midi-parser-js
Version:
JSON Human readable MIDI sequences. Read from ArrayBuffers, Base64 encoded strings, or FileInput Element in Browsers.
356 lines (327 loc) • 22.3 kB
JavaScript
/*
Project Name : midi-parser-js
Project Url : https://github.com/colxi/midi-parser-js/
Author : colxi
Author URL : http://www.colxi.info/
Description : MidiParser library reads .MID binary files, Base64 encoded MIDI Data,
or UInt8 Arrays, and outputs as a readable and structured JS object.
*/
(function(){
'use strict';
/**
* CROSSBROWSER & NODEjs POLYFILL for ATOB() -
* By: https://github.com/MaxArt2501 (modified)
* @param {string} string [description]
* @return {[type]} [description]
*/
const _atob = function(string) {
// base64 character set, plus padding character (=)
let b64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
// Regular expression to check formal correctness of base64 encoded strings
let b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/;
// remove data type signatures at the begining of the string
// eg : "data:audio/mid;base64,"
string = string.replace( /^.*?base64,/ , '');
// atob can work with strings with whitespaces, even inside the encoded part,
// but only \t, \n, \f, \r and ' ', which can be stripped.
string = String(string).replace(/[\t\n\f\r ]+/g, '');
if (!b64re.test(string))
throw new TypeError('Failed to execute _atob() : The string to be decoded is not correctly encoded.');
// Adding the padding if missing, for semplicity
string += '=='.slice(2 - (string.length & 3));
let bitmap, result = '';
let r1, r2, i = 0;
for (; i < string.length;) {
bitmap = b64.indexOf(string.charAt(i++)) << 18 | b64.indexOf(string.charAt(i++)) << 12
| (r1 = b64.indexOf(string.charAt(i++))) << 6 | (r2 = b64.indexOf(string.charAt(i++)));
result += r1 === 64 ? String.fromCharCode(bitmap >> 16 & 255)
: r2 === 64 ? String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255)
: String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255, bitmap & 255);
}
return result;
};
/**
* [MidiParser description]
* @type {Object}
*/
const MidiParser = {
// debug (bool), when enabled will log in console unimplemented events
// warnings and internal handled errors.
debug: false,
/**
* [parse description]
* @param {[type]} input [description]
* @param {[type]} _callback [description]
* @return {[type]} [description]
*/
parse: function(input, _callback){
if(input instanceof Uint8Array) return MidiParser.Uint8(input);
else if(typeof input === 'string') return MidiParser.Base64(input);
else if(input instanceof HTMLElement && input.type === 'file') return MidiParser.addListener(input , _callback);
else throw new Error('MidiParser.parse() : Invalid input provided');
},
/**
* addListener() should be called in order attach a listener to the INPUT HTML element
* that will provide the binary data automating the conversion, and returning
* the structured data to the provided callback function.
*/
addListener: function(_fileElement, _callback){
if(!File || !FileReader) throw new Error('The File|FileReader APIs are not supported in this browser. Use instead MidiParser.Base64() or MidiParser.Uint8()');
// validate provided element
if( _fileElement === undefined ||
!(_fileElement instanceof HTMLElement) ||
_fileElement.tagName !== 'INPUT' ||
_fileElement.type.toLowerCase() !== 'file'
){
console.warn('MidiParser.addListener() : Provided element is not a valid FILE INPUT element');
return false;
}
_callback = _callback || function(){};
_fileElement.addEventListener('change', function(InputEvt){ // set the 'file selected' event handler
if (!InputEvt.target.files.length) return false; // return false if no elements where selected
console.log('MidiParser.addListener() : File detected in INPUT ELEMENT processing data..');
let reader = new FileReader(); // prepare the file Reader
reader.readAsArrayBuffer(InputEvt.target.files[0]); // read the binary data
reader.onload = function(e){
_callback( MidiParser.Uint8(new Uint8Array(e.target.result))); // encode data with Uint8Array and call the parser
};
});
},
/**
* Base64() : convert baset4 string into uint8 array buffer, before performing the
* parsing subroutine.
*/
Base64 : function(b64String){
b64String = String(b64String);
let raw = _atob(b64String);
let rawLength = raw.length;
let t_array = new Uint8Array(new ArrayBuffer(rawLength));
for(let i=0; i<rawLength; i++) t_array[i] = raw.charCodeAt(i);
return MidiParser.Uint8(t_array) ;
},
/**
* parse() : function reads the binary data, interpreting and spliting each chuck
* and parsing it to a structured Object. When job is finised returns the object
* or 'false' if any error was generated.
