cubiomes/finders.c

#include "finders.h"

#include <stdio.h>
#include <string.h>
#include <pthread.h>
#include <stdlib.h>
#include <math.h>


STRUCT(quad_threadinfo_t)
{
    int64_t start, end;
    StructureConfig sconf;
    int threadID;
    int quality;
    const char *fnam;
};


//==============================================================================
// Globals
//==============================================================================


Biome biomes[256];


const int64_t lowerBaseBitsQ1[] = // for quad-structure with quality 1
        {
                0x3f18,0x520a,0x751a,0x9a0a
        };

const int64_t lowerBaseBitsQ2[] = // for quad-structure with quality 2
        {
                0x0770,0x0775,0x07ad,0x07b2,0x0c3a,0x0c58,0x0cba,0x0cd8,0x0e38,
                0x0e5a,0x0ed8,0x0eda,0x111c,0x1c96,0x2048,0x20e8,0x2248,0x224a,
                0x22c8,0x258d,0x272d,0x2732,0x2739,0x2758,0x275d,0x27c8,0x27c9,
                0x2aa9,0x2c3a,0x2cba,0x2eb8,0x308c,0x3206,0x371a,0x3890,0x3d0a,
                0x3f18,0x4068,0x40ca,0x40e8,0x418a,0x4248,0x426a,0x42ea,0x4732,
                0x4738,0x4739,0x4765,0x4768,0x476a,0x47b0,0x47b5,0x47d4,0x47d9,
                0x47e8,0x4c58,0x4e38,0x4eb8,0x4eda,0x5118,0x520a,0x5618,0x5918,
                0x591d,0x5a08,0x5e18,0x5f1c,0x60ca,0x6739,0x6748,0x6749,0x6758,
                0x6776,0x67b4,0x67b9,0x67c9,0x67d8,0x67dd,0x67ec,0x6c3a,0x6c58,
                0x6cba,0x6d9a,0x6e5a,0x6ed8,0x6eda,0x7108,0x717a,0x751a,0x7618,
                0x791c,0x8068,0x8186,0x8248,0x824a,0x82c8,0x82ea,0x8730,0x8739,
                0x8748,0x8768,0x87b9,0x87c9,0x87ce,0x87d9,0x898d,0x8c3a,0x8cda,
                0x8e38,0x8eb8,0x951e,0x9718,0x9a0a,0xa04a,0xa068,0xa0ca,0xa0e8,
                0xa18a,0xa26a,0xa2e8,0xa2ea,0xa43d,0xa4e1,0xa589,0xa76d,0xa7ac,
                0xa7b1,0xa7ed,0xa85d,0xa86d,0xaa2d,0xb1f8,0xb217,0xb9f8,0xba09,
                0xba17,0xbb0f,0xc54c,0xc6f9,0xc954,0xc9ce,0xd70b,0xd719,0xdc55,
                0xdf0b,0xe1c4,0xe556,0xe589,0xea5d
        };


//==============================================================================
// Saving & Loading Seeds
//==============================================================================


int64_t *loadSavedSeeds(const char *fnam, int64_t *scnt)
{
    FILE *fp = fopen(fnam, "r");

    int64_t seed;
    int64_t *baseSeeds;

    if (fp == NULL)
    {
        perror("ERR loadSavedSeeds: ");
        return NULL;
    }

    *scnt = 0;

    while (!feof(fp))
    {
        if (fscanf(fp, "%"PRId64, &seed) == 1) (*scnt)++;
        else while (!feof(fp) && fgetc(fp) != '\n');
    }

    baseSeeds = (int64_t*) calloc(*scnt, sizeof(*baseSeeds));

    rewind(fp);

    for (int64_t i = 0; i < *scnt && !feof(fp);)
    {
        if (fscanf(fp, "%"PRId64, &baseSeeds[i]) == 1) i++;
        else while (!feof(fp) && fgetc(fp) != '\n');
    }

    fclose(fp);

    return baseSeeds;
}


//==============================================================================
// Multi-Structure Checks
//==============================================================================

int isQuadFeatureBase(const StructureConfig sconf, const int64_t seed, const int qual)
{
    // seed offsets for the regions (0,0) to (1,1)
    const int64_t reg00base = sconf.seed;
    const int64_t reg01base = 341873128712 + sconf.seed;
    const int64_t reg10base = 132897987541 + sconf.seed;
    const int64_t reg11base = 341873128712 + 132897987541 + sconf.seed;

    const int range = sconf.chunkRange;
    const int upper = range - qual - 1;
    const int lower = qual;

    int64_t s;

    s = (reg00base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range < upper) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range < upper) return 0;

    s = (reg01base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range > lower) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range < upper) return 0;

    s = (reg10base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range < upper) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range > lower) return 0;

    s = (reg11base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range > lower) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range > lower) return 0;

    return 1;
}


int isTriFeatureBase(const StructureConfig sconf, const int64_t seed, const int qual)
{
    // seed offsets for the regions (0,0) to (1,1)
    const int64_t reg00base = sconf.seed;
    const int64_t reg01base = 341873128712 + sconf.seed;
    const int64_t reg10base = 132897987541 + sconf.seed;
    const int64_t reg11base = 341873128712 + 132897987541 + sconf.seed;

    const int range = sconf.chunkRange;
    const int upper = range - qual - 1;
    const int lower = qual;

    int64_t s;
    int missing = 0;

    s = (reg00base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range < upper ||
        (int)(((s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff) >> 17) % range < upper)
    {
        missing++;
    }

    s = (reg01base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range > lower ||
        (int)(((s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff) >> 17) % range < upper)
    {
        if (missing) return 0;
        missing++;
    }

