c-api: Create and instantiate a component model linker (#10598)

* c-api: Create and instantiate a component model linker

Co-authored-by: Tyler Rockwood <rockwood@redpanda.com>
Co-authored-by: Jean-Jacques Lafay <jean-jacques@secretarium.org>

* c-api: Accept `wat` in `wasmtime_component_new()`

* Add a test

* c-api: Include `wasmtime/conf.h` in `component/component.h`

* Add `wasmtime/conf.h` include to `instance.h` and `linker.h`

* Make wasmtime_component_instance_t non-opaque

* Defer `wasmtime_component_linker_instance()`

---------

Co-authored-by: Tyler Rockwood <rockwood@redpanda.com>
Co-authored-by: Jean-Jacques Lafay <jean-jacques@secretarium.org>

Author: 3 people

crates/c-api/include/wasmtime/component.h

@@ -2,5 +2,7 @@
 #define WASMTIME_COMPONENT_H
 
 #include <wasmtime/component/component.h>
+#include <wasmtime/component/instance.h>
+#include <wasmtime/component/linker.h>
 
 #endif // WASMTIME_COMPONENT_H

crates/c-api/include/wasmtime/component/component.h

@@ -1,11 +1,12 @@
 #ifndef WASMTIME_COMPONENT_COMPONENT_H
 #define WASMTIME_COMPONENT_COMPONENT_H
 
-#ifdef WASMTIME_FEATURE_COMPONENT_MODEL
-
 #include <wasm.h>
+#include <wasmtime/conf.h>
 #include <wasmtime/error.h>
 
+#ifdef WASMTIME_FEATURE_COMPONENT_MODEL
+
 #ifdef __cplusplus
 extern "C" {
 #endif

crates/c-api/include/wasmtime/component/instance.h

@@ -0,0 +1,32 @@
+#ifndef WASMTIME_COMPONENT_INSTANCE_H
+#define WASMTIME_COMPONENT_INSTANCE_H
+
+#include <wasmtime/conf.h>
+
+#ifdef WASMTIME_FEATURE_COMPONENT_MODEL
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/// \brief Representation of a instance in Wasmtime.
+///
+/// Instances are represented with a 64-bit identifying integer in Wasmtime.
+/// They do not have any destructor associated with them. Instances cannot
+/// interoperate between #wasmtime_store_t instances and if the wrong instance
+/// is passed to the wrong store then it may trigger an assertion to abort the
+/// process.
+typedef struct wasmtime_component_instance {
+  /// Internal identifier of what store this belongs to, never zero.
+  uint64_t store_id;
+  /// Internal index within the store.
+  size_t index;
+} wasmtime_component_instance_t;
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif // WASMTIME_FEATURE_COMPONENT_MODEL
+
+#endif // WASMTIME_COMPONENT_INSTANCE_H

crates/c-api/include/wasmtime/component/linker.h

@@ -0,0 +1,63 @@
+#ifndef WASMTIME_COMPONENT_LINKER_H
+#define WASMTIME_COMPONENT_LINKER_H
+
+#include <wasm.h>
+#include <wasmtime/component/component.h>
+#include <wasmtime/component/instance.h>
+#include <wasmtime/conf.h>
+#include <wasmtime/error.h>
+#include <wasmtime/store.h>
+
+#ifdef WASMTIME_FEATURE_COMPONENT_MODEL
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct wasmtime_component_linker_t wasmtime_component_linker_t;
+
+/**
+ * \brief Creates a new #wasmtime_component_linker_t for the specified engine.
+ *
+ * \param engine the compilation environment and configuration
+ *
+ * \return a pointer to the newly created #wasmtime_component_linker_t
+ */
+WASM_API_EXTERN wasmtime_component_linker_t *
+wasmtime_component_linker_new(const wasm_engine_t *engine);
+
+/**
+ * \brief Instantiates a component instance in a given #wasmtime_context_t
+ *
+ * \param linker a #wasmtime_component_linker_t that will help provide host
+ *        functions
+ * \param context the #wasmtime_context_t in which the instance should be
+ *        created
+ * \param component the #wasmtime_component_t to instantiate
+ * \param instance_out on success, the instantiated
+ *        #wasmtime_component_instance_t
+ *
+ * \return wasmtime_error_t* on success `NULL` is returned, otherwise an error
+ *         is returned which describes why the build failed.
+ */
+WASM_API_EXTERN wasmtime_error_t *wasmtime_component_linker_instantiate(
+    const wasmtime_component_linker_t *linker, wasmtime_context_t *context,
+    const wasmtime_component_t *component,
+    wasmtime_component_instance_t *instance_out);
+
+/**
+ * \brief Deletes a #wasmtime_component_linker_t created by
+ * #wasmtime_component_linker_new
+ *
+ * \param linker the #wasmtime_component_linker_t to delete
+ */
+WASM_API_EXTERN void
+wasmtime_component_linker_delete(wasmtime_component_linker_t *linker);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif // WASMTIME_FEATURE_COMPONENT_MODEL
+
+#endif // WASMTIME_COMPONENT_LINKER_H

