finders.h

#ifndef FINDERS_H_
#define FINDERS_H_


#include "generator.h"


#ifdef __cplusplus
extern "C"
{
#endif

#define MASK48 (((int64_t)1 << 48) - 1)

#define LARGE_STRUCT 1
#define CHUNK_STRUCT 2

enum StructureType
{
    Feature, // for locations of temple generation attempts pre 1.13
    Desert_Pyramid,
    Jungle_Temple, Jungle_Pyramid = Jungle_Temple,
    Swamp_Hut,
    Igloo,
    Village,
    Ocean_Ruin,
    Shipwreck,
    Monument,
    Mansion,
    Outpost,
    Ruined_Portal,
    Ruined_Portal_N,
    Ancient_City,
    Treasure,
    Mineshaft,
    Fortress,
    Bastion,
    End_City,
    End_Gateway,
    FEATURE_NUM
};

STRUCT(StructureConfig)
{
    int             salt;
    char            regionSize;
    char            chunkRange;
    unsigned char   structType;
    unsigned char   properties;
};

#define _sc static const StructureConfig

/* for desert pyramids, jungle temples, witch huts and igloos prior to 1.13 */
_sc FEATURE_CONFIG            = { 14357617, 32, 24, Feature, 0};
_sc IGLOO_CONFIG_112          = { 14357617, 32, 24, Igloo, 0};
_sc SWAMP_HUT_CONFIG_112      = { 14357617, 32, 24, Swamp_Hut, 0};
_sc DESERT_PYRAMID_CONFIG_112 = { 14357617, 32, 24, Desert_Pyramid, 0};
_sc JUNGLE_PYRAMID_CONFIG_112 = { 14357617, 32, 24, Jungle_Pyramid, 0};

/* ocean features before 1.16 */
_sc OCEAN_RUIN_CONFIG_115     = { 14357621, 16,  8, Ocean_Ruin, 0};
_sc SHIPWRECK_CONFIG_115      = {165745295, 15,  7, Shipwreck, 0};

/* 1.13 separated feature seeds by type */
_sc DESERT_PYRAMID_CONFIG     = { 14357617, 32, 24, Desert_Pyramid, 0};
_sc IGLOO_CONFIG              = { 14357618, 32, 24, Igloo, 0};
_sc JUNGLE_PYRAMID_CONFIG     = { 14357619, 32, 24, Jungle_Pyramid, 0};
_sc SWAMP_HUT_CONFIG          = { 14357620, 32, 24, Swamp_Hut, 0};
_sc OUTPOST_CONFIG            = {165745296, 32, 24, Outpost, 0};
_sc VILLAGE_CONFIG_117        = { 10387312, 32, 24, Village, 0};
_sc VILLAGE_CONFIG            = { 10387312, 34, 26, Village, 0};
_sc OCEAN_RUIN_CONFIG         = { 14357621, 20, 12, Ocean_Ruin, 0};
_sc SHIPWRECK_CONFIG          = {165745295, 24, 20, Shipwreck, 0};
_sc MONUMENT_CONFIG           = { 10387313, 32, 27, Monument, LARGE_STRUCT};
_sc MANSION_CONFIG            = { 10387319, 80, 60, Mansion, LARGE_STRUCT};
_sc RUINED_PORTAL_CONFIG      = { 34222645, 40, 25, Ruined_Portal, 0}; // overworld
_sc RUINED_PORTAL_N_CONFIG_117= { 34222645, 25, 15, Ruined_Portal_N, 0}; // nether
_sc ANCIENT_CITY_CONFIG       = { 20083232, 24, 16, Ancient_City, 0};

_sc TREASURE_CONFIG           = { 10387320,  1,  1, Treasure, CHUNK_STRUCT};
_sc MINESHAFT_CONFIG          = {        0,  1,  1, Mineshaft, CHUNK_STRUCT};

// nether and end structures
_sc FORTRESS_CONFIG_115       = {        0, 16,  8, Fortress, 0};
_sc FORTRESS_CONFIG           = { 30084232, 27, 23, Fortress, 0};
_sc BASTION_CONFIG            = { 30084232, 27, 23, Bastion, 0};
_sc END_CITY_CONFIG           = { 10387313, 20,  9, End_City, LARGE_STRUCT};

