Shortening of dynamic arrays.

1 files changed, 284 insertions, 0 deletions

diff --git a/ArrayUtils.cpp b/ArrayUtils.cpp
new file mode 100644
index 00000000..07949c79
--- /dev/null
+++ b/ArrayUtils.cpp
@@ -0,0 +1,284 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum 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.
+
+	cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/**
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ * Code generation utils that handle arrays.
+ */
+
+#include <libsolidity/ArrayUtils.h>
+#include <libevmcore/Instruction.h>
+#include <libsolidity/CompilerContext.h>
+#include <libsolidity/CompilerUtils.h>
+#include <libsolidity/Types.h>
+#include <libsolidity/Utils.h>
+#include <libsolidity/LValue.h>
+
+using namespace std;
+using namespace dev;
+using namespace solidity;
+
+void ArrayUtils::copyArrayToStorage(ArrayType const& _targetType, ArrayType const& _sourceType) const
+{
+	// stack layout: [source_ref] target_ref (top)
+	// need to leave target_ref on the stack at the end
+	solAssert(_targetType.getLocation() == ArrayType::Location::Storage, "");
+	solAssert(_targetType.isByteArray(), "Non byte arrays not yet implemented here.");
+	solAssert(_sourceType.isByteArray(), "Non byte arrays not yet implemented here.");
+
+	switch (_sourceType.getLocation())
+	{
+	case ArrayType::Location::CallData:
+	{
+		// This also assumes that after "length" we only have zeros, i.e. it cannot be used to
+		// slice a byte array from calldata.
+
+		// stack: source_offset source_len target_ref
+		// fetch old length and convert to words
+		m_context << eth::Instruction::DUP1 << eth::Instruction::SLOAD;
+		convertLengthToSize(_targetType);
+		// stack here: source_offset source_len target_ref target_length_words
+		// actual array data is stored at SHA3(storage_offset)
+		m_context << eth::Instruction::DUP2;
+		CompilerUtils(m_context).computeHashStatic();
+		// compute target_data_end
+		m_context << eth::Instruction::DUP1 << eth::Instruction::SWAP2 << eth::Instruction::ADD
+				  << eth::Instruction::SWAP1;
+		// stack here: source_offset source_len target_ref target_data_end target_data_ref
+		// store length (in bytes)
+		m_context << eth::Instruction::DUP4 << eth::Instruction::DUP1 << eth::Instruction::DUP5
+			<< eth::Instruction::SSTORE;
+		// jump to end if length is zero
+		m_context << eth::Instruction::ISZERO;
+		eth::AssemblyItem copyLoopEnd = m_context.newTag();
+		m_context.appendConditionalJumpTo(copyLoopEnd);
+		// store start offset
+		m_context << eth::Instruction::DUP5;
+		// stack now: source_offset source_len target_ref target_data_end target_data_ref calldata_offset
+		eth::AssemblyItem copyLoopStart = m_context.newTag();
+		m_context << copyLoopStart
+				  // copy from calldata and store
+				  << eth::Instruction::DUP1 << eth::Instruction::CALLDATALOAD
+				  << eth::Instruction::DUP3 << eth::Instruction::SSTORE
+				  // increment target_data_ref by 1
+				  << eth::Instruction::SWAP1 << u256(1) << eth::Instruction::ADD
+				  // increment calldata_offset by 32
+				  << eth::Instruction::SWAP1 << u256(32) << eth::Instruction::ADD
+				  // check for loop condition
+				  << eth::Instruction::DUP1 << eth::Instruction::DUP6 << eth::Instruction::GT;
+		m_context.appendConditionalJumpTo(copyLoopStart);
+		m_context << eth::Instruction::POP;
+		m_context << copyLoopEnd;
+
+		// now clear leftover bytes of the old value
+		// stack now: source_offset source_len target_ref target_data_end target_data_ref
+		clearStorageLoop(IntegerType(256));
+		// stack now: source_offset source_len target_ref target_data_end
+
+		m_context << eth::Instruction::POP << eth::Instruction::SWAP2
+			<< eth::Instruction::POP << eth::Instruction::POP;
+		break;
+	}
+	case ArrayType::Location::Storage:
+	{
+		// this copies source to target and also clears target if it was larger
+