crates/c-api/src/component/component.rs

@@ -24,13 +24,10 @@ pub unsafe extern "C" fn wasmtime_component_new(
     len: usize,
     component_out: &mut *mut wasmtime_component_t,
 ) -> Option<Box<wasmtime_error_t>> {
-    let binary = unsafe { crate::slice_from_raw_parts(buf, len) };
-    crate::handle_result(
-        Component::from_binary(&engine.engine, binary),
-        |component| {
-            *component_out = Box::into_raw(Box::new(wasmtime_component_t { component }));
-        },
-    )
+    let bytes = unsafe { crate::slice_from_raw_parts(buf, len) };
+    crate::handle_result(Component::new(&engine.engine, bytes), |component| {
+        *component_out = Box::into_raw(Box::new(wasmtime_component_t { component }));
+    })
 }
 
 #[unsafe(no_mangle)]

crates/c-api/src/component/linker.rs

@@ -0,0 +1,36 @@
+use wasmtime::component::{Instance, Linker};
+
+use crate::{wasm_engine_t, wasmtime_error_t, WasmtimeStoreContextMut, WasmtimeStoreData};
+
+use super::wasmtime_component_t;
+
+#[repr(transparent)]
+pub struct wasmtime_component_linker_t {
+    pub(crate) linker: Linker<WasmtimeStoreData>,
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn wasmtime_component_linker_new(
+    engine: &wasm_engine_t,
+) -> Box<wasmtime_component_linker_t> {
+    Box::new(wasmtime_component_linker_t {
+        linker: Linker::new(&engine.engine),
+    })
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn wasmtime_component_linker_instantiate(
+    linker: &wasmtime_component_linker_t,
+    context: WasmtimeStoreContextMut<'_>,
+    component: &wasmtime_component_t,
+    instance_out: &mut Instance,
+) -> Option<Box<wasmtime_error_t>> {
+    let result = linker.linker.instantiate(context, &component.component);
+    crate::handle_result(result, |instance| *instance_out = instance)
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn wasmtime_component_linker_delete(
+    _linker: Box<wasmtime_component_linker_t>,
+) {
+}

crates/c-api/src/component/mod.rs

@@ -1,3 +1,5 @@
 mod component;
+mod linker;
 
 pub use component::*;
+pub use linker::*;

crates/c-api/tests/CMakeLists.txt

@@ -9,15 +9,16 @@ FetchContent_MakeAvailable(googletest)
 
 include(GoogleTest)
 
-function(add_capi_test name)
-  add_executable(test-${name} ${name}.cc)
+function(add_capi_test name path)
+  add_executable(test-${name} ${path})
   target_link_libraries(test-${name} PRIVATE wasmtime-cpp gtest_main)
   gtest_discover_tests(test-${name})
 endfunction()
 
-add_capi_test(simple)
-add_capi_test(types)
-add_capi_test(func)
+add_capi_test(simple simple.cc)
+add_capi_test(types types.cc)
+add_capi_test(func func.cc)
+add_capi_test(component-instantiate component/instantiate.cc)
 
 # Add a custom test where two files include `wasmtime.hh` and are compiled into
 # the same executable (basically makes sure any defined functions in the header

crates/c-api/tests/component/instantiate.cc

@@ -0,0 +1,42 @@
+#include <gtest/gtest.h>
+#include <wasmtime.h>
+
+TEST(component, instantiate) {
+  static constexpr auto bytes = std::string_view{
+      R"END(
+      (component
+          (core module)
+      )
+      )END",
+  };
+
+  const auto engine = wasm_engine_new();
+  EXPECT_NE(engine, nullptr);
+
+  const auto store = wasmtime_store_new(engine, nullptr, nullptr);
+  EXPECT_NE(store, nullptr);
+  const auto context = wasmtime_store_context(store);
+  EXPECT_NE(context, nullptr);
+
+  wasmtime_component_t *component = nullptr;
+
+  auto error = wasmtime_component_new(
+      engine, reinterpret_cast<const uint8_t *>(bytes.data()), bytes.size(),
+      &component);
+
+  EXPECT_EQ(error, nullptr);
+  EXPECT_NE(component, nullptr);
+
+  const auto linker = wasmtime_component_linker_new(engine);
+  EXPECT_NE(linker, nullptr);
+
+  wasmtime_component_instance_t instance = {};
+  error = wasmtime_component_linker_instantiate(linker, context, component,
+                                                &instance);
+  EXPECT_EQ(error, nullptr);
+
+  wasmtime_component_linker_delete(linker);
+
+  wasmtime_store_delete(store);
+  wasm_engine_delete(engine);
+}