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/**
Calcul de CRC32
*/
public class ClassCRC32 {
private long pcrc;
private long[] ptabConst = new long[256];
private long DefaultPoly = StaticDefaultPoly;
final private static long StaticDefaultPoly = 0x04c11db7L; // AUTODIN II, Ethernet, FDDI
//*******************************************
public ClassCRC32(){
pcrc = initCRC(ptabConst, DefaultPoly);
}
public ClassCRC32(long crc32_poly){
pcrc = initCRC(ptabConst, crc32_poly);
}
/**
* @param tab : tableau de byte a tester
*/
public ClassCRC32(int[] tab){
pcrc = initCRC(ptabConst, DefaultPoly);
add(tab);
}
/**
*
* @param tab : tableau de byte a tester
* @param crc_poly : valeur définissant la complexité de la focntion CRC polynominal
*/
public ClassCRC32(int[] tab, long crc32_poly){
pcrc = initCRC(ptabConst, crc32_poly);
add(tab);
}
//*******************************************
/**
* @param tab : tableau de byte a tester
*/
public void add(int[] tab){
pcrc = addData(pcrc, tab, ptabConst);
}
//*******************************************
public long getCRC(){
return getVal(pcrc);
}
// **************************************************************
// **************************************************************
private static long initCRC(long[] tabCRC, long poly){
long i, j;
long c;
for (i = 0; i < 256; ++i){
for (c = i << 24, j = 8; j > 0; --j) {
if((c & 0x80000000L) != 0){
c = (c << 1) ^ poly;
} else {
c = (c << 1);
}
}
tabCRC[(int)i] = c & 0xFFFFFFFFL;
}
return 0xffffffffL;
}
private static long addData(long crc, int[] tab, long[] tabCRC){
long crcTmp = crc;
for(int valInt : tab){
long val = (long)(valInt & 0xFF); // on ne traite que 8 bits (utilisation de int pour éviter les problème de signes)
System.out.println("1- crcTmp: " + String.format("%08X", crcTmp)); // debug
long val1 = (crcTmp << 8) & 0xFFFFFFFFL;
System.out.println("2a- val1: " + String.format("%08X", val1)); // debug
long val2 = ((crcTmp & 0xFFFFFFFFL) >>> 24);
System.out.println("3- val2: " + String.format("%08X", val2)); // debug
val2 ^= val;
System.out.println("4- val2: " + String.format("%08X", val2) + " / val: " + String.format("%08X", val)); // debug
val2 = tabCRC[(int)(val2 & 0xFF)];
System.out.println("5- val2: " + String.format("%08X", val2)); // debug
crcTmp = val1 ^ val2;
System.out.println("6- crcTmp: " + String.format("%08X", crcTmp)); // debug
//crcTmp = (crcTmp << 8) ^ tabCRC[(crcTmp >> 24) ^ val];
}
return crcTmp;
}
private static long getVal(long crc){
return (~crc) & 0xFFFFFFFFL;
}
// *******************************************************
// *******************************************************
/**
* Récupération du CRC avec paramêtrage de la formule polynomiale
*/
static public long getCRC(int[] tab, long poly){
long[] tabConst = new long[256];
long crc;
crc = initCRC(tabConst, poly);
crc = addData(crc, tab, tabConst);
crc = getVal(crc);
return crc;
}
/**
* Récupération du CRC
*/
static public long getCRC(int[] tab){
long[] tabConst = new long[256];
long crc;
crc = initCRC(tabConst, StaticDefaultPoly);
crc = addData(crc, tab, tabConst);
return getVal(crc);
}
// **************************************************************
// **************************************************************
/**
* Récupération du CRC en chaine de caractères
*/
public String toString(){
return String.format("%08X", getVal(pcrc));
}
} |