*/
Uint8: function(FileAsUint8Array){
let file = {
data: null,
pointer: 0,
movePointer: function(_bytes){ // move the pointer negative and positive direction
this.pointer += _bytes;
return this.pointer;
},
readInt: function(_bytes){ // get integer from next _bytes group (big-endian)
_bytes = Math.min(_bytes, this.data.byteLength-this.pointer);
if (_bytes < 1) return -1; // EOF
let value = 0;
if(_bytes > 1){
for(let i=1; i<= (_bytes-1); i++){
value += this.data.getUint8(this.pointer) * Math.pow(256, (_bytes - i));
this.pointer++;
}
}
value += this.data.getUint8(this.pointer);
this.pointer++;
return value;
},
readStr: function(_bytes){ // read as ASCII chars, the followoing _bytes
let text = '';
for(let char=1; char <= _bytes; char++) text += String.fromCharCode(this.readInt(1));
return text;
},
readIntVLV: function(){ // read a variable length value
let value = 0;
if ( this.pointer >= this.data.byteLength ){
return -1; // EOF
}else if(this.data.getUint8(this.pointer) < 128){ // ...value in a single byte
value = this.readInt(1);
}else{ // ...value in multiple bytes
let FirstBytes = [];
while(this.data.getUint8(this.pointer) >= 128){
FirstBytes.push(this.readInt(1) - 128);
}
let lastByte = this.readInt(1);
for(let dt = 1; dt <= FirstBytes.length; dt++){
value += FirstBytes[FirstBytes.length - dt] * Math.pow(128, dt);
}
value += lastByte;
}
return value;
}
};
file.data = new DataView(FileAsUint8Array.buffer, FileAsUint8Array.byteOffset, FileAsUint8Array.byteLength); // 8 bits bytes file data array
// ** read FILE HEADER
if(file.readInt(4) !== 0x4D546864){
console.warn('Header validation failed (not MIDI standard or file corrupt.)');
return false; // Header validation failed (not MIDI standard or file corrupt.)
}
let headerSize = file.readInt(4); // header size (unused var), getted just for read pointer movement
let MIDI = {}; // create new midi object
MIDI.formatType = file.readInt(2); // get MIDI Format Type
MIDI.tracks = file.readInt(2); // get ammount of track chunks
MIDI.track = []; // create array key for track data storing
let timeDivisionByte1 = file.readInt(1); // get Time Division first byte
let timeDivisionByte2 = file.readInt(1); // get Time Division second byte
if(timeDivisionByte1 >= 128){ // discover Time Division mode (fps or tpf)
MIDI.timeDivision = [];
MIDI.timeDivision[0] = timeDivisionByte1 - 128; // frames per second MODE (1st byte)
MIDI.timeDivision[1] = timeDivisionByte2; // ticks in each frame (2nd byte)
}else MIDI.timeDivision = (timeDivisionByte1 * 256) + timeDivisionByte2;// else... ticks per beat MODE (2 bytes value)
// ** read TRACK CHUNK
for(let t=1; t <= MIDI.tracks; t++){
MIDI.track[t-1] = {event: []}; // create new Track entry in Array
let headerValidation = file.readInt(4);
if ( headerValidation === -1 ) break; // EOF
if(headerValidation !== 0x4D54726B) return false; // Track chunk header validation failed.
file.readInt(4); // move pointer. get chunk size (bytes length)
let e = 0; // init event counter
let endOfTrack = false; // FLAG for track reading secuence breaking
// ** read EVENT CHUNK
let statusByte;
let laststatusByte;
while(!endOfTrack){
e++; // increase by 1 event counter
MIDI.track[t-1].event[e-1] = {}; // create new event object, in events array
MIDI.track[t-1].event[e-1].deltaTime = file.readIntVLV(); // get DELTA TIME OF MIDI event (Variable Length Value)
statusByte = file.readInt(1); // read EVENT TYPE (STATUS BYTE)
if(statusByte === -1) break; // EOF
else if(statusByte >= 128) laststatusByte = statusByte; // NEW STATUS BYTE DETECTED
else{ // 'RUNNING STATUS' situation detected
statusByte = laststatusByte; // apply last loop, Status Byte
file.movePointer(-1); // move back the pointer (cause readed byte is not status byte)
}
//
// ** IS META EVENT
//
if(statusByte === 0xFF){ // Meta Event type
MIDI.track[t-1].event[e-1].type = 0xFF; // assign metaEvent code to array
MIDI.track[t-1].event[e-1].metaType = file.readInt(1); // assign metaEvent subtype
let metaEventLength = file.readIntVLV(); // get the metaEvent length
switch(MIDI.track[t-1].event[e-1].metaType){
case 0x2F: // end of track, has no data byte
case -1: // EOF
endOfTrack = true; // change FLAG to force track reading loop breaking
break;
case 0x01: // Text Event
case 0x02: // Copyright Notice
case 0x03:
case 0x04: // Instrument Name
case 0x05: // Lyrics)
case 0x07: // Cue point // Sequence/Track Name (documentation: http://www.ta7.de/txt/musik/musi0006.htm)
case 0x06: // Marker
