Generalize runtime block data serialization

we want to reuse this code for item type data

src/data/runtime/RuntimeDataReader.php

@@ -0,0 +1,124 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+ */
+
+declare(strict_types=1);
+
+namespace pocketmine\data\runtime;
+
+use pocketmine\block\utils\WallConnectionType;
+use pocketmine\math\Axis;
+use pocketmine\math\Facing;
+use pocketmine\utils\AssumptionFailedError;
+
+final class RuntimeDataReader{
+
+	private int $offset = 0;
+
+	public function __construct(
+		private int $maxBits,
+		private int $value
+	){}
+
+	public function readInt(int $bits) : int{
+		$bitsLeft = $this->maxBits - $this->offset;
+		if($bits > $bitsLeft){
+			throw new \InvalidArgumentException("No bits left in buffer (need $bits, have $bitsLeft");
+		}
+
+		$value = ($this->value >> $this->offset) & ~(~0 << $bits);
+		$this->offset += $bits;
+		return $value;
+	}
+
+	public function readBoundedInt(int $bits, int $min, int $max) : int{
+		$result = $this->readInt($bits);
+		if($result < $min || $result > $max){
+			throw new InvalidSerializedRuntimeDataException("Value is outside the range $min - $max");
+		}
+		return $result;
+	}
+
+	public function readBool() : bool{
+		return $this->readInt(1) === 1;
+	}
+
+	public function readHorizontalFacing() : int{
+		return match($this->readInt(2)){
+			0 => Facing::NORTH,
+			1 => Facing::EAST,
+			2 => Facing::SOUTH,
+			3 => Facing::WEST,
+			default => throw new AssumptionFailedError("Unreachable")
+		};
+	}
+
+	public function readFacing() : int{
+		return match($this->readInt(3)){
+			0 => Facing::DOWN,
+			1 => Facing::UP,
+			2 => Facing::NORTH,
+			3 => Facing::SOUTH,
+			4 => Facing::WEST,
+			5 => Facing::EAST,
+			default => throw new InvalidSerializedRuntimeDataException("Invalid facing value")
+		};
+	}
+
+	public function readAxis() : int{
+		return match($this->readInt(2)){
+			0 => Axis::X,
+			1 => Axis::Z,
+			2 => Axis::Y,
+			default => throw new InvalidSerializedRuntimeDataException("Invalid axis value")
+		};
+	}
+
+	public function readHorizontalAxis() : int{
+		return match($this->readInt(1)){
+			0 => Axis::X,
+			1 => Axis::Z,
+			default => throw new AssumptionFailedError("Unreachable")
+		};
+	}
+
+	/**
+	 * @return WallConnectionType[]
+	 * @phpstan-return array<Facing::NORTH|Facing::EAST|Facing::SOUTH|Facing::WEST, WallConnectionType>
+	 */
+	public function readWallConnections() : array{
+		$connections = [];
+		//TODO: we can pack this into 7 bits instead of 8
+		foreach(Facing::HORIZONTAL as $facing){
+			$type = $this->readBoundedInt(2, 0, 2);
+			if($type !== 0){
+				$connections[$facing] = match($type){
+					1 => WallConnectionType::SHORT(),
+					2 => WallConnectionType::TALL(),
+					default => throw new AssumptionFailedError("Unreachable")
+				};
+			}
+		}
+
+		return $connections;
+	}
+
+	public function getOffset() : int{ return $this->offset; }
+}