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, "");

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

    switch (_sourceType.getLocation())
    {
    case ArrayType::Location::CallData:
    {
        solAssert(_targetType.isByteArray(), "Non byte arrays not yet implemented here.");
        solAssert(_sourceType.isByteArray(), "Non byte arrays not yet implemented here.");
        // 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);
        // add length to source offset
        m_context << eth::Instruction::DUP5 << eth::Instruction::DUP5 << eth::Instruction::ADD;
        // stack now: source_offset source_len target_ref target_data_end target_data_ref source_end
        // store start offset
        m_context << eth::Instruction::DUP6;
        // stack now: source_offset source_len target_ref target_data_end target_data_ref source_end calldata_offset
        eth::AssemblyItem copyLoopStart = m_context.newTag();
        m_context << copyLoopStart
                  // copy from calldata and store
                  << eth::Instruction::DUP1 << eth::Instruction::CALLDATALOAD
                  << eth::Instruction::DUP4 << eth::Instruction::SSTORE
                  // increment target_data_ref by 1
                  << eth::Instruction::SWAP2 << u256(1) << eth::Instruction::ADD
                  // increment calldata_offset by 32
                  << eth::Instruction::SWAP2 << u256(32) << eth::Instruction::ADD
                  // check for loop condition
                  << eth::Instruction::DUP1 << eth::Instruction::DUP3 << eth::Instruction::GT;
        m_context.appendConditionalJumpTo(copyLoopStart);
        m_context << eth::Instruction::POP << 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

        solAssert(sourceBaseType->getStorageSize() == targetBaseType->getStorageSize(),
            "Copying with different storage sizes not yet implemented.");
        // stack: source_ref target_ref
        // store target_ref
        m_context << eth::Instruction::SWAP1 << eth::Instruction::DUP2;
        // stack: target_ref source_ref target_ref
        // fetch lengthes
        retrieveLength(_targetType);
        m_context << eth::Instruction::SWAP2;
        // stack: target_ref target_len target_ref source_ref
        retrieveLength(_sourceType);
        // stack: target_ref target_len target_ref source_ref source_len
        if (_targetType.isDynamicallySized())
            // store new target length
            m_context << eth::Instruction::DUP1 << eth::Instruction::DUP4 << eth::Instruction::SSTORE;
        // compute hashes (data positions)
        m_context << eth::Instruction::SWAP2;
        if (_targetType.isDynamicallySized())
            CompilerUtils(m_context).computeHashStatic();
        m_context << eth::Instruction::SWAP1;
        if (_sourceType.isDynamicallySized())
            CompilerUtils(m_context).computeHashStatic();
        // stack: target_ref target_len source_len target_data_pos source_data_pos
        m_context << eth::Instruction::DUP4;
        convertLengthToSize(_sourceType);
        m_context << eth::Instruction::DUP4;
        convertLengthToSize(_sourceType);
        // stack: target_ref target_len source_len target_data_pos source_data_pos target_size source_size
        // @todo we might be able to go without a third counter
        m_context << u256(0);
        // stack: target_ref target_len source_len target_data_pos source_data_pos target_size source_size 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;
        StorageItem(m_context, *sourceBaseType).retrieveValue(SourceLocation(), true);
        m_context << eth::dupInstruction(5 + sourceBaseType->getSizeOnStack())
            << eth::dupInstruction(2 + sourceBaseType->getSizeOnStack()) << eth::Instruction::ADD;
        StorageItem(m_context, *targetBaseType).storeValue(*sourceBaseType, SourceLocation(), true);
        // increment
        m_context << targetBaseType->getStorageSize() << eth::Instruction::ADD;
        m_context.appendJumpTo(copyLoopStart);
        m_context << copyLoopEnd;

        // zero-out leftovers in target
        // stack: target_ref target_len source_len target_data_pos source_data_pos target_size source_size 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 target_data_pos_updated target_data_pos source_data_pos target_size source_size
        // add size 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(*targetBaseType);
        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
    {
        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
{
    // 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;
}

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;
        }
    }
}