bitarray.service.js

bitarray.service.js

/**
 * bitarray.js
 *
 * Utility for working with JS TypedArrays at bit level. (Angular Service)
 *
 * @author kevincharm
 * @license MIT
 */

angular
    .module('ShockWiz')
    .service('BitArray', [
        BitArrayService
    ]);

function BitArray(buffer, endian) {
    if (buffer) {
        this.dataView = new DataView(buffer);
        this.bitArray = _getBitArray(this.dataView, this.endian);
    } else {
        this.bitArray = [];
    }

    if (typeof endian === 'string') {
        this.endian = !!(endian.toUpperCase() === 'LITTLE');
    } else if (typeof endian === 'boolean') {
        this.endian = endian;
    } else {
        // defaults to little endian
        this.endian = true;
    }
}

function _getBitArray(data, endian) {
    var bitString = '';

    for (var i = 0; i < data.byteLength; i++) {
        var currentByteBitString = data.getUint8(i, endian).toString(2);
        if (currentByteBitString.length < 8) {
            var offset = 8 - currentByteBitString.length;
            var pad = '';
            while (offset--) pad += '0';
            currentByteBitString += pad;
        }

        bitString += currentByteBitString;
    }

    return bitString.split('').map(s => parseInt(s));
}

function _packBitArray(srcBitArray) {
    var byteSize = Math.ceil(srcBitArray.length / 8);
    var destinationBuffer = new Uint8Array(byteSize);
    var destinationBufferBitCounter = 0;

    for (var i = 0; i < srcBitArray.length; i++) {
        var destinationBufferIndex = Math.floor(destinationBufferBitCounter / 8);
        var destinationBufferBitOffset = destinationBufferBitCounter % 8;
        destinationBuffer[destinationBufferIndex] |= srcBitArray[i] << destinationBufferBitOffset;
        destinationBufferBitCounter++;
    }

    return destinationBuffer.buffer;
}

BitArray.prototype.toArray = function () {
    return this.bitArray;
};

BitArray.prototype.toString = function () {
    return this.bitArray.join('');
};

BitArray.prototype.toBuffer = function () {
    return _packBitArray(this.bitArray);
};

BitArray.prototype.getBit = function (index) {
    return this.bitArray[index];
};

BitArray.prototype.setBit = function (index, value) {
    value = +(!!(+value)); /* coerce to number -> bool -> binary int */
    this.bitArray[index] = value;
};

BitArray.prototype.getBitChunk = function (index, size) {
    return this.bitArray.slice(index, index + size);
};

BitArray.prototype.setBitChunk = function (index, chunkBitArray) {
    if (typeof chunkBitArray === 'string') chunkBitArray = chunkBitArray.split('');
    for (var i = 0; i < chunkBitArray.length; i++) {
        this.bitArray[index + i] = chunkBitArray[i];
    }
};

function BitArrayService() {
    return BitArray;
}