====== Open Sound Control ======

Open Sound Control (OSC) is a messaging protocol that is used for sending control signals between many popular digital music tools. We can write a small script in Folk to easily transform Folk signals into OSC messages.

===== The OSC Script =====

This script adds two utility functions for turning Tcl values into serialized OSC values, and also starts watching for a ''Wish the NetAddr is /n/'' assertion to start running an OSC producer.

<code>
# Null terminates a Tcl value and pads it's length to a multiple of four 
# (needed for OSC spec)
# \x01 -> \x01\x00\x00\x00
# \x01\x02\x03 -> \x01\x02\x03\x00
# \x01\x02\x03\x04 -> \x01\x02\x03\x04\x00\x00\x00\x00
fn oscPad {s} {
    set n [string bytelength $s]
    set count [expr {4 - $n % 4}]
    set nulls [string repeat \x00 $count]
    return $s$nulls
}

fn oscPacket {target args} {
    set tags ","
    set payload ""
    foreach a $args {
        if {[string is integer $a]} {
            append tags i
            append payload [binary format I $a]
        } elseif {[string is double $a]} {
            append tags f
            append payload [binary format R $a]
        } else {
            append tags s
            append payload [oscPad $a]
        }
    }
    return "[oscPad $target][oscPad $tags]$payload"
}

When the NetAddr is /n/ {
    Subscribe: OSC at /target/ with args /...arguments/ {
        set s [socket dgram]         
        $s sendto [oscPacket $target {*}$arguments] $n
        $s close
    }
}
</code>

===== Start the Subscriber: =====

Place a program that asserts ''Claim the NetAddr is /addr/''. NetAddr is a string with form ''<IP>:<PORT>''
For my current SuperCollider-based setup the assertion looks like this: 

<code>
Claim the NetAddr is 192.168.4.71:57120
</code>


This script currently only //sends// values to a single OSC receiver. Features like multiple targets and OSC Bundles are still TODO. 

===== Send OSC Packets =====

When the OSC Script and NetAddr claims are being run, we can now easily send messages using Folk via the syntax:

<code>
Notify: OSC at /tone with args 440
</code>

This sends an OSC message to NetAddr with path ''/tone'' and value ''220'' the OSC helper utils will parse 220 into an int and send it as a proper OSC integer.

For any questions please tag Paul on the discord!