extractBits

extractBits.js

/**
 * Extracts bits out of the decimal num from msb to lsb
 * 
 * @param num 
 * @param msb the most significant bit
 * @param lsb the least significant bit
 * @returns {number}
 */
function extractBits(num, msb, lsb) {
  msb = msb || 0;
  lsb = lsb || 8;

  let msbCount = msb;
  let mask = 255;
  for(let pow = 7; msbCount > 0; msbCount--, pow--) {
    mask -= Math.pow(2, pow);
  }

  return (num & mask) >> (8 - lsb);
}

module.exports = extractBits;