    s = (reg10base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range < upper ||
        (int)(((s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff) >> 17) % range > lower)
    {
        if (missing) return 0;
        missing++;
    }

    s = (reg11base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    if ((int)(s >> 17) % range > lower ||
        (int)(((s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff) >> 17) % range > lower)
    {
        if (missing) return 0;
    }

    return 1;
}


int isLargeQuadBase(const StructureConfig sconf, const int64_t seed, const int qual)
{
    // seed offsets for the regions (0,0) to (1,1)
    const int64_t reg00base = sconf.seed;
    const int64_t reg01base = 341873128712 + sconf.seed;
    const int64_t reg10base = 132897987541 + sconf.seed;
    const int64_t reg11base = 341873128712 + 132897987541 + sconf.seed;

    const int range = sconf.chunkRange;
    const int rmin1 = range - 1;

    int64_t s;
    int p;

    s = (reg00base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p < rmin1-qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p < 2*rmin1-qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p < rmin1-qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p < 2*rmin1-qual) return 0;

    s = (reg01base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p > qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p > qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p < rmin1-qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p < 2*rmin1-qual) return 0;

    s = (reg10base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p < rmin1-qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p < 2*rmin1-qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p > qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p > qual) return 0;

    s = (reg11base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p > qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p > qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p > qual) return 0;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p > qual) return 0;

    return 1;
}


int isLargeTriBase(const StructureConfig sconf, const int64_t seed, const int qual)
{
    // seed offsets for the regions (0,0) to (1,1)
    const int64_t reg00base = sconf.seed;
    const int64_t reg01base = 341873128712 + sconf.seed;
    const int64_t reg10base = 132897987541 + sconf.seed;
    const int64_t reg11base = 341873128712 + 132897987541 + sconf.seed;

    const int range = sconf.chunkRange;
    const int rmin1 = range - 1;

    int64_t s;
    int p;

    int incomplete = 0;

    s = (reg00base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p < rmin1-qual) goto incomp11;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p < 2*rmin1-qual) goto incomp11;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p < rmin1-qual) goto incomp11;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p < 2*rmin1-qual) goto incomp11;

    if (0)
    {
        incomp11:
        incomplete = 1;
    }

    s = (reg01base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p > qual) goto incomp01;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p > qual) goto incomp01;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p < rmin1-qual) goto incomp01;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p < 2*rmin1-qual) goto incomp01;

    if (0)
    {
        incomp01:
        if (incomplete) return 0;
        incomplete = 2;
    }

    s = (reg10base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p < rmin1-qual) goto incomp10;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p < 2*rmin1-qual) goto incomp10;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p > qual) goto incomp10;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p > qual) goto incomp10;

    if (0)
    {
        incomp10:
        if (incomplete) return 0;
        incomplete = 3;
    }

    s = (reg11base + seed) ^ 0x5deece66dLL; // & 0xffffffffffff;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p > qual) goto incomp00;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p > qual) goto incomp00;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p = (int)(s >> 17) % range;
    if (p > qual) goto incomp00;
    s = (s * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    p += (int)(s >> 17) % range;
    if (p > qual) goto incomp00;

    if (0)
    {
        incomp00:
        if (incomplete) return 0;
        incomplete = 4;
    }

    return incomplete ? incomplete : -1;
}


/* Calls the correct quad-base finder for the structure config, if available.
 * (Exits program otherwise.)
 */
int isQuadBase(const StructureConfig sconf, const int64_t seed, const int64_t qual)
{
    switch(sconf.properties)
    {
    case 0:
        return isQuadFeatureBase(sconf, seed, qual);
    case LARGE_STRUCT:
        return isLargeQuadBase(sconf, seed, qual);
    case USE_POW2_RNG:
        fprintf(stderr,
                "Quad-finder using power of 2 RNG is not implemented yet.\n");
        exit(-1);
    case LARGE_STRUCT | USE_POW2_RNG:
        fprintf(stderr,
                "Quad-finder for large structures using power of 2 RNG"
                " is not implemented yet.\n");
        exit(-1);
    default:
        fprintf(stderr,
                "Unknown properties field for structure: 0x%04X\n",
                sconf.properties);
        exit(-1);
    }
}

/* Calls the correct triple-base finder for the structure config, if available.
 * (Exits program otherwise.)
 */
int isTriBase(const StructureConfig sconf, const int64_t seed, const int64_t qual)
{
    switch(sconf.properties)
    {
    case 0:
        return isTriFeatureBase(sconf, seed, qual);
    case LARGE_STRUCT:
        return isLargeTriBase(sconf, seed, qual);
    case USE_POW2_RNG:
        fprintf(stderr,
                "Quad-finder using power of 2 RNG is not implemented yet.\n");
        exit(-1);
    case LARGE_STRUCT | USE_POW2_RNG:
        fprintf(stderr,
                "Quad-finder for large structures using power of 2 RNG"
                " is not implemented yet.\n");
        exit(-1);
    default:
        fprintf(stderr,
                "Unknown properties field for structure: 0x%04X\n",
                sconf.properties);
        exit(-1);
    }
}



/* Searches for the optimal AFK position given four structures at positions 'p',
 * each of volume (ax,ay,az).
 *
 * Returned is the number of spawning spaces within reach.
 */
int countBlocksInSpawnRange(Pos p[4], const int ax, const int ay, const int az)
{
    int minX = 3e7, minZ = 3e7, maxX = -3e7, maxZ = -3e7;
    int best;


