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#pragma once
#include <cstdint>
#include <list>
#include <vector>
#include <utility>
#include "types.h"
struct BlockPos {
int16_t x;
int16_t y;
int16_t z;
BlockPos() : x(0), y(0), z(0) {}
explicit BlockPos(int16_t v) : x(v), y(v), z(v) {}
BlockPos(int16_t x, int16_t y, int16_t z) : x(x), y(y), z(z) {}
// Implements the inverse ordering so that (2,2,2) < (1,1,1)
bool operator < (const BlockPos &p) const
{
if (z > p.z)
return true;
if (z < p.z)
return false;
if (y > p.y)
return true;
if (y < p.y)
return false;
if (x > p.x)
return true;
if (x < p.x)
return false;
return false;
}
};
typedef std::pair<BlockPos, ustring> Block;
typedef std::list<Block> BlockList;
class DB {
protected:
// Helpers that implement the hashed positions used by most backends
inline int64_t encodeBlockPos(const BlockPos pos) const;
inline BlockPos decodeBlockPos(int64_t hash) const;
public:
/* Return all block positions inside the range given by min and max,
* so that min.x <= x < max.x, ...
*/
virtual std::vector<BlockPos> getBlockPos(BlockPos min, BlockPos max) = 0;
/* Read all blocks in column given by x and z
* and inside the given Y range (min_y <= y < max_y) into list
*/
virtual void getBlocksOnXZ(BlockList &blocks, int16_t x, int16_t z,
int16_t min_y, int16_t max_y) = 0;
/* Read blocks at given positions into list
*/
virtual void getBlocksByPos(BlockList &blocks,
const std::vector<BlockPos> &positions) = 0;
/* Can this database efficiently do range queries?
* (for large data sets, more efficient that brute force)
*/
virtual bool preferRangeQueries() const = 0;
virtual ~DB() {}
};
/****************
* Black magic! *
****************
* The position hashing is seriously messed up,
* and is a lot more complicated than it looks.
*/
static inline int16_t unsigned_to_signed(uint16_t i, uint16_t max_positive)
{
if (i < max_positive) {
return i;
} else {
return i - (max_positive * 2);
}
}
// Modulo of a negative number does not work consistently in C
static inline int64_t pythonmodulo(int64_t i, int64_t mod)
{
if (i >= 0) {
return i % mod;
}
return mod - ((-i) % mod);
}
inline int64_t DB::encodeBlockPos(const BlockPos pos) const
{
return (uint64_t) pos.z * 0x1000000 +
(uint64_t) pos.y * 0x1000 +
(uint64_t) pos.x;
}
inline BlockPos DB::decodeBlockPos(int64_t hash) const
{
BlockPos pos;
pos.x = unsigned_to_signed(pythonmodulo(hash, 4096), 2048);
hash = (hash - pos.x) / 4096;
pos.y = unsigned_to_signed(pythonmodulo(hash, 4096), 2048);
hash = (hash - pos.y) / 4096;
pos.z = unsigned_to_signed(pythonmodulo(hash, 4096), 2048);
return pos;
}
/*******************
* End black magic *
*******************/
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