Merge pull request #4390 from ethereum/abidecode

Add abi.decode

Changelog.md

@@ -77,6 +77,7 @@ Language Features:
  * General: Allow ``enum``s in interfaces.
  * General: Allow ``mapping`` storage pointers as arguments and return values in all internal functions.
  * General: Allow ``struct``s in interfaces.
+ * General: Provide access to the ABI decoder through ``abi.decode(bytes memory data, (...))``.
 
 Compiler Features:
  * C API (``libsolc``): Export the ``solidity_license``, ``solidity_version`` and ``solidity_compile`` methods.

docs/miscellaneous.rst

@@ -318,6 +318,7 @@ The following is the order of precedence for operators, listed in order of evalu
 Global Variables
 ================
 
+- ``abi.decode(bytes encodedData, (...)) returns (...)``: :ref:`ABI <ABI>`-decodes the provided data. The types are given in parentheses as second argument. Example: ``(uint a, uint[2] memory b, bytes memory c) = abi.decode(data, (uint, uint[2], bytes))``
 - ``abi.encode(...) returns (bytes)``: :ref:`ABI <ABI>`-encodes the given arguments
 - ``abi.encodePacked(...) returns (bytes)``: Performs :ref:`packed encoding <abi_packed_mode>` of the given arguments
 - ``abi.encodeWithSelector(bytes4 selector, ...) returns (bytes)``: :ref:`ABI <ABI>`-encodes the given arguments

docs/units-and-global-variables.rst

@@ -96,9 +96,10 @@ Block and Transaction Properties
 
 .. index:: abi, encoding, packed
 
-ABI Encoding Functions
-----------------------
+ABI Encoding and Decoding Functions
+-----------------------------------
 
+- ``abi.decode(bytes encodedData, (...)) returns (...)``: ABI-decodes the given data, while the types are given in parentheses as second argument. Example: ``(uint a, uint[2] memory b, bytes memory c) = abi.decode(data, (uint, uint[2], bytes))``
 - ``abi.encode(...) returns (bytes)``: ABI-encodes the given arguments
 - ``abi.encodePacked(...) returns (bytes)``: Performs :ref:`packed encoding <abi_packed_mode>` of the given arguments
 - ``abi.encodeWithSelector(bytes4 selector, ...) returns (bytes)``: ABI-encodes the given arguments starting from the second and prepends the given four-byte selector

libsolidity/analysis/TypeChecker.cpp

@@ -525,6 +525,75 @@ void TypeChecker::checkDoubleStorageAssignment(Assignment const& _assignment)
 		);
 }
 
+TypePointer TypeChecker::typeCheckABIDecodeAndRetrieveReturnType(FunctionCall const& _functionCall, bool _abiEncoderV2)
+{
+	vector<ASTPointer<Expression const>> arguments = _functionCall.arguments();
+	if (arguments.size() != 2)
+		m_errorReporter.typeError(
+			_functionCall.location(),
+			"This function takes two arguments, but " +
+			toString(arguments.size()) +
+			" were provided."
+		);
+	if (arguments.size() >= 1 && !type(*arguments.front())->isImplicitlyConvertibleTo(ArrayType(DataLocation::Memory)))
+		m_errorReporter.typeError(
+			arguments.front()->location(),
+			"Invalid type for argument in function call. "
+			"Invalid implicit conversion from " +
+			type(*arguments.front())->toString() +
+			" to bytes memory requested."
+		);
+
+	TypePointer returnType = make_shared<TupleType>();
+
+	if (arguments.size() < 2)
+		return returnType;
+
+	// The following is a rather syntactic restriction, but we check it here anyway:
+	// The second argument has to be a tuple expression containing type names.
+	TupleExpression const* tupleExpression = dynamic_cast<TupleExpression const*>(arguments[1].get());
+	if (!tupleExpression)
+	{
+		m_errorReporter.typeError(
+			arguments[1]->location(),
+			"The second argument to \"abi.decode\" has to be a tuple of types."
+		);
+		return returnType;
+	}
+
+	vector<TypePointer> components;
+	for (auto const& typeArgument: tupleExpression->components())
+	{
+		solAssert(typeArgument, "");
+		if (TypeType const* argTypeType = dynamic_cast<TypeType const*>(type(*typeArgument).get()))
+		{
+			TypePointer actualType = argTypeType->actualType();
+			solAssert(actualType, "");
+			// We force memory because the parser currently cannot handle
+			// data locations. Furthermore, storage can be a little dangerous and
+			// calldata is not really implemented anyway.
+			actualType = ReferenceType::copyForLocationIfReference(DataLocation::Memory, actualType);
+			solAssert(
+				!actualType->dataStoredIn(DataLocation::CallData) &&
+				!actualType->dataStoredIn(DataLocation::Storage),
+				""
+			);
+			if (!actualType->fullEncodingType(false, _abiEncoderV2, false))
+				m_errorReporter.typeError(
+					typeArgument->location(),
+					"Decoding type " + actualType->toString(false)  + " not supported."
+				);
+			components.push_back(actualType);
+		}
+		else
+		{
+			m_errorReporter.typeError(typeArgument->location(), "Argument has to be a type name.");
+			components.push_back(make_shared<TupleType>());
+		}
+	}
+	return make_shared<TupleType>(components);
+}
+
 void TypeChecker::endVisit(InheritanceSpecifier const& _inheritance)
 {
 	auto base = dynamic_cast<ContractDefinition const*>(&dereference(_inheritance.name()));
@@ -1727,7 +1796,11 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
 		}
 	}
 