    // Find corners
    for (int i = 0; i < 4; i++)
    {
        if (p[i].x < minX) minX = p[i].x;
        if (p[i].z < minZ) minZ = p[i].z;
        if (p[i].x > maxX) maxX = p[i].x;
        if (p[i].z > maxZ) maxZ = p[i].z;
    }


    // assume that the search area is bound by the inner corners
    maxX += ax;
    maxZ += az;
    best = 0;

    double thsq = 128.0*128.0 - az*az/4.0;

    for (int x = minX; x < maxX; x++)
    {
        for (int z = minZ; z < maxZ; z++)
        {
            int inrange = 0;

            for (int i = 0; i < 4; i++)
            {
                double dx = p[i].x - (x+0.5);
                double dz = p[i].z - (z+0.5);

                for (int px = 0; px < ax; px++)
                {
                    for (int pz = 0; pz < az; pz++)
                    {
                        double ddx = px + dx;
                        double ddz = pz + dz;
                        inrange += (ddx*ddx + ddz*ddz <= thsq);
                    }
                }
            }

            if (inrange > best)
            {
                best = inrange;
            }
        }
    }

    return best;
}


static void *search4QuadBasesThread(void *data)
{
    quad_threadinfo_t info = *(quad_threadinfo_t*)data;

    const int64_t start = info.start;
    const int64_t end   = info.end;
    const int64_t structureSeed = info.sconf.seed;

    int64_t seed;

    int64_t *lowerBits;
    int lowerBitsCnt;
    int lowerBitsIdx = 0;
    int i;

    lowerBits = (int64_t *) malloc(0x10000 * sizeof(int64_t));

    if (info.quality == 1)
    {
        lowerBitsCnt = sizeof(lowerBaseBitsQ1) / sizeof(lowerBaseBitsQ1[0]);
        for (i = 0; i < lowerBitsCnt; i++)
        {
            lowerBits[i] = (lowerBaseBitsQ1[i] - structureSeed) & 0xffff;
        }
    }
    else if (info.quality == 2)
    {
        lowerBitsCnt = sizeof(lowerBaseBitsQ2) / sizeof(lowerBaseBitsQ2[0]);
        for (i = 0; i < lowerBitsCnt; i++)
        {
            lowerBits[i] = (lowerBaseBitsQ2[i] - structureSeed) & 0xffff;
        }
    }
    else
    {
        printf("WARN search4QuadBasesThread: "
               "Lower bits for quality %d have not been defined => "
               "will try all combinations.\n", info.quality);

        lowerBitsCnt = 0x10000;
        for (i = 0; i < lowerBitsCnt; i++) lowerBits[i] = i;
    }

    char fnam[256];
    sprintf(fnam, "%s.part%d", info.fnam, info.threadID);

    FILE *fp = fopen(fnam, "a+");
    if (fp == NULL)
    {
        fprintf(stderr, "Could not open \"%s\" for writing.\n", fnam);
        free(lowerBits);
        exit(-1);
    }

    seed = start;

    // Check the last entry in the file and use it as a starting point if it
    // exists. (I.e. loading the saved progress.)
    if (!fseek(fp, -31, SEEK_END))
    {
        char buf[32];
        if (fread(buf, 30, 1, fp) > 0)
        {
            char *last_newline = strrchr(buf, '\n');

            if (sscanf(last_newline, "%"PRId64, &seed) == 1)
            {
                while (lowerBits[lowerBitsIdx] <= (seed & 0xffff))
                    lowerBitsIdx++;

                seed = (seed & 0x0000ffffffff0000) + lowerBits[lowerBitsIdx];

                printf("Thread %d starting from: %"PRId64"\n", info.threadID, seed);
            }
            else
            {
                seed = start;
            }
        }
    }


    fseek(fp, 0, SEEK_END);


    while (seed < end)
    {
        if (isQuadBase(info.sconf, seed, info.quality))
        {
            fprintf(fp, "%"PRId64"\n", seed);
            fflush(fp);
            //printf("Thread %d: %"PRId64"\n", info.threadID, seed);
        }

        lowerBitsIdx++;
        if (lowerBitsIdx >= lowerBitsCnt)
        {
            lowerBitsIdx = 0;
            seed += 0x10000;
        }
        seed = (seed & 0x0000ffffffff0000) + lowerBits[lowerBitsIdx];
    }

    fclose(fp);
    free(lowerBits);

    return NULL;
}


void search4QuadBases(const char *fnam, const int threads,
        const StructureConfig structureConfig, const int quality)
{
    pthread_t threadID[threads];
    quad_threadinfo_t info[threads];
    int64_t t;

    for (t = 0; t < threads; t++)
    {
        info[t].threadID = t;
        info[t].start = (t * SEED_BASE_MAX / threads) & 0x0000ffffffff0000;
        info[t].end = ((info[t].start + (SEED_BASE_MAX-1) / threads) & 0x0000ffffffff0000) + 1;
        info[t].fnam = fnam;
        info[t].quality = quality;
        info[t].sconf = structureConfig;
    }

    for (t = 0; t < threads; t++)
    {
        pthread_create(&threadID[t], NULL, search4QuadBasesThread, (void*)&info[t]);
    }

    for (t = 0; t < threads; t++)
    {
        pthread_join(threadID[t], NULL);
    }

