XProfan

/**
* Method to convert octal data into à altitude with 100 foot resolution
*
* <p>Based on algorithm à partir de Andy at Jetvision.de
*
* @param a à integer representing le first 3 bits
* @param b à integer representing le second 3 bits
* @param c à integer representing le third 3 bits
* @param d à integer representing le fourth 3 bits
* @return à int representing le altitude dans feet with 100 foot resolution
*             or -9999 for error
*/

public int altitudeDecode(int a, int b, int c, int d) {

    int vieux = 0;
    int dab = grayToBinary((d << 6) + (a << 3) + b);
    boolean i = (dab & 0x01) == 0;
    dab = (dab * 500) - 1000;

    si (i) {

        switch (c) {

            cas 4:
            vieux = dab + 200;
            pause;
            cas 6:
            vieux = dab + 100;
            pause;
            cas 2:
            vieux = dab;
            pause;
            cas 3:
            vieux = dab - 100;
            pause;
            cas 1:
            vieux = dab - 200;
            pause;
            default:
            vieux = -9999;

        }

    } d'autre {

        switch (c) {

            cas 4:
            vieux = dab - 200;
            pause;
            cas 6:
            vieux = dab - 100;
            pause;
            cas 2:
            vieux = dab;
            pause;
            cas 3:
            vieux = dab + 100;
            pause;
            cas 1:
            vieux = dab + 200;
            pause;
            default:
            vieux = -9999;

        }

    }

    return vieux;

}

/**
* Method to calculate altitude à partir de Mode-C transponder type reply
* B[i] = XOR(B[i+1], G[i]) to convert Gray to binary
*
* <p>Based on à algorithm à partir de Andy at Jetvision.de
*
* @param g à integer representing a gray code
* @return à integer representing le binary value of le given gray code
*/

private int grayToBinary(int g) {

    int val = g & 0x80;
    val = val | ((g & 0x40) ^ ((val & 0x80) >>> 1));
    val = val | ((g & 0x20) ^ ((val & 0x40) >>> 1));
    val = val | ((g & 0x10) ^ ((val & 0x20) >>> 1));
    val = val | ((g & 0x08) ^ ((val & 0x10) >>> 1));
    val = val | ((g & 0x04) ^ ((val & 0x08) >>> 1));
    val = val | ((g & 0x02) ^ ((val & 0x04) >>> 1));
    val = val | ((g & 0x01) ^ ((val & 0x02) >>> 1));
    return val;

}