state: Use StateView from State

Modify the `State` to require `StateView` interface as a parameter
and use it to read the initial state values.

This drops `TestState` dependency on `State`.

test/state/account.hpp

@@ -12,6 +12,7 @@ namespace evmone::state
 using evmc::address;
 using evmc::bytes;
 using evmc::bytes32;
+using namespace evmc::literals;
 
 /// The representation of the account storage value.
 struct StorageValue
@@ -31,25 +32,38 @@ struct Account
     /// The maximum allowed nonce value.
     static constexpr auto NonceMax = std::numeric_limits<uint64_t>::max();
 
+    /// The keccak256 hash of the empty input. Used to identify empty account's code.
+    static constexpr auto EMPTY_CODE_HASH =
+        0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470_bytes32;
+
     /// The account nonce.
     uint64_t nonce = 0;
 
     /// The account balance.
     intx::uint256 balance;
 
-    /// The account storage map.
+    bytes32 code_hash = EMPTY_CODE_HASH;
+
+    /// If the account has non-empty initial storage (when accessing the cold account).
+    bool has_initial_storage = false;
+
+    /// The cached and modified account storage entries.
     std::unordered_map<bytes32, StorageValue> storage;
 
+    /// The EIP-1153 transient (transaction-level lifetime) storage.
     std::unordered_map<bytes32, bytes32> transient_storage;
 
-    /// The account code.
+    /// The cache of the account code.
+    ///
+    /// Check code_hash to know if an account code is empty.
+    /// Empty here only means it has not been loaded from the initial storage.
     bytes code;
 
-    /// The account has been destructed and should be erased at the end of of a transaction.
+    /// The account has been destructed and should be erased at the end of a transaction.
     bool destructed = false;
 
     /// The account should be erased if it is empty at the end of a transaction.
-    /// This flag means the account has been "touched" as defined in EIP-161
+    /// This flag means the account has been "touched" as defined in EIP-161,
     /// or it is a newly created temporary account.
     ///
     /// Yellow Paper uses term "delete" but it is a keyword in C++ while
@@ -63,7 +77,7 @@ struct Account
 
     [[nodiscard]] bool is_empty() const noexcept
     {
-        return code.empty() && nonce == 0 && balance == 0;
+        return nonce == 0 && balance == 0 && code_hash == EMPTY_CODE_HASH;
     }
 };
 }  // namespace evmone::state

test/state/host.cpp

@@ -18,10 +18,7 @@ bool Host::account_exists(const address& addr) const noexcept
 
 bytes32 Host::get_storage(const address& addr, const bytes32& key) const noexcept
 {
-    const auto& acc = m_state.get(addr);
-    if (const auto it = acc.storage.find(key); it != acc.storage.end())
-        return it->second.current;
-    return {};
+    return m_state.get_storage(addr, key).current;
 }
 
 evmc_storage_status Host::set_storage(
@@ -30,7 +27,7 @@ evmc_storage_status Host::set_storage(
     // Follow EVMC documentation https://evmc.ethereum.org/storagestatus.html#autotoc_md3
     // and EIP-2200 specification https://eips.ethereum.org/EIPS/eip-2200.
 
-    auto& storage_slot = m_state.get(addr).storage[key];
+    auto& storage_slot = m_state.get_storage(addr, key);
     const auto& [current, original, _] = storage_slot;
 
     const auto dirty = original != current;
@@ -92,41 +89,49 @@ bytes_view extcode(bytes_view code) noexcept
 /// as defined in the [EIP-7610](https://eips.ethereum.org/EIPS/eip-7610).
 [[nodiscard]] bool is_create_collision(const Account& acc) noexcept
 {
-    if (acc.nonce != 0 || !acc.code.empty())
+    // TODO: This requires much more testing:
+    // - what if an account had storage but is destructed?
+    // - what if an account had cold storage but it was emptied?
+    // - what if an account without cold storage gain one?
+    if (acc.nonce != 0)
         return true;
-
-    // acc.storage may have entries from access list, even if account storage is empty.
-    // Check for non-zero current values.
-    if (std::ranges::any_of(
-            acc.storage, [](auto& e) noexcept { return !is_zero(e.second.current); }))
+    if (acc.code_hash != Account::EMPTY_CODE_HASH)
+        return true;
+    if (acc.has_initial_storage)
         return true;
 
