unmarshal full subtree as element

main_test.go

package main

import (
	"bytes"
	"encoding/xml"
	"io"
	"log"

	"testing"
)

const s = `
<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom"
      xml:lang="en"
      xml:base="http://www.example.org">
  <id>http://www.example.org/myfeed</id>
  <title>My Simple Feed</title>
  <updated>2005-07-15T12:00:00Z</updated>
  <link href="/blog" />
  <link rel="self" href="/myfeed" />
  <entry>
    <id>http://www.example.org/entries/1</id>
    <title>A simple blog entry</title>
    <link href="/blog/2005/07/1" />
    <updated>2005-07-15T12:00:00Z</updated>
    <summary>This is a simple blog entry</summary>
  </entry>
  <entry>
    <id>http://www.example.org/entries/2</id>
    <title />
    <link href="/blog/2005/07/2" />
    <updated>2005-07-15T12:00:00Z</updated>
    <summary>This is simple blog entry without a title</summary>
  </entry>
  <entry>
    <id>tag:update:20050718</id>
    <title>Update: 20050718</title>
    <updated>2005-07-18T12:00:00Z</updated>
    <link rel="alternate"
          type="text/html"
          href="/updates/2005/07/18/readme.html_20050718" />
    <content type="application/zip" 
          src="/updates/2005/07/18/update_20050718.zip" />
  </entry>
  <entry>
    <id>tag:update:20050717</id>
    <title>Update: 20050717</title>
    <updated>2005-17-17T12:00:00Z</updated>
    <link rel="alternate" 
          type="text/html"
          href="/updates/2005/07/17/readme_20050717.html" />
    <content type="application/zip" 
          src="/updates/2005/07/17/update_20050717.zip" />
  </entry>
</feed>
`

func TestUnmarshal(t *testing.T) {
	var feed Feed
	r := bytes.NewBufferString(s)

	dec := xml.NewDecoder(r)
	err := dec.Decode(&feed)
	if err != nil {
		panic(err)
	}

	for _, e := range feed.Entries {
		log.Println(string(e.Content))
	}
}

func BenchmarkUnmarshal(b *testing.B) {
	b.StopTimer()
	var (
		feed Feed
		err  error
		r    io.Reader
	)
	b.StartTimer()

	for i := 0; i < b.N; i++ {
		r = bytes.NewBufferString(s)
		err = xml.NewDecoder(r).Decode(&feed)
		if err != nil {
			b.Error(err)
		}
	}
}

type Feed struct {
	ID      string  `xml:"id"`
	Entries []Entry `xml:"entry"`
}

type Entry struct {
	Content []byte
}

func (e *Entry) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	var buf bytes.Buffer
	enc := xml.NewEncoder(&buf)
	err := enc.EncodeToken(start)
	if err != nil {
		return err
	}

	for {
		tok, err := d.Token()
		if err != nil {
			return err
		}

		err = enc.EncodeToken(tok)
		if err != nil {
			return err
		}

		switch x := tok.(type) {
		case xml.EndElement:
			if x.Name == start.Name {
				err = enc.Flush()
				if err != nil {
					return err
				}
				e.Content = buf.Bytes()
				return nil
			}
		}
	}
}

the namespace output is not so nice as long as golang/go#13400 is not fixed. there is a workaround though