VarInt: fix data loss when reading large varlongs (#17)

The result of the bitwise AND was an integer, which when shifted left by more than 31, results in zero.
This led to incorrect decoding of varlongs larger than 5 bytes.

Author: JuraSciix

Serializers.h

@@ -112,7 +112,7 @@ static inline bool readUnsignedVarInt(unsigned char* bytes, size_t used, size_t&
 		}
 
 		auto byte = bytes[offset++];
-		result |= (byte & VarIntConstants::VALUE_MASK) << shift;
+		result |= static_cast<TValue>(byte & VarIntConstants::VALUE_MASK) << shift;
 		if ((byte & VarIntConstants::MSB_MASK) == 0) {
 			return true;
 		}

tests/read-varint-unsigned-long.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Test that reading varlongs (> 5 bytes) works correctly
+--DESCRIPTION--
+The result of the bitwise AND operation has a result of int regardless of the input.
+When shifting this to the left by more than 31, the result will be 0 if not explicitly
+casted to a larger type before shifting. For varlongs this led to all bits above 32
+to be discarded. This test verifies the result of the fix.
+--FILE--
+<?php
+
+use pmmp\encoding\ByteBuffer;
+use pmmp\encoding\VarInt;
+
+//unsigned
+$buffer_2 = str_repeat("\x81", 8) . "\x01";
+$buf_2 = new ByteBuffer($buffer_2);
+var_dump(VarInt::readUnsignedLong($buf_2));
+
+//negative signed
+$buffer_3 = str_repeat("\x81", 8) . "\x01";
+$buf_3 = new ByteBuffer($buffer_3);
+var_dump(VarInt::readSignedLong($buf_3));
+
+//positive signed
+$buffer_3 = "\x80" . str_repeat("\x81", 7) . "\x01";
+$buf_3 = new ByteBuffer($buffer_3);
+var_dump(VarInt::readSignedLong($buf_3));
+
+?>
+--EXPECT--
+int(72624976668147841)
+int(-36312488334073921)
+int(36312488334073920)