Emberveil sourcegame/2006Scape Server/src/main/java/org/apollo/util/security/IsaacRandom.java
package org.apollo.util.security;
/**
* <p>
* An implementation of the <a href="http://www.burtleburtle.net/bob/rand/isaacafa.html">ISAAC</a> psuedorandom number
* generator.
* </p>
*
* <pre>
* ------------------------------------------------------------------------------
* Rand.java: By Bob Jenkins. My random number generator, ISAAC.
* rand.init() -- initialize
* rand.val() -- get a random value
* MODIFIED:
* 960327: Creation (addition of randinit, really)
* 970719: use context, not global variables, for internal state
* 980224: Translate to Java
* ------------------------------------------------------------------------------
* </pre>
* <p>
* This class has been changed to be more conformant to Java and javadoc conventions.
* </p>
*
* @author Bob Jenkins
*/
public final class IsaacRandom {
/**
* The golden ratio.
*/
private static final int GOLDEN_RATIO = 0x9e3779b9;
/**
* The log of the size of the result and state arrays.
*/
private static final int LOG_SIZE = Long.BYTES;
/**
* The size of the result and states arrays.
*/
private static final int SIZE = 1 << LOG_SIZE;
/**
* A mask for pseudo-random lookup.
*/
private static int MASK = SIZE - 1 << 2;
/**
* The results given to the user.
*/
private final int[] results = new int[SIZE];
/**
* The internal state.
*/
private final int[] state = new int[SIZE];
/**
* The count through the results in the results array.
*/
private int count = SIZE;
/**
* The accumulator.
*/
private int accumulator;
/**
* The last result.
*/
private int last;
/**
* The counter.
*/
private int counter;
/**
* Creates the random number generator with the specified seed.
*
* @param seed The seed.
*/
public IsaacRandom(int[] seed) {
int length = Math.min(seed.length, results.length);
System.arraycopy(seed, 0, results, 0, length);
init();
}
/**
* Generates 256 results.
*/
private void isaac() {
int i, j, x, y;
last += ++counter;
for (i = 0, j = SIZE / 2; i < SIZE / 2;) {
x = state[i];
accumulator ^= accumulator << 13;
accumulator += state[j++];
state[i] = y = state[(x & MASK) >> 2] + accumulator + last;
results[i++] = last = state[(y >> LOG_SIZE & MASK) >> 2] + x;
x = state[i];
accumulator ^= accumulator >>> 6;
accumulator += state[j++];
state[i] = y = state[(x & MASK) >> 2] + accumulator + last;
results[i++] = last = state[(y >> LOG_SIZE & MASK) >> 2] + x;
x = state[i];
accumulator ^= accumulator << 2;
accumulator += state[j++];
state[i] = y = state[(x & MASK) >> 2] + accumulator + last;
results[i++] = last = state[(y >> LOG_SIZE & MASK) >> 2] + x;
x = state[i];
accumulator ^= accumulator >>> 16;
accumulator += state[j++];
state[i] = y = state[(x & MASK) >> 2] + accumulator + last;
results[i++] = last = state[(y >> LOG_SIZE & MASK) >> 2] + x;
}
for (j = 0; j < SIZE / 2;) {
x = state[i];
accumulator ^= accumulator << 13;
accumulator += state[j++];
state[i] = y = state[(x & MASK) >> 2] + accumulator + last;
results[i++] = last = state[(y >> LOG_SIZE & MASK) >> 2] + x;
x = state[i];
accumulator ^= accumulator >>> 6;
accumulator += state[j++];
state[i] = y = state[(x & MASK) >> 2] + accumulator + last;
results[i++] = last = state[(y >> LOG_SIZE & MASK) >> 2] + x;
x = state[i];
accumulator ^= accumulator << 2;
accumulator += state[j++];
state[i] = y = state[(x & MASK) >> 2] + accumulator + last;
results[i++] = last = state[(y >> LOG_SIZE & MASK) >> 2] + x;
x = state[i];
accumulator ^= accumulator >>> 16;
accumulator += state[j++];
state[i] = y = state[(x & MASK) >> 2] + accumulator + last;
results[i++] = last = state[(y >> LOG_SIZE & MASK) >> 2] + x;
}
}
/**
* Initializes this random number generator.
*/
private void init() {
int i;
int a, b, c, d, e, f, g, h;
a = b = c = d = e = f = g = h = GOLDEN_RATIO;
for (i = 0; i < 4; ++i) {
a ^= b << 11;
d += a;
b += c;
b ^= c >>> 2;
e += b;
c += d;
c ^= d << 8;
f += c;
d += e;
d ^= e >>> 16;
g += d;
e += f;
e ^= f << 10;
h += e;
f += g;
f ^= g >>> 4;
a += f;
g += h;
g ^= h << 8;
b += g;
h += a;
h ^= a >>> 9;
c += h;
a += b;
}
for (i = 0; i < SIZE; i += 8) { /* fill in mem[] with messy stuff */
a += results[i];
b += results[i + 1];
c += results[i + 2];
d += results[i + 3];
e += results[i + 4];
f += results[i + 5];
g += results[i + 6];
h += results[i + 7];
a ^= b << 11;
d += a;
b += c;
b ^= c >>> 2;
e += b;
c += d;
c ^= d << 8;
f += c;
d += e;
d ^= e >>> 16;
g += d;
e += f;
e ^= f << 10;
h += e;
f += g;
f ^= g >>> 4;
a += f;
g += h;
g ^= h << 8;
b += g;
h += a;
h ^= a >>> 9;
c += h;
a += b;
state[i] = a;
state[i + 1] = b;
state[i + 2] = c;
state[i + 3] = d;
state[i + 4] = e;
state[i + 5] = f;
state[i + 6] = g;
state[i + 7] = h;
}
for (i = 0; i < SIZE; i += 8) {
a += state[i];
b += state[i + 1];
c += state[i + 2];
d += state[i + 3];
e += state[i + 4];
f += state[i + 5];
g += state[i + 6];
h += state[i + 7];
a ^= b << 11;
d += a;
b += c;
b ^= c >>> 2;
e += b;
c += d;
c ^= d << 8;
f += c;
d += e;
d ^= e >>> 16;
g += d;
e += f;
e ^= f << 10;
h += e;
f += g;
f ^= g >>> 4;
a += f;
g += h;
g ^= h << 8;
b += g;
h += a;
h ^= a >>> 9;
c += h;
a += b;
state[i] = a;
state[i + 1] = b;
state[i + 2] = c;
state[i + 3] = d;
state[i + 4] = e;
state[i + 5] = f;
state[i + 6] = g;
state[i + 7] = h;
}
isaac();
}
/**
* Gets the next random value.
*
* @return The next random value.
*/
public int nextInt() {
if (0 == count--) {
isaac();
count = SIZE - 1;
}
return results[count];
}
}