Handling commands, Example: handle_set, Writing streamnet device drivers 3-2 – ClearOne Writing StreamNet User Manual

Page 12: Figure 3-2 command routing within the driver

Writing StreamNet Device Drivers

3-2

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NOTE

Figure 3-2

Command routing within the driver

Handling Commands

It is always possible to
define an appropriate
command-specific
handler, so that the
default_command_hand
ler is not needed.
Programming best-
practices state that a
fallback
default_command_hand
ler should be defined
even if it is not intended
for use.

For a device driver to receive and handle commands, it is necessary to define Lua
functions with predefined names based on the command to be handled. The routine
that needs to be defined is “handle_” (where is replaced with
the lower cased version of the ASCII command). For example, if a driver needs to
handle #SET commands, it needs to define a function handle_set within the driver. As
a fall-back mechanism, if no command-specific function is defined, the function
“default_command_handler” will be invoked if defined.

If the command is generic to the entire device, the necessary function should be
defined in the outermost control scope of the Lua file, and will be invoked with only
the command as a parameter.

Example: Handle_Set

function

handle_set(cmd)

(cmd.params[1] == “heat”)

then

… handle the #set heat command

end

function

default_command_handler(cmd)

Is the command

addressed to a

subnode?

Is there a subnode

specific command

handler?

Is there a Control

specific command

handler?

Is there a subnode

default command

handler?

Is there a Control

specific command

handler?

Streamnet command is routed to the appropriate section of the Lua driver code

Start

Call Control default

command handler

Call Control specific

command handler

Call Control specific

command handler

Call Control default

command handler

Call subnode specific

command handler

Call subnode default

command handler