Merge pull request #11047 from ethereum/bytesToBytesNNConversion

Bytes to bytesNN conversion

Changelog.md

@@ -1,6 +1,7 @@
 ### 0.8.5 (unreleased)
 
 Language Features:
+* Allowing conversion from ``bytes`` and ``bytes`` slices to ``bytes1``/.../``bytes32``.
 
 
 Compiler Features:

docs/types/conversion.rst

@@ -99,6 +99,27 @@ rules explicit::
     uint8 d = uint8(uint16(a)); // d will be 0x34
     uint8 e = uint8(bytes1(a)); // e will be 0x12
 
+``bytes`` arrays and ``bytes`` calldata slices can be converted explicitly to fixed bytes types (``bytes1``/.../``bytes32``).
+In case the array is longer than the target fixed bytes type, truncation at the end will happen.
+If the array is shorter than the target type, it will be padded with zeros at the end.
+
+::
+
+    // SPDX-License-Identifier: GPL-3.0
+    pragma solidity ^0.8.5;
+
+    contract C {
+        bytes s = "abcdefgh";
+        function f(bytes calldata c, bytes memory m) public view returns (bytes16, bytes3) {
+            require(c.length == 16, "");
+            bytes16 b = bytes16(m);  // if length of m is greater than 16, truncation will happen
+            b = bytes16(s);  // padded on the right, so result is "abcdefgh\0\0\0\0\0\0\0\0"
+            bytes3 b1 = bytes3(s); // truncated, b1 equals to "abc"
+            b = bytes16(c[:8]);  // also padded with zeros
+            return (b, b1);
+        }
+    }
+
 .. _types-conversion-literals:
 
 Conversions between Literals and Elementary Types

docs/types/reference-types.rst

@@ -492,7 +492,7 @@ Array slices are useful to ABI-decode secondary data passed in function paramete
 ::
 
     // SPDX-License-Identifier: GPL-3.0
-    pragma solidity >=0.7.0 <0.9.0;
+    pragma solidity >0.8.4 <0.9.0;
     contract Proxy {
         /// @dev Address of the client contract managed by proxy i.e., this contract
         address client;
@@ -504,13 +504,9 @@ Array slices are useful to ABI-decode secondary data passed in function paramete
         /// Forward call to "setOwner(address)" that is implemented by client
         /// after doing basic validation on the address argument.
         function forward(bytes calldata _payload) external {
-            // Since ABI decoding requires padded data, we cannot
-            // use abi.decode(_payload[:4], (bytes4)).
-            bytes4 sig =
-                _payload[0] |
-                (bytes4(_payload[1]) >> 8) |
-                (bytes4(_payload[2]) >> 16) |
-                (bytes4(_payload[3]) >> 24);
+            bytes4 sig = bytes4(_payload[:4]);
+            // Due to truncating behaviour, bytes4(_payload) performs identically.
+            // bytes4 sig = bytes4(_payload);
             if (sig == bytes4(keccak256("setOwner(address)"))) {
                 address owner = abi.decode(_payload[4:], (address));
                 require(owner != address(0), "Address of owner cannot be zero.");

libsolidity/analysis/TypeChecker.cpp

@@ -1710,19 +1710,23 @@ Type const* TypeChecker::typeCheckTypeConversionAndRetrieveReturnType(
 		{
 			if (auto argArrayType = dynamic_cast<ArrayType const*>(argType))
 			{
-				auto resultArrayType = dynamic_cast<ArrayType const*>(resultType);
-				solAssert(!!resultArrayType, "");
-				solAssert(
-					argArrayType->location() != DataLocation::Storage ||
-					(
+				if (auto resultArrayType = dynamic_cast<ArrayType const*>(resultType))
+					solAssert(
+						argArrayType->location() != DataLocation::Storage ||
 						(
-							resultArrayType->isPointer() ||
-							(argArrayType->isByteArray() && resultArrayType->isByteArray())
-						) &&
-						resultArrayType->location() == DataLocation::Storage
-					),
-					"Invalid explicit conversion to storage type."
-				);
+							(
+								resultArrayType->isPointer() ||
+								(argArrayType->isByteArray() && resultArrayType->isByteArray())
+							) &&
+							resultArrayType->location() == DataLocation::Storage
+						),
+						"Invalid explicit conversion to storage type."
+					);
+				else
+					solAssert(
+						argArrayType->isByteArray() && !argArrayType->isString() && resultType->category() == Type::Category::FixedBytes,
+						""
+					);
 			}
 		}
 		else

