Implement RFC 11: Redesigning Wasmtime's APIs (#2897)

Implement Wasmtime's new API as designed by RFC 11. This is quite a large commit which has had lots of discussion externally, so for more information it's best to read the RFC thread and the PR thread.

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

@@ -0,0 +1,158 @@
+/**
+ * \file wasmtime/instance.h
+ *
+ * Wasmtime APIs for interacting with wasm instances.
+ */
+
+#ifndef WASMTIME_INSTANCE_H
+#define WASMTIME_INSTANCE_H
+
+#include <wasm.h>
+#include <wasmtime/extern.h>
+#include <wasmtime/module.h>
+#include <wasmtime/store.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \brief An opaque object representing the type of an instance.
+ */
+typedef struct wasmtime_instancetype wasmtime_instancetype_t;
+
+/// \brief Deletes an instance type
+WASM_API_EXTERN void wasmtime_instancetype_delete(wasmtime_instancetype_t *ty);
+
+/**
+ * \brief Returns the list of exports that this instance type provides.
+ *
+ * This function does not take ownership of the provided instance type but
+ * ownership of `out` is passed to the caller. Note that `out` is treated as
+ * uninitialized when passed to this function.
+ */
+WASM_API_EXTERN void wasmtime_instancetype_exports(const wasmtime_instancetype_t*, wasm_exporttype_vec_t* out);
+
+/**
+ * \brief Converts a #wasmtime_instancetype_t to a #wasm_externtype_t
+ *
+ * The returned value is owned by the #wasmtime_instancetype_t argument and should not
+ * be deleted.
+ */
+WASM_API_EXTERN wasm_externtype_t* wasmtime_instancetype_as_externtype(wasmtime_instancetype_t*);
+
+/**
+ * \brief Attempts to convert a #wasm_externtype_t to a #wasmtime_instancetype_t
+ *
+ * The returned value is owned by the #wasmtime_instancetype_t argument and should not
+ * be deleted. Returns `NULL` if the provided argument is not a
+ * #wasmtime_instancetype_t.
+ */
+WASM_API_EXTERN wasmtime_instancetype_t* wasmtime_externtype_as_instancetype(wasm_externtype_t*);
+
+/**
+ * \brief Instantiate a wasm module.
+ *
+ * This function will instantiate a WebAssembly module with the provided
+ * imports, creating a WebAssembly instance. The returned instance can then
+ * afterwards be inspected for exports.
+ *
+ * \param store the store in which to create the instance
+ * \param module the module that's being instantiated
+ * \param imports the imports provided to the module
+ * \param nimports the size of `imports`
+ * \param instance where to store the returned instance
+ * \param trap where to store the returned trap
+ *
+ * This function requires that `imports` is the same size as the imports that
+ * `module` has. Additionally the `imports` array must be 1:1 lined up with the
+ * imports of the `module` specified. This is intended to be relatively low
+ * level, and #wasmtime_linker_instantiate is provided for a more ergonomic
+ * name-based resolution API.
+ *
+ * The states of return values from this function are similar to
+ * #wasmtime_func_call where an error can be returned meaning something like a
+ * link error in this context. A trap can be returned (meaning no error or
+ * instance is returned), or an instance can be returned (meaning no error or
+ * trap is returned).
+ *
+ * Note that this function requires that all `imports` specified must be owned
+ * by the `store` provided as well.
+ *
+ * This function does not take ownership of any of its arguments, but all return
+ * values are owned by the caller.
+ */
+WASM_API_EXTERN wasmtime_error_t *wasmtime_instance_new(
+    wasmtime_context_t *store,
+    const wasmtime_module_t *module,
+    const wasmtime_extern_t* imports,
+    size_t nimports,
+    wasmtime_instance_t *instance,
+    wasm_trap_t **trap
+);
+
+/**
+ * \brief Returns the type of the specified instance.
+ *
+ * The returned type is owned by the caller.
+ */
+WASM_API_EXTERN wasmtime_instancetype_t *wasmtime_instance_type(
+    const wasmtime_context_t *store,
+    const wasmtime_instance_t *instance
+);
+
+/**
+ * \brief Get an export by name from an instance.
+ *
+ * \param store the store that owns `instance`
+ * \param instance the instance to lookup within
+ * \param name the export name to lookup
+ * \param name_len the byte length of `name`
+ * \param item where to store the returned value
+ *
+ * Returns nonzero if the export was found, and `item` is filled in. Otherwise
+ * returns 0.
+ *
+ * Doesn't take ownership of any arguments but does return ownership of the
+ * #wasmtime_extern_t.
+ */
+WASM_API_EXTERN bool wasmtime_instance_export_get(
+    wasmtime_context_t *store,
+    const wasmtime_instance_t *instance,
+    const char *name,
+    size_t name_len,
+    wasmtime_extern_t *item
+);
+
+/**
+ * \brief Get an export by index from an instance.
+ *
+ * \param store the store that owns `instance`
+ * \param instance the instance to lookup within
+ * \param index the index to lookup
+ * \param name where to store the name of the export
+ * \param name_len where to store the byte length of the name
+ * \param item where to store the export itself
+ *
+ * Returns nonzero if the export was found, and `name`, `name_len`, and `item`
+ * are filled in. Otherwise returns 0.
+ *
+ * Doesn't take ownership of any arguments but does return ownership of the
+ * #wasmtime_extern_t. The `name` pointer return value is owned by the `store`
+ * and must be immediately used before calling any other APIs on
+ * #wasmtime_context_t.
+ */
+WASM_API_EXTERN bool wasmtime_instance_export_nth(
+    wasmtime_context_t *store,
+    const wasmtime_instance_t *instance,
+    size_t index,
+    char **name,
+    size_t *name_len,
+    wasmtime_extern_t *item
+);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif // WASMTIME_INSTANCE_H