# osc-min

simple utilities for open sound control in node.js

This package provides some node.js utilities for working with OSC, a format for sound and systems control.
Here we implement the OSC 1.1 specification. OSC is a transport-independent protocol, so we don't provide any server objects, as you should be able to use OSC over any transport you like. The most common is probably udp, but tcp is not unheard of.

## Installation

The easiest way to get osc-min is through NPM. After install npm, you can install osc-min in the current directory with

`npm install osc-min`

If you'd rather get osc-min through github (for example, if you're forking it), you still need npm to install dependencies, which you can do with

`npm install --dev`

Once you've got all the dependencies you should be able to run the unit tests with

`npm test npm run-script coverage`

## Examples

### A simple OSC printer

        sock = udp.createSocket "udp4", (msg, rinfo) ->
            try
                console.log osc.fromBuffer msg
            catch error
                console.log "invalid OSC packet"
        sock.bind inport

### Send a bunch of arguments every two seconds

        sendHeartbeat = () ->
            buf = osc.toBuffer(
                address : "/heartbeat"
                arguments : [
                    12
                    "sttttring"
                    new Buffer "beat"
                    {type : "integer", value : 7}
                ]
            )

            udp.send buf, 0, buf.length, outport, "localhost"

        setInterval sendHeartbeat, 2000

### A simple OSC redirecter

        sock = udp.createSocket "udp4", (msg, rinfo) ->
            try
                redirected = osc.applyAddressTransform msg, (address) -> "/redirect" + address
                sock.send(
                    redirected,
                    0,
                    redirected.length,
                    outport,
                    "localhost"
                )
            catch error
                console.log "error redirecting: " + error
        sock.bind inport

more examples are available in the `examples/` directory.

## Exported functions

### .fromBuffer(buffer, [strict])

takes a node.js Buffer of a complete OSC Packet and outputs the javascript representation, or throws if the buffer is ill-formed.

`strict` is an optional parameter that makes the function fail more often.

### .toBuffer(object, [strict])

takes a OSC packet javascript representation as defined below and returns a node.js Buffer, or throws if the representation is ill-formed.

### .toBuffer(address, arguments[], [strict])

alternative syntax for above. Assumes this is an OSC Message as defined below, and `arguments` is an array of OSC Arguments or single OSC Argument

### .applyAddressTransform(buffer, transform)

takes a callback that takes a string and outputs a string, and applies that to the address of the message encoded in the buffer, and outputs an encoded buffer.

If the buffer encodes an OSC Bundle, this applies the function to each address in the bundle.

There's two subtle reasons you'd want to use this function rather than composing `fromBuffer` and `toBuffer`: - Future-proofing - if the OSC message uses an argument typecode that we don't understand, calling `fromBuffer` will throw. The only time when `applyAddressTranform` might fail is if the address is malformed. - Accuracy - javascript represents numbers as 64-bit floats, so some OSC types will not be able to be represented accurately. If accuracy is important to you, then, you should never convert the OSC message to a javascript representation.

### .applyMessageTransform(buffer, transform)

takes a function that takes and returns a javascript OSC Message representation, and applies that to each message encoded in the buffer, and outputs a new buffer with the new address.

If the buffer encodes an osc-bundle, this applies the function to each message in the bundle.

See notes above for applyAddressTransform for why you might want to use this. While this does parse and re-pack the messages, the bundle timetags are left in their accurate and prestine state.

## Javascript representations of the OSC types.

See the spec for more information on the OSC types.

- An OSC Packet is an OSC Message or an OSC Bundle.

- An OSC Message:

        {
            oscType : "message"
            address : "/address/pattern/might/have/wildcards"
            arguments : [arg1,arg2]
        }

  Where arguments is an array of OSC Arguments. `oscType` is optional. `arguments` can be a single element.

- An OSC Argument is represented as a javascript object with the following layout:

        {
            type : "string"
            value : "value"
        }

  Where the `type` is one of the following:

  - `string` - string value
  - `float` - numeric value
  - `integer` - numeric value
  - `blob` - node.js Buffer value
  - `true` - value is boolean true
  - `false` - value is boolean false
  - `null` - no value
  - `bang` - no value (this is the `I` type tag)
  - `timetag` - numeric value

  Note that `type` is always a string - i.e. `"true"` rather than `true`.

  The following non-standard types are also supported:

  - `double` - numeric value (encodes to a float64 value)

  For messages sent to the `toBuffer` function, `type` is optional. If the argument is not an object, it will be interpreted as either `string`, `float`, or `blob`, depending on its javascript type.

- An OSC Bundle is represented as a javascript object with the following layout

        {
            oscType : "bundle"
            timetag : 7
            elements : [element1, element]
        }

  Where the timetag is a javascript-native numeric value of the timetag, and elements is an array of either an OSC Bundle or an OSC Message The `oscType` field is optional, but is always returned by api functions.