-	if (functionType->takesArbitraryParameters() && arguments.size() < parameterTypes.size())
+	bool const abiEncoderV2 = m_scope->sourceUnit().annotation().experimentalFeatures.count(ExperimentalFeature::ABIEncoderV2);
+
+	if (functionType->kind() == FunctionType::Kind::ABIDecode)
+		_functionCall.annotation().type = typeCheckABIDecodeAndRetrieveReturnType(_functionCall, abiEncoderV2);
+	else if (functionType->takesArbitraryParameters() && arguments.size() < parameterTypes.size())
 	{
 		solAssert(_functionCall.annotation().kind == FunctionCallKind::FunctionCall, "");
 		m_errorReporter.typeError(
@@ -1782,8 +1855,6 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
 	}
 	else if (isPositionalCall)
 	{
-		bool const abiEncodeV2 = m_scope->sourceUnit().annotation().experimentalFeatures.count(ExperimentalFeature::ABIEncoderV2);
-
 		for (size_t i = 0; i < arguments.size(); ++i)
 		{
 			auto const& argType = type(*arguments[i]);
@@ -1796,7 +1867,7 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
 						m_errorReporter.typeError(arguments[i]->location(), "Invalid rational number (too large or division by zero).");
 						errored = true;
 					}
-				if (!errored && !argType->fullEncodingType(false, abiEncodeV2, !functionType->padArguments()))
+				if (!errored && !argType->fullEncodingType(false, abiEncoderV2, !functionType->padArguments()))
 					m_errorReporter.typeError(arguments[i]->location(), "This type cannot be encoded.");
 			}
 			else if (!type(*arguments[i])->isImplicitlyConvertibleTo(*parameterTypes[i]))

libsolidity/analysis/TypeChecker.h

@@ -91,6 +91,11 @@ private:
 	// and reports an error, if not.
 	void checkExpressionAssignment(Type const& _type, Expression const& _expression);
 
+	/// Performs type checks for ``abi.decode(bytes memory, (...))`` and returns the
+	/// return type (which is basically the second argument) if successful. It returns
+	/// the empty tuple type or error.
+	TypePointer typeCheckABIDecodeAndRetrieveReturnType(FunctionCall const& _functionCall, bool _abiEncoderV2);
+
 	virtual void endVisit(InheritanceSpecifier const& _inheritance) override;
 	virtual void endVisit(UsingForDirective const& _usingFor) override;
 	virtual bool visit(StructDefinition const& _struct) override;

