WebMIDIAPI.js

/* Copyright 2013 Chris Wilson

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

// Initialize the MIDI library.
(function (global) {
    'use strict';
    var midiIO, _requestMIDIAccess, MIDIAccess, _onReady, MIDIPort, MIDIInput, MIDIOutput, _midiProc;

    function Promise() {

    }

    Promise.prototype.then = function(accept, reject) {
        this.accept = accept; 
        this.reject = reject;
    }

    Promise.prototype.succeed = function(access) {
        if (this.accept)
            this.accept(access);
    }

    Promise.prototype.fail = function(error) {
        if (this.reject)
            this.reject(error);
    }

    function _JazzInstance() {
        this.inputInUse = false;
        this.outputInUse = false;

        // load the Jazz plugin
        var o1 = document.createElement("object");
        o1.id = "_Jazz" + Math.random() + "ie";
        o1.classid = "CLSID:1ACE1618-1C7D-4561-AEE1-34842AA85E90";

        this.activeX = o1;

        var o2 = document.createElement("object");
        o2.id = "_Jazz" + Math.random();
        o2.type="audio/x-jazz";
        o1.appendChild(o2);

        this.objRef = o2;

        var e = document.createElement("p");
        e.appendChild(document.createTextNode("This page requires the "));

        var a = document.createElement("a");
        a.appendChild(document.createTextNode("Jazz plugin"));
        a.href = "http://jazz-soft.net/";

        e.appendChild(a);
        e.appendChild(document.createTextNode("."));
        o2.appendChild(e);

        var insertionPoint = document.getElementById("MIDIPlugin");
        if (!insertionPoint) {
            // Create hidden element
            var insertionPoint = document.createElement("div");
            insertionPoint.id = "MIDIPlugin";
            insertionPoint.style.position = "absolute";
            insertionPoint.style.visibility = "hidden";
            insertionPoint.style.left = "-9999px";
            insertionPoint.style.top = "-9999px";
            document.body.appendChild(insertionPoint);
        }
        insertionPoint.appendChild(o1);

        if (this.objRef.isJazz)
            this._Jazz = this.objRef;
        else if (this.activeX.isJazz)
            this._Jazz = this.activeX;
        else
            this._Jazz = null;
        if (this._Jazz) {
            this._Jazz._jazzTimeZero = this._Jazz.Time();
            this._Jazz._perfTimeZero = window.performance.now();
        }
    }

    _requestMIDIAccess = function _requestMIDIAccess() {
        var access = new MIDIAccess();
        return access._promise;
    };

    // API Methods

    MIDIAccess = function() {
        this._jazzInstances = new Array();
        this._jazzInstances.push( new _JazzInstance() );
        this._promise = new Promise;

        if (this._jazzInstances[0]._Jazz) {
            this._Jazz = this._jazzInstances[0]._Jazz;
            window.setTimeout( _onReady.bind(this), 3 );
        } else {
            window.setTimeout( _onNotReady.bind(this), 3 );
        }
    };

    _onReady = function _onReady() {
        if (this._promise)
            this._promise.succeed(this);
    };

    function _onNotReady() {
        if (this._promise)
            this._promise.fail( { code: 1 } );
    };

    MIDIAccess.prototype.inputs = function(  ) {
        if (!this._Jazz)
              return null;
        var list=this._Jazz.MidiInList();
        var inputs = new Array( list.length );

        for ( var i=0; i<list.length; i++ ) {
            inputs[i] = new MIDIInput( this, list[i], i );
        }
        return inputs;
    }

    MIDIAccess.prototype.outputs = function(  ) {
        if (!this._Jazz)
            return null;
        var list=this._Jazz.MidiOutList();
        var outputs = new Array( list.length );

        for ( var i=0; i<list.length; i++ ) {
            outputs[i] = new MIDIOutput( this, list[i], i );
        }
        return outputs;
    };

