EVM-C: Reduce query_fn to account_exists_fn

examples/capi.c

@@ -24,19 +24,12 @@ static void print_address(const struct evm_uint160be* address)
         printf("%x", address->bytes[i] & 0xff);
 }
 
-static void query(union evm_variant* result,
+static int account_exists(struct evm_env* env,
-                  struct evm_env* env,
+                           const struct evm_uint160be* address) {
-                  enum evm_query_key key,
+    printf("EVM-C: EXISTS @");
-                  const struct evm_uint160be* address) {
+    print_address(address);
-    printf("EVM-C: QUERY %d\n", key);
+    printf("\n");
-    switch (key) {
+    return 0;
-    case EVM_ACCOUNT_EXISTS:
-        result->int64 = 0;
-        break;
-
-    default:
-        result->int64 = 0;
-    }
 }
 
 static void get_storage(struct evm_uint256be* result,
@@ -119,7 +112,7 @@ static void evm_log(struct evm_env* env, const struct evm_uint160be* address,
 }
 
 static const struct evm_host example_host = {
-    query,
+    account_exists,
     get_storage,
     set_storage,
     get_balance,

include/evm.h

@@ -190,61 +190,16 @@ struct evm_result {
     } reserved;
 };
 
-/// The query callback key.
+/// Check account existence callback function
-enum evm_query_key {
-    EVM_ACCOUNT_EXISTS = 14,  ///< Check if an account exists.
-};
-
-
-/// Variant type to represent possible types of values used in EVM.
 ///
-/// Type-safety is lost around the code that uses this type. We should have
+/// This callback function is used by the EVM to check if
-/// complete set of unit tests covering all possible cases.
+/// there exists an account at given address.
-/// The size of the type is 64 bytes and should fit in single cache line.
+/// @param      env      Pointer to execution environment managed by the host
-union evm_variant {
+///                      application.
-    /// A host-endian 64-bit integer.
-    int64_t int64;
-
-    /// A big-endian 256-bit integer or hash.
-    struct evm_uint256be uint256be;
-
-    /// A memory reference.
-    struct {
-        /// Pointer to the data.
-        uint8_t const* data;
-
-        /// Size of the referenced memory/data.
-        size_t data_size;
-    };
-};
-
-/// Query callback function.
-///
-/// This callback function is used by the EVM to query the host application
-/// about additional information about accounts in the state required to
-/// execute EVM code.
-/// @param[out] result  The result of the query.
-/// @param      env     Pointer to execution environment managed by the host
-///                     application.
-/// @param      key     The kind of the query. See evm_query_key
-///                     and details below.
 /// @param      address  The address of the account the query is about.
-///
+/// @return              1 if exists, 0 otherwise.
-/// ## Types of queries
+typedef int (*evm_account_exists_fn)(struct evm_env* env,
-///
+                                     const struct evm_uint160be* address);
-/// - ::EVM_ACCOUNT_EXISTS
-///   @result evm_variant::int64      1 if exists, 0 if not.
-///
-///
-/// @todo
-/// - Consider swapping key and address arguments,
-///   e.g. `query(result, env, addr, EVM_SLOAD, k)`.
-/// - Consider renaming key argument to something else. Key is confusing
-///   especially for SSTORE and SLOAD. Maybe "kind"?
-typedef void (*evm_query_state_fn)(union evm_variant* result,
-                                   struct evm_env* env,
-                                   enum evm_query_key key,
-                                   const struct evm_uint160be* address);
 
 /// Get storage callback function.
 ///
@@ -352,7 +307,7 @@ typedef void (*evm_call_fn)(
 ///
 /// @todo Merge evm_host with evm_env?
 struct evm_host {
-    evm_query_state_fn query;
+    evm_account_exists_fn account_exists;
     evm_get_storage_fn get_storage;
     evm_set_storage_fn set_storage;
     evm_get_balance_fn get_balance;