--- a/include/relpipe/reader/typedefs.h	Tue Dec 10 19:37:50 2019 +0100
+++ b/include/relpipe/reader/typedefs.h	Fri Dec 13 22:19:39 2019 +0100
@@ -26,7 +26,7 @@
 namespace reader {
 
 using octet_t = uint8_t;
-using integer_t = uint64_t;
+using integer_t = int64_t;
 using boolean_t = bool;
 using string_t = std::wstring;
 

--- a/src/types/IntegerDataTypeReader.h	Tue Dec 10 19:37:50 2019 +0100
+++ b/src/types/IntegerDataTypeReader.h	Fri Dec 13 22:19:39 2019 +0100
@@ -38,14 +38,14 @@
 using namespace relpipe::reader;
 
 /**
- * Unsigned variable-length integer.
- * ULEB128
+ * Signed variable-length integer.
+ * LEB128
  */
 class IntegerDataTypeReader : public DataTypeReader<integer_t> {
 private:
 
-	uint8_t readNextOctet(std::istream &input) {
-		uint8_t value = input.get();
+	octet_t readNextOctet(std::istream &input) {
+		octet_t value = input.get();
 		if (input.good()) return value;
 		else throw RelpipeReaderException(L"Unable to read next octet of the integer.");
 	}
@@ -64,6 +64,9 @@
 			value += integer_t(octet & 0x7F) << shift;
 			shift += 7;
 		} while (octet >= 128);
+
+		if ((shift < (sizeof (integer_t) * 8)) && (octet & 0x40))
+			value |= (~0 << shift);
 		return value;
 	}
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/types/UnsignedIntegerDataTypeReader.h	Fri Dec 13 22:19:39 2019 +0100
@@ -0,0 +1,78 @@
+/**
+ * Relational pipes (library)
+ * Copyright © 2018 František Kučera (Frantovo.cz, GlobalCode.info)
+ *
+ * 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;
+ *    version 3 of the License or (at your option)
+ *  - GNU General Public License as published by the Free Software Foundation;
+ *    version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <string>
+#include <iostream>
+#include <cassert>
+#include <limits>
+
+#include <relpipe/protocol/constants.h>
+
+#include "../../include/relpipe/reader/RelpipeReaderException.h"
+#include "../../include/relpipe/reader/typedefs.h"
+#include "../DataTypeReader.h"
+
+namespace relpipe {
+namespace reader {
+namespace types {
+
+using namespace relpipe::protocol;
+using namespace relpipe::reader;
+
+/**
+ * Unsigned variable-length integer.
+ * ULEB128
+ */
+class IntegerDataTypeReader : public DataTypeReader<integer_t> { // FIXME: relpipe::common::type::UnsignedInteger
+private:
+
+	octet_t readNextOctet(std::istream &input) {
+		octet_t value = input.get();
+		if (input.good()) return value;
+		else throw RelpipeReaderException(L"Unable to read next octet of the integer.");
+	}
+
+public:
+
+	IntegerDataTypeReader() : DataTypeReader<integer_t>(TypeId::INTEGER, DATA_TYPE_CODE_INTEGER) {
+	}
+
+	integer_t readValue(std::istream &input) override {
+		integer_t value = 0;
+		integer_t shift = 0;
+		octet_t octet;
+		do {
+			octet = readNextOctet(input);
+			value += integer_t(octet & 0x7F) << shift;
+			shift += 7;
+		} while (octet >= 128);
+		return value;
+	}
+
+	string_t toString(const integer_t &value) override {
+		return std::to_wstring(value);
+	}
+
+};
+
+}
+}
+}