// for the scattered return gateways
_sc END_GATEWAY_CONFIG_115    = {    30000,  1,  1, End_Gateway, CHUNK_STRUCT};
_sc END_GATEWAY_CONFIG        = {    40013,  1,  1, End_Gateway, CHUNK_STRUCT};

#undef _sc

STRUCT(Pos)
{
    int x, z;
};

enum
{
    CFB_APPROX      = 0x01, // enabled aggresive filtering, trading accuracy
};
STRUCT(BiomeFilter)
{
    // bitfields for biomes required at their respecive layers
    uint64_t tempsToFind; // Special (1:1024)
    uint64_t otempToFind; // OceanTemp (1:256)
    uint64_t majorToFind; // Biome (1:256)
    uint64_t edgesToFind; // Edge (1:64) [mod64: as special case for bamboo]
    // bitfields for biomes to find at RareBiome(1:64), Shore(1:16) and Mix(1:4)
    // layers for (biomeID < 64) and modified (biomeID >= 128 && biomeID < 192)
    uint64_t raresToFind, raresToFindM;
    uint64_t shoreToFind, shoreToFindM;
    uint64_t riverToFind, riverToFindM;
    uint64_t oceanToFind; // all required ocean types

    int specialCnt; // number of special temperature categories required

    uint32_t flags;

    // the biome exclusion aborts generation when the area contains no biomes
    // that can generate the excluded biomes
    uint64_t tempsToExcl;
    uint64_t majorToExcl;
    uint64_t edgesToExcl;
    uint64_t raresToExcl, raresToExclM;
    uint64_t shoreToExcl, shoreToExclM;
    uint64_t riverToExcl, riverToExclM;

    uint64_t biomeToExcl, biomeToExclM;
    uint64_t biomeToFind, biomeToFindM;
    uint64_t biomeToPick, biomeToPickM;
};

STRUCT(StrongholdIter)
{
    Pos pos;        // accurate location of current stronghold
    Pos nextapprox; // approxmimate location (+/-112 blocks) of next stronghold
    int index;      // stronghold index counter
    int ringnum;    // ring number for index
    int ringmax;    // max index within ring
    int ringidx;    // index within ring
    double angle;   // next angle within ring
    double dist;    // next distance from origin (in chunks)
    uint64_t rnds;  // random number seed (48 bit)
    int mc;         // minecraft version
};


STRUCT(StructureVariant)
{
    uint8_t abandoned;      // is zombie village
    uint8_t giant;          // giant portal variant
    uint8_t underground;    // underground portal
    uint8_t airpocket;
    char variant;
    const char *name;
    short biome;
    uint8_t rotation;       // 0:0, 1:cw90, 2:cw180, 3:cw270=ccw90
    uint8_t mirror;
    char x, y, z;
    char sx, sy, sz;
};


/***************************** Structure Positions *****************************
 *
 *  For most structure positions, Minecraft divides the world into a grid of
 *  regions (usually 32x32 chunks) and performs one generation attempt
 *  somewhere in each region. The position of this attempt is governed by the
 *  structure type, the region coordiates and the lower 48-bits of the world
 *  seed. The remaining top 16 bits do not influence structure positions.
 *  The dependency on the region coordinates is linear for both the X and Z
 *  directions, which means that the positions of most structures in a world
 *  can be translated by applying the following transformation to a seed:
 *
 *  seed2 = seed1 - dregX * 341873128712 - dregZ * 132897987541;
 *
 *  Here seed1 and seed2 have the same structure positioning, but moved by a
 *  region offset of (dregX,dregZ).
 *
 *  Another property of note is that seed1 at region (0,0) is simply the world
 *  seed plus a constant that is specific to the stucture type (its salt). This
 *  means that some structure types share quad-bases which are just offset by
 *  their respective salt differences.
 */

//==============================================================================
// Moving Structures
//==============================================================================

/* Transposes a base seed such that structures are moved by the specified region
 * vector, (regX, regZ).
 */
static inline uint64_t moveStructure(uint64_t baseSeed, int regX, int regZ)
{
    return (baseSeed - regX*341873128712 - regZ*132897987541) & 0xffffffffffff;
}


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


/* Selects the structure configuration for a given version. Returns zero upon
 * failure (e.g. version does not support structure type).
 */
int getStructureConfig(int structureType, int mc, StructureConfig *sconf);