    // merge thread parts

    char fnamThread[256];
    char buffer[4097];
    FILE *fp = fopen(fnam, "w");
    if (fp == NULL) {
        fprintf(stderr, "Could not open \"%s\" for writing.\n", fnam);
        exit(-1);
    }
    FILE *fpart;
    int n;

    for (t = 0; t < threads; t++)
    {
        sprintf(fnamThread, "%s.part%d", info[t].fnam, info[t].threadID);

        fpart = fopen(fnamThread, "r");

        if (fpart == NULL)
        {
            perror("ERR search4QuadBases: ");
            break;
        }

        while ((n = fread(buffer, sizeof(char), 4096, fpart)))
        {
            if (!fwrite(buffer, sizeof(char), n, fp))
            {
                perror("ERR search4QuadBases: ");
                fclose(fp);
                fclose(fpart);
                return;
            }
        }

        fclose(fpart);

        remove(fnamThread);
    }

    fclose(fp);
}


//==============================================================================
// Finding Structure Positions
//==============================================================================


Pos getStructurePos(const StructureConfig config, int64_t seed,
        const int regionX, const int regionZ)
{
    Pos pos;

    // set seed
    seed = regionX*341873128712 + regionZ*132897987541 + seed + config.seed;
    seed = (seed ^ 0x5deece66dLL);// & ((1LL << 48) - 1);

    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;

    if (config.properties & USE_POW2_RNG)
    {
        // Java RNG treats powers of 2 as a special case.
        pos.x = (config.chunkRange * (seed >> 17)) >> 31;

        seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
        pos.z = (config.chunkRange * (seed >> 17)) >> 31;
    }
    else
    {
        pos.x = (int)(seed >> 17) % config.chunkRange;

        seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
        pos.z = (int)(seed >> 17) % config.chunkRange;
    }

    pos.x = ((regionX*config.regionSize + pos.x) << 4) + 8;
    pos.z = ((regionZ*config.regionSize + pos.z) << 4) + 8;
    return pos;
}

Pos getStructureChunkInRegion(const StructureConfig config, int64_t seed,
        const int regionX, const int regionZ)
{
    /*
    // Vanilla like implementation.
    seed = regionX*341873128712 + regionZ*132897987541 + seed + structureSeed;
    setSeed(&(seed));

    Pos pos;
    pos.x = nextInt(&seed, 24);
    pos.z = nextInt(&seed, 24);
    */
    Pos pos;

    seed = regionX*341873128712 + regionZ*132897987541 + seed + config.seed;
    seed = (seed ^ 0x5deece66dLL);// & ((1LL << 48) - 1);

    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;

    if (config.properties & USE_POW2_RNG)
    {
        // Java RNG treats powers of 2 as a special case.
        pos.x = (config.chunkRange * (seed >> 17)) >> 31;

        seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
        pos.z = (config.chunkRange * (seed >> 17)) >> 31;
    }
    else
    {
        pos.x = (int)(seed >> 17) % config.chunkRange;

        seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
        pos.z = (int)(seed >> 17) % config.chunkRange;
    }

    return pos;
}


Pos getLargeStructurePos(StructureConfig config, int64_t seed,
        const int regionX, const int regionZ)
{
    Pos pos;

    //TODO: if (config.properties & USE_POW2_RNG)...

    // set seed
    seed = regionX*341873128712 + regionZ*132897987541 + seed + config.seed;
    seed = (seed ^ 0x5deece66dLL) & ((1LL << 48) - 1);

    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.x = (seed >> 17) % config.chunkRange;
    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.x += (seed >> 17) % config.chunkRange;

    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.z = (seed >> 17) % config.chunkRange;
    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.z += (seed >> 17) % config.chunkRange;

    pos.x = regionX*config.regionSize + (pos.x >> 1);
    pos.z = regionZ*config.regionSize + (pos.z >> 1);
    pos.x = pos.x*16 + 8;
    pos.z = pos.z*16 + 8;
    return pos;
}


Pos getLargeStructureChunkInRegion(StructureConfig config, int64_t seed,
        const int regionX, const int regionZ)
{
    Pos pos;

    //TODO: if (config.properties & USE_POW2_RNG)...

    // set seed
    seed = regionX*341873128712 + regionZ*132897987541 + seed + config.seed;
    seed = (seed ^ 0x5deece66dLL) & ((1LL << 48) - 1);

    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.x = (seed >> 17) % config.chunkRange;
    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.x += (seed >> 17) % config.chunkRange;

    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.z = (seed >> 17) % config.chunkRange;
    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.z += (seed >> 17) % config.chunkRange;

    pos.x >>= 1;
    pos.z >>= 1;

    return pos;
}


//==============================================================================
// Checking Biomes & Biome Helper Functions
//==============================================================================


int getBiomeAtPos(const LayerStack g, const Pos pos)
{
    int *map = allocCache(&g.layers[g.layerNum-1], 1, 1);
    genArea(&g.layers[g.layerNum-1], map, pos.x, pos.z, 1, 1);
    int biomeID = map[0];
    free(map);
    return biomeID;
}

Pos findBiomePosition(
        const int mcversion,
        const LayerStack g,
        int *cache,
        const int centerX,
        const int centerZ,
        const int range,
        const int *isValid,
        int64_t *seed,
        int *passes
        )
{
    int x1 = (centerX-range) >> 2;
    int z1 = (centerZ-range) >> 2;
    int x2 = (centerX+range) >> 2;
    int z2 = (centerZ+range) >> 2;
    int width  = x2 - x1 + 1;
    int height = z2 - z1 + 1;
    int *map;
    int i, j, found;

