Add a basic C based wasmtime runtime

This can be used for creating an equivalent rust based runtime with C
bindings.

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

4 files changed, 173 insertions, 0 deletions

diff --git a/c/wasmtime-basic/.gitignore b/c/wasmtime-basic/.gitignore
new file mode 100644
index 0000000..17d08f1
--- /dev/null
+++ b/c/wasmtime-basic/.gitignore
@@ -0,0 +1,2 @@
+test.wasm
+wasmtime
diff --git a/c/wasmtime-basic/Makefile b/c/wasmtime-basic/Makefile
new file mode 100644
index 0000000..ad70fce
--- /dev/null
+++ b/c/wasmtime-basic/Makefile
@@ -0,0 +1,17 @@
+CC      = gcc
+CFLAGS  = -Wall -Wextra -g -I$(WASMTIME_C_API)/include -L$(WASMTIME_C_API)/lib
+LDFLAGS = -Wl,-rpath,$(WASMTIME_C_API)/lib
+
+WASM_CC     = clang
+WASM_CFLAGS = -Wall -Wextra -fno-strict-aliasing --target=wasm32-wasi --sysroot=$(WASI_SYSROOT)
+
+all: wasmtime test.wasm
+
+wasmtime: wasmtime.c
+	$(CC) $(CFLAGS) $(CFLAGS) $(LDFLAGS) -o $@ $< -lwasmtime
+
+test.wasm: test.c
+	$(WASM_CC) $(WASM_CFLAGS) -o $@ $<
+
+clean:
+	rm -f wasmtime test.wasm
diff --git a/c/wasmtime-basic/test.c b/c/wasmtime-basic/test.c
new file mode 100644
index 0000000..f6e8723
--- /dev/null
+++ b/c/wasmtime-basic/test.c
@@ -0,0 +1,26 @@
+/*
+ * test.c
+ */
+
+#include <stdint.h>
+
+typedef uint32_t u32;
+typedef uint8_t   u8;
+
+__attribute__((import_module("env"), import_name("imported_func")))
+void imported_func(void);
+
+__attribute__((export_name("exported_func")))
+int exported_func(u8 *addr, u32 mem_size)
+{
+	(void)addr;
+	(void)mem_size;
+	imported_func();
+
+	return 0;
+}
+
+int main(void)
+{
+	return 0;
+}
diff --git a/c/wasmtime-basic/wasmtime.c b/c/wasmtime-basic/wasmtime.c
new file mode 100644
index 0000000..90ff0a3
--- /dev/null
+++ b/c/wasmtime-basic/wasmtime.c
@@ -0,0 +1,128 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <wasm.h>
+#include <wasi.h>
+#include <wasmtime.h>
+
+static void exit_with_error(const char *message, wasmtime_error_t *error,
+			    wasm_trap_t *trap)
+{
+	wasm_byte_vec_t error_message;
+
+	fprintf(stderr, "error: %s\n", 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);
+}
+
+static wasm_trap_t *imported_func(void *env, wasmtime_caller_t *caller,
+				  const wasmtime_val_t *args, size_t nargs,
+				  wasmtime_val_t *results, size_t nresults)
+{
+	(void)env;
+	(void)caller;
+	(void)args;
+	(void)nargs;
+	(void)results;
+	(void)nresults;
+
+	return NULL;
+}
+
+int main(void)
+{
+	wasm_engine_t *engine;
+	wasmtime_store_t *store;
+	wasmtime_context_t *context;
+	wasmtime_module_t *module = NULL;
+	wasmtime_linker_t *linker;
+	wasmtime_error_t *error;
+	wasm_byte_vec_t wasm;
+	wasmtime_extern_t item;
+	wasm_functype_t *func_ty;
+	wasi_config_t *wasi_config;
+	FILE *file;
+	size_t file_size;
+	bool ok;
+
+	printf("Initializing...\n");
+	engine = wasm_engine_new();
+	store = wasmtime_store_new(engine, NULL, NULL);
+	context = wasmtime_store_context(store);
+
+	linker = wasmtime_linker_new(engine);
+	error = wasmtime_linker_define_wasi(linker);
+	if (error != NULL)
+		exit_with_error("failed to link wasi", error, NULL);
+
+	printf("Loading binary...\n");
+	file = fopen("test.wasm", "rb");
+	if (!file) {
+		printf("> Error loading file!\n");
+		exit(1);
+	}
+	fseek(file, 0L, SEEK_END);
+	file_size = ftell(file);
+	wasm_byte_vec_new_uninitialized(&wasm, file_size);
+	fseek(file, 0L, SEEK_SET);
+	if (fread(wasm.data, file_size, 1, file) != 1) {
+		printf("> Error loading module!\n");
+		exit(1);
+	}
+	fclose(file);
+
+	printf("Compiling module...\n");
+	error = wasmtime_module_new(engine, (uint8_t*)wasm.data, wasm.size,
+				    &module);
+	if (!module)
+		exit_with_error("failed to compile module", error, NULL);
+	wasm_byte_vec_delete(&wasm);
+
+	printf("Setting fumction import...\n");
+	func_ty = wasm_functype_new_0_0();
+	wasmtime_linker_define_func(linker, "env", 3,
+				    "imported_func", 13, func_ty,
+				    imported_func, context, NULL);
+	wasm_functype_delete(func_ty);
+
+	printf("Initialising WASI...\n");
+	wasi_config = wasi_config_new();
+	wasi_config_inherit_env(wasi_config);
+	wasi_config_inherit_stdin(wasi_config);
+	wasi_config_inherit_stdout(wasi_config);
+	wasi_config_inherit_stderr(wasi_config);
+	error = wasmtime_context_set_wasi(context, wasi_config);
+	if (error)
+		exit_with_error("failed to initialise WASI", error, NULL);
+
+	printf("Instantiating module...\n");
+	error = wasmtime_linker_module(linker, context, "", 0, module);
+	if (error != NULL)
+		exit_with_error("failed to instantiate module", error, NULL);
+
+	printf("Getting function export...\n");
+	ok = wasmtime_linker_get(linker, context, "", 0, "exported_func", 13,
+				 &item);
+	if (!ok) {
+		printf("> Error getting function export\n");
+		exit(1);
+	}
+
+	printf("Shutting down...\n");
+	wasmtime_module_delete(module);
+	wasmtime_store_delete(store);
+	wasm_engine_delete(engine);
+
+	printf("Done.\n");
+
+	return 0;
+}