libsolidity/ast/Types.cpp

@@ -1570,9 +1570,9 @@ BoolResult ArrayType::isExplicitlyConvertibleTo(Type const& _convertTo) const
 {
 	if (isImplicitlyConvertibleTo(_convertTo))
 		return true;
-	// allow conversion bytes <-> string
+	// allow conversion bytes <-> string and bytes -> bytesNN
 	if (_convertTo.category() != category())
-		return false;
+		return isByteArray() && !isString() && _convertTo.category() == Type::Category::FixedBytes;
 	auto& convertTo = dynamic_cast<ArrayType const&>(_convertTo);
 	if (convertTo.location() != location())
 		return false;
@@ -1929,6 +1929,13 @@ BoolResult ArraySliceType::isImplicitlyConvertibleTo(Type const& _other) const
 		);
 }
 
+BoolResult ArraySliceType::isExplicitlyConvertibleTo(Type const& _convertTo) const
+{
+	return
+		isImplicitlyConvertibleTo(_convertTo) ||
+		m_arrayType.isExplicitlyConvertibleTo(_convertTo);
+}
+
 string ArraySliceType::richIdentifier() const
 {
 	return m_arrayType.richIdentifier() + "_slice";

libsolidity/ast/Types.h

@@ -889,6 +889,7 @@ public:
 	Category category() const override { return Category::ArraySlice; }
 
 	BoolResult isImplicitlyConvertibleTo(Type const& _other) const override;
+	BoolResult isExplicitlyConvertibleTo(Type const& _convertTo) const override;
 	std::string richIdentifier() const override;
 	bool operator==(Type const& _other) const override;
 	unsigned calldataEncodedSize(bool) const override { solAssert(false, ""); }

libsolidity/codegen/CompilerUtils.cpp

@@ -961,8 +961,31 @@ void CompilerUtils::convertType(
 	}
 	case Type::Category::Array:
 	{
-		solAssert(targetTypeCategory == stackTypeCategory, "");
 		auto const& typeOnStack = dynamic_cast<ArrayType const&>(_typeOnStack);
+		if (_targetType.category() == Type::Category::FixedBytes)
+		{
+			solAssert(
+				typeOnStack.isByteArray() && !typeOnStack.isString(),
+				"Array types other than bytes not convertible to bytesNN."
+			);
+			solAssert(typeOnStack.isDynamicallySized(), "");
+
+			bool fromCalldata = typeOnStack.dataStoredIn(DataLocation::CallData);
+			solAssert(typeOnStack.sizeOnStack() == (fromCalldata ? 2 : 1), "");
+			if (fromCalldata)
+				m_context << Instruction::SWAP1;
+
+			m_context.callYulFunction(
+				m_context.utilFunctions().bytesToFixedBytesConversionFunction(
+					typeOnStack,
+					dynamic_cast<FixedBytesType const &>(_targetType)
+				),
+				typeOnStack.sizeOnStack(),
+				1
+			);
+			break;
+		}
+		solAssert(targetTypeCategory == stackTypeCategory, "");
 		auto const& targetType = dynamic_cast<ArrayType const&>(_targetType);
 		switch (targetType.location())
 		{
@@ -1066,8 +1089,30 @@ void CompilerUtils::convertType(
 	}
 	case Type::Category::ArraySlice:
 	{
-		solAssert(_targetType.category() == Type::Category::Array, "");
 		auto& typeOnStack = dynamic_cast<ArraySliceType const&>(_typeOnStack);
+		if (_targetType.category() == Type::Category::FixedBytes)
+		{
+			solAssert(
+				typeOnStack.arrayType().isByteArray() && !typeOnStack.arrayType().isString(),
+				"Array types other than bytes not convertible to bytesNN."
+			);
+			solAssert(typeOnStack.isDynamicallySized(), "");
+			solAssert(typeOnStack.dataStoredIn(DataLocation::CallData), "");
+			solAssert(typeOnStack.sizeOnStack() == 2, "");
+
+			m_context << Instruction::SWAP1;
+			m_context.callYulFunction(
+				m_context.utilFunctions().bytesToFixedBytesConversionFunction(
+					typeOnStack.arrayType(),
+					dynamic_cast<FixedBytesType const &>(_targetType)
+				),
+				2,
+				1
+			);
+			break;
+		}
+
+		solAssert(_targetType.category() == Type::Category::Array, "");
 		auto const& targetArrayType = dynamic_cast<ArrayType const&>(_targetType);
 		solAssert(typeOnStack.arrayType().isImplicitlyConvertibleTo(targetArrayType), "");
 		solAssert(