    Layer *layer = &g.layers[L_RIVER_MIX_4];
    Pos out;

    if (layer->scale != 4)
    {
        printf("WARN findBiomePosition: The generator has unexpected scale %d at layer %d.\n",
                layer->scale, L_RIVER_MIX_4);
    }

    map = cache ? cache : allocCache(layer, width, height);

    genArea(layer, map, x1, z1, width, height);

    out.x = centerX;
    out.z = centerZ;
    found = 0;

    if (mcversion >= MC_1_13)
    {
        for (i = 0, j = 2; i < width*height; i++)
        {
            if (!isValid[map[i] & 0xff]) continue;
            if ((found == 0 || nextInt(seed, j++) == 0))
            {
                out.x = (x1 + i%width) << 2;
                out.z = (z1 + i/width) << 2;
                found = 1;
            }
        }
        found = j - 2;
    }
    else
    {
        for (i = 0; i < width*height; i++)
        {
            if (isValid[map[i] & 0xff] &&
                (found == 0 || nextInt(seed, found + 1) == 0))
            {
                out.x = (x1 + i%width) << 2;
                out.z = (z1 + i/width) << 2;
                ++found;
            }
        }
    }


    if (cache == NULL)
    {
        free(map);
    }

    if (passes != NULL)
    {
        *passes = found;
    }

    return out;
}


int areBiomesViable(
        const LayerStack    g,
        int *               cache,
        const int           posX,
        const int           posZ,
        const int           radius,
        const int *         isValid
        )
{
    int x1 = (posX - radius) >> 2;
    int z1 = (posZ - radius) >> 2;
    int x2 = (posX + radius) >> 2;
    int z2 = (posZ + radius) >> 2;
    int width = x2 - x1 + 1;
    int height = z2 - z1 + 1;
    int i;
    int *map;

    Layer *layer = &g.layers[L_RIVER_MIX_4];

    if (layer->scale != 4)
    {
        printf("WARN areBiomesViable: The generator has unexpected scale %d at layer %d.\n",
                layer->scale, L_RIVER_MIX_4);
    }

    map = cache ? cache : allocCache(layer, width, height);
    genArea(layer, map, x1, z1, width, height);

    for (i = 0; i < width*height; i++)
    {
        if (!isValid[ map[i] & 0xff ])
        {
            if (cache == NULL) free(map);
            return 0;
        }
    }

    if (cache == NULL) free(map);
    return 1;
}


int getBiomeRadius(
        const int *         map,
        const int           mapSide,
        const int *         biomes,
        const int           bnum,
        const int           ignoreMutations)
{
    int r, i, b;
    int blist[0x100];
    int mask = ignoreMutations ? 0x7f : 0xff;
    int radiusMax = mapSide / 2;

    if ((mapSide & 1) == 0)
    {
        printf("WARN getBiomeRadius: Side length of the square map should be an odd integer.\n");
    }

    memset(blist, 0, sizeof(blist));

    for (r = 1; r < radiusMax; r++)
    {
        for (i = radiusMax-r; i <= radiusMax+r; i++)
        {
            blist[ map[(radiusMax-r) * mapSide+ i]    & mask ] = 1;
            blist[ map[(radiusMax+r-1) * mapSide + i] & mask ] = 1;
            blist[ map[mapSide*i + (radiusMax-r)]     & mask ] = 1;
            blist[ map[mapSide*i + (radiusMax+r-1)]   & mask ] = 1;
        }

        for (b = 0; b < bnum && blist[biomes[b] & mask]; b++);
        if (b >= bnum)
        {
            break;
        }
    }

    return r != radiusMax ? r : -1;
}



//==============================================================================
// Finding Strongholds and Spawn
//==============================================================================


int* getValidStrongholdBiomes()
{
    static int validStrongholdBiomes[256];

    if (!validStrongholdBiomes[plains])
    {
        int id;
        for (id = 0; id < 256; id++)
        {
            if (biomeExists(id) && biomes[id].height > 0.0)
                validStrongholdBiomes[id] = 1;
        }
    }

    return validStrongholdBiomes;
}


int findStrongholds(const int mcversion, LayerStack *g, int *cache,
        Pos *locations, int64_t worldSeed, int maxSH, const int maxRadius)
{
    const int *validStrongholdBiomes = getValidStrongholdBiomes();
    int i, x, z;
    double distance;

    int currentRing = 0;
    int currentCount = 0;
    int perRing = 3;

    setSeed(&worldSeed);
    double angle = nextDouble(&worldSeed) * PI * 2.0;

    if (mcversion >= MC_1_9)
    {
        if (maxSH <= 0) maxSH = 128;

        for (i = 0; i < maxSH; i++)
        {
            distance = (4.0 * 32.0) + (6.0 * currentRing * 32.0) +
                (nextDouble(&worldSeed) - 0.5) * 32 * 2.5;

            if (maxRadius && distance*16 > maxRadius)
                return i;

            x = (int)round(cos(angle) * distance);
            z = (int)round(sin(angle) * distance);

            locations[i] = findBiomePosition(mcversion, *g, cache,
                    (x << 4) + 8, (z << 4) + 8, 112, validStrongholdBiomes,
                    &worldSeed, NULL);

            angle += 2 * PI / perRing;

            currentCount++;
            if (currentCount == perRing)
            {
                // Current ring is complete, move to next ring.
                currentRing++;
                currentCount = 0;
                perRing = perRing + 2*perRing/(currentRing+1);
                if (perRing > 128-i)
                    perRing = 128-i;
                angle = angle + nextDouble(&worldSeed) * PI * 2.0;
            }
        }
    }
    else
    {
        if (maxSH <= 0) maxSH = 3;

        for (i = 0; i < maxSH; i++)
        {
            distance = (1.25 + nextDouble(&worldSeed)) * 32.0;

            if (maxRadius && distance*16 > maxRadius)
                return i;

            x = (int)round(cos(angle) * distance);
            z = (int)round(sin(angle) * distance);