MIDI.track[t-1].event[e-1].data = file.readStr(metaEventLength);
break;
case 0x21: // MIDI PORT
case 0x59: // Key Signature
case 0x51: // Set Tempo
MIDI.track[t-1].event[e-1].data = file.readInt(metaEventLength);
break;
case 0x54: // SMPTE Offset
MIDI.track[t-1].event[e-1].data = [];
MIDI.track[t-1].event[e-1].data[0] = file.readInt(1);
MIDI.track[t-1].event[e-1].data[1] = file.readInt(1);
MIDI.track[t-1].event[e-1].data[2] = file.readInt(1);
MIDI.track[t-1].event[e-1].data[3] = file.readInt(1);
MIDI.track[t-1].event[e-1].data[4] = file.readInt(1);
break;
case 0x58: // Time Signature
MIDI.track[t-1].event[e-1].data = [];
MIDI.track[t-1].event[e-1].data[0] = file.readInt(1);
MIDI.track[t-1].event[e-1].data[1] = file.readInt(1);
MIDI.track[t-1].event[e-1].data[2] = file.readInt(1);
MIDI.track[t-1].event[e-1].data[3] = file.readInt(1);
break;
default :
// if user provided a custom interpreter, call it
// and assign to event the returned data
if( this.customInterpreter !== null){
MIDI.track[t-1].event[e-1].data = this.customInterpreter( MIDI.track[t-1].event[e-1].metaType, file, metaEventLength);
}
// if no customInterpretr is provided, or returned
// false (=apply default), perform default action
if(this.customInterpreter === null || MIDI.track[t-1].event[e-1].data === false){
file.readInt(metaEventLength);
MIDI.track[t-1].event[e-1].data = file.readInt(metaEventLength);
if (this.debug) console.info('Unimplemented 0xFF meta event! data block readed as Integer');
}
}
}
//
// IS REGULAR EVENT
//
else{ // MIDI Control Events OR System Exclusive Events
statusByte = statusByte.toString(16).split(''); // split the status byte HEX representation, to obtain 4 bits values
if(!statusByte[1]) statusByte.unshift('0'); // force 2 digits
MIDI.track[t-1].event[e-1].type = parseInt(statusByte[0], 16);// first byte is EVENT TYPE ID
MIDI.track[t-1].event[e-1].channel = parseInt(statusByte[1], 16);// second byte is channel
switch(MIDI.track[t-1].event[e-1].type){
case 0xF:{ // System Exclusive Events
// if user provided a custom interpreter, call it
// and assign to event the returned data
if( this.customInterpreter !== null){
MIDI.track[t-1].event[e-1].data = this.customInterpreter( MIDI.track[t-1].event[e-1].type, file , false);
}
// if no customInterpretr is provided, or returned
// false (=apply default), perform default action
if(this.customInterpreter === null || MIDI.track[t-1].event[e-1].data === false){
let event_length = file.readIntVLV();
MIDI.track[t-1].event[e-1].data = file.readInt(event_length);
if (this.debug) console.info('Unimplemented 0xF exclusive events! data block readed as Integer');
}
break;
}
case 0xA: // Note Aftertouch
case 0xB: // Controller
case 0xE: // Pitch Bend Event
case 0x8: // Note off
case 0x9: // Note On
MIDI.track[t-1].event[e-1].data = [];
MIDI.track[t-1].event[e-1].data[0] = file.readInt(1);
MIDI.track[t-1].event[e-1].data[1] = file.readInt(1);
break;
case 0xC: // Program Change
case 0xD: // Channel Aftertouch
MIDI.track[t-1].event[e-1].data = file.readInt(1);
break;
case -1: // EOF
endOfTrack = true; // change FLAG to force track reading loop breaking
break;
default:
// if user provided a custom interpreter, call it
// and assign to event the returned data
if( this.customInterpreter !== null){
MIDI.track[t-1].event[e-1].data = this.customInterpreter( MIDI.track[t-1].event[e-1].metaType, file , false);
}
// if no customInterpretr is provided, or returned
// false (=apply default), perform default action
if(this.customInterpreter === null || MIDI.track[t-1].event[e-1].data === false){
console.log('Unknown EVENT detected... reading cancelled!');
return false;
}
}
}
}
}
return MIDI;
},
/**
* custom function to handle unimplemented, or custom midi messages.
* If message is a meta-event, the value of metaEventLength will be >0.
* Function must return the value to store, and pointer of dataView needs
* to be manually increased
* If you want default action to be performed, return false
*/
customInterpreter : null // function( e_type , arrayByffer, metaEventLength){ return e_data_int }
};
// if running in NODE export module
if(typeof module !== 'undefined') module.exports = MidiParser;
else{
// if running in Browser, set a global variable.
let _global = typeof window === 'object' && window.self === window && window ||
typeof self === 'object' && self.self === self && self ||
typeof global === 'object' && global.global === global && global;
_global.MidiParser = MidiParser;
}
})();