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/src/extern.rs

@@ -1,11 +1,13 @@
 use crate::{
     wasm_externkind_t, wasm_externtype_t, wasm_func_t, wasm_global_t, wasm_instance_t,
-    wasm_memory_t, wasm_module_t, wasm_table_t,
+    wasm_memory_t, wasm_module_t, wasm_table_t, wasmtime_module_t, CStoreContext, StoreRef,
 };
-use wasmtime::Extern;
+use std::mem::ManuallyDrop;
+use wasmtime::{Extern, Func, Global, Instance, Memory, Table};
 
 #[derive(Clone)]
 pub struct wasm_extern_t {
+    pub(crate) store: StoreRef,
     pub(crate) which: Extern,
 }
 
@@ -24,8 +26,8 @@ pub extern "C" fn wasm_extern_kind(e: &wasm_extern_t) -> wasm_externkind_t {
 }
 
 #[no_mangle]
-pub extern "C" fn wasm_extern_type(e: &wasm_extern_t) -> Box<wasm_externtype_t> {
-    Box::new(wasm_externtype_t::new(e.which.ty()))
+pub unsafe extern "C" fn wasm_extern_type(e: &wasm_extern_t) -> Box<wasm_externtype_t> {
+    Box::new(wasm_externtype_t::new(e.which.ty(&e.store.context())))
 }
 
 #[no_mangle]
@@ -87,3 +89,97 @@ pub extern "C" fn wasm_extern_as_instance(e: &wasm_extern_t) -> Option<&wasm_ins
 pub extern "C" fn wasm_extern_as_instance_const(e: &wasm_extern_t) -> Option<&wasm_instance_t> {
     wasm_extern_as_instance(e)
 }
+
+#[repr(C)]
+pub struct wasmtime_extern_t {
+    pub kind: wasmtime_extern_kind_t,
+    pub of: wasmtime_extern_union,
+}
+
+pub type wasmtime_extern_kind_t = u8;
+pub const WASMTIME_EXTERN_FUNC: wasmtime_extern_kind_t = 0;
+pub const WASMTIME_EXTERN_GLOBAL: wasmtime_extern_kind_t = 1;
+pub const WASMTIME_EXTERN_TABLE: wasmtime_extern_kind_t = 2;
+pub const WASMTIME_EXTERN_MEMORY: wasmtime_extern_kind_t = 3;
+pub const WASMTIME_EXTERN_INSTANCE: wasmtime_extern_kind_t = 4;
+pub const WASMTIME_EXTERN_MODULE: wasmtime_extern_kind_t = 5;
+
+#[repr(C)]
+pub union wasmtime_extern_union {
+    pub func: Func,
+    pub table: Table,
+    pub global: Global,
+    pub instance: Instance,
+    pub memory: Memory,
+    pub module: ManuallyDrop<Box<wasmtime_module_t>>,
+}
+
+impl wasmtime_extern_t {
+    pub unsafe fn to_extern(&self) -> Extern {
+        match self.kind {
+            WASMTIME_EXTERN_FUNC => Extern::Func(self.of.func),
+            WASMTIME_EXTERN_GLOBAL => Extern::Global(self.of.global),
+            WASMTIME_EXTERN_TABLE => Extern::Table(self.of.table),
+            WASMTIME_EXTERN_MEMORY => Extern::Memory(self.of.memory),
+            WASMTIME_EXTERN_INSTANCE => Extern::Instance(self.of.instance),
+            WASMTIME_EXTERN_MODULE => Extern::Module(self.of.module.module.clone()),
+            other => panic!("unknown wasm_extern_kind_t: {}", other),
+        }
+    }
+}
+
+impl From<Extern> for wasmtime_extern_t {
+    fn from(item: Extern) -> wasmtime_extern_t {
+        match item {
+            Extern::Func(func) => wasmtime_extern_t {
+                kind: WASMTIME_EXTERN_FUNC,
+                of: wasmtime_extern_union { func },
+            },
+            Extern::Global(global) => wasmtime_extern_t {
+                kind: WASMTIME_EXTERN_GLOBAL,
+                of: wasmtime_extern_union { global },
+            },
+            Extern::Table(table) => wasmtime_extern_t {
+                kind: WASMTIME_EXTERN_TABLE,
+                of: wasmtime_extern_union { table },
+            },
+            Extern::Memory(memory) => wasmtime_extern_t {
+                kind: WASMTIME_EXTERN_MEMORY,
+                of: wasmtime_extern_union { memory },
+            },
+            Extern::Instance(instance) => wasmtime_extern_t {
+                kind: WASMTIME_EXTERN_INSTANCE,
+                of: wasmtime_extern_union { instance },
+            },
+            Extern::Module(module) => wasmtime_extern_t {
+                kind: WASMTIME_EXTERN_MODULE,
+                of: wasmtime_extern_union {
+                    module: ManuallyDrop::new(Box::new(wasmtime_module_t { module })),
+                },
+            },
+        }
+    }
+}
+
+impl Drop for wasmtime_extern_t {
+    fn drop(&mut self) {
+        if self.kind == WASMTIME_EXTERN_MODULE {
+            unsafe {
+                ManuallyDrop::drop(&mut self.of.module);
+            }
+        }
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasmtime_extern_delete(e: &mut ManuallyDrop<wasmtime_extern_t>) {
+    ManuallyDrop::drop(e);
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn wasmtime_extern_type(
+    store: CStoreContext<'_>,
+    e: &wasmtime_extern_t,
+) -> Box<wasm_externtype_t> {
+    Box::new(wasm_externtype_t::new(e.to_extern().ty(store)))
+}