libsolidity/codegen/YulUtilFunctions.cpp

@@ -3084,8 +3084,13 @@ string YulUtilFunctions::conversionFunction(Type const& _from, Type const& _to)
 	}
 	else if (_from.category() == Type::Category::ArraySlice)
 	{
-		solAssert(_to.category() == Type::Category::Array, "");
 		auto const& fromType = dynamic_cast<ArraySliceType const&>(_from);
+		if (_to.category() == Type::Category::FixedBytes)
+		{
+			solAssert(fromType.arrayType().isByteArray(), "Array types other than bytes not convertible to bytesNN.");
+			return bytesToFixedBytesConversionFunction(fromType.arrayType(), dynamic_cast<FixedBytesType const &>(_to));
+		}
+		solAssert(_to.category() == Type::Category::Array, "");
 		auto const& targetType = dynamic_cast<ArrayType const&>(_to);
 
 		solAssert(fromType.arrayType().isImplicitlyConvertibleTo(targetType), "");
@@ -3117,11 +3122,14 @@ string YulUtilFunctions::conversionFunction(Type const& _from, Type const& _to)
 	}
 	else if (_from.category() == Type::Category::Array)
 	{
+		auto const& fromArrayType =  dynamic_cast<ArrayType const&>(_from);
+		if (_to.category() == Type::Category::FixedBytes)
+		{
+			solAssert(fromArrayType.isByteArray(), "Array types other than bytes not convertible to bytesNN.");
+			return bytesToFixedBytesConversionFunction(fromArrayType, dynamic_cast<FixedBytesType const &>(_to));
+		}
 		solAssert(_to.category() == Type::Category::Array, "");
-		return arrayConversionFunction(
-			dynamic_cast<ArrayType const&>(_from),
-			dynamic_cast<ArrayType const&>(_to)
-		);
+		return arrayConversionFunction(fromArrayType, dynamic_cast<ArrayType const&>(_to));
 	}
 
 	if (_from.sizeOnStack() != 1 || _to.sizeOnStack() != 1)
@@ -3342,6 +3350,64 @@ string YulUtilFunctions::conversionFunction(Type const& _from, Type const& _to)
 	});
 }
 
