bcd2number.js

/**
 * bcd2number -> takes a nodejs buffer with a BCD and returns the corresponding number.
 * @param buffer The node.js Buffer object
 * @param offset The byte offset in the buffer where the BCD starts
 * @param length The number of bytes to read (a single byte represents 2 digits)
 * @return number 
 */
    var bcd2number = function(buffer, offset, length)
    {
        var n = 0;
        var m = 1;
        for(var i = 0; i<length; i+=1) {
            n += (buffer[length-1-i+offset] & 0x0F) * m;
            n += ((buffer[length-1-i+offset]>>4) & 0x0F) * m * 10;
            m *= 100;
        }
        return n;
    }

/**
 * number2bcd -> takes a number and returns the corresponding BCD in a nodejs buffer object.
 * @param number 32 bit positive number
 * @param size nodejs buffer size
 * @return nodejs buffer 
 */
    var number2bcd = function(number, size) {
        var s = size || 4; //default value: 4
        var bcd = new Buffer(s);
        bcd.fill(0);
        while(number !== 0 && s !== 0) {
            s-=1;
            bcd[s] = (number % 10);
            number = (number / 10)|0;
            bcd[s] += (number % 10) << 4;
            number = (number / 10)|0;
        }
        return bcd;
    }