+    // The hot storage is ignored because it can contain elements from access list.
+    // TODO: Is this correct for destructed accounts?
+    assert(!acc.destructed && "untested");
     return false;
 }
 }  // namespace
 
 size_t Host::get_code_size(const address& addr) const noexcept
 {
-    const auto* const acc = m_state.find(addr);
-    return (acc != nullptr) ? extcode(acc->code).size() : 0;
+    const auto raw_code = m_state.get_code(addr);
+    return extcode(raw_code).size();
 }
 
 bytes32 Host::get_code_hash(const address& addr) const noexcept
 {
     const auto* const acc = m_state.find(addr);
     if (acc == nullptr || acc->is_empty())
         return {};
-    if (is_eof_container(acc->code))
+
+    // Load code and check if not EOF.
+    // TODO: Optimize the second account lookup here.
+    if (is_eof_container(m_state.get_code(addr)))
         return EOF_CODE_HASH_SENTINEL;
-    // TODO: Cache code hash. It will be needed also to compute the MPT hash.
-    return keccak256(acc->code);
+
+    return acc->code_hash;
 }
 
 size_t Host::copy_code(const address& addr, size_t code_offset, uint8_t* buffer_data,
     size_t buffer_size) const noexcept
 {
-    const auto* const acc = m_state.find(addr);
-    const auto code = (acc != nullptr) ? extcode(acc->code) : bytes_view{};
+    const auto raw_code = m_state.get_code(addr);
+    const auto code = extcode(raw_code);
     const auto code_slice = code.substr(std::min(code_offset, code.size()));
     const auto num_bytes = std::min(buffer_size, code_slice.size());
     std::copy_n(code_slice.begin(), num_bytes, buffer_data);
@@ -367,6 +372,7 @@ evmc::Result Host::create(const evmc_message& msg) noexcept
         }
     }
 
+    new_acc->code_hash = keccak256(code);
     new_acc->code = code;
 
     return evmc::Result{result.status_code, gas_left, result.gas_refund, msg.recipient};
@@ -409,9 +415,8 @@ evmc::Result Host::execute_message(const evmc_message& msg) noexcept
     if (is_precompile(m_rev, msg.code_address))
         return call_precompile(m_rev, msg);
 
-    // In case msg.recipient == msg.code_address, this is the second lookup of the same address.
-    const auto* const code_acc = m_state.find(msg.code_address);
-    const auto code = code_acc != nullptr ? bytes_view{code_acc->code} : bytes_view{};
+    // TODO: get_code() performs the account lookup. Add a way to get an account with code?
+    const auto code = m_state.get_code(msg.code_address);
     return m_vm.execute(*this, m_rev, msg, code.data(), code.size());
 }
 
@@ -503,7 +508,7 @@ evmc_access_status Host::access_account(const address& addr) noexcept
 
 evmc_access_status Host::access_storage(const address& addr, const bytes32& key) noexcept
 {
-    auto& storage_slot = m_state.get(addr).storage[key];
+    auto& storage_slot = m_state.get_storage(addr, key);
     m_state.journal_storage_change(addr, key, storage_slot);
     return std::exchange(storage_slot.access_status, EVMC_ACCESS_WARM);
 }

test/state/state.cpp

@@ -5,6 +5,7 @@
 #include "state.hpp"
 #include "../utils/stdx/utility.hpp"
 #include "host.hpp"
+#include "state_view.hpp"
 #include <evmone/constants.hpp>
 #include <evmone/eof.hpp>
 #include <algorithm>
@@ -81,7 +82,7 @@ evmc_message build_message(
 StateDiff State::build_diff(evmc_revision rev) const
 {
     StateDiff diff;
-    for (const auto& [addr, m] : m_accounts)
+    for (const auto& [addr, m] : m_modified)
     {
         if (m.destructed)
         {
@@ -103,6 +104,9 @@ StateDiff State::build_diff(evmc_revision rev) const
         // TODO(clang): In old Clang emplace_back without Account doesn't compile.
         //   NOLINTNEXTLINE(modernize-use-emplace)
         auto& a = diff.modified_accounts.emplace_back(StateDiff::Entry{addr, m.nonce, m.balance});
+
+        // Output only the new code.
+        // TODO: Output also the code hash. It will be needed for DB update and MPT hash.
         if (m.just_created && !m.code.empty())
             a.code = m.code;
 