+string YulUtilFunctions::bytesToFixedBytesConversionFunction(ArrayType const& _from, FixedBytesType const& _to)
+{
+	solAssert(_from.isByteArray() && !_from.isString(), "");
+	solAssert(_from.isDynamicallySized(), "");
+	string functionName = "convert_bytes_to_fixedbytes_from_" + _from.identifier() + "_to_" + _to.identifier();
+	return m_functionCollector.createFunction(functionName, [&](auto& _args, auto& _returnParams) {
+		_args = { "array" };
+		bool fromCalldata = _from.dataStoredIn(DataLocation::CallData);
+		if (fromCalldata)
+			_args.emplace_back("len");
+		_returnParams = {"value"};
+		Whiskers templ(R"(
+			let length := <arrayLen>(array<?fromCalldata>, len</fromCalldata>)
+			let dataArea := array
+			<?fromMemory>
+				dataArea := <dataArea>(array)
+			</fromMemory>
+			<?fromStorage>
+				if gt(length, 31) { dataArea := <dataArea>(array) }
+			</fromStorage>
+
+			<?fromCalldata>
+				value := <cleanup>(calldataload(dataArea))
+			<!fromCalldata>
+				value := <extractValue>(dataArea)
+			</fromCalldata>
+
+			if lt(length, <fixedBytesLen>) {
+				value := and(
+					value,
+					<shl>(
+						mul(8, sub(<fixedBytesLen>, length)),
+						<mask>
+					)
+				)
+			}
+		)");
+		templ("fromCalldata", fromCalldata);
+		templ("arrayLen", arrayLengthFunction(_from));
+		templ("fixedBytesLen", to_string(_to.numBytes()));
+		templ("fromMemory", _from.dataStoredIn(DataLocation::Memory));
+		templ("fromStorage", _from.dataStoredIn(DataLocation::Storage));
+		templ("dataArea", arrayDataAreaFunction(_from));
+		if (fromCalldata)
+			templ("cleanup", cleanupFunction(_to));
+		else
+			templ(
+				"extractValue",
+				_from.dataStoredIn(DataLocation::Storage) ?
+				readFromStorage(_to, 32 - _to.numBytes(), false) :
+				readFromMemory(_to)
+			);
+		templ("shl", shiftLeftFunctionDynamic());
+		templ("mask", formatNumber(~((u256(1) << (256 - _to.numBytes() * 8)) - 1)));
+		return templ.render();
+	});
+}
+
 string YulUtilFunctions::copyStructToStorageFunction(StructType const& _from, StructType const& _to)
 {
 	solAssert(_to.dataStoredIn(DataLocation::Storage), "");

libsolidity/codegen/YulUtilFunctions.h

@@ -411,6 +411,10 @@ public:
 	/// This is used for data being encoded or general type conversions in the code.
 	std::string conversionFunction(Type const& _from, Type const& _to);
 
+	/// @returns the name of a function that converts bytes array to fixed bytes type
+	/// signature: (array) -> value
+	std::string bytesToFixedBytesConversionFunction(ArrayType const& _from, FixedBytesType const& _to);
+
 	/// @returns the name of the cleanup function for the given type and
 	/// adds its implementation to the requested functions.
 	/// The cleanup function defers to the validator function with "assert"

test/libsolidity/semanticTests/array/bytes_to_fixed_bytes_cleanup.sol

@@ -0,0 +1,24 @@
+contract C {
+    bytes s = "abcdefghabcdefghabcdefghabcdefg";
+
+    function fromMemory(bytes memory m) public returns (bytes16) {
+        assembly { mstore(m, 14) }
+        return bytes16(m);
+    }
+    function fromCalldata(bytes calldata c) external returns (bytes16) {
+        return bytes16(c);
+    }
+    function fromStorage() external returns (bytes32) {
+        return bytes32(s);
+    }
+    function fromSlice(bytes calldata c) external returns (bytes8) {
+        return bytes8(c[0:6]);
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// fromMemory(bytes): 0x20, 16, "abcdefghabcdefgh" -> "abcdefghabcdef\0\0"
+// fromCalldata(bytes): 0x20, 15, "abcdefghabcdefgh" -> "abcdefghabcdefg\0"
+// fromStorage() -> "abcdefghabcdefghabcdefghabcdefg\0"
+// fromSlice(bytes): 0x20, 15, "abcdefghabcdefgh" -> "abcdef\0\0"