libsolidity/analysis/ViewPureChecker.cpp

@@ -295,7 +295,7 @@ void ViewPureChecker::endVisit(MemberAccess const& _memberAccess)
 	{
 		// we can ignore the kind of magic and only look at the name of the member
 		set<string> static const pureMembers{
-			"encode", "encodePacked", "encodeWithSelector", "encodeWithSignature", "data", "sig", "blockhash"
+			"encode", "encodePacked", "encodeWithSelector", "encodeWithSignature", "decode", "data", "sig", "blockhash"
 		};
 		if (!pureMembers.count(member))
 			mutability = StateMutability::View;

libsolidity/ast/Types.cpp

@@ -2553,6 +2553,7 @@ string FunctionType::richIdentifier() const
 	case Kind::ABIEncodePacked: id += "abiencodepacked"; break;
 	case Kind::ABIEncodeWithSelector: id += "abiencodewithselector"; break;
 	case Kind::ABIEncodeWithSignature: id += "abiencodewithsignature"; break;
+	case Kind::ABIDecode: id += "abidecode"; break;
 	default: solAssert(false, "Unknown function location."); break;
 	}
 	id += "_" + stateMutabilityToString(m_stateMutability);
@@ -2959,7 +2960,8 @@ bool FunctionType::isPure() const
 		m_kind == Kind::ABIEncode ||
 		m_kind == Kind::ABIEncodePacked ||
 		m_kind == Kind::ABIEncodeWithSelector ||
-		m_kind == Kind::ABIEncodeWithSignature;
+		m_kind == Kind::ABIEncodeWithSignature ||
+		m_kind == Kind::ABIDecode;
 }
 
 TypePointers FunctionType::parseElementaryTypeVector(strings const& _types)
@@ -3315,6 +3317,15 @@ MemberList::MemberMap MagicType::nativeMembers(ContractDefinition const*) const
 				FunctionType::Kind::ABIEncodeWithSignature,
 				true,
 				StateMutability::Pure
+			)},
+			{"decode", make_shared<FunctionType>(
+				TypePointers(),
+				TypePointers(),
+				strings{},
+				strings{},
+				FunctionType::Kind::ABIDecode,
+				true,
+				StateMutability::Pure
 			)}
 		});
 	default:

libsolidity/ast/Types.h

@@ -934,6 +934,7 @@ public:
 		ABIEncodePacked,
 		ABIEncodeWithSelector,
 		ABIEncodeWithSignature,
+		ABIDecode,
 		GasLeft ///< gasleft()
 	};
 

libsolidity/codegen/ExpressionCompiler.cpp

@@ -1070,6 +1070,27 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
 			// stack now: <memory pointer>
 			break;
 		}
+		case FunctionType::Kind::ABIDecode:
+		{
+			arguments.front()->accept(*this);
+			TypePointer firstArgType = arguments.front()->annotation().type;
+			TypePointers const& targetTypes = dynamic_cast<TupleType const&>(*_functionCall.annotation().type).components();
+			if (
+				*firstArgType == ArrayType(DataLocation::CallData) ||
+				*firstArgType == ArrayType(DataLocation::CallData, true)
+			)
+				utils().abiDecode(targetTypes, false);
+			else
+			{
+				utils().convertType(*firstArgType, ArrayType(DataLocation::Memory));
+				m_context << Instruction::DUP1 << u256(32) << Instruction::ADD;
+				m_context << Instruction::SWAP1 << Instruction::MLOAD;
+				// stack now: <mem_pos> <length>
+
+				utils().abiDecode(targetTypes, true);
+			}
+			break;
+		}
 		case FunctionType::Kind::GasLeft:
 			m_context << Instruction::GAS;
 			break;

test/libsolidity/SolidityEndToEndTest.cpp

@@ -13195,6 +13195,203 @@ BOOST_AUTO_TEST_CASE(senders_balance)
 	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(27)));
 }
 
