/*

  This file is part of solidity.

  solidity 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.

  solidity 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 solidity.  If not, see <http://www.gnu.org/licenses/>.

*/

// SPDX-License-Identifier: GPL-3.0

/**

 * @file KnownState.h

 * @author Christian <c@ethdev.com>

 * @date 2015

 * Contains knowledge about the state of the virtual machine at a specific instruction.

 */

#pragma once

#if defined(__clang__)

#pragma clang diagnostic push

#pragma clang diagnostic ignored "-Wredeclared-class-member"

#endif // defined(__clang__)

// Disable warning about nodiscard. Could be a compiler bug, might be removed in the future.

#if defined(_MSC_VER)

#pragma warning(push)

#pragma warning(disable: 4834)

#endif

#include <boost/bimap.hpp>

#if defined(_MSC_VER)

#pragma warning(pop)

#endif

#if defined(__clang__)

#pragma clang diagnostic pop

#endif // defined(__clang__)

#include <libsolutil/CommonIO.h>

#include <libsolutil/Exceptions.h>

#include <libevmasm/ExpressionClasses.h>

#include <libevmasm/SemanticInformation.h>

#include <limits>

#include <utility>

#include <vector>

#include <map>

#include <set>

#include <tuple>

#include <memory>

#include <ostream>

namespace solidity::langutil

{

struct SourceLocation;

}

namespace solidity::evmasm

{

class AssemblyItem;

using AssemblyItems = std::vector<AssemblyItem>;

/**

 * Class to infer and store knowledge about the state of the virtual machine at a specific

 * instruction.

 *

 * The general workings are that for each assembly item that is fed, an equivalence class is

 * derived from the operation and the equivalence class of its arguments. DUPi, SWAPi and some

 * arithmetic instructions are used to infer equivalences while these classes are determined.

 */

class KnownState

{

public:

  using Id = ExpressionClasses::Id;

  struct StoreOperation

  {

    enum Target { Invalid, Memory, Storage };

    bool isValid() const { return target != Invalid; }

    Target target{Invalid};

    Id slot{std::numeric_limits<Id>::max()};

    unsigned sequenceNumber{std::numeric_limits<unsigned>::max()};

    Id expression{std::numeric_limits<Id>::max()};

  };

  explicit KnownState(

    std::shared_ptr<ExpressionClasses> _expressionClasses = std::make_shared<ExpressionClasses>()

  ): m_expressionClasses(std::move(_expressionClasses))

  {

  }

  /// Streams debugging information to @a _out.

  std::ostream& stream(std::ostream& _out) const;

  /// Feeds the item into the system for analysis.

  /// @returns a possible store operation

  StoreOperation feedItem(AssemblyItem const& _item, bool _copyItem = false);

  /// Resets any knowledge about storage.

  void resetStorage() { m_storageContent.clear(); }

  /// Resets any knowledge about storage.

  void resetMemory() { m_memoryContent.clear(); }

  /// Resets known Keccak-256 hashes

  void resetKnownKeccak256Hashes() { m_knownKeccak256Hashes.clear(); }

  /// Resets any knowledge about the current stack.

  void resetStack() { m_stackElements.clear(); m_stackHeight = 0; }

  /// Resets any knowledge.

  void reset() { resetStorage(); resetMemory(); resetKnownKeccak256Hashes(); resetStack(); }

  unsigned sequenceNumber() const { return m_sequenceNumber; }

  /// Replaces the state by the intersection with _other, i.e. only equal knowledge is retained.

  /// If the stack heighht is different, the smaller one is used and the stack is compared

  /// relatively.

  /// @param _combineSequenceNumbers if true, sets the sequence number to the maximum of both

  void reduceToCommonKnowledge(KnownState const& _other, bool _combineSequenceNumbers);

  /// @returns a shared pointer to a copy of this state.

  std::shared_ptr<KnownState> copy() const { return std::make_shared<KnownState>(*this); }

  /// @returns true if the knowledge about the state of both objects is (known to be) equal.

  bool operator==(KnownState const& _other) const;

  /// Retrieves the current equivalence class for the given stack element (or generates a new

  /// one if it does not exist yet).

  Id stackElement(int _stackHeight, langutil::SourceLocation const& _location);

  /// @returns the stackElement relative to the current stack height.

  Id relativeStackElement(int _stackOffset, langutil::SourceLocation const& _location = {});

  /// @returns its set of tags if the given expression class is a known tag union; returns a set

  /// containing the tag if it is a PushTag expression and the empty set otherwise.

  std::set<u256> tagsInExpression(Id _expressionId);

  /// During analysis, different tags on the stack are partially treated as the same class.

  /// This removes such classes not to confuse later analyzers.

  void clearTagUnions();

  int stackHeight() const { return m_stackHeight; }

  std::map<int, Id> const& stackElements() const { return m_stackElements; }

  ExpressionClasses& expressionClasses() const { return *m_expressionClasses; }

  std::map<Id, Id> const& storageContent() const { return m_storageContent; }

private:

  /// Assigns a new equivalence class to the next sequence number of the given stack element.

  void setStackElement(int _stackHeight, Id _class);

  /// Swaps the given stack elements in their next sequence number.

  void swapStackElements(int _stackHeightA, int _stackHeightB, langutil::SourceLocation const& _location);

  /// Increments the sequence number, deletes all storage information that might be overwritten

  /// and stores the new value at the given slot.

  /// @returns the store operation, which might be invalid if storage was not modified

  StoreOperation storeInStorage(Id _slot, Id _value, langutil::SourceLocation const& _location);

  /// Retrieves the current value at the given slot in storage or creates a new special sload class.

  Id loadFromStorage(Id _slot, langutil::SourceLocation const& _location);

  /// Increments the sequence number, deletes all memory information that might be overwritten

  /// and stores the new value at the given slot.

  /// @returns the store operation, which might be invalid if memory was not modified

  StoreOperation storeInMemory(Id _slot, Id _value, langutil::SourceLocation const& _location);

  /// Retrieves the current value at the given slot in memory or creates a new special mload class.

  Id loadFromMemory(Id _slot, langutil::SourceLocation const& _location);

  /// Finds or creates a new expression that applies the Keccak-256 hash function to the contents in memory.

  Id applyKeccak256(Id _start, Id _length, langutil::SourceLocation const& _location);

  /// @returns a new or already used Id representing the given set of tags.

  Id tagUnion(std::set<u256> _tags);

  /// Current stack height, can be negative.

  int m_stackHeight = 0;

  /// Current stack layout, mapping stack height -> equivalence class

  std::map<int, Id> m_stackElements;

  /// Current sequence number, this is incremented with each modification to storage or memory.

  unsigned m_sequenceNumber = 1;

  /// Knowledge about storage content.

  std::map<Id, Id> m_storageContent;

  /// Knowledge about memory content. Keys are memory addresses, note that the values overlap

  /// and are not contained here if they are not completely known.

  std::map<Id, Id> m_memoryContent;

  /// Keeps record of all Keccak-256 hashes that are computed. The first parameter in the

  /// std::pair corresponds to memory content and the second parameter corresponds to the length

  /// that is accessed.

  std::map<std::pair<std::vector<Id>, unsigned>, Id> m_knownKeccak256Hashes;

  /// Structure containing the classes of equivalent expressions.

  std::shared_ptr<ExpressionClasses> m_expressionClasses;

  /// Container for unions of tags stored on the stack.

  boost::bimap<Id, std::set<u256>> m_tagUnions;

};

}