/* The library can be compiled to use a custom internal getter for structure
 * configurations. For this, the macro STRUCT_CONFIG_OVERRIDE should be defined
 * as true and the function getStructureConfig_override() should be defined
 * with a custom function body. However, note this is experimental and not all
 * structure configs may work. (Ideally only change structure salts.)
 */
#if STRUCT_CONFIG_OVERRIDE
int getStructureConfig_override(int stype, int mc, StructureConfig *sconf);
#endif

/* Finds the block position of the structure generation attempt in a given
 * region. You can use isViableStructurePos() to test if the necessary biome
 * requirements are met for the structure to actually generate at that position.
 * Some structure types may fail to produce a valid position in the given
 * region regardless of biomes, in which case the function returns zero.
 *
 * @structureType   : structure type
 * @mc              : minecraft version
 * @seed            : world seed (only the lower 48-bits are relevant)
 * @regX,regZ       : region coordinates (the region size depends on type)
 * @pos             : output block position
 *
 * Returns zero if the position is invalid, or non-zero otherwise.
 */
int getStructurePos(int structureType, int mc, uint64_t seed, int regX, int regZ, Pos *pos);

/* The inline functions below get the generation attempt position given a
 * structure configuration. Most small structures use the getFeature..
 * variants, which have a uniform distribution, while large structures
 * (monuments and mansions) have a triangular distribution.
 */
static inline ATTR(const)
Pos getFeaturePos(StructureConfig config, uint64_t seed, int regX, int regZ);

static inline ATTR(const)
Pos getFeatureChunkInRegion(StructureConfig config, uint64_t seed, int regX, int regZ);

static inline ATTR(const)
Pos getLargeStructurePos(StructureConfig config, uint64_t seed, int regX, int regZ);

static inline ATTR(const)
Pos getLargeStructureChunkInRegion(StructureConfig config, uint64_t seed, int regX, int regZ);

/* Checks a chunk area, starting at (chunkX, chunkZ) with size (chunkW, chunkH)
 * for Mineshaft positions. If not NULL, positions are written to the buffer
 * 'out' up to a maximum number of 'nout'. The return value is the number of
 * chunks with Mineshafts in the area.
 */
int getMineshafts(int mc, uint64_t seed, int chunkX, int chunkZ,
        int chunkW, int chunkH, Pos *out, int nout);

// not exacly a structure
static inline ATTR(const)
int isSlimeChunk(uint64_t seed, int chunkX, int chunkZ)
{
    uint64_t rnd = seed;
    rnd += (int)(chunkX * 0x5ac0db);
    rnd += (int)(chunkX * chunkX * 0x4c1906);
    rnd += (int)(chunkZ * 0x5f24f);
    rnd += (int)(chunkZ * chunkZ) * 0x4307a7ULL;
    rnd ^= 0x3ad8025fULL;
    setSeed(&rnd, rnd);
    return nextInt(&rnd, 10) == 0;
}


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

/* Finds the approximate location of the first stronghold (+/-112 blocks),
 * which can be determined from the lower 48 bits of the world seed without
 * biome checks. If 'sh' is not NULL, it will be initialized for iteration
 * using nextStronghold() to get the accurate stronghold locations, as well as
 * the subsequent approximate stronghold positions.
 *
 * @sh      : stronghold iterator to be initialized (nullable)
 * @mc      : minecraft version (changes in 1.7, 1.9, 1.13)
 * @s48     : world seed (only 48-bit are relevant)
 *
 * Returns the approximate block position of the first stronghold.
 */
Pos initFirstStronghold(StrongholdIter *sh, int mc, uint64_t s48);

/* Performs the biome checks for the stronghold iterator and finds its accurate
 * location, as well as the approximate location of the next stronghold.
 *
 * @sh      : stronghold iteration state, holding position info
 * @g       : generator, should be initialized for Overworld generation
 *
 * Returns the number of further strongholds after this one.
 */
int nextStronghold(StrongholdIter *sh, const Generator *g);

/* Finds the spawn point in the world.
 * Warning: Slow, and may be inaccurate because the world spawn depends on
 * grass blocks!
 */
Pos getSpawn(const Generator *g);

/* Finds the approximate spawn point in the world.
 */
Pos estimateSpawn(const Generator *g);


