[Qemu-devel] Re: [RFC][PATCH v5 08/21] virtagent: add agent_viewfile qmp/hmp command

[Michael Roth <mdroth@linux.vnet.ibm.com>]

On 12/06/2010 04:08 PM, Adam Litke wrote:
> On Fri, 2010-12-03 at 12:03 -0600, Michael Roth wrote:
>> Utilize the getfile RPC to provide a means to view text files in the
>> guest. Getfile can handle binary files as well but we don't advertise
>> that here due to the special handling requiring to store it and provide
>> it back to the user (base64 encoding it for instance). Hence the
>> otherwise confusing "viewfile" as opposed to "getfile".
>
> What happens to the monitor if you use this to view a binary file?

At the very least we probably get a lot of truncated files from the 
binary->string conversion via monitor_printf(). Im not sure how the 
qobject/json layer would deal with things.

> Retrieving binary files progmatically using the QMP interface is a valid
> use case right?

For getfile (the RPC), but not for viewfile (HMP/QMP). It's doable, but 
we'd *have to* pass this data to the user as base64-encoded data at the 
QMP level. At the HMP level I think we're good either way, since we 
could just base64 decode in the print function.

So in the case of QMP we'd be pushing complexity to the user in exchange 
for not having a seperate plain-text-only interface.

Either way seems reasonable, but I'd been planning on adding a seperate 
`agent_copyfile <remote_path> <local_path>` command for dealing with 
binary data, and making viewfile quick and easy for plain text (both for 
HMP and QMP).