    MIDIInput = function MIDIInput( midiAccess, name, index ) {
        this._listeners = [];
        this._midiAccess = midiAccess;
        this._index = index;
        this._inLongSysexMessage = false;
        this._sysexBuffer = new Uint8Array();
        this.id = "" + index + "." + name;
        this.manufacturer = "";
        this.name = name;
        this.type = "input";
        this.version = "";
        this.onmidimessage = null;

        var inputInstance = null;
        for (var i=0; (i<midiAccess._jazzInstances.length)&&(!inputInstance); i++) {
            if (!midiAccess._jazzInstances[i].inputInUse)
                inputInstance=midiAccess._jazzInstances[i];
        }
        if (!inputInstance) {
            inputInstance = new _JazzInstance();
            midiAccess._jazzInstances.push( inputInstance );
        }
        inputInstance.inputInUse = true;

        this._jazzInstance = inputInstance._Jazz;
        this._input = this._jazzInstance.MidiInOpen( this._index, _midiProc.bind(this) );
    };

    // Introduced in DOM Level 2:
    MIDIInput.prototype.addEventListener = function (type, listener, useCapture ) {
        if (type !== "midimessage")
            return;
        for (var i=0; i<this._listeners.length; i++)
            if (this._listeners[i] == listener)
                return;
        this._listeners.push( listener );
    };

    MIDIInput.prototype.removeEventListener = function (type, listener, useCapture ) {
        if (type !== "midimessage")
            return;
        for (var i=0; i<this._listeners.length; i++)
            if (this._listeners[i] == listener) {
                this._listeners.splice( i, 1 );  //remove it
                return;
            }
    };

    MIDIInput.prototype.preventDefault = function() {
        this._pvtDef = true;
    };

    MIDIInput.prototype.dispatchEvent = function (evt) {
        this._pvtDef = false;

        // dispatch to listeners
        for (var i=0; i<this._listeners.length; i++)
            if (this._listeners[i].handleEvent)
                this._listeners[i].handleEvent.bind(this)( evt );
            else
                this._listeners[i].bind(this)( evt );

        if (this.onmidimessage)
            this.onmidimessage( evt );

        return this._pvtDef;
    };

    MIDIInput.prototype.appendToSysexBuffer = function ( data ) {
        var oldLength = this._sysexBuffer.length;
        var tmpBuffer = new Uint8Array( oldLength + data.length );
        tmpBuffer.set( this._sysexBuffer );
        tmpBuffer.set( data, oldLength );
        this._sysexBuffer = tmpBuffer;
    };

    MIDIInput.prototype.bufferLongSysex = function ( data, initialOffset ) {
        var j = initialOffset;
        while (j<data.length) {
            if (data[j] == 0xF7) {
                // end of sysex!
                j++;
                this.appendToSysexBuffer( data.slice(initialOffset, j) );
                return j;
            }
            j++;
        }
        // didn't reach the end; just tack it on.
        this.appendToSysexBuffer( data.slice(initialOffset, j) );
        this._inLongSysexMessage = true;
        return j;
    };

    _midiProc = function _midiProc( timestamp, data ) {
        // Have to use createEvent/initEvent because IE10 fails on new CustomEvent.  Thanks, IE!
        var length = 0;
        var i,j;
        var isSysexMessage = false;

        // Jazz sometimes passes us multiple messages at once, so we need to parse them out
        // and pass them one at a time.

        for (i=0; i<data.length; i+=length) {
            if (this._inLongSysexMessage) {
                i = this.bufferLongSysex(data,i);
                if ( data[i-1] != 0xf7 ) {
                    // ran off the end without hitting the end of the sysex message
                    return;
                }
                isSysexMessage = true;
            } else {
                isSysexMessage = false;
                switch (data[i] & 0xF0) {
                    case 0x80:  // note off
                    case 0x90:  // note on
                    case 0xA0:  // polyphonic aftertouch
                    case 0xB0:  // control change
                    case 0xE0:  // channel mode
                        length = 3;
                        break;

                    case 0xC0:  // program change
                    case 0xD0:  // channel aftertouch
                        length = 2;
                        break;

                    case 0xF0:
                        switch (data[i]) {
                            case 0xf0:  // variable-length sysex.
                                i = this.bufferLongSysex(data,i);
                                if ( data[i-1] != 0xf7 ) {
                                    // ran off the end without hitting the end of the sysex message
                                    return;
                                }
                                isSysexMessage = true;
                                break;