+		// stack: source_ref target_ref
+		// store target_ref
+		m_context << eth::Instruction::SWAP1 << eth::Instruction::DUP2;
+		// fetch lengthes
+		m_context << eth::Instruction::DUP1 << eth::Instruction::SLOAD << eth::Instruction::SWAP2
+				  << eth::Instruction::DUP1 << eth::Instruction::SLOAD;
+		// stack: target_ref target_len_bytes target_ref source_ref source_len_bytes
+		// store new target length
+		m_context << eth::Instruction::DUP1 << eth::Instruction::DUP4 << eth::Instruction::SSTORE;
+		// compute hashes (data positions)
+		m_context << eth::Instruction::SWAP2;
+		CompilerUtils(m_context).computeHashStatic();
+		m_context << eth::Instruction::SWAP1;
+		CompilerUtils(m_context).computeHashStatic();
+		// stack: target_ref target_len_bytes source_len_bytes target_data_pos source_data_pos
+		// convert lengthes from bytes to storage slots
+		m_context << u256(31) << u256(32) << eth::Instruction::DUP1 << eth::Instruction::DUP3
+				  << eth::Instruction::DUP8 << eth::Instruction::ADD << eth::Instruction::DIV
+				  << eth::Instruction::SWAP2
+				  << eth::Instruction::DUP6 << eth::Instruction::ADD << eth::Instruction::DIV;
+		// stack: target_ref target_len_bytes source_len_bytes target_data_pos source_data_pos target_len source_len
+		// @todo we might be able to go without a third counter
+		m_context << u256(0);
+		// stack: target_ref target_len_bytes source_len_bytes target_data_pos source_data_pos target_len source_len counter
+		eth::AssemblyItem copyLoopStart = m_context.newTag();
+		m_context << copyLoopStart;
+		// check for loop condition
+		m_context << eth::Instruction::DUP1 << eth::Instruction::DUP3
+				   << eth::Instruction::GT << eth::Instruction::ISZERO;
+		eth::AssemblyItem copyLoopEnd = m_context.newTag();
+		m_context.appendConditionalJumpTo(copyLoopEnd);
+		// copy
+		m_context << eth::Instruction::DUP4 << eth::Instruction::DUP2 << eth::Instruction::ADD
+				  << eth::Instruction::SLOAD
+				  << eth::Instruction::DUP6 << eth::Instruction::DUP3 << eth::Instruction::ADD
+				  << eth::Instruction::SSTORE;
+		// increment
+		m_context << u256(1) << eth::Instruction::ADD;
+		m_context.appendJumpTo(copyLoopStart);
+		m_context << copyLoopEnd;
+
+		// zero-out leftovers in target
+		// stack: target_ref target_len_bytes source_len_bytes target_data_pos source_data_pos target_len source_len counter
+		// add counter to target_data_pos
+		m_context << eth::Instruction::DUP5 << eth::Instruction::ADD
+				  << eth::Instruction::SWAP5 << eth::Instruction::POP;
+		// stack: target_ref target_len_bytes target_data_pos_updated target_data_pos source_data_pos target_len source_len
+		// add length to target_data_pos to get target_data_end
+		m_context << eth::Instruction::POP << eth::Instruction::DUP3 << eth::Instruction::ADD
+				  << eth::Instruction::SWAP4
+				  << eth::Instruction::POP  << eth::Instruction::POP << eth::Instruction::POP;
+		// stack: target_ref target_data_end target_data_pos_updated
+		clearStorageLoop(IntegerType(256));
+		m_context << eth::Instruction::POP;
+		break;
+	}
+	default:
+		solAssert(false, "Given byte array location not implemented.");
+	}
+}
+
+void ArrayUtils::clearArray(ArrayType const& _type) const
+{
+	solAssert(_type.getLocation() == ArrayType::Location::Storage, "");
+	if (_type.isDynamicallySized())
+		clearDynamicArray(_type);
+	else if (_type.getLength() == 0)
+		m_context << eth::Instruction::POP;
+	else if (_type.getLength() < 5) // unroll loop for small arrays @todo choose a good value
+	{
+		for (unsigned i = 1; i < _type.getLength(); ++i)
+		{
+			StorageItem(m_context, *_type.getBaseType()).setToZero(SourceLocation(), false);
+			m_context << u256(_type.getBaseType()->getStorageSize()) << eth::Instruction::ADD;
+		}
+		StorageItem(m_context, *_type.getBaseType()).setToZero(SourceLocation(), true);
+	}
+	else
+	{
+		m_context
+			<< eth::Instruction::DUP1 << u256(_type.getLength())