/* Finds a suitable pseudo-random location in the specified area.
 * This function is used to determine the positions of spawn and strongholds.
 * Warning: accurate, but slow!
 *
 * @g           : generator for Overworld biomes
 * @x,y,z       : origin for the search
 * @radius      : square 'radius' of the search
 * @validBiomes : boolean array of valid biome ids (size = 256)
 * @rnd         : random obj, initialise using setSeed(rnd, world_seed)
 * @passes      : (output) number of valid biomes passed, NULL to ignore
 */
Pos locateBiome(
        const Generator *g, int x, int y, int z, int radius,
        const char *validBiomes, uint64_t *rng, int *passes);

/* Get the shadow seed.
 */
static inline uint64_t getShadow(uint64_t seed)
{
    return -7379792620528906219LL - seed;
}



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

/* Performs a biome check near the specified block coordinates to determine
 * whether a structure of the given type could spawn there. You can get the
 * block positions using getStructurePos().
 * The generator, 'g', should be initialized for the correct MC version,
 * dimension and seed. The generator may be temporarily modified during the
 * function call, but will be restored upon return.
 * The 'flags' argument is optional structure specific information, such as the
 * biome variant for villages.
 */
int isViableStructurePos(int structType, Generator *g, int blockX, int blockZ, uint32_t flags);

/* Checks if the specified structure type could generate in the given biome.
 */
int isViableFeatureBiome(int mc, int structureType, int biomeID);

/* Some structures in 1.18 now only spawn if the surface is sufficiently high
 * at all four bounding box corners. This affects primarily Desert_Pyramids,
 * Jungle_Temples and Mansions.
 * Currently cubiomes does not provide overworld surface height and cannot
 * check it, but we can rule out some unlikely positions based biomes.
 *
 * This function is meant only for the 1.18 Overworld and is subject to change.
 */
int isViableStructureTerrain(int structType, Generator *g, int blockX, int blockZ);

/* End Cities require a sufficiently high surface in addition to a biome check.
 * The world seed should be applied to the EndNoise and SurfaceNoise before
 * calling this function. (Use initSurfaceNoiseEnd() for initialization.)
 */
int isViableEndCityTerrain(const EndNoise *en, const SurfaceNoise *sn,
        int blockX, int blockZ);


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

/* Initialises and returns a random seed used in the (16x16) chunk generation.
 * This random object is used for recursiveGenerate() which is responsible for
 * generating caves, ravines, mineshafts, and virtually all other structures.
 */
inline static
uint64_t chunkGenerateRnd(uint64_t worldSeed, int chunkX, int chunkZ)
{
    uint64_t rnd;
    setSeed(&rnd, worldSeed);
    rnd = (nextLong(&rnd) * chunkX) ^ (nextLong(&rnd) * chunkZ) ^ worldSeed;
    setSeed(&rnd, rnd);
    return rnd;
}

/* Get data, such as rotation and bounding box of a structure instance.
 * (Supports only some structure types.)
 */
int getVariant(StructureVariant *sv, int structType, int mc, uint64_t seed,
        int blockX, int blockZ, int biomeID);

/* Find the number of each type of house that generate in a village
 * (mc < MC_1_14)
 * @worldSeed      : world seed
 * @chunkX, chunkZ : 16x16 chunk position of the village origin
 * @housesOut      : output number of houses for each entry in the house type
 *                   enum (i.e this should be an array of length HOUSE_NUM)
 *
 * Returns the random object seed after finding these numbers.
 */
enum
{
    HouseSmall, Church, Library, WoodHut, Butcher, FarmLarge, FarmSmall,
    Blacksmith, HouseLarge, HOUSE_NUM
};
uint64_t getHouseList(uint64_t worldSeed, int chunkX, int chunkZ, int *housesOut);



//==============================================================================
// Seed Filters (for versions up to 1.17)
//==============================================================================


/* Creates a biome filter configuration from a given list of required and
 * excluded biomes. Biomes should not appear in both lists. Lists of length
 * zero may be passed as null.
 */
void setupBiomeFilter(
    BiomeFilter *bf,
    int mc, uint32_t flags,
    const int *required, int requiredLen,
    const int *excluded, int excludedLen,
    const int *matchany, int matchanyLen);