                            case 0xF1:  // MTC quarter frame
                            case 0xF3:  // song select
                                length = 2;
                                break;

                            case 0xF2:  // song position pointer
                                length = 3;
                                break;

                            default:
                                length = 1;
                                break;
                        }
                        break;
                }
            }
            var evt = document.createEvent( "Event" );
            evt.initEvent( "midimessage", false, false );
            evt.receivedTime = parseFloat( timestamp.toString()) + this._jazzInstance._perfTimeZero;
            if (isSysexMessage || this._inLongSysexMessage) {
                evt.data = new Uint8Array( this._sysexBuffer );
                this._sysexBuffer = new Uint8Array(0);
                this._inLongSysexMessage = false;
            } else
                evt.data = new Uint8Array(data.slice(i, length+i));
            this.dispatchEvent( evt );
        }
    };

    MIDIOutput = function MIDIOutput( midiAccess, name, index ) {
        this._listeners = [];
        this._midiAccess = midiAccess;
        this._index = index;
        this.id = "" + index + "." + name;
        this.manufacturer = "";
        this.name = name;
        this.type = "output";
        this.version = "";

        var outputInstance = null;
        for (var i=0; (i<midiAccess._jazzInstances.length)&&(!outputInstance); i++) {
            if (!midiAccess._jazzInstances[i].outputInUse)
                outputInstance=midiAccess._jazzInstances[i];
        }
        if (!outputInstance) {
            outputInstance = new _JazzInstance();
            midiAccess._jazzInstances.push( outputInstance );
        }
        outputInstance.outputInUse = true;

        this._jazzInstance = outputInstance._Jazz;
        this._jazzInstance.MidiOutOpen(this.name);
    };

    function _sendLater() {
        this.jazz.MidiOutLong( this.data );    // handle send as sysex
    }

    MIDIOutput.prototype.send = function( data, timestamp ) {
        var delayBeforeSend = 0;
        if (data.length === 0)
            return false;

        if (timestamp)
            delayBeforeSend = Math.floor( timestamp - window.performance.now() );

        if (timestamp && (delayBeforeSend>1)) {
            var sendObj = new Object();
            sendObj.jazz = this._jazzInstance;
            sendObj.data = data;

            window.setTimeout( _sendLater.bind(sendObj), delayBeforeSend );
        } else {
            this._jazzInstance.MidiOutLong( data );
        }
        return true;
    };

    //init: create plugin
    if (!window.navigator.requestMIDIAccess)
        window.navigator.requestMIDIAccess = _requestMIDIAccess;

}(window));

// Polyfill window.performance.now() if necessary.
(function (exports) {
    var perf = {}, props;

    function findAlt() {
        var prefix = ['moz', 'webkit', 'o', 'ms'],
        i = prefix.length,
            //worst case, we use Date.now()
            props = {
                value: (function (start) {
                    return function () {
                        return Date.now() - start;
                    };
                }(Date.now()))
            };

        //seach for vendor prefixed version
        for (; i >= 0; i--) {
            if ((prefix[i] + "Now") in exports.performance) {
                props.value = function (method) {
                    return function () {
                        exports.performance[method]();
                    }
                }(prefix[i] + "Now");
                return props;
            }
        }

        //otherwise, try to use connectionStart
        if ("timing" in exports.performance && "connectStart" in exports.performance.timing) {
            //this pretty much approximates performance.now() to the millisecond
            props.value = (function (start) {
                return function() {
                    Date.now() - start;
                };
            }(exports.performance.timing.connectStart));
        }
        return props;
    }

    //if already defined, bail
    if (("performance" in exports) && ("now" in exports.performance))
        return;
    if (!("performance" in exports))
        Object.defineProperty(exports, "performance", {
            get: function () {
                return perf;
            }});
        //otherwise, performance is there, but not "now()"

    props = findAlt();
    Object.defineProperty(exports.performance, "now", props);
}(window));