+			<< u256(_type.getBaseType()->getStorageSize())
+			<< eth::Instruction::MUL << eth::Instruction::ADD << eth::Instruction::SWAP1;
+		clearStorageLoop(*_type.getBaseType());
+		m_context << eth::Instruction::POP;
+	}
+}
+
+void ArrayUtils::clearDynamicArray(ArrayType const& _type) const
+{
+	solAssert(_type.getLocation() == ArrayType::Location::Storage, "");
+	solAssert(_type.isDynamicallySized(), "");
+
+	// fetch length
+	m_context << eth::Instruction::DUP1 << eth::Instruction::SLOAD;
+	// set length to zero
+	m_context << u256(0) << eth::Instruction::DUP3 << eth::Instruction::SSTORE;
+	// stack: ref old_length
+	convertLengthToSize(_type);
+	// compute data positions
+	m_context << eth::Instruction::SWAP1;
+	CompilerUtils(m_context).computeHashStatic();
+	// stack: len data_pos (len is in slots for byte array and in items for other arrays)
+	m_context << eth::Instruction::SWAP1 << eth::Instruction::DUP2 << eth::Instruction::ADD
+		<< eth::Instruction::SWAP1;
+	// stack: data_pos_end data_pos
+	if (_type.isByteArray())
+		clearStorageLoop(IntegerType(256));
+	else
+		clearStorageLoop(*_type.getBaseType());
+	// cleanup
+	m_context << eth::Instruction::POP;
+}
+
+void ArrayUtils::resizeDynamicArray(const ArrayType& _type) const
+{
+	solAssert(_type.getLocation() == ArrayType::Location::Storage, "");
+	solAssert(_type.isDynamicallySized(), "");
+
+	eth::AssemblyItem resizeEnd = m_context.newTag();
+
+	// stack: ref new_length
+	// fetch old length
+	m_context << eth::Instruction::DUP2 << eth::Instruction::SLOAD;
+	// stack: ref new_length old_length
+	// store new length
+	m_context << eth::Instruction::DUP2 << eth::Instruction::DUP4 << eth::Instruction::SSTORE;
+	// skip if size is not reduced
+	m_context << eth::Instruction::DUP2 << eth::Instruction::DUP2
+		<< eth::Instruction::ISZERO << eth::Instruction::GT;
+	m_context.appendConditionalJumpTo(resizeEnd);
+
+	// size reduced, clear the end of the array
+	// stack: ref new_length old_length
+	convertLengthToSize(_type);
+	m_context << eth::Instruction::DUP2;
+	convertLengthToSize(_type);
+	// stack: ref new_length old_size new_size
+	// compute data positions
+	m_context << eth::Instruction::DUP4;
+	CompilerUtils(m_context).computeHashStatic();
+	// stack: ref new_length old_size new_size data_pos
+	m_context << eth::Instruction::SWAP2 << eth::Instruction::DUP3 << eth::Instruction::ADD;
+	// stack: ref new_length data_pos new_size delete_end
+	m_context << eth::Instruction::SWAP2 << eth::Instruction::ADD;
+	// stack: ref new_length delete_end delete_start
+	if (_type.isByteArray())
+		clearStorageLoop(IntegerType(256));
+	else
+		clearStorageLoop(*_type.getBaseType());
+
+	m_context << resizeEnd;
+	// cleanup
+	m_context << eth::Instruction::POP << eth::Instruction::POP << eth::Instruction::POP;
+}
+
+void ArrayUtils::clearStorageLoop(Type const& _type) const
+{
+	// stack: end_pos pos
+	eth::AssemblyItem loopStart = m_context.newTag();
+	m_context << loopStart;
+	// check for loop condition
+	m_context << eth::Instruction::DUP1 << eth::Instruction::DUP3
+			   << eth::Instruction::GT << eth::Instruction::ISZERO;
+	eth::AssemblyItem zeroLoopEnd = m_context.newTag();
+	m_context.appendConditionalJumpTo(zeroLoopEnd);
+	// delete
+	StorageItem(m_context, _type).setToZero(SourceLocation(), false);
+	// increment
+	m_context << u256(1) << eth::Instruction::ADD;
+	m_context.appendJumpTo(loopStart);
+	// cleanup
+	m_context << zeroLoopEnd;
+	m_context << eth::Instruction::POP;
+}
+
+void ArrayUtils::convertLengthToSize(ArrayType const& _arrayType) const
+{
+	if (_arrayType.isByteArray())
+		m_context << u256(31) << eth::Instruction::ADD
+			<< u256(32) << eth::Instruction::SWAP1 << eth::Instruction::DIV;
+	else if (_arrayType.getBaseType()->getStorageSize() > 1)
+		m_context << _arrayType.getBaseType()->getStorageSize() << eth::Instruction::MUL;
+}
+