@@ -117,16 +121,22 @@ StateDiff State::build_diff(evmc_revision rev) const
 
 Account& State::insert(const address& addr, Account account)
 {
-    const auto r = m_accounts.insert({addr, std::move(account)});
+    const auto r = m_modified.insert({addr, std::move(account)});
     assert(r.second);
     return r.first->second;
 }
 
 Account* State::find(const address& addr) noexcept
 {
-    const auto it = m_accounts.find(addr);
-    if (it != m_accounts.end())
+    // TODO: Avoid double lookup (find+insert) and not cached initial state lookup for non-existent
+    //   accounts. If we want to cache non-existent account we need a proper flag for it.
+    if (const auto it = m_modified.find(addr); it != m_modified.end())
         return &it->second;
+    if (const auto cacc = m_initial.get_account(addr); cacc)
+        return &insert(addr, {.nonce = cacc->nonce,
+                                 .balance = cacc->balance,
+                                 .code_hash = cacc->code_hash,
+                                 .has_initial_storage = cacc->has_storage});
     return nullptr;
 }
 
@@ -144,6 +154,18 @@ Account& State::get_or_insert(const address& addr, Account account)
     return insert(addr, std::move(account));
 }
 
+bytes_view State::get_code(const address& addr)
+{
+    auto* a = find(addr);
+    if (a == nullptr)
+        return {};
+    if (a->code_hash == Account::EMPTY_CODE_HASH)
+        return {};
+    if (a->code.empty())
+        a->code = m_initial.get_account_code(addr);
+    return a->code;
+}
+
 Account& State::touch(const address& addr)
 {
     auto& acc = get_or_insert(addr, {.erase_if_empty = true});
@@ -155,6 +177,19 @@ Account& State::touch(const address& addr)
     return acc;
 }
 
+StorageValue& State::get_storage(const address& addr, const bytes32& key)
+{
+    // TODO: Avoid account lookup by giving the reference to the account's storage to Host.
+    auto& acc = get(addr);
+    const auto [it, missing] = acc.storage.try_emplace(key);
+    if (missing)
+    {
+        const auto initial_value = m_initial.get_storage(addr, key);
+        it->second = {initial_value, initial_value};
+    }
+    return it->second;
+}
+
 void State::journal_balance_change(const address& addr, const intx::uint256& prev_balance)
 {
     m_journal.emplace_back(JournalBalanceChange{{addr}, prev_balance});
@@ -222,6 +257,7 @@ void State::rollback(size_t checkpoint)
                         // This account is not always "touched". TODO: Why?
                         auto& a = get(e.addr);
                         a.nonce = 0;
+                        a.code_hash = Account::EMPTY_CODE_HASH;
                         a.code.clear();
                     }
                     else
@@ -230,7 +266,7 @@ void State::rollback(size_t checkpoint)
                         //       so we need to delete them here explicitly.
                         //       This should be changed by tuning "erasable" flag
                         //       and clear in all revisions.
-                        m_accounts.erase(e.addr);
+                        m_modified.erase(e.addr);
                     }
                 }
                 else if constexpr (std::is_same_v<T, JournalStorageChange>)
@@ -314,7 +350,7 @@ std::variant<int64_t, std::error_code> validate_transaction(const Account& sende
     if (tx.max_gas_price < block.base_fee)
         return make_error_code(FEE_CAP_LESS_THEN_BLOCKS);
 
-    if (!sender_acc.code.empty())
+    if (sender_acc.code_hash != Account::EMPTY_CODE_HASH)
         return make_error_code(SENDER_NOT_EOA);  // Origin must not be a contract (EIP-3607).
 
     if (sender_acc.nonce == Account::NonceMax)  // Nonce value limit (EIP-2681).
@@ -352,10 +388,11 @@ std::variant<int64_t, std::error_code> validate_transaction(const Account& sende
     return execution_gas_limit;
 }
 
-StateDiff finalize(State& state, evmc_revision rev, const address& coinbase,
+StateDiff finalize(const StateView& state_view, evmc_revision rev, const address& coinbase,
     std::optional<uint64_t> block_reward, std::span<const Ommer> ommers,
     std::span<const Withdrawal> withdrawals)
 {
+    State state{state_view};
     // TODO: The block reward can be represented as a withdrawal.
     if (block_reward.has_value())
     {
@@ -378,10 +415,11 @@ StateDiff finalize(State& state, evmc_revision rev, const address& coinbase,
     return state.build_diff(rev);
 }
 