/* Starts to generate the specified range and checks if the biomes meet the
 * requirements of the biome filter, returning either:
 * 0 (failed),
 * 1 (okay, area is fully generated), or
 * 2 (okay, incomplete generation).
 *
 * The area will be generated inside the cache (if != NULL) but is only
 * defined if the generation was fully completed (check return value).
 * More aggressive filtering can be enabled with the flags which may yield
 * some false negatives in exchange for speed.
 *
 * The generator should be set up for the correct version, however the
 * dimension and seed will be applied internally. This will modify the
 * generator into a partially initialized state that is not valid to use
 * outside this function without re-applying a seed.
 *
 * @g           : biome generator
 * @cache       : working buffer and output (nullable)
 * @r           : range to be checked
 * @dim         : dimension (0:Overworld, -1:Nether, +1:End)
 * @seed        : world seed
 * @filter      : biome requirements to be met
 * @flags       : enables features (see below)
 * @stop        : occasional check for abort (nullable)
 */
int checkForBiomes(
        Generator         * g,
        int               * cache,
        Range               r,
        int                 dim,
        uint64_t            seed,
        const BiomeFilter * filter,
        volatile char     * stop // should be atomic, but is fine as stop flag
        );

/* Specialization of checkForBiomes() for a LayerStack, i.e. the Overworld up
 * to 1.17.
 *
 * @ls          : layered generator (will be modified!)
 * @entry       : generation entry point (setLayerSeed() may be applied here)
 * @cache       : working buffer, and output (if != NULL)
 * @seed        : world seed
 * @x,z,w,h     : requested area
 * @filter      : biomes to be checked for
 */
int checkForBiomesAtLayer(
        LayerStack        * ls,
        Layer             * entry,
        int               * cache,
        uint64_t            seed,
        int                 x,
        int                 z,
        unsigned int        w,
        unsigned int        h,
        const BiomeFilter * filter
        );

/* Checks that the area (x,z,w,h) at layer Special, scale 1:1024 contains the
 * temperature category requirements defined by 'tc' as:
 * if (tc[TEMP_CAT] >= 0) require at least this many entries of this category
 * if (tc[TEMP_CAT] <  0) avoid, there shall be no entries of this category
 * TEMP_CAT is any of:
 * Oceanic, Warm, Lush, Cold, Freeing, Special+Warm, Special+Lush, Special+Cold
 * For 1.7-1.17 only.
 */
int checkForTemps(LayerStack *g, uint64_t seed, int x, int z, int w, int h, const int tc[9]);

/* Checks if a biome may generate given a version and layer ID as entry point.
 * The supported layers are:
 * L_BIOME_256, L_BAMBOO_256, L_BIOME_EDGE_64, L_HILLS_64, L_SUNFLOWER_64,
 * L_SHORE_16, L_RIVER_MIX_4, L_OCEAN_MIX_4, L_VORONOI_1
 * (provided the version matches)
 */
int canBiomeGenerate(int layerId, int mc, int biomeID);

/* Given a biome 'id' at a generation 'layerId', this functions finds which
 * biomes may generate from it. The result is stored in the bitfields:
 * mL : for ids 0-63
 * mM : for ids 128-191
 */
void genPotential(uint64_t *mL, uint64_t *mM, int layerId, int mc, int id);

/* Gets the biomes that can generate in the given version and layer ID.
 * In contrast to canBiomeGenerate() and genPotential() it also supports 1.18+,
 * where the layerId is ignored.
 * mL : for ids 0-63
 * mM : for ids 128-191
 */
void getAvailableBiomes(uint64_t *mL, uint64_t *mM, int layerId, int mc);

//==============================================================================
// Biome Noise Finders (for 1.18+)
//==============================================================================

/**
 * Runs a gradient descent towards the minimum of the noise parameter times a
 * given factor. The algorithm is restricted to the area (x,z,w,h) and starts
 * at (i0,j0) relative to (x,z). The iteration is terminated when either
 * 1) a fix point has been reached,
 * 2) maxiter iterations have been completed,
 * 3) or the sampling position has moved more than maxrad away from (i0,j0).
 *
 * Alpha is an optimization argument that is used to determine the length of
 * large steps based on the current gradient.
 *
 * Optionally, the iteration can also call the custom function:
 *  func(data, x, z, factor*para_noise(x,z));
 *
 * The return value is the minimum value reached.
 */
double getParaDescent(const DoublePerlinNoise *para, double factor,
    int x, int z, int w, int h, int i0, int j0, int maxrad,
    int maxiter, double alpha, void *data, int (*func)(void*,int,int,double));