            locations[i] = findBiomePosition(mcversion, *g, cache,
                    (x << 4) + 8, (z << 4) + 8, 112, validStrongholdBiomes,
                    &worldSeed, NULL);

            angle += 2 * PI / 3.0;
        }
    }

    return maxSH;
}


static double getGrassProbability(int64_t seed, int biome, int x, int z)
{
    // TODO: Use ChunkGeneratorOverworld.generateHeightmap for better estimate.
    // TODO: Try to determine the actual probabilities and build a statistic.
    switch (biome)
    {
    case plains:            return 1.0;
    case extremeHills:      return 0.8; // height dependent
    case forest:            return 1.0;
    case taiga:             return 1.0;
    case swampland:         return 0.6; // height dependent
    case river:             return 0.2;
    case beach:             return 0.1;
    case forestHills:       return 1.0;
    case taigaHills:        return 1.0;
    case extremeHillsEdge:  return 1.0; // height dependent
    case jungle:            return 1.0;
    case jungleHills:       return 1.0;
    case jungleEdge:        return 1.0;
    case birchForest:       return 1.0;
    case birchForestHills:  return 1.0;
    case roofedForest:      return 0.9;
    case coldTaiga:         return 0.1; // below trees
    case coldTaigaHills:    return 0.1; // below trees
    case megaTaiga:         return 0.6;
    case megaTaigaHills:    return 0.6;
    case extremeHillsPlus:  return 0.2; // height dependent
    case savanna:           return 1.0;
    case savannaPlateau:    return 1.0;
    case mesaPlateau_F:     return 0.1; // height dependent
    case mesaPlateau:       return 0.1; // height dependent
    // NOTE: in rare circumstances you can get also get grass islands that are
    // completely ocean variants...
    default: return 0;
    }
}

static int canCoordinateBeSpawn(const int64_t seed, LayerStack *g, int *cache, Pos pos)
{
    int biome = getBiomeAtPos(*g, pos);
    return getGrassProbability(seed, biome, pos.x, pos.z) >= 0.5;
}

static int* getValidSpawnBiomes()
{
    static int isSpawnBiome[256];
    unsigned int i;

    if (!isSpawnBiome[biomesToSpawnIn[0]])
    {
        for (i = 0; i < sizeof(biomesToSpawnIn) / sizeof(int); i++)
        {
            isSpawnBiome[ biomesToSpawnIn[i] ] = 1;
        }
    }

    return isSpawnBiome;
}


Pos getSpawn(const int mcversion, LayerStack *g, int *cache, int64_t worldSeed)
{
    const int *isSpawnBiome = getValidSpawnBiomes();
    Pos spawn;
    int found;
    int i;

    setSeed(&worldSeed);
    spawn = findBiomePosition(mcversion, *g, cache, 0, 0, 256, isSpawnBiome,
            &worldSeed, &found);

    if (!found)
    {
        //printf("Unable to find spawn biome.\n");
        spawn.x = spawn.z = 8;
    }

    if (mcversion >= MC_1_13)
    {
        // TODO: The 1.13 section may need further checking!
        int n2 = 0;
        int n3 = 0;
        int n4 = 0;
        int n5 = -1;

        for (i = 0; i < 1024; i++)
        {
            if (n2 > -16 && n2 <= 16 && n3 > -16 && n3 <= 16)
            {
                int cx = ((spawn.x >> 4) + n2) << 4;
                int cz = ((spawn.z >> 4) + n3) << 4;

                for (int i2 = cx; i2 <= cx+15; i2++)
                {
                    for (int i3 = cz; i3 <= cz+15; i3++)
                    {
                        Pos pos = {i2, i3};
                        if (canCoordinateBeSpawn(worldSeed, g, cache, pos))
                        {
                            return pos;
                        }
                    }
                }
            }

            if (n2 == n3 || (n2 < 0 && n2 == - n3) || (n2 > 0 && n2 == 1 - n3))
            {
                int n7 = n4;
                n4 = - n5;
                n5 = n7;
            }
            n2 += n4;
            n3 += n5;
        }
    }
    else
    {
        for (i = 0; i < 1000 && !canCoordinateBeSpawn(worldSeed, g, cache, spawn); i++)
        {
            spawn.x += nextInt(&worldSeed, 64) - nextInt(&worldSeed, 64);
            spawn.z += nextInt(&worldSeed, 64) - nextInt(&worldSeed, 64);
        }
    }

    return spawn;
}



//==============================================================================
// Validating Structure Positions
//==============================================================================


int isViableFeaturePos(const int structureType, const LayerStack g, int *cache,
        const int blockX, const int blockZ)
{
    int *map = cache ? cache : allocCache(&g.layers[g.layerNum-1], 1, 1);
    genArea(&g.layers[g.layerNum-1], map, blockX, blockZ, 1, 1);
    int biomeID = map[0];
    if (!cache) free(map);

    switch(structureType)
    {
    case Desert_Pyramid:
        return biomeID == desert || biomeID == desertHills;
    case Igloo:
        return biomeID == icePlains || biomeID == coldTaiga;
    case Jungle_Pyramid:
        return biomeID == jungle || biomeID == jungleHills;
    case Swamp_Hut:
        return biomeID == swampland;
    case Ocean_Ruin:
    case Shipwreck:
        return isOceanic(biomeID);
    default:
        fprintf(stderr, "Structure type is not valid for the scattered feature biome check.\n");
        exit(1);
    }
}

int isViableVillagePos(const LayerStack g, int *cache,
        const int blockX, const int blockZ)
{
    static int isVillageBiome[0x100];

    if (!isVillageBiome[villageBiomeList[0]])
    {
        unsigned int i;
        for (i = 0; i < sizeof(villageBiomeList) / sizeof(int); i++)
        {
            isVillageBiome[ villageBiomeList[i] ] = 1;
        }
    }

