/book[]", errorResult("etree: path contains an empty filter expression.")},
+	{"./bookstore/book[@category='WEB'", errorResult("etree: path has invalid filter [brackets].")},
+	{"./bookstore/book[@category='WEB]", errorResult("etree: path has mismatched filter quotes.")},
+	{"./bookstore/book[author]a", errorResult("etree: path has invalid filter [brackets].")},
+}
+
+func TestPath(t *testing.T) {
+	doc := NewDocument()
+	err := doc.ReadFromString(testXML)
+	if err != nil {
+		t.Error(err)
+	}
+
+	for _, test := range tests {
+		path, err := CompilePath(test.path)
+		if err != nil {
+			if r, ok := test.result.(errorResult); !ok || err.Error() != string(r) {
+				fail(t, test)
+			}
+			continue
+		}
+
+		// Test both FindElementsPath and FindElementPath
+		element := doc.FindElementPath(path)
+		elements := doc.FindElementsPath(path)
+
+		switch s := test.result.(type) {
+		case errorResult:
+			fail(t, test)
+		case nil:
+			if element != nil || len(elements) != 0 {
+				fail(t, test)
+			}
+		case string:
+			if element == nil || element.Text() != s ||
+				len(elements) != 1 || elements[0].Text() != s {
+				fail(t, test)
+			}
+		case []string:
+			if element == nil || element.Text() != s[0] || len(elements) != len(s) {
+				fail(t, test)
+				continue
+			}
+			for i := 0; i < len(elements); i++ {
+				if elements[i].Text() != s[i] {
+					fail(t, test)
+					break
+				}
+			}
+		}
+
+	}
+}
+
+func fail(t *testing.T, test test) {
+	t.Helper()
+	t.Errorf("etree: failed test '%s'\n", test.path)
+}
+
+func TestAbsolutePath(t *testing.T) {
+	doc := NewDocument()
+	err := doc.ReadFromString(testXML)
+	if err != nil {
+		t.Error(err)
+	}
+
+	elements := doc.FindElements("//book/author")
+	for _, e := range elements {
+		title := e.FindElement("/bookstore/book[1]/title")
+		if title == nil || title.Text() != "Everyday Italian" {
+			t.Errorf("etree: absolute path test failed")
+		}
+
+		title = e.FindElement("//book[p:price='29.99']/title")
+		if title == nil || title.Text() != "Harry Potter" {
+			t.Errorf("etree: absolute path test failed")
+		}
+	}
+}