-std::variant<TransactionReceipt, std::error_code> transition(State& state, const BlockInfo& block,
-    const Transaction& tx, evmc_revision rev, evmc::VM& vm, int64_t block_gas_left,
-    int64_t blob_gas_left)
+std::variant<TransactionReceipt, std::error_code> transition(const StateView& state_view,
+    const BlockInfo& block, const Transaction& tx, evmc_revision rev, evmc::VM& vm,
+    int64_t block_gas_left, int64_t blob_gas_left)
 {
+    State state{state_view};
     auto* sender_ptr = state.find(tx.sender);
 
     // Validate transaction. The validation needs the sender account, so in case
@@ -429,10 +467,9 @@ std::variant<TransactionReceipt, std::error_code> transition(State& state, const
         host.access_account(*tx.to);
     for (const auto& [a, storage_keys] : tx.access_list)
     {
-        host.access_account(a);  // TODO: Return account ref.
-        auto& storage = state.get(a).storage;
+        host.access_account(a);
         for (const auto& key : storage_keys)
-            storage[key].access_status = EVMC_ACCESS_WARM;
+            state.get_storage(a, key).access_status = EVMC_ACCESS_WARM;
     }
     // EIP-3651: Warm COINBASE.
     // This may create an empty coinbase account. The account cannot be created unconditionally

test/state/state.hpp

@@ -15,6 +15,8 @@
 
 namespace evmone::state
 {
+class StateView;
+
 /// The Ethereum State: the collection of accounts mapped by their addresses.
 class State
 {
@@ -62,17 +64,21 @@ class State
         std::variant<JournalBalanceChange, JournalTouched, JournalStorageChange, JournalNonceBump,
             JournalCreate, JournalTransientStorageChange, JournalDestruct, JournalAccessAccount>;
 
-    std::unordered_map<address, Account> m_accounts;
+    /// The read-only view of the initial (cold) state.
+    const StateView& m_initial;
+
+    /// The accounts loaded from the initial state and potentially modified.
+    std::unordered_map<address, Account> m_modified;
 
-    /// The state journal: the list of changes made in the state
+    /// The state journal: the list of changes made to the state
     /// with information how to revert them.
     std::vector<JournalEntry> m_journal;
 
 public:
-    State() = default;
+    explicit State(const StateView& state_view) noexcept : m_initial{state_view} {}
     State(const State&) = delete;
-    State(State&&) = default;
-    State& operator=(State&&) = default;
+    State(State&&) = delete;
+    State& operator=(State&&) = delete;
 
     /// Inserts the new account at the address.
     /// There must not exist any account under this address before.
@@ -87,6 +93,10 @@ class State
     /// Gets an existing account or inserts new account.
     Account& get_or_insert(const address& addr, Account account = {});
 
+    bytes_view get_code(const address& addr);
+
+    StorageValue& get_storage(const address& addr, const bytes32& key);
+
     StateDiff build_diff(evmc_revision rev) const;
 
     /// Returns the state journal checkpoint. It can be later used to in rollback()
@@ -124,11 +134,11 @@ class State
 ///
 /// Applies block reward to coinbase, withdrawals (post Shanghai) and deletes empty touched accounts
 /// (post Spurious Dragon).
-[[nodiscard]] StateDiff finalize(State& state, evmc_revision rev, const address& coinbase,
-    std::optional<uint64_t> block_reward, std::span<const Ommer> ommers,
+[[nodiscard]] StateDiff finalize(const StateView& state_view, evmc_revision rev,
+    const address& coinbase, std::optional<uint64_t> block_reward, std::span<const Ommer> ommers,
     std::span<const Withdrawal> withdrawals);
 
-[[nodiscard]] std::variant<TransactionReceipt, std::error_code> transition(State& state,
+[[nodiscard]] std::variant<TransactionReceipt, std::error_code> transition(const StateView& state,
     const BlockInfo& block, const Transaction& tx, evmc_revision rev, evmc::VM& vm,
     int64_t block_gas_left, int64_t blob_gas_left);