vendor

vendor/github.com/beevik/etree/.travis.yml

@@ -0,0 +1,19 @@
+language: go
+sudo: false
+
+go:
+  - 1.5.x
+  - 1.6.x
+  - 1.7.x
+  - 1.8.x
+  - 1.9.x
+  - 1.10.x
+  - tip
+
+matrix:
+  allow_failures:
+    - go: tip
+
+script:
+  - go vet ./...
+  - go test -v ./...

vendor/github.com/beevik/etree/CONTRIBUTORS

@@ -0,0 +1,9 @@
+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)

vendor/github.com/beevik/etree/LICENSE

@@ -0,0 +1,24 @@
+Copyright 2015 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.

vendor/github.com/beevik/etree/README.md

@@ -0,0 +1,203 @@
+[![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 features include:
+
+* 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!

vendor/github.com/beevik/etree/RELEASE_NOTES.md

@@ -0,0 +1,27 @@
+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.
+
+
+Release v1.0.0
+==============
+
+Initial release.

vendor/github.com/beevik/etree/helpers.go

@@ -0,0 +1,188 @@
+// Copyright 2015 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 (
+	"io"
+	"strings"
+)
+
+// 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 crIndent
+const (
+	crsp  = "\n                                                                "
+	crtab = "\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"
+)
+
+// crIndent returns a carriage return followed by n copies of the
+// first non-CR character in the source string.
+func crIndent(n int, source string) string {
+	switch {
+	case n < 0:
+		return source[:1]
+	case n < len(source):
+		return source[:n+1]
+	default:
+		return source + strings.Repeat(source[1:2], n-len(source)+1)
+	}
+}
+
+// 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
+}

vendor/github.com/beevik/etree/path.go

@@ -0,0 +1,533 @@
+// Copyright 2015 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 an object that represents an optimized version of an XPath-like
+search string. A path search string is a slash-separated series of "selectors"
+allowing traversal through an XML hierarchy. Although etree path strings are
+similar to XPath strings, they have a more limited set of selectors and
+filtering options. The following selectors and filters 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. If used at
+                      the start of a path, select all descendants of the root.
+    tag             Select all child elements with the given tag.
+    [#]             Select the element of the given index (1-based,
+                      negative starts from the end).
+    [@attrib]       Select all elements with the given attribute.
+    [@attrib='val'] Select all elements with the given attribute set to val.
+    [tag]           Select all elements with a child element named tag.
+    [tag='val']     Select all elements with a child element named tag
+                      and text matching val.
+    [text()]        Select all elements with non-empty text.
+    [text()='val']  Select all elements whose text matches val.
+
+Examples:
+
+Select the bookstore child element of the root element:
+    /bookstore
+
+Beginning a search from the root element, select the title elements of all
+descendant book elements having a 'category' attribute of 'WEB':
+    //book[@category='WEB']/title
+
+Beginning a search from the current element, select the first descendant book
+element with a title child containing the text 'Great Expectations':
+    .//book[title='Great Expectations'][1]
+
+Beginning a search from the current element, select all children of book
+elements with an attribute 'language' set to 'english':
+    ./book/*[@language='english']
+
+Beginning a search from the current element, select all children of book
+elements containing the text 'special':
+    ./book/*[text()='special']
+
+Beginning a search from the current element, select all descendant book
+elements whose title element has an attribute 'language' equal to 'french':
+    .//book/title[@language='french']/..
+
+*/
+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 = 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 {
+	pieces := make([]string, 0)
+	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)
+	}
+}
+
+// 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'], [text()='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
+		}
+		switch {
+		case path[0] == '@':
+			return newFilterAttrVal(path[1:eqindex], path[eqindex+2:rindex])
+		case strings.HasPrefix(path, "text()"):
+			return newFilterTextVal(path[eqindex+2 : rindex])
+		default:
+			return newFilterChildText(path[:eqindex], path[eqindex+2:rindex])
+		}
+	}
+
+	// Filter contains [@attr], [N], [tag] or [text()]
+	switch {
+	case path[0] == '@':
+		return newFilterAttr(path[1:])
+	case path == "text()":
+		return newFilterText()
+	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]
+}
+
+// filterText filters the candidate list for elements having text.
+type filterText struct{}
+
+func newFilterText() *filterText {
+	return &filterText{}
+}
+
+func (f *filterText) apply(p *pather) {
+	for _, c := range p.candidates {
+		if c.Text() != "" {
+			p.scratch = append(p.scratch, c)
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
+// filterTextVal filters the candidate list for elements having
+// text equal to the specified value.
+type filterTextVal struct {
+	val string
+}
+
+func newFilterTextVal(value string) *filterTextVal {
+	return &filterTextVal{value}
+}
+
+func (f *filterTextVal) apply(p *pather) {
+	for _, c := range p.candidates {
+		if c.Text() == 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]
+}