Merge pull request #9917 from ethereum/leb-encoding

Add LEB128 encoding functions & tests.

libsolutil/CMakeLists.txt

@@ -20,6 +20,7 @@ set(sources
 	Keccak256.cpp
 	Keccak256.h
 	LazyInit.h
+	LEB128.h
 	picosha2.h
 	Result.h
 	SetOnce.h

libsolutil/LEB128.h

@@ -0,0 +1,59 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity 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 solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+#pragma once
+
+
+#include <libsolutil/Common.h>
+
+namespace solidity::util
+{
+
+inline bytes lebEncode(uint64_t _n)
+{
+	bytes encoded;
+	while (_n > 0x7f)
+	{
+		encoded.emplace_back(uint8_t(0x80 | (_n & 0x7f)));
+		_n >>= 7;
+	}
+	encoded.emplace_back(_n);
+	return encoded;
+}
+
+// signed right shift is an arithmetic right shift
+static_assert((-1 >> 1) == -1, "Arithmetic shift not supported.");
+
+inline bytes lebEncodeSigned(int64_t _n)
+{
+	// Based on https://github.com/llvm/llvm-project/blob/master/llvm/include/llvm/Support/LEB128.h
+	bytes result;
+	bool more;
+	do
+	{
+		uint8_t v = _n & 0x7f;
+		_n >>= 7;
+		more = !((((_n == 0) && ((v & 0x40) == 0)) || ((_n == -1) && ((v & 0x40) != 0))));
+		if (more)
+			v |= 0x80; // Mark this byte to show that more bytes will follow.
+		result.emplace_back(v);
+	}
+	while (more);
+	return result;
+}
+
+}

libyul/backends/wasm/BinaryTransform.cpp

@@ -24,6 +24,7 @@
 #include <libyul/Exceptions.h>
 #include <libsolutil/CommonData.h>
 #include <libsolutil/Visitor.h>
+#include <libsolutil/LEB128.h>
 
 #include <boost/range/adaptor/reversed.hpp>
 #include <boost/range/adaptor/map.hpp>
@@ -239,28 +240,6 @@ static map<string, uint8_t> const builtins = {
 	{"i64.extend_i32_u", 0xad},
 };
 
-bytes lebEncode(uint64_t _n)
-{
-	bytes encoded;
-	while (_n > 0x7f)
-	{
-		encoded.emplace_back(uint8_t(0x80 | (_n & 0x7f)));
-		_n >>= 7;
-	}
-	encoded.emplace_back(_n);
-	return encoded;
-}
-
-bytes lebEncodeSigned(int64_t _n)
-{
-	if (_n >= 0 && _n < 0x40)
-		return toBytes(uint8_t(uint64_t(_n) & 0xff));
-	else if (-_n > 0 && -_n < 0x40)
-		return toBytes(uint8_t(uint64_t(_n + 0x80) & 0xff));
-	else
-		return toBytes(uint8_t(0x80 | uint8_t(_n & 0x7f))) + lebEncodeSigned(_n / 0x80);
-}
-
 bytes prefixSize(bytes _data)
 {
 	size_t size = _data.size();

test/CMakeLists.txt

@@ -35,6 +35,7 @@ set(libsolutil_sources
     libsolutil/JSON.cpp
     libsolutil/Keccak256.cpp
     libsolutil/LazyInit.cpp
+    libsolutil/LEB128.cpp
     libsolutil/StringUtils.cpp
     libsolutil/SwarmHash.cpp
     libsolutil/UTF8.cpp

test/libsolutil/LEB128.cpp

@@ -0,0 +1,101 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity 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 solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+// SPDX-License-Identifier: GPL-3.0
+/**
+ * Unit tests for LEB128.
+ */
+
+#include <libsolutil/LEB128.h>
+
+#include <boost/test/unit_test.hpp>
+
+using namespace std;
+
+namespace solidity::util::test
+{
+
+BOOST_AUTO_TEST_SUITE(LEB128Test)
+
+BOOST_AUTO_TEST_CASE(encode_unsigned)
+{
+	bytes zero = solidity::util::lebEncode(0);
+	BOOST_REQUIRE(zero.size() == 1);
+	BOOST_REQUIRE(zero[0] == 0x00);
+
+	bytes one = solidity::util::lebEncode(1);
+	BOOST_REQUIRE(one.size() == 1);
+	BOOST_REQUIRE(one[0] == 0x01);
+
+	bytes large = solidity::util::lebEncode(624485);
+	BOOST_REQUIRE(large.size() == 3);
+	BOOST_REQUIRE(large[0] == 0xE5);
+	BOOST_REQUIRE(large[1] == 0x8E);
+	BOOST_REQUIRE(large[2] == 0x26);
+
+	bytes larger = solidity::util::lebEncodeSigned(123456123456);
+	BOOST_REQUIRE(larger.size() == 6);
+	BOOST_REQUIRE(larger[0] == 0xC0);
+	BOOST_REQUIRE(larger[1] == 0xE4);
+	BOOST_REQUIRE(larger[2] == 0xBB);
+	BOOST_REQUIRE(larger[3] == 0xF4);
+	BOOST_REQUIRE(larger[4] == 0xCB);
+	BOOST_REQUIRE(larger[5] == 0x03);
+}
+
+BOOST_AUTO_TEST_CASE(encode_signed)
+{
+	bytes zero = solidity::util::lebEncodeSigned(0);
+	BOOST_REQUIRE(zero.size() == 1);
+	BOOST_REQUIRE(zero[0] == 0x00);
+
+	bytes one = solidity::util::lebEncodeSigned(1);
+	BOOST_REQUIRE(one.size() == 1);
+	BOOST_REQUIRE(one[0] == 0x01);
+
+	bytes negative_one = solidity::util::lebEncodeSigned(-1);
+	BOOST_REQUIRE(negative_one.size() == 1);
+	BOOST_REQUIRE(negative_one[0] == 0x7f);
+
+	bytes negative_two = solidity::util::lebEncodeSigned(-2);
+	BOOST_REQUIRE(negative_two.size() == 1);
+	BOOST_REQUIRE(negative_two[0] == 0x7e);
+
+	bytes large = solidity::util::lebEncodeSigned(624485);
+	BOOST_REQUIRE(large.size() == 3);
+	BOOST_REQUIRE(large[0] == 0xE5);
+	BOOST_REQUIRE(large[1] == 0x8E);
+	BOOST_REQUIRE(large[2] == 0x26);
+
+	bytes negative_large = solidity::util::lebEncodeSigned(-123456);
+	BOOST_REQUIRE(negative_large.size() == 3);
+	BOOST_REQUIRE(negative_large[0] == 0xC0);
+	BOOST_REQUIRE(negative_large[1] == 0xBB);
+	BOOST_REQUIRE(negative_large[2] == 0x78);
+
+	bytes negative_larger = solidity::util::lebEncodeSigned(-123456123456);
+	BOOST_REQUIRE(negative_larger.size() == 6);
+	BOOST_REQUIRE(negative_larger[0] == 0xC0);
+	BOOST_REQUIRE(negative_larger[1] == 0x9B);
+	BOOST_REQUIRE(negative_larger[2] == 0xC4);
+	BOOST_REQUIRE(negative_larger[3] == 0x8B);
+	BOOST_REQUIRE(negative_larger[4] == 0xB4);
+	BOOST_REQUIRE(negative_larger[5] == 0x7C);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
+
+}