test/libsolidity/semanticTests/array/bytes_to_fixed_bytes_simple.sol

@@ -0,0 +1,28 @@
+contract C {
+    bytes s = "abcdefghabcdefgh";
+    bytes sLong = "abcdefghabcdefghabcdefghabcdefgh";
+
+    function fromMemory(bytes memory m) public returns (bytes16) {
+        return bytes16(m);
+    }
+    function fromCalldata(bytes calldata c) external returns (bytes16) {
+        return bytes16(c);
+    }
+    function fromStorage() external returns (bytes16) {
+        return bytes16(s);
+    }
+    function fromStorageLong() external returns (bytes32) {
+        return bytes32(sLong);
+    }
+    function fromSlice(bytes calldata c) external returns (bytes8) {
+        return bytes8(c[1:9]);
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// fromMemory(bytes): 0x20, 16, "abcdefghabcdefgh" -> "abcdefghabcdefgh"
+// fromCalldata(bytes): 0x20, 16, "abcdefghabcdefgh" -> "abcdefghabcdefgh"
+// fromStorage() -> "abcdefghabcdefgh"
+// fromStorageLong() -> "abcdefghabcdefghabcdefghabcdefgh"
+// fromSlice(bytes): 0x20, 16, "abcdefghabcdefgh" -> "bcdefgha"

test/libsolidity/semanticTests/array/bytes_to_fixed_bytes_too_long.sol

@@ -0,0 +1,23 @@
+contract C {
+    bytes s = "abcdefghabcdefghabcdefghabcdefgha";
+
+    function fromMemory(bytes memory m) public returns (bytes32) {
+        return bytes32(m);
+    }
+    function fromCalldata(bytes calldata c) external returns (bytes32) {
+        return bytes32(c);
+    }
+    function fromStorage() external returns (bytes32) {
+        return bytes32(s);
+    }
+    function fromSlice(bytes calldata c) external returns (bytes32) {
+        return bytes32(c[0:33]);
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// fromMemory(bytes): 0x20, 33, "abcdefghabcdefghabcdefghabcdefgh", "a" -> "abcdefghabcdefghabcdefghabcdefgh"
+// fromCalldata(bytes): 0x20, 33, "abcdefghabcdefghabcdefghabcdefgh", "a" -> "abcdefghabcdefghabcdefghabcdefgh"
+// fromStorage() -> "abcdefghabcdefghabcdefghabcdefgh"
+// fromSlice(bytes): 0x20, 33, "abcdefghabcdefghabcdefghabcdefgh", "a" -> "abcdefghabcdefghabcdefghabcdefgh"

test/libsolidity/syntaxTests/array/bytes_to_fixed_bytes.sol

@@ -0,0 +1,7 @@
+contract C {
+    bytes s;
+    function f(bytes calldata c, string memory m) public view returns (bytes3, bytes8, bytes16, bytes32) {
+        return (bytes3(c[0:3]), bytes8(s), bytes16(c), bytes32(bytes(m)));
+    }
+}
+// ----

test/libsolidity/syntaxTests/array/invalid/bytes_to_fixed_bytes.sol

@@ -0,0 +1,15 @@
+contract C {
+    bytes s;
+    function f(bytes calldata c, string memory m) public view returns (bytes3 r1, bytes16 r2, bytes32 r3) {
+        require(c.length >= 3, "");
+        r2 = s;
+        r1 = c[0:3];
+        r3 = bytes32(m);
+        r3 = m;
+    }
+}
+// ----
+// TypeError 7407: (183-184): Type bytes storage ref is not implicitly convertible to expected type bytes16.
+// TypeError 7407: (199-205): Type bytes calldata slice is not implicitly convertible to expected type bytes3.
+// TypeError 9640: (220-230): Explicit type conversion not allowed from "string memory" to "bytes32".
+// TypeError 7407: (245-246): Type string memory is not implicitly convertible to expected type bytes32.