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N-Number & ICAO address converter
public class NConverter {
private final String base9; // The first digit (after the "N")
// is always one of these.
private final String base10; // The possible second and third digits
// are one of these.
// Note that "I" and "O" are never used as letters,
// to prevent confusion with "1" and "0"
private final String base34;
private final int icaooffset; // The lowest possible number
private final int b1; // basis between N1... and N2...
private final int b2; // basis between N10.... and N11....
public NConverter() {
base9 = "123456789";
base10 = "0123456789";
base34 = "ABCDEFGHJKLMNPQRSTUVWXYZ0123456789";
icaooffset = 0xA00001;
b1 = 101711;
b2 = 10111;
}
private String suffix(int rem) {
String suf;
// Produces the alpha(numeric) suffix from a number 0 - 950
if (rem == 0) {
suf = "";
} else if (rem <= 600) { // Class A suffix -- only letters.
rem--;
suf = Character.toString(base34.charAt(rem / 25));
if (rem % 25 > 0) {
suf += Character.toString(base34.charAt((rem % 25) - 1)); // second class A letter, if present.
}
} else { // rem > 600 : First digit of suffix is a number. Second digit may be blank, letter, or number.
rem -= 601;
suf = Character.toString(base10.charAt(rem / 35));
if (rem % 35 > 0) {
suf += Character.toString(base34.charAt((rem % 35) - 1));
}
}
return suf;
}
private int enc_suffix(String suf) {
int r0;
int r1;
// Produces a remainder from a 0 - 2 digit suffix.
// No error checking. Using illegal strings will have strange results."""
if (suf.length() == 0) {
return 0;
}
r0 = base34.indexOf(suf.charAt(0));
if (suf.length() == 1) {
r1 = 0;
} else {
r1 = base34.indexOf(suf.charAt(1)) + 1;
}
if (r0 < 24) {
return r0 * 25 + r1 + 1; // first char is a letter, use base 25
} else {
return r0 * 35 + r1 - 239; // first is a number -- base 35.
}
}
public String icao_to_n(String val) {
String nnum;
int d1;
int d2;
int d3;
int r1;
int r2;
int r3;
int icao = Integer.parseInt(val.toUpperCase(), 16);
/*
* N Numbers fit in this range. Other ICAO not decoded.
*/
if ((icao < 0xA00001) || (icao > 0xADF7C7)) {
return "";
}
icao -= icaooffset; // A00001
d1 = icao / b1;
nnum = "N" + Character.toString(base9.charAt(d1));
r1 = icao % b1;
if (r1 < 601) {
nnum += suffix(r1); // of the form N1ZZ
} else {
d2 = (r1 - 601) / b2; // find second digit.
nnum += Character.toString(base10.charAt(d2));
r2 = (r1 - 601) % b2; // and residue after that
if (r2 < 601) {
nnum += suffix(r2); // No third digit.(form N12ZZ
} else {
d3 = (r2 - 601) / 951; // Three-digits have extended suffix.
r3 = (r2 - 601) % 951;
nnum += Character.toString(base10.charAt(d3)) + suffix(r3);
}
}
return nnum;
}
public int n_to_icao(String tail) {
int d2;
int d3;
int icao;
tail = tail.toUpperCase();
if (!tail.startsWith("N")) {
return -1;
}
icao = icaooffset;
icao += base9.indexOf(tail.charAt(1)) * b1;
if (tail.length() == 2) { // simple 'N3' etc.
return icao;
}
d2 = base10.indexOf(tail.charAt(2));
if (d2 == -1) {
icao += enc_suffix(tail.substring(2, 4)); // Form N1A
} else {
icao += d2 * b2 + 601; // Form N11... or N111..
if (tail.length() != 3) { // simple 'N34' etc.
d3 = base10.indexOf(tail.charAt(3));
if (d3 > -1) { // Form N111 Suffix is base 35.
icao += d3 * 951 + 601;
icao += enc_suffix(tail.substring(4, 6));
} else { // Form N11A
icao += enc_suffix(tail.substring(3, 5));
}
}
}
return icao;
}
}
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