Parsing plist xml - go

Question

How to parse xml in such silly format:
<key>KEY1</key><string>VALUE OF KEY1</string>
<key>KEY2</key><string>VALUE OF KEY2</string>
<key>KEY3</key><integer>42</integer>
<key>KEY3</key><array>
<integer>1</integer>
<integer>2</integer>
</array>
Parsing would be very simple if all values would have same type - for example strings. But in my case each value could be string, data, integer, boolean, array or dict.
This xml looks nearly like json, but unfortunately format is fixed, and I cannot change it. And I would prefer solution without any external packages.

Answer 1

Use a lower-level parsing interface provided by encoding/xml which allows you to iterate over individual tokens in the XML stream (such as "start element", "end element" etc).
See the Token() method of the encoding/xml's Decoder type.

Answer 2

Since the data is not well structured, and you can't modify the format, you can't use xml.Unmarshal, so you can process the XML elements by creating a new Decoder, then iterate over the tokens and use DecodeElement to process them one by one. In my sample code below, it puts everything in a map. The code is also on github here...
package main
import (
"encoding/xml"
"strings"
"fmt"
)
type PlistArray struct {
Integer []int `xml:"integer"`
}
const in = "<key>KEY1</key><string>VALUE OF KEY1</string><key>KEY2</key><string>VALUE OF KEY2</string><key>KEY3</key><integer>42</integer><key>KEY3</key><array><integer>1</integer><integer>2</integer></array>"
func main() {
result := map[string]interface{}{}
dec := xml.NewDecoder(strings.NewReader(in))
dec.Strict = false
var workingKey string
for {
token, _ := dec.Token()
if token == nil {
break
}
switch start := token.(type) {
case xml.StartElement:
fmt.Printf("startElement = %+v\n", start)
switch start.Name.Local {
case "key":
var k string
err := dec.DecodeElement(&k, &start)
if err != nil {
fmt.Println(err.Error())
}
workingKey = k
case "string":
var s string
err := dec.DecodeElement(&s, &start)
if err != nil {
fmt.Println(err.Error())
}
result[workingKey] = s
workingKey = ""
case "integer":
var i int
err := dec.DecodeElement(&i, &start)
if err != nil {
fmt.Println(err.Error())
}
result[workingKey] = i
workingKey = ""
case "array":
var ai PlistArray
err := dec.DecodeElement(&ai, &start)
if err != nil {
fmt.Println(err.Error())
}
result[workingKey] = ai
workingKey = ""
default:
fmt.Errorf("Unrecognized token")
}
}
}
fmt.Printf("%+v", result)
}