Merge #261

261: feat(runtime-c-api) Add an API to update `vm::Ctx.data` r=Hywan a=Hywan

This patch adds 2 functions for the runtime C API, respectively
`wasmer_instance_context_data_set` and
`wasmer_instance_context_data_get`. The goal is to modify the
`vm::Ctx.data` field in the `runtime-core` library.

Since all imported functions receive this context, that's the
simplest way to pass dynamic data to them.

Co-authored-by: Ivan Enderlin <ivan.enderlin@hoa-project.net>
Co-authored-by: Syrus Akbary <me@syrusakbary.com>

lib/runtime-c-api/src/lib.rs

@@ -947,6 +947,18 @@ pub unsafe extern "C" fn wasmer_instance_exports(
     *exports = Box::into_raw(named_exports) as *mut wasmer_exports_t;
 }
 
+/// Sets the `data` field of the instance context. This context will be
+/// passed to all imported function for instance.
+#[allow(clippy::cast_ptr_alignment)]
+#[no_mangle]
+pub extern "C" fn wasmer_instance_context_data_set(
+    instance: *mut wasmer_instance_t,
+    data_ptr: *mut c_void,
+) {
+    let instance_ref = unsafe { &mut *(instance as *mut Instance) };
+    instance_ref.context_mut().data = data_ptr;
+}
+
 pub struct NamedExports(Vec<NamedExport>);
 
 /// Frees the memory for the given exports
@@ -1350,6 +1362,16 @@ pub extern "C" fn wasmer_instance_context_memory(
     memory as *const Memory as *const wasmer_memory_t
 }
 
+/// Gets the `data` field within the context.
+#[allow(clippy::cast_ptr_alignment)]
+#[no_mangle]
+pub extern "C" fn wasmer_instance_context_data_get(
+    ctx: *const wasmer_instance_context_t,
+) -> *mut c_void {
+    let ctx = unsafe { &*(ctx as *const Ctx) };
+    ctx.data
+}
+
 /// Gets the start pointer to the bytes within a Memory
 #[allow(clippy::cast_ptr_alignment)]
 #[no_mangle]

lib/runtime-c-api/tests/test-import-function.c

@@ -8,6 +8,11 @@ static bool print_str_called = false;
 static int memory_len = 0;
 static int ptr_len = 0;
 static char actual_str[14] = {};
+static int actual_context_data_value = 0;
+
+typedef struct {
+  int value;
+} context_data;
 
 void print_str(wasmer_instance_context_t *ctx, int32_t ptr, int32_t len)
 {
@@ -23,6 +28,8 @@ void print_str(wasmer_instance_context_t *ctx, int32_t ptr, int32_t len)
     print_str_called = true;
     memory_len = mem_len;
     ptr_len = len;
+
+    actual_context_data_value = ((context_data *) wasmer_instance_context_data_get(ctx))->value;
 }
 
 int main()
@@ -65,6 +72,11 @@ int main()
 
     assert(compile_result == WASMER_OK);
 
+    context_data* context_data = malloc(sizeof(context_data));
+    int context_data_value = 42;
+    context_data->value = context_data_value;
+    wasmer_instance_context_data_set(instance, context_data);
+
     wasmer_value_t params[] = {};
     wasmer_value_t results[] = {};
     wasmer_result_t call_result = wasmer_instance_call(instance, "hello_wasm", params, 0, results, 0);
@@ -82,10 +94,12 @@ int main()
     assert(memory_len == 17);
     assert(ptr_len == 13);
     assert(0 == strcmp(actual_str, "Hello, World!"));
+    assert(context_data_value == actual_context_data_value);
 
     printf("Destroying func\n");
     wasmer_import_func_destroy(func);
     printf("Destroy instance\n");
     wasmer_instance_destroy(instance);
+    free(context_data);
     return 0;
 }

lib/runtime-c-api/wasmer.h

@@ -95,11 +95,11 @@ typedef struct {
 
 typedef struct {
 
-} wasmer_memory_t;
+} wasmer_instance_context_t;
 
 typedef struct {
 
-} wasmer_instance_context_t;
+} wasmer_memory_t;
 
 typedef struct {
 
@@ -382,6 +382,17 @@ wasmer_result_t wasmer_instance_call(wasmer_instance_t *instance,
                                      wasmer_value_t *results,
                                      int results_len);
 
+/**
+ * Gets the `data` field within the context.
+ */
+void *wasmer_instance_context_data_get(const wasmer_instance_context_t *ctx);
+
+/**
+ * Sets the `data` field of the instance context. This context will be
+ * passed to all imported function for instance.
+ */
+void wasmer_instance_context_data_set(wasmer_instance_t *instance, void *data_ptr);
+
 /**
  * Gets the memory within the context at the index `memory_idx`.
  * The index is always 0 until multiple memories are supported.

lib/runtime-c-api/wasmer.hh

@@ -90,11 +90,11 @@ struct wasmer_instance_t {
 
 };
 
-struct wasmer_memory_t {
+struct wasmer_instance_context_t {
 
 };
 
-struct wasmer_instance_context_t {
+struct wasmer_memory_t {
 
 };
 
@@ -307,6 +307,13 @@ wasmer_result_t wasmer_instance_call(wasmer_instance_t *instance,
                                      wasmer_value_t *results,
                                      int results_len);
 
+/// Gets the `data` field within the context.
+void *wasmer_instance_context_data_get(const wasmer_instance_context_t *ctx);
+
+/// Sets the `data` field of the instance context. This context will be
+/// passed to all imported function for instance.
+void wasmer_instance_context_data_set(wasmer_instance_t *instance, void *data_ptr);
+
 /// Gets the memory within the context at the index `memory_idx`.
 /// The index is always 0 until multiple memories are supported.
 const wasmer_memory_t *wasmer_instance_context_memory(const wasmer_instance_context_t *ctx,