+BOOST_AUTO_TEST_CASE(abi_decode_trivial)
+{
+	char const* sourceCode = R"(
+		contract C {
+			function f(bytes memory data) public pure returns (uint) {
+				return abi.decode(data, (uint));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(callContractFunction("f(bytes)", 0x20, 0x20, 33), encodeArgs(u256(33)));
+}
+
+BOOST_AUTO_TEST_CASE(abi_encode_decode_simple)
+{
+	char const* sourceCode = R"XX(
+		contract C {
+			function f() public pure returns (uint, bytes memory) {
+				bytes memory arg = "abcdefg";
+				return abi.decode(abi.encode(uint(33), arg), (uint, bytes));
+			}
+		}
+	)XX";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f()"),
+		encodeArgs(33, 0x40, 7, "abcdefg")
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_simple)
+{
+	char const* sourceCode = R"(
+		contract C {
+			function f(bytes memory data) public pure returns (uint, bytes memory) {
+				return abi.decode(data, (uint, bytes));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f(bytes)", 0x20, 0x20 * 4, 33, 0x40, 7, "abcdefg"),
+		encodeArgs(33, 0x40, 7, "abcdefg")
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_v2)
+{
+	char const* sourceCode = R"(
+		pragma experimental ABIEncoderV2;
+		contract C {
+			struct S { uint a; uint[] b; }
+			function f() public pure returns (S memory) {
+				S memory s;
+				s.a = 8;
+				s.b = new uint[](3);
+				s.b[0] = 9;
+				s.b[1] = 10;
+				s.b[2] = 11;
+				return abi.decode(abi.encode(s), (S));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f()"),
+		encodeArgs(0x20, 8, 0x40, 3, 9, 10, 11)
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_simple_storage)
+{
+	char const* sourceCode = R"(
+		contract C {
+			bytes data;
+			function f(bytes memory _data) public returns (uint, bytes memory) {
+				data = _data;
+				return abi.decode(data, (uint, bytes));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f(bytes)", 0x20, 0x20 * 4, 33, 0x40, 7, "abcdefg"),
+		encodeArgs(33, 0x40, 7, "abcdefg")
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_v2_storage)
+{
+	char const* sourceCode = R"(
+		pragma experimental ABIEncoderV2;
+		contract C {
+			bytes data;
+			struct S { uint a; uint[] b; }
+			function f() public returns (S memory) {
+				S memory s;
+				s.a = 8;
+				s.b = new uint[](3);
+				s.b[0] = 9;
+				s.b[1] = 10;
+				s.b[2] = 11;
+				data = abi.encode(s);
+				return abi.decode(data, (S));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f()"),
+		encodeArgs(0x20, 8, 0x40, 3, 9, 10, 11)
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_calldata)
+{
+	char const* sourceCode = R"(
+		contract C {
+			function f(bytes calldata data) external pure returns (uint, bytes memory r) {
+				return abi.decode(data, (uint, bytes));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f(bytes)", 0x20, 0x20 * 4, 33, 0x40, 7, "abcdefg"),
+		encodeArgs(33, 0x40, 7, "abcdefg")
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_v2_calldata)
+{
+	char const* sourceCode = R"(
+		pragma experimental ABIEncoderV2;
+		contract C {
+			struct S { uint a; uint[] b; }
+			function f(bytes calldata data) external pure returns (S memory) {
+				return abi.decode(data, (S));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f(bytes)", 0x20, 0x20 * 7, 0x20, 33, 0x40, 3, 10, 11, 12),
+		encodeArgs(0x20, 33, 0x40, 3, 10, 11, 12)
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_static_array)
+{
+	char const* sourceCode = R"(
+		contract C {
+			function f(bytes calldata data) external pure returns (uint[2][3] memory) {
+				return abi.decode(data, (uint[2][3]));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f(bytes)", 0x20, 6 * 0x20, 1, 2, 3, 4, 5, 6),
+		encodeArgs(1, 2, 3, 4, 5, 6)
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_static_array_v2)
+{
+	char const* sourceCode = R"(
+		pragma experimental ABIEncoderV2;
+		contract C {
+			function f(bytes calldata data) external pure returns (uint[2][3] memory) {
+				return abi.decode(data, (uint[2][3]));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f(bytes)", 0x20, 6 * 0x20, 1, 2, 3, 4, 5, 6),
+		encodeArgs(1, 2, 3, 4, 5, 6)
+	);
+}
+
+BOOST_AUTO_TEST_CASE(abi_decode_dynamic_array)
+{
+	char const* sourceCode = R"(
+		contract C {
+			function f(bytes calldata data) external pure returns (uint[] memory) {
+				return abi.decode(data, (uint[]));
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	ABI_CHECK(
+		callContractFunction("f(bytes)", 0x20, 6 * 0x20, 0x20, 4, 3, 4, 5, 6),
+		encodeArgs(0x20, 4, 3, 4, 5, 6)
+	);
+}
+
 BOOST_AUTO_TEST_CASE(write_storage_external)
 {
 	char const* sourceCode = R"(

