Convert hash into libvirt domain XML

libvirt-xmlsimple.rb

require 'rubygems'
# xml-simple has a bug that needs to be fixed before this works, see:
#   https://github.com/pdf/xml-simple/commit/b4da34165c88fe912b45af614b326ed512a666c7
require 'xmlsimple'

# domain1 omits the __value__ key except where required
domain1 = {
  "@type"=>"kvm",
  "name"=>"demo1",
  "uuid"=>"4dea24b3-1d52-d8f3-2516-782e98a23fa1",
  "devices"=>
  {
    "graphics"=>
    {
      "@keymap"=>"de",
      "@port"=>"-1",
      "@type"=>"vnc"
    },
    "interface"=>
    {
      "mac"=>{"@address"=>"24:42:53:21:52:45"},
      "@type"=>"network",
      "source"=>{"@network"=>"default"}
    },
    "disk"=>
    {
      "@device"=>"disk",
      "@type"=>"file",
      "target"=>{"@dev"=>"hda"},
      "source"=>{"@file"=>"/var/lib/libvirt/images/demo2.img"}
    },
    "emulator"=>"/usr/bin/qemu-kvm"
  },
  "clock"=>{"@sync"=>"localtime"},
  "sysinfo"=>
  {
    "bios"=>{"entry"=>{"@name"=>"vendor", "__value__"=>"LENOVO"}},
    "system"=>{"entry"=>[{"@name"=>"manufacturer", "__value__"=>"Fedora"},
                         {"@name"=>"vendor", "__value__"=>"Virt-Manager"}]},
    "@type"=>"smbios"
  },
  "memory"=>"131072",
  "os"=>
  {
    "type"=>{"@arch"=>"i686", "__value__"=>"hvm"},
    "boot"=>[{"@dev"=>"hd"},
             {"@dev"=>"cdrom"}]
  },
  "vcpu"=>
  {
    "__value__"=>"2",
    "@cpuset"=>"1-4,^3,6",
    "@current"=>"1"
  }
}

# domain2 uses the __value__ key always
domain2 = {
  "@type"=>"kvm",
  "name"=>{"__value__"=>"demo2"},
  "uuid"=>{"__value__"=>"4dea24b3-1d52-d8f3-2516-782e98a23fa0"},
  "devices"=>
  {
    "graphics"=>
    {
      "@keymap"=>"de",
      "@port"=>"-1",
      "@type"=>"vnc"
    },
    "interface"=>
    {
      "mac"=>{"@address"=>"24:42:53:21:52:45"},
      "@type"=>"network",
      "source"=>{"@network"=>"default"}
    },
    "disk"=>
    {
      "@device"=>"disk",
      "@type"=>"file",
      "target"=>{"@dev"=>"hda"},
      "source"=>{"@file"=>"/var/lib/libvirt/images/demo2.img"}
    },
    "emulator"=>{"__value__"=>"/usr/bin/qemu-kvm"}
  },
  "clock"=>{"@sync"=>"localtime"},
  "sysinfo"=>
  {
    "bios"=> {"entry"=>{"@name"=>"vendor", "__value__"=>"LENOVO"}},
    "system"=> {"entry"=>[{"@name"=>"manufacturer", "__value__"=>"Fedora"},
                          {"@name"=>"vendor", "__value__"=>"Virt-Manager"}]},
    "@type"=>"smbios"
  },
  "memory"=>{"__value__"=>"131072"},
  "os"=>
  {
    "type"=>{"@arch"=>"i686", "__value__"=>"hvm"},
    "boot"=>[{"@dev"=>"hd"},
             {"@dev"=>"cdrom"}]
  },
  "vcpu"=>
  {
    "__value__"=>"2",
    "@cpuset"=>"1-4,^3,6",
    "@current"=>"1"
  }
}

# Either way works, just a matter of preference
puts XmlSimple.xml_out(domain1, {'RootName' => 'domain', 'AttrPrefix' => true, 'ContentKey' => '__value__'})
puts XmlSimple.xml_out(domain2, {'RootName' => 'domain', 'AttrPrefix' => true, 'ContentKey' => '__value__'})