SeedPool.java

import java.util.Random;

public class SeedPool {
  int seedDataA[];
  int seedDataB[];

  public SeedPool(int seedData[]) {
    assert(seedData.length == 8);

    this.seedDataA = new int[4];
    this.seedDataB = new int[4];
    int i;
    for (i = 0; i < 4; ++i) {
      seedDataA[i] = seedData[i];
      seedDataB[i] = seedData[i + 4];
    }
  }

  public long seedForPurpose(SeedPool.Purpose purpose) {
    // Expand purpose in to integer pair
    Random random = new Random(purpose.getCode());
    return randomSeed(random);
  }

  public long randomSeed(Random random) {
    int[] data = new int[2];
    int i;
    for (i = 0; i < 2; i++) {
      data[i] = random.nextInt();
    }

    // Encrypt integer pair with seed data
    data = run_xtea(seedDataA, data);
    data = run_xtea(seedDataB, data);

    // Turn integer pair in to long seed
    return (((long) data[0]) << 32) | ((long) data[1]);
  }

  /* Encrypt the purpose using the seed data */
  private int[] run_xtea(int[] key, int[] data) {
    int i;
    int[] v = new int[2];
    v[0] = data[0];
    v[1] = data[1];
    int sum = 0;
    int delta = 0x9E3779B9;
    for (i=0; i < 20; i++) {
        v[0] += (((v[1] << 4) ^ (v[1] >> 5)) + v[1]) ^ (sum + key[sum & 3]);
        sum += delta;
        v[1] += (((v[0] << 4) ^ (v[0] >> 5)) + v[0]) ^ (sum + key[(sum>>11) & 3]);
    }
    return v;
  }

  public enum Purpose {
    HEIGHT_MAP(1),
    COAL_VEINS(2),
    LAPIS_VEINS(3);

    private int code;

    private Purpose(int code) {
      this.code = code;
    }
    public int getCode() {
      return code;
    }
  };

  public static void main(String[] argv) {
    int[] testSeedData = {221442586, 1725827729, 373678985, 1759486438, 1799993957, 1448443797, 60942502, 2112571401};
    SeedPool testPool = new SeedPool(testSeedData);

    long seedForHeightMap = testPool.seedForPurpose(SeedPool.Purpose.HEIGHT_MAP);
    System.out.println(String.format("Height map seed: %d", seedForHeightMap));

    long seedForCoalVeins = testPool.seedForPurpose(SeedPool.Purpose.COAL_VEINS);
    System.out.println(String.format("Coal vein seed: %d", seedForCoalVeins));

    long seedForLapisVeins = testPool.seedForPurpose(SeedPool.Purpose.LAPIS_VEINS);
    System.out.println(String.format("Lapis vein seed: %d", seedForLapisVeins));
  }
}