Serialize and deserialize compilation artifacts. (#2020)

* Serialize and deserialize Module
* Use bincode to serialize
* Add wasm_module_serialize; docs
* Simple tests

examples/serialize.c

@@ -0,0 +1,169 @@
+/*
+Example of instantiating of the WebAssembly module and invoking its exported
+function.
+
+You can compile and run this example on Linux with:
+
+   cargo build --release -p wasmtime
+   cc examples/hello.c \
+       -I crates/c-api/include \
+       -I crates/c-api/wasm-c-api/include \
+       target/release/libwasmtime.a \
+       -lpthread -ldl -lm \
+       -o hello
+   ./hello
+
+Note that on Windows and macOS the command will be similar, but you'll need
+to tweak the `-lpthread` and such annotations as well as the name of the
+`libwasmtime.a` file on Windows.
+*/
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <wasm.h>
+#include <wasmtime.h>
+
+static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap);
+
+static wasm_trap_t* hello_callback(const wasm_val_t args[], wasm_val_t results[]) {
+  printf("Calling back...\n");
+  printf("> Hello World!\n");
+  return NULL;
+}
+
+int serialize(wasm_byte_vec_t* buffer) {
+  // Set up our compilation context. Note that we could also work with a
+  // `wasm_config_t` here to configure what feature are enabled and various
+  // compilation settings.
+  printf("Initializing...\n");
+  wasm_engine_t *engine = wasm_engine_new();
+  assert(engine != NULL);
+
+  // Read our input file, which in this case is a wasm text file.
+  FILE* file = fopen("examples/hello.wat", "r");
+  assert(file != NULL);
+  fseek(file, 0L, SEEK_END);
+  size_t file_size = ftell(file);
+  fseek(file, 0L, SEEK_SET);
+  wasm_byte_vec_t wat;
+  wasm_byte_vec_new_uninitialized(&wat, file_size);
+  assert(fread(wat.data, file_size, 1, file) == 1);
+  fclose(file);
+
+  // Parse the wat into the binary wasm format
+  wasm_byte_vec_t wasm;
+  wasmtime_error_t *error = wasmtime_wat2wasm(&wat, &wasm);
+  if (error != NULL)
+    exit_with_error("failed to parse wat", error, NULL);
+  wasm_byte_vec_delete(&wat);
+
+  // Now that we've got our binary webassembly we can compile our module
+  // and serialize into buffer.
+  printf("Compiling and serializing module...\n");
+  wasm_module_t *module = NULL;
+  error = wasmtime_module_new(engine, &wasm, &module);
+  wasm_byte_vec_delete(&wasm);
+  if (error != NULL)
+    exit_with_error("failed to compile module", error, NULL);
+  error = wasmtime_module_serialize(module, buffer);
+  wasm_module_delete(module);
+  if (error != NULL)
+    exit_with_error("failed to serialize module", error, NULL);
+
+  printf("Serialized.\n");
+
+  wasm_engine_delete(engine);
+  return 0;
+}
+
+int deserialize(wasm_byte_vec_t* buffer) {
+  // Set up our compilation context. Note that we could also work with a
+  // `wasm_config_t` here to configure what feature are enabled and various
+  // compilation settings.
+  printf("Initializing...\n");
+  wasm_engine_t *engine = wasm_engine_new();
+  assert(engine != NULL);
+
+  // With an engine we can create a *store* which is a long-lived group of wasm
+  // modules.
+  wasm_store_t *store = wasm_store_new(engine);
+  assert(store != NULL);
+
+  // Deserialize compiled module.
+  printf("Deserialize module...\n");
+  wasm_module_t *module = NULL;
+  wasmtime_error_t *error = wasmtime_module_deserialize(engine, buffer, &module);
+  if (error != NULL)
+    exit_with_error("failed to compile module", error, NULL);
+
+  // Next up we need to create the function that the wasm module imports. Here
+  // we'll be hooking up a thunk function to the `hello_callback` native
+  // function above.
+  printf("Creating callback...\n");
+  wasm_functype_t *hello_ty = wasm_functype_new_0_0();
+  wasm_func_t *hello = wasm_func_new(store, hello_ty, hello_callback);
+
+  // With our callback function we can now instantiate the compiled module,
+  // giving us an instance we can then execute exports from. Note that
+  // instantiation can trap due to execution of the `start` function, so we need
+  // to handle that here too.
+  printf("Instantiating module...\n");
+  wasm_trap_t *trap = NULL;
+  wasm_instance_t *instance = NULL;
+  const wasm_extern_t *imports[] = { wasm_func_as_extern(hello) };
+  error = wasmtime_instance_new(store, module, imports, 1, &instance, &trap);
+  if (instance == NULL)
+    exit_with_error("failed to instantiate", error, trap);
+
+  // Lookup our `run` export function
+  printf("Extracting export...\n");
+  wasm_extern_vec_t externs;
+  wasm_instance_exports(instance, &externs);
+  assert(externs.size == 1);
+  wasm_func_t *run = wasm_extern_as_func(externs.data[0]);
+  assert(run != NULL);
+
+  // And call it!
+  printf("Calling export...\n");
+  error = wasmtime_func_call(run, NULL, 0, NULL, 0, &trap);
+  if (error != NULL || trap != NULL)
+    exit_with_error("failed to call function", error, trap);
+
+  // Clean up after ourselves at this point
+  printf("All finished!\n");
+
+  wasm_extern_vec_delete(&externs);
+  wasm_instance_delete(instance);
+  wasm_module_delete(module);
+  wasm_store_delete(store);
+  wasm_engine_delete(engine);
+  return 0;
+}
+
+int main() {
+  wasm_byte_vec_t buffer;
+  if (serialize(&buffer)) {
+    return 1;
+  }
+  if (deserialize(&buffer)) {
+    return 1;
+  }
+  wasm_byte_vec_delete(&buffer);
+  return 0;
+}
+
+static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap) {
+  fprintf(stderr, "error: %s\n", message);
+  wasm_byte_vec_t error_message;
+  if (error != NULL) {
+    wasmtime_error_message(error, &error_message);
+    wasmtime_error_delete(error);
+  } else {
+    wasm_trap_message(trap, &error_message);
+    wasm_trap_delete(trap);
+  }
+  fprintf(stderr, "%.*s\n", (int) error_message.size, error_message.data);
+  wasm_byte_vec_delete(&error_message);
+  exit(1);
+}