Move source files into folder

src/db.h

@@ -0,0 +1,123 @@
+#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 *
+ *******************/
+