From 9badaa3bc06bf59953e6c11f17e1cd0d3d74b208 Mon Sep 17 00:00:00 2001
From: Andrei Maiboroda <andrei@ethereum.org>
Date: Thu, 21 Nov 2024 17:31:53 +0100
Subject: [PATCH] Add get_delegate_address() host function

---
 include/evmc/evmc.h          | 20 ++++++++++++++++++++
 include/evmc/evmc.hpp        | 14 ++++++++++++++
 include/evmc/mocked_host.hpp |  7 +++++++
 3 files changed, 41 insertions(+)

diff --git a/include/evmc/evmc.h b/include/evmc/evmc.h
index 4fc513f7a..5849a5b28 100644
--- a/include/evmc/evmc.h
+++ b/include/evmc/evmc.h
@@ -834,6 +834,23 @@ typedef enum evmc_access_status (*evmc_access_storage_fn)(struct evmc_host_conte
 typedef struct evmc_result (*evmc_call_fn)(struct evmc_host_context* context,
                                            const struct evmc_message* msg);
 
+/**
+ * Get delegate address function.
+ *
+ * This callback function is used by a VM to get target address of EIP-7702 delegation designation,
+ * in case it is set for given account.
+ * If account's code does not contain delegation designation, this function returns address
+ * 0x0000000000000000000000000000000000000000.
+ *
+ * @param context  The pointer to the Host execution context.
+ * @param address  The address of the account.
+ * @return         The address of delegation designation target account
+ *                 or 0 if delegation is not set.
+ */
+typedef evmc_address (*evmc_get_delegate_address_fn)(struct evmc_host_context* context,
+                                                     const evmc_address* address);
+
+
 /**
  * The Host interface.
  *
@@ -891,6 +908,9 @@ struct evmc_host_interface
 
     /** Set transient storage callback function. */
     evmc_set_transient_storage_fn set_transient_storage;
+
+    /** Get delegate address function. */
+    evmc_get_delegate_address_fn get_delegate_address;
 };
 
 
diff --git a/include/evmc/evmc.hpp b/include/evmc/evmc.hpp
index 2dfabf826..2104d80ad 100644
--- a/include/evmc/evmc.hpp
+++ b/include/evmc/evmc.hpp
@@ -499,6 +499,9 @@ class HostInterface
     virtual void set_transient_storage(const address& addr,
                                        const bytes32& key,
                                        const bytes32& value) noexcept = 0;
+
+    /// @copydoc evmc_host_interface::get_delegate_address
+    virtual address get_delegate_address(const address& addr) const noexcept = 0;
 };
 
 
@@ -609,6 +612,11 @@ class HostContext : public HostInterface
     {
         host->set_transient_storage(context, &address, &key, &value);
     }
+
+    address get_delegate_address(const address& address) const noexcept final
+    {
+        return host->get_delegate_address(context, &address);
+    }
 };
 
 
@@ -877,6 +885,11 @@ inline void set_transient_storage(evmc_host_context* h,
 {
     Host::from_context(h)->set_transient_storage(*addr, *key, *value);
 }
+
+inline evmc_address get_delegate_address(evmc_host_context* h, const evmc_address* addr) noexcept
+{
+    return Host::from_context(h)->get_delegate_address(*addr);
+}
 }  // namespace internal
 
 inline const evmc_host_interface& Host::get_interface() noexcept
@@ -898,6 +911,7 @@ inline const evmc_host_interface& Host::get_interface() noexcept
         ::evmc::internal::access_storage,
         ::evmc::internal::get_transient_storage,
         ::evmc::internal::set_transient_storage,
+        ::evmc::internal::get_delegate_address,
     };
     return interface;
 }
diff --git a/include/evmc/mocked_host.hpp b/include/evmc/mocked_host.hpp
index 8aad17c46..7147b2377 100644
--- a/include/evmc/mocked_host.hpp
+++ b/include/evmc/mocked_host.hpp
@@ -507,5 +507,12 @@ class MockedHost : public Host
         record_account_access(addr);
         accounts[addr].transient_storage[key] = value;
     }
+
+    /// Get account's delegate address.
+    address get_delegate_address(const address& addr) const noexcept override
+    {
+        record_account_access(addr);
+        return {};
+    }
 };
 }  // namespace evmc