Attaching portmonitor scripts with specified parameters

[pattacini]

Hi @apaikan

Do you know whether there's the possibility to specify a parameter in the syntax we use to attach a lua script to a connection?

@Tobias-Fischer is interested in this.

[apaikan]

There is not yet a standard way to pass the parameters to a portmonitor plugin (lua/C++) at the connection time due to the limitation imposed by YARP carrier syntax.

However there are still some ways to do that:

Using the YARP administrative commands
the parameters can be set/configured after establishing the connection via yarp administrative commands.

• See An example which shows how to use a Lua script to modify image data

Using the carrier string parameter
There are also some predefined attributes which can be accessed from the plugin scripts such as

• source : the source port name
• destination: the destination port name
• carrier: the full carrier string

These are formatted as the YARP property and given to the portmonitor create method:

-- create is called when the port monitor is created 
PortMonitor.create = function(options)
    local sourcePort = options:find("source"):asString()
    print(sourcePort)
    return true;
end

Similarly, the carrier attribute holds all complete carrier parameter used for connecting ports:
For example, if a lua plugin is attached using the following command:

$ yarp connect /write /read tcp+recv.portmonitor+type.lua+file.codec+myparam.foo

Then, the carrier attribute holds the tcp+recv.portmonitor+type.lua+file.codec+myparam.foo string. Therefore, a workaround would be to parse this string within the lua code to extract the user-defined parameter (myparam = foo):

PortMonitor.create = function(options)
    local carrier = options:find("carrier"):asString()
    print(carrier)
    for attr in string.gmatch(carrier,'([^+]+)') do
        k, v = attr:match("([^.]+).([^.]+)")
        print(k,v)
    end
    return true
end

You will get:

t   p
recv    portmonitor
type    lua
file    codec
myparam foo

Ignore the t p ;)

[Tobias-Fischer]

Thanks @apaikan! That's great. I'll give it a go soon.

[pattacini]

Thanks @apaikan for the suggestion!
Closing for now; @Tobias-Fischer feel free to post here again.