    return areBiomesViable(g, cache, blockX, blockZ, 0, isVillageBiome);
}

int isViableOceanMonumentPos(const LayerStack g, int *cache,
        const int blockX, const int blockZ)
{
    static int isWaterBiome[0x100];
    static int isDeepOcean[0x100];

    if (!isWaterBiome[oceanMonumentBiomeList1[1]])
    {
        unsigned int i;
        for (i = 0; i < sizeof(oceanMonumentBiomeList1) / sizeof(int); i++)
        {
            isWaterBiome[ oceanMonumentBiomeList1[i] ] = 1;
        }

        for (i = 0; i < sizeof(oceanMonumentBiomeList2) / sizeof(int); i++)
        {
            isDeepOcean[ oceanMonumentBiomeList2[i] ] = 1;
        }
    }

    return areBiomesViable(g, cache, blockX, blockZ, 16, isDeepOcean) &&
            areBiomesViable(g, cache, blockX, blockZ, 29, isWaterBiome);
}

int isViableMansionPos(const LayerStack g, int *cache,
        const int blockX, const int blockZ)
{
    static int isMansionBiome[0x100];

    if (!isMansionBiome[mansionBiomeList[0]])
    {
        unsigned int i;
        for (i = 0; i < sizeof(mansionBiomeList) / sizeof(int); i++)
        {
            isMansionBiome[ mansionBiomeList[i] ] = 1;
        }
    }

    return areBiomesViable(g, cache, blockX, blockZ, 32, isMansionBiome);
}




//==============================================================================
// Finding Properties of Structures
//==============================================================================


int isZombieVillage(const int mcversion, const int64_t worldSeed,
        const int regionX, const int regionZ)
{
    Pos pos;
    int64_t seed = worldSeed;

    if (mcversion < MC_1_10)
    {
        printf("Warning: Zombie villages were only introduced in MC 1.10.\n");
    }

    // get the chunk position of the village
    seed = regionX*341873128712 + regionZ*132897987541 + seed + VILLAGE_CONFIG.seed;
    seed = (seed ^ 0x5deece66dLL);// & ((1LL << 48) - 1);

    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.x = (seed >> 17) % VILLAGE_CONFIG.chunkRange;

    seed = (seed * 0x5deece66dLL + 0xbLL) & 0xffffffffffff;
    pos.z = (seed >> 17) % VILLAGE_CONFIG.chunkRange;

    pos.x += regionX * VILLAGE_CONFIG.regionSize;
    pos.z += regionZ * VILLAGE_CONFIG.regionSize;

    // jump to the random number check that determines whether this is village
    // is zombie infested
    int64_t rnd = chunkGenerateRnd(worldSeed, pos.x , pos.z);
    // TODO: check for versions <= 1.11
    skipNextN(&rnd, mcversion >= MC_1_13 ? 10 : 11);

    return nextInt(&rnd, 50) == 0;
}


int isBabyZombieVillage(const int mcversion, const int64_t worldSeed,
        const int regionX, const int regionZ)
{
    if (!isZombieVillage(mcversion, worldSeed, regionX, regionZ))
        return 0;

    // Whether the zombie is a child or not is dependent on the world random
    // object which is not reset for villages. The last reset is instead
    // performed during the positioning of Mansions.
    int64_t rnd = worldSeed;
    rnd = regionX*341873128712 + regionZ*132897987541 + rnd + MANSION_CONFIG.seed;
    setSeed(&rnd);
    skipNextN(&rnd, 5);

    int isChild = nextFloat(&rnd) < 0.05;
    //int mountNearbyChicken = nextFloat(&rnd) < 0.05;
    //int spawnNewChicken = nextFloat(&rnd) < 0.05;

    return isChild;
}



//==============================================================================
// Seed Filters
//==============================================================================


int64_t filterAllTempCats(
        LayerStack *        g,
        int *               cache,
        const int64_t *     seedsIn,
        int64_t *           seedsOut,
        const int64_t       seedCnt,
        const int           centX,
        const int           centZ)
{
    /* We require all temperature categories, including the special variations
     * in order to get all main biomes. This gives 8 required values:
     * Oceanic, Warm, Lush, Cold, Freezing,
     * Special Warm, Special Lush, Special Cold
     * These categories generate at Layer 13: Edge, Special.
     *
     * Note: The scale at this layer is 1:1024 and each element can "leak" its
     * biome values up to 1024 blocks outwards into the negative coordinates
     * (due to the Zoom layers).
     *
     * The plan is to check if the 3x3 area contains all 8 temperature types.
     * For this, we can check even earlier at Layer 10: Add Island, that each of
     * the Warm, Cold and Freezing categories are present.
     */

    /* Edit:
     * All the biomes that are generated by a simple Cold climate can actually
     * be generated later on. So I have commented out the Cold requirements.
     */

    const int pX = centX-1, pZ = centZ-1;
    const int sX = 3, sZ = 3;
    int *map;

    Layer *lFilterSnow = &g->layers[L_ADD_SNOW_1024];
    Layer *lFilterSpecial = &g->layers[L_SPECIAL_1024];

    map = cache ? cache : allocCache(lFilterSpecial, sX, sZ);

    // Construct a dummy Edge,Special layer.
    Layer layerSpecial;
    setupLayer(1024, &layerSpecial, NULL, 3, NULL);

    int64_t sidx, hits, seed;
    int types[9];
    int specialCnt;
    int i, j;

    hits = 0;

    for (sidx = 0; sidx < seedCnt; sidx++)
    {
        seed = seedsIn[sidx];