/**
 * Determines the value range of a climate noise parameter over the given area.
 * The sampling has scale 1:4 and sampling shift is not considered, so biomes
 * could potentially *leak* in at the boarders.
 * An optional function:
 *  func(data, x, z, climate_noise(x,z))
 * is called in each gradient descent iteration. If this function returns
 * non-zero the search is aborted, the results are undefined and a non-zero
 * error is returned.
 *
 * The results are written to pmin and pmax (which would be cast to an integer
 * during boime mapping).
 */
int getParaRange(const DoublePerlinNoise *para, double *pmin, double *pmax,
    int x, int z, int w, int h, void *data, int (*func)(void*,int,int,double));

/**
 * Gets the min/max parameter values within which a biome change can occur.
 */
const int *getBiomeParaExtremes(int mc);

/**
 * Gets the min/max possible noise parameter values at which the given biome
 * can generate. The values are in min/max pairs in order of:
 * temperature, humidity, continentalness, erosion, depth, weirdness.
 */
const int *getBiomeParaLimits(int mc, int id);

/**
 * Determines which biomes are able to generate given a set of climate
 * parameter limits. Possible biomes are marked non-zero in the 'ids'.
 */
void getPossibleBiomesForLimits(char ids[256], int mc, int limits[6][2]);


//==============================================================================
// Implementaions for Functions that Ideally Should be Inlined
//==============================================================================


static inline ATTR(const)
Pos getFeatureChunkInRegion(StructureConfig config, uint64_t seed, int regX, int regZ)
{
    /*
    // Vanilla like implementation.
    setSeed(&seed, regX*341873128712 + regZ*132897987541 + seed + config.salt);

    Pos pos;
    pos.x = nextInt(&seed, 24);
    pos.z = nextInt(&seed, 24);
    */
    Pos pos;
    const uint64_t K = 0x5deece66dULL;
    const uint64_t M = (1ULL << 48) - 1;
    const uint64_t b = 0xb;

    // set seed
    seed = seed + regX*341873128712ULL + regZ*132897987541ULL + config.salt;
    seed = (seed ^ K);
    seed = (seed * K + b) & M;

    uint64_t r = config.chunkRange;
    if (r & (r-1))
    {
        pos.x = (int)(seed >> 17) % r;
        seed = (seed * K + b) & M;
        pos.z = (int)(seed >> 17) % r;
    }
    else
    {
        // Java RNG treats powers of 2 as a special case.
        pos.x = (int)((r * (seed >> 17)) >> 31);
        seed = (seed * K + b) & M;
        pos.z = (int)((r * (seed >> 17)) >> 31);
    }

    return pos;
}

static inline ATTR(const)
Pos getFeaturePos(StructureConfig config, uint64_t seed, int regX, int regZ)
{
    Pos pos = getFeatureChunkInRegion(config, seed, regX, regZ);

    pos.x = (int)(((uint64_t)regX*config.regionSize + pos.x) << 4);
    pos.z = (int)(((uint64_t)regZ*config.regionSize + pos.z) << 4);
    return pos;
}

static inline ATTR(const)
Pos getLargeStructureChunkInRegion(StructureConfig config, uint64_t seed, int regX, int regZ)
{
    Pos pos;
    const uint64_t K = 0x5deece66dULL;
    const uint64_t M = (1ULL << 48) - 1;
    const uint64_t b = 0xb;

    //TODO: power of two chunk ranges...

    // set seed
    seed = seed + regX*341873128712ULL + regZ*132897987541ULL + config.salt;
    seed = (seed ^ K);

    seed = (seed * K + b) & M;
    pos.x = (int)(seed >> 17) % config.chunkRange;
    seed = (seed * K + b) & M;
    pos.x += (int)(seed >> 17) % config.chunkRange;

    seed = (seed * K + b) & M;
    pos.z = (int)(seed >> 17) % config.chunkRange;
    seed = (seed * K + b) & M;
    pos.z += (int)(seed >> 17) % config.chunkRange;

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

    return pos;
}

static inline ATTR(const)
Pos getLargeStructurePos(StructureConfig config, uint64_t seed, int regX, int regZ)
{
    Pos pos = getLargeStructureChunkInRegion(config, seed, regX, regZ);

    pos.x = (int)(((uint64_t)regX*config.regionSize + pos.x) << 4);
    pos.z = (int)(((uint64_t)regZ*config.regionSize + pos.z) << 4);
    return pos;
}



#ifdef __cplusplus
}
#endif

#endif // FINDERS_H_