How to mount a URL as a CD-ROM on QEMU?

I'm wondering if it's possible to specify a URL for the cdrom option on QEMU, and if so how would I go about doing that?

Normally I'd mount an iso like this:

<disk type='file' device='cdrom'>
<source file='/path/to/iso'/><target dev='hdc'/><readonly/>
</disk>

However I figure there must be a good method to mount a URL instead as frankly if it's read only it doesn't need to be on the local FS...

Ideas? I'm open to trying random suggestions...

Assuming a url of: http://example.com/url_path

<disk type='network' device='cdrom'>
    <driver name='qemu' type='raw'/>
    <source protocol="http" name="url_path">
        <host name="example.com" port="80"/>
    </source>
    <target dev='hdc' bus='ide' tray='open'/>
    <readonly/>
</disk>