        /***  Pre-Generation Checks  ***/

        // We require at least 3 special temperature categories which can be
        // tested for without going through the previous layers. (We'll get
        // false positives due to Oceans, but this works fine to rule out some
        // seeds early on.)
        setWorldSeed(&layerSpecial, seed);
        specialCnt = 0;
        for (i = 0; i < sX; i++)
        {
            for (j = 0; j < sZ; j++)
            {
                setChunkSeed(&layerSpecial, (int64_t)(i+pX), (int64_t)(j+pZ));
                if (mcNextInt(&layerSpecial, 13) == 0)
                    specialCnt++;
            }
        }

        if (specialCnt < 3)
        {
            continue;
        }

        /***  Cold/Warm Check  ***/

        // Continue by checking if enough cold and warm categories are present.
        setWorldSeed(lFilterSnow, seed);
        genArea(lFilterSnow, map, pX,pZ, sX,sZ);

        memset(types, 0, sizeof(types));
        for (i = 0; i < sX*sZ; i++)
            types[map[i]]++;

        // 1xOcean needs to be present
        // 4xWarm need to turn into Warm, Lush, Special Warm and Special Lush
        // 1xFreezing that needs to stay Freezing
        // 3x(Cold + Freezing) for Cold, Special Cold and Freezing
        if ( types[Ocean] < 1 || types[Warm] < 4 || types[Freezing] < 1 ||
            types[Cold]+types[Freezing] < 2)
        {
            continue;
        }

        /***  Complete Temperature Category Check  ***/

        // Check that all temperature variants are present.
        setWorldSeed(lFilterSpecial, seed);
        genArea(lFilterSpecial, map, pX,pZ, sX,sZ);

        memset(types, 0, sizeof(types));
        for (i = 0; i < sX*sZ; i++)
            types[ map[i] > 4 ? (map[i]&0xf) + 4 : map[i] ]++;

        if ( types[Ocean] < 1  || types[Warm] < 1     || types[Lush] < 1 ||
            /*types[Cold] < 1   ||*/ types[Freezing] < 1 ||
            types[Warm+4] < 1 || types[Lush+4] < 1   || types[Cold+4] < 1)
        {
            continue;
        }

        /*
        for (i = 0; i < sX*sZ; i++)
        {
            printf("%c%d ", " s"[cache[i] > 4], cache[i]&0xf);
            if (i % sX == sX-1) printf("\n");
        }
        printf("\n");*/

        // Save the candidate.
        seedsOut[hits] = seed;
        hits++;
    }

    if (cache == NULL) free(map);
    return hits;
}




const int majorBiomes[] = {
        ocean, plains, desert, extremeHills, forest, taiga, swampland,
        icePlains, mushroomIsland, jungle, deepOcean, birchForest, roofedForest,
        coldTaiga, megaTaiga, savanna, mesaPlateau_F, mesaPlateau
};

int64_t filterAllMajorBiomes(
        LayerStack *        g,
        int *               cache,
        const int64_t *     seedsIn,
        int64_t *           seedsOut,
        const int64_t       seedCnt,
        const int           pX,
        const int           pZ,
        const unsigned int  sX,
        const unsigned int  sZ)
{
    Layer *lFilterMushroom = &g->layers[L_ADD_MUSHROOM_ISLAND_256];
    Layer *lFilterBiomes = &g->layers[L_BIOME_256];

    int *map;
    int64_t sidx, seed, hits;
    unsigned int i, id, hasAll;

    int types[BIOME_NUM];

    map = cache ? cache : allocCache(lFilterBiomes, sX, sZ);

    hits = 0;

    for (sidx = 0; sidx < seedCnt; sidx++)
    {
        /* We can use the Mushroom layer both to check for mushroomIsland biomes
         * and to make sure all temperature categories are present in the area.
         */
        seed = seedsIn[sidx];
        setWorldSeed(lFilterMushroom, seed);
        genArea(lFilterMushroom, map, pX,pZ, sX,sZ);

        memset(types, 0, sizeof(types));
        for (i = 0; i < sX*sZ; i++)
        {
            id = map[i];
            if (id >= BIOME_NUM) id = (id & 0xf) + 4;
            types[id]++;
        }

        if ( types[Ocean] < 1  || types[Warm] < 1     || types[Lush] < 1 ||
         /* types[Cold] < 1   || */ types[Freezing] < 1 ||
            types[Warm+4] < 1 || types[Lush+4] < 1   || types[Cold+4] < 1 ||
            types[mushroomIsland] < 1)
        {
            continue;
        }

        /***  Find all major biomes  ***/

        setWorldSeed(lFilterBiomes, seed);
        genArea(lFilterBiomes, map, pX,pZ, sX,sZ);

        memset(types, 0, sizeof(types));
        for (i = 0; i < sX*sZ; i++)
        {
            types[map[i]]++;
        }

        hasAll = 1;
        for (i = 0; i < sizeof(majorBiomes) / sizeof(*majorBiomes); i++)
        {
            // plains, taiga and deepOcean can be generated in later layers.
            // Also small islands of Forests can be generated in deepOcean
            // biomes, but we are going to ignore those.
            if (majorBiomes[i] == plains ||
               majorBiomes[i] == taiga ||
               majorBiomes[i] == deepOcean)
            {
                continue;
            }

            if (types[majorBiomes[i]] < 1)
            {
                hasAll = 0;
                break;
            }
        }
        if (!hasAll)
        {
            continue;
        }

        seedsOut[hits] = seed;
        hits++;
    }

    if (cache == NULL) free(map);
    return hits;
}