EVM-C: Collect callbacks in evm_host struct

examples/capi.c

@@ -108,19 +108,24 @@ static void evm_log(struct evm_env* env, const struct evm_uint160be* address,
     printf("EVM-C: LOG%d\n", (int)topics_count);
 }
 
+static const struct evm_host example_host = {
+    query,
+    get_storage,
+    set_storage,
+    selfdestruct,
+    call,
+    get_tx_context,
+    get_block_hash,
+    evm_log
+};
+
 /// Example how the API is supposed to be used.
 int main(int argc, char *argv[]) {
     struct evm_factory factory = examplevm_get_factory();
     if (factory.abi_version != EVM_ABI_VERSION)
         return 1;  // Incompatible ABI version.
 
-    struct evm_instance* jit = factory.create(query,
-                                              get_storage,
-                                              set_storage,
-                                              selfdestruct,
-                                              call,
-                                              get_tx_context, get_block_hash,
-                                              evm_log);
+    struct evm_instance* jit = factory.create(&example_host);
 
     uint8_t const code[] = "Place some EVM bytecode here";
     const size_t code_size = sizeof(code);

examples/examplevm.c

@@ -7,14 +7,7 @@
 struct examplevm
 {
     struct evm_instance instance;
-    evm_query_state_fn query_fn;
-    evm_get_storage_fn get_storage_fn;
-    evm_set_storage_fn set_storage_fn;
-    evm_selfdestruct_fn selfdestruct_fn;
-    evm_call_fn call_fn;
-    evm_get_tx_context_fn get_tx_context_fn;
-    evm_get_block_hash_fn get_block_hash_fn;
-    evm_log_fn log_fn;
+    const struct evm_host* host;
 
     int example_option;
 };
@@ -103,9 +96,9 @@ static struct evm_result execute(struct evm_instance* instance,
         strncmp((const char*)code, counter, code_size)) {
         struct evm_uint256be value;
         const struct evm_uint256be index = {{0,}};
-        vm->get_storage_fn(&value, env, &msg->address, &index);
+        vm->host->get_storage(&value, env, &msg->address, &index);
         value.bytes[31] += 1;
-        vm->set_storage_fn(env, &msg->address, &index, &value);
+        vm->host->set_storage(env, &msg->address, &index, &value);
         ret.code = EVM_SUCCESS;
         return ret;
     }
@@ -117,28 +110,14 @@ static struct evm_result execute(struct evm_instance* instance,
     return ret;
 }
 
-static struct evm_instance* evm_create(evm_query_state_fn query_fn,
-                                       evm_get_storage_fn get_storage_fn,
-                                       evm_set_storage_fn set_storage_fn,
-                                       evm_selfdestruct_fn selfdestruct_fn,
-                                       evm_call_fn call_fn,
-                                       evm_get_tx_context_fn get_tx_context_fn,
-                                       evm_get_block_hash_fn get_block_hash_fn,
-                                       evm_log_fn log_fn)
+static struct evm_instance* evm_create(const struct evm_host* host)
 {
     struct examplevm* vm = calloc(1, sizeof(struct examplevm));
     struct evm_instance* interface = &vm->instance;
     interface->destroy = evm_destroy;
     interface->execute = execute;
     interface->set_option = evm_set_option;
-    vm->query_fn = query_fn;
-    vm->get_storage_fn = get_storage_fn;
-    vm->set_storage_fn = set_storage_fn;
-    vm->selfdestruct_fn = selfdestruct_fn;
-    vm->call_fn = call_fn;
-    vm->get_tx_context_fn = get_tx_context_fn;
-    vm->get_block_hash_fn = get_block_hash_fn;
-    vm->log_fn = log_fn;
+    vm->host = host;
     return interface;
 }
 

include/evm.h

@@ -328,6 +328,23 @@ typedef void (*evm_call_fn)(
     struct evm_env* env,
     const struct evm_message* msg);
 
+/// EVM Host interface.
+///
+/// The set of all callback functions expected by EVM instances. This is C
+/// realisation of OOP interface (only virtual methods, no data).
+/// Host implementations SHOULD create constant singletons of this (similar
+/// to vtables) to lower the maintenance and memory management cost.
+struct evm_host {
+    evm_query_state_fn query;
+    evm_get_storage_fn get_storage;
+    evm_set_storage_fn set_storage;
+    evm_selfdestruct_fn selfdestruct;
+    evm_call_fn call;
+    evm_get_tx_context_fn get_tx_context;
+    evm_get_block_hash_fn get_block_hash;
+    evm_log_fn log;
+};
+
 
 struct evm_instance;  ///< Forward declaration.
 
@@ -336,20 +353,10 @@ struct evm_instance;  ///< Forward declaration.
 /// Creates and initializes an EVM instance by providing the information
 /// about runtime callback functions.
 ///
-/// @param query_fn   Pointer to query callback function. Nonnull.
-/// @param update_fn  Pointer to update callback function. Nonnull.
-/// @param call_fn    Pointer to call callback function. Nonnull.
-/// @param get_tx_context_fn  Pointer to get tx context function. Nonnull.
-/// @param get_block_hash_fn  Pointer to get block hash function. Nonnull.
-/// @return           Pointer to the created EVM instance.
-typedef struct evm_instance* (*evm_create_fn)(evm_query_state_fn query_fn,
-                                              evm_get_storage_fn get_storage_fn,
-                                              evm_set_storage_fn set_storage_fn,
-                                              evm_selfdestruct_fn selfdestruct_fn,
-                                              evm_call_fn call_fn,
-                                              evm_get_tx_context_fn get_tx_context_fn,
-                                              evm_get_block_hash_fn get_block_hash_fn,
-                                              evm_log_fn log_fn);
+/// @param host  Pointer to an EVM Host controlling the created EVM
+///              instance. MUST NOT be null.
+/// @return      Pointer to the created EVM instance.
+typedef struct evm_instance* (*evm_create_fn)(const struct evm_host* host);
 
 /// Destroys the EVM instance.
 ///