midi-json-parser/src/worker/midi-json-parser.js

This module is parsing midi files into a human-readable JSON object.

'use strict';

var arrayBuffers = new Map(),
    midiFileParser,
    MidiFileParser = require('../parser/midi-file.js').MidiFileParser;

midiFileParser = new MidiFileParser();

self.addEventListener('message', function (event) {
    var arrayBuffer,
        destination,
        data = event.data,
        i,
        length,
        source;

    arrayBuffer = arrayBuffers.get(data.index);

    if (arrayBuffer === undefined) {
        arrayBuffer = new ArrayBuffer(data.byteLength);
        arrayBuffers.set(data.index, arrayBuffer);
    }

    destination = new Uint8Array(arrayBuffer);
    length = Math.min(data.byteIndex + 1048576, data.byteLength);
    source = new Uint8Array(data.arrayBuffer);

    for (i = data.byteIndex; i < length; i += 1) {
        destination[i] = source[i - data.byteIndex];
    }

    if (length === data.byteLength) {
        self.postMessage({
            index: data.index,
            midiFile: midiFileParser.parseArrayBuffer(arrayBuffer)
        });

        arrayBuffers.delete(data.index);
    }
});