path: root/ArrayUtils.cpp

/*
    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(
        _sourceType.getLocation() == ArrayType::Location::CallData ||
            _sourceType.getLocation() == ArrayType::Location::Storage,
        "Given array location not implemented."
    );

    IntegerType uint256(256);
    Type const* targetBaseType = _targetType.isByteArray() ? &uint256 : &(*_targetType.getBaseType());
    Type const* sourceBaseType = _sourceType.isByteArray() ? &uint256 : &(*_sourceType.getBaseType());

    // this copies source to target and also clears target if it was larger

    // TODO unroll loop for small sizes

    // stack: source_ref [source_length] target_ref
    // store target_ref
    for (unsigned i = _sourceType.getSizeOnStack(); i > 0; --i)
        m_context << eth::swapInstruction(i);
    if (_sourceType.getLocation() != ArrayType::Location::CallData || !_sourceType.isDynamicallySized())
        retrieveLength(_sourceType); // otherwise, length is already there
    // stack: target_ref source_ref source_length
    m_context << eth::Instruction::DUP3;
    // stack: target_ref source_ref source_length target_ref
    retrieveLength(_targetType);
    // stack: target_ref source_ref source_length target_ref target_length
    if (_targetType.isDynamicallySized())
        // store new target length
        m_context << eth::Instruction::DUP3 << eth::Instruction::DUP3 << eth::Instruction::SSTORE;
    if (sourceBaseType->getCategory() == Type::Category::Mapping)
    {
        solAssert(targetBaseType->getCategory() == Type::Category::Mapping, "");
        solAssert(_sourceType.getLocation() == ArrayType::Location::Storage, "");
        // nothing to copy
        m_context
            << eth::Instruction::POP << eth::Instruction::POP
            << eth::Instruction::POP << eth::Instruction::POP;
        return;
    }
    // compute hashes (data positions)
    m_context << eth::Instruction::SWAP1;
    if (_targetType.isDynamicallySized())
        CompilerUtils(m_context).computeHashStatic();
    // stack: target_ref source_ref source_length target_length target_data_pos
    m_context << eth::Instruction::SWAP1;
    convertLengthToSize(_targetType);
    m_context << eth::Instruction::DUP2 << eth::Instruction::ADD;
    // stack: target_ref source_ref source_length target_data_pos target_data_end
    m_context << eth::Instruction::SWAP3;
    // stack: target_ref target_data_end source_length target_data_pos source_ref
    // skip copying if source length is zero
    m_context << eth::Instruction::DUP3 << eth::Instruction::ISZERO;
    eth::AssemblyItem copyLoopEnd = m_context.newTag();
    m_context.appendConditionalJumpTo(copyLoopEnd);

    if (_sourceType.getLocation() == ArrayType::Location::Storage && _sourceType.isDynamicallySized())
        CompilerUtils(m_context).computeHashStatic();
    // stack: target_ref target_data_end source_length target_data_pos source_data_pos
    m_context << eth::Instruction::SWAP2;
    convertLengthToSize(_sourceType);
    m_context << eth::Instruction::DUP3 << eth::Instruction::ADD;
    // stack: target_ref target_data_end source_data_pos target_data_pos source_data_end
    eth::AssemblyItem copyLoopStart = m_context.newTag();
    m_context << copyLoopStart;
    // check for loop condition
    m_context
        << eth::Instruction::DUP3 << eth::Instruction::DUP2
        << eth::Instruction::GT << eth::Instruction::ISZERO;
    m_context.appendConditionalJumpTo(copyLoopEnd);
    // stack: target_ref target_data_end source_data_pos target_data_pos source_data_end
    // copy
    if (sourceBaseType->getCategory() == Type::Category::Array)
    {
        m_context << eth::Instruction::DUP3 << eth::Instruction::DUP3;
        copyArrayToStorage(
            dynamic_cast<ArrayType const&>(*targetBaseType),
            dynamic_cast<ArrayType const&>(*sourceBaseType)
        );
        m_context << eth::Instruction::POP;
    }
    else
    {
        m_context << eth::Instruction::DUP3;
        if (_sourceType.getLocation() == ArrayType::Location::Storage)
            StorageItem(m_context, *sourceBaseType).retrieveValue(SourceLocation(), true);
        else if (sourceBaseType->isValueType())
            CompilerUtils(m_context).loadFromMemoryDynamic(*sourceBaseType, true, true, false);
        else
            solAssert(false, "Copying of unknown type requested: " + sourceBaseType->toString());
        m_context << eth::dupInstruction(2 + sourceBaseType->getSizeOnStack());
        StorageItem(m_context, *targetBaseType).storeValue(*sourceBaseType, SourceLocation(), true);
    }
    // increment source
    m_context
        << eth::Instruction::SWAP2
        << (_sourceType.getLocation() == ArrayType::Location::Storage ?
            sourceBaseType->getStorageSize() :
            sourceBaseType->getCalldataEncodedSize())
        << eth::Instruction::ADD
        << eth::Instruction::SWAP2;
    // increment target
    m_context
        << eth::Instruction::SWAP1
        << targetBaseType->getStorageSize()
        << eth::Instruction::ADD
        << eth::Instruction::SWAP1;
    m_context.appendJumpTo(copyLoopStart);
    m_context << copyLoopEnd;

    // zero-out leftovers in target
    // stack: target_ref target_data_end source_data_pos target_data_pos source_data_end
    m_context << eth::Instruction::POP << eth::Instruction::SWAP1 << eth::Instruction::POP;
    // stack: target_ref target_data_end target_data_pos_updated
    clearStorageLoop(*targetBaseType);
    m_context << eth::Instruction::POP;
}

void ArrayUtils::clearArray(ArrayType const& _type) const
{
    solAssert(_type.getLocation() == ArrayType::Location::Storage, "");
    if (_type.isDynamicallySized())
        clearDynamicArray(_type);
    else if (_type.getLength() == 0 || _type.getBaseType()->getCategory() == Type::Category::Mapping)
        m_context << eth::Instruction::POP;
    else if (_type.getLength() < 5) // unroll loop for small arrays @todo choose a good value
    {
        solAssert(!_type.isByteArray(), "");
        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
    {
        solAssert(!_type.isByteArray(), "");
        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
{
    if (_type.getCategory() == Type::Category::Mapping)
    {
        m_context << eth::Instruction::POP;
        return;
    }
    // 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, bool _pad) const
{
    if (_arrayType.getLocation() == ArrayType::Location::Storage)
    {
        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;
    }
    else
    {
        if (!_arrayType.isByteArray())
            m_context << _arrayType.getBaseType()->getCalldataEncodedSize() << eth::Instruction::MUL;
        else if (_pad)
            m_context << u256(31) << eth::Instruction::ADD
                << u256(32) << eth::Instruction::DUP1
                << eth::Instruction::SWAP2 << eth::Instruction::DIV << eth::Instruction::MUL;
    }
}

void ArrayUtils::retrieveLength(ArrayType const& _arrayType) const
{
    if (!_arrayType.isDynamicallySized())
        m_context << _arrayType.getLength();
    else
    {
        m_context << eth::Instruction::DUP1;
        switch (_arrayType.getLocation())
        {
        case ArrayType::Location::CallData:
            // length is stored on the stack
            break;
        case ArrayType::Location::Memory:
            m_context << eth::Instruction::MLOAD;
            break;
        case ArrayType::Location::Storage:
            m_context << eth::Instruction::SLOAD;
            break;
        }
    }
}