improve handling of 64 bit values

aternosorg · Sep 10, 2021 · c0cffc1 · c0cffc1
1 parent 60b5bc6
commit c0cffc1
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Showing 4 changed files with 45 additions and 25 deletions.
diff --git a/seedValueTest b/seedValueTest
@@ -0,0 +1 @@
+��\��$�
diff --git a/src/MachineByteOrder.php b/src/MachineByteOrder.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Aternos\Nbt;
+
+class MachineByteOrder
+{
+    protected static ?bool $isLittle = null;
+
+    /**
+     * Test whether the machine byte order is little endian or big endian
+     */
+    protected static function testByteOrder(): void
+    {
+        if(is_null(static::$isLittle)) {
+            static::$isLittle = pack("S", 0x1234) === hex2bin("3412");
+        }
+    }
+
+    /**
+     * @return bool
+     */
+    public static function isLittleEndian(): bool
+    {
+        static::testByteOrder();
+        return static::$isLittle;
+    }
+
+    /**
+     * @return bool
+     */
+    public static function isBigEndian(): bool
+    {
+        static::testByteOrder();
+        return !static::$isLittle;
+    }
+}
diff --git a/src/Serializer/BedrockEditionNbtSerializer.php b/src/Serializer/BedrockEditionNbtSerializer.php
@@ -3,6 +3,7 @@
 namespace Aternos\Nbt\Serializer;
 
 use Aternos\Nbt\IO\Reader\Reader;
+use Aternos\Nbt\MachineByteOrder;
 use Aternos\Nbt\NbtFormat;
 use pocketmine\utils\Binary;
 
@@ -101,26 +102,16 @@ public function encodeInt(int $value): string
      */
     protected function decodeLong(string $data): int
     {
-        $data = strrev($data);
-        $firstHalf = Binary::readInt(substr($data, 0, 4));
-        $secondHalf = Binary::readInt(substr($data, 4));
-
-        $negative = boolval($firstHalf & pow(2, 31));
-
-        $firstHalf &= (pow(2, 31) - 1);
-        $result = ($firstHalf << 32) + $secondHalf;
-
-        return $negative ? $result*-1 : $result;
+        return @unpack("q", MachineByteOrder::isBigEndian() ? strrev($data) : $data)[1] ?? 0;
     }
 
     /**
      * @inheritDoc
      */
     public function encodeLong(int $value): string
     {
-        $firstHalf = ($value & 0xFFFFFFFF00000000) >> 32;
-        $secondHalf = $value & 0xFFFFFFFF;
-        return strrev(pack('VV', $firstHalf, $secondHalf));
+        $packed = pack("q", $value);
+        return MachineByteOrder::isBigEndian() ? strrev($packed) : $packed;
     }
 
     /**

diff --git a/src/Serializer/JavaEditionNbtSerializer.php b/src/Serializer/JavaEditionNbtSerializer.php
@@ -3,6 +3,7 @@
 namespace Aternos\Nbt\Serializer;
 
 use Aternos\Nbt\IO\Reader\Reader;
+use Aternos\Nbt\MachineByteOrder;
 use Aternos\Nbt\NbtFormat;
 use pocketmine\utils\Binary;
 
@@ -96,25 +97,16 @@ public function encodeInt(int $value): string
      */
     public function decodeLong(string $data): int
     {
-        $firstHalf = Binary::readInt(substr($data, 0, 4));
-        $secondHalf = Binary::readInt(substr($data, 4));
-
-        $negative = boolval($firstHalf & pow(2, 31));
-
-        $firstHalf &= (pow(2, 31) - 1);
-        $result = ($firstHalf << 32) + $secondHalf;
-
-        return $negative ? $result*-1 : $result;
+        return @unpack("q", MachineByteOrder::isLittleEndian() ? strrev($data) : $data)[1] ?? 0;
     }
 
     /**
      * @inheritDoc
      */
     public function encodeLong(int $value): string
     {
-        $firstHalf = ($value & 0xFFFFFFFF00000000) >> 32;
-        $secondHalf = $value & 0xFFFFFFFF;
-        return pack('NN', $firstHalf, $secondHalf);
+        $packed = pack("q", $value);
+        return MachineByteOrder::isLittleEndian() ? strrev($packed) : $packed;
     }
 
     /**