1 files changed, 103 insertions, 0 deletions
diff --git a/ext/napi/function.rs b/ext/napi/function.rs
new file mode 100644
index 000000000..853283b08
--- /dev/null
+++ b/ext/napi/function.rs
@@ -0,0 +1,103 @@
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+use crate::*;
+
+#[repr(C)]
+#[derive(Debug)]
+pub struct CallbackInfo {
+  pub env: napi_env,
+  pub cb: napi_callback,
+  pub cb_info: napi_callback_info,
+  pub args: *const c_void,
+}
+
+impl CallbackInfo {
+  #[inline]
+  pub fn new_raw(
+    env: napi_env,
+    cb: napi_callback,
+    cb_info: napi_callback_info,
+  ) -> *mut Self {
+    Box::into_raw(Box::new(Self {
+      env,
+      cb,
+      cb_info,
+      args: std::ptr::null(),
+    }))
+  }
+}
+
+extern "C" fn call_fn(info: *const v8::FunctionCallbackInfo) {
+  let args =
+    unsafe { v8::FunctionCallbackArguments::from_function_callback_info(info) };
+  let mut rv = unsafe { v8::ReturnValue::from_function_callback_info(info) };
+  // SAFETY: create_function guarantees that the data is a CallbackInfo external.
+  let info_ptr: *mut CallbackInfo = unsafe {
+    let external_value =
+      v8::Local::<v8::External>::cast(args.data().unwrap_unchecked());
+    external_value.value() as _
+  };
+
+  // SAFETY: pointer from Box::into_raw.
+  let mut info = unsafe { &mut *info_ptr };
+  info.args = &args as *const _ as *const c_void;
+
+  if let Some(f) = info.cb {
+    // SAFETY: calling user provided function pointer.
+    let value = unsafe { f(info.env, info_ptr as *mut _) };
+    // SAFETY: napi_value is reprsented as v8::Local<v8::Value> internally.
+    rv.set(unsafe { transmute::<napi_value, v8::Local<v8::Value>>(value) });
+  }
+}
+
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn create_function<'a>(
+  env_ptr: *mut Env,
+  name: Option<&str>,
+  cb: napi_callback,
+  cb_info: napi_callback_info,
+) -> v8::Local<'a, v8::Function> {
+  let env: &mut Env = unsafe { &mut *env_ptr };
+  let scope = &mut env.scope();
+
+  let external = v8::External::new(
+    scope,
+    CallbackInfo::new_raw(env_ptr as _, cb, cb_info) as *mut _,
+  );
+  let function = v8::Function::builder_raw(call_fn)
+    .data(external.into())
+    .build(scope)
+    .unwrap();
+
+  if let Some(name) = name {
+    let v8str = v8::String::new(scope, name).unwrap();
+    function.set_name(v8str);
+  }
+
+  function
+}
+
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+pub fn create_function_template<'a>(
+  env_ptr: *mut Env,
+  name: Option<&str>,
+  cb: napi_callback,
+  cb_info: napi_callback_info,
+) -> v8::Local<'a, v8::FunctionTemplate> {
+  let env: &mut Env = unsafe { &mut *env_ptr };
+  let scope = &mut env.scope();
+
+  let external = v8::External::new(
+    scope,
+    CallbackInfo::new_raw(env_ptr as _, cb, cb_info) as *mut _,
+  );
+  let function = v8::FunctionTemplate::builder_raw(call_fn)
+    .data(external.into())
+    .build(scope);
+
+  if let Some(name) = name {
+    let v8str = v8::String::new(scope, name).unwrap();
+    function.set_class_name(v8str);
+  }
+
+  function
+}