test/libsolidity/syntaxTests/specialFunctions/abidecode/abi_decode_calldata.sol

@@ -0,0 +1,8 @@
+// This restriction might be lifted in the future
+contract C {
+  function f() public pure {
+    abi.decode("abc", (bytes calldata));
+  }
+}
+// ----
+// ParserError: (121-129): Expected ',' but got 'calldata'

test/libsolidity/syntaxTests/specialFunctions/abidecode/abi_decode_invalid_arg_count.sol

@@ -0,0 +1,12 @@
+contract C {
+  function f() public pure {
+    abi.decode();
+    abi.decode(msg.data);
+    abi.decode(msg.data, uint, uint);
+  }
+}
+// ----
+// TypeError: (46-58): This function takes two arguments, but 0 were provided.
+// TypeError: (64-84): This function takes two arguments, but 1 were provided.
+// TypeError: (90-122): This function takes two arguments, but 3 were provided.
+// TypeError: (111-115): The second argument to "abi.decode" has to be a tuple of types.

test/libsolidity/syntaxTests/specialFunctions/abidecode/abi_decode_memory.sol

@@ -0,0 +1,7 @@
+contract C {
+  function f() public pure {
+    abi.decode("abc", (bytes memory, uint[][2] memory));
+  }
+}
+// ----
+// ParserError: (71-77): Expected ',' but got 'memory'

test/libsolidity/syntaxTests/specialFunctions/abidecode/abi_decode_memory_v2.sol

@@ -0,0 +1,10 @@
+pragma experimental "ABIEncoderV2";
+
+contract C {
+  struct S { uint x; uint[] b; }
+  function f() public pure returns (S memory, bytes memory, uint[][2] memory) {
+    return abi.decode("abc", (S, bytes, uint[][2]));
+  }
+}
+// ----
+// Warning: (0-35): Experimental features are turned on. Do not use experimental features on live deployments.

test/libsolidity/syntaxTests/specialFunctions/abidecode/abi_decode_nontuple.sol

@@ -0,0 +1,11 @@
+contract C {
+  function f() public pure {
+    abi.decode("abc", uint);
+    abi.decode("abc", this);
+    abi.decode("abc", f());
+  }
+}
+// ----
+// TypeError: (64-68): The second argument to "abi.decode" has to be a tuple of types.
+// TypeError: (93-97): The second argument to "abi.decode" has to be a tuple of types.
+// TypeError: (122-125): The second argument to "abi.decode" has to be a tuple of types.

test/libsolidity/syntaxTests/specialFunctions/abidecode/abi_decode_simple.sol

@@ -0,0 +1,5 @@
+contract C {
+  function f() public pure returns (uint, bytes32, C) {
+    return abi.decode("abc", (uint, bytes32, C));
+  }
+}

test/libsolidity/syntaxTests/specialFunctions/abidecode/abi_decode_singletontuple.sol

@@ -0,0 +1,6 @@
+contract C {
+  function f() public pure returns (uint) {
+    return abi.decode("abc", (uint));
+  }
+}
+// ----

test/libsolidity/syntaxTests/specialFunctions/abidecode/abi_decode_storage.sol

@@ -0,0 +1,8 @@
+// This restriction might be lifted in the future
+contract C {
+  function f() {
+    abi.decode("abc", (bytes storage));
+  }
+}
+// ----
+// ParserError: (109